Cross-linking of stromal collagen with Riboflavin and UVA radiation is an alternative treatment of keratoconus. After the cross-linking a wound healing process starts with the regeneration of the abraded epithelial layer and the stromal keratocyte-network. To clarify possible side effects by visualization we established an imaging platform for the multimodal three-dimensional imaging of the cornea and looked for differences between normal and cross-linked rabbit corneae. The microscopy system utilizes femtosecond laser light for two photon excitation of autofluorescent metabolic compounds, second harmonic imaging in forward and backward direction for the study of stromal collagen-I structure and confocal detection of the backscattered femtosecond laser light for cell detection. Preliminary results show signatures of treatment 5 weeks after the intervention in all imaging modalities.

Contemporary retinal microsurgery is performed by skilled surgeons through operating microscopes, utilizing free hand techniques and manually operated micro-instruments. One technically challenging procedure is the incising and peeling of the internal limiting membrane (ILM) while minimizing damage to the underlying retina. One strategy for minimizing damage is to improve visualization of the ILM layer. Here we present a preliminary evaluation of a prototype tool that integrates an ultra high resolution Fourier domain common path Optical Coherence Tomography (OCT) with an intelligent microsurgical instrument. The tool provides OCT guided visualization of the ILM layer at the point of tissue contact by the surgical tool. We have evaluated the imaging properties of the common path OCT system. The common path OCT system used in this study has a maximum imaging depth of 1.3mm and a sensitivity of 91dB. We have achieved an experimental axial resolution of 3μm in air and this appears to be sufficient to both identify the ILM and to perform surgical maneuvers. We scanned the single mode fiber probe using an intelligent microsurgical instrument to form B-Mode images. We imaged a porcine eye with both anterior eye segment and the vitreous removed. The image obtained show distinct functional layers of retina.

Experimental assessment of stiffness of crystalline lens of the eye can help in understanding several ocular diseases. Studies have shown that stiffness of the eye lens increases with age that might contribute to loss of accommodation. The stiffness of the lens could be assessed by measuring mechanically induced surface waves propagating on its surface. Here we present preliminary results on phase sensitive spectral domain optical coherence tomography (PhS-SDOCT) measurements of the vibrations induced on surface of an eye lens. The system shows an axial resolution of 8 μm, phase sensitivity of 0.01 radians, imaging depth of up to 3.4 mm in air and a scanning speed of 29 kHz for a single A-line. The results indicate that the system could detect vibrations as small as 0.45 μm induced on the surface of crystalline lens, and hence, PhS-SDOCT could be potentially used to assess stiffness of a crystalline lens.

Purpose: Subjects after cataract removal and intra-ocular lens (IOL) implantation lose their accommodation capability and are left with a monofocal visual system. The IOL refraction and the precision of the surgery determine the focal distance and amount of astigmatic aberrations. We present a design, simulations and experimental bench testing of a novel, non-diffractive, non-multifocal, extended depth of focus (EDOF) technology incorporated into an IOL that allows the subject to have astigmatic and chromatic aberrations-free continuous focusing ability from 35cm to infinity as well as increased tolerance to IOL decentration. Methods: The EDOF element was engraved on a surface of a monofocal rigid IOL as a series of shallow (less than one micron deep) concentric grooves around the optical axis. These grooves create an interference pattern extending the focus from a point to a length of about one mm providing a depth of focus of 3.00D (D stands for Diopters) with negligible loss of energy at any point of the focus while significantly reducing the astigmatic aberration of the eye and that generated during the IOL implantation. The EDOF IOL was tested on an optical bench simulating the eye model. In the experimental testing we have explored the characteristics of the obtained EDOF capability, the tolerance to astigmatic aberrations and decentration. Results: The performance of the proposed IOL was tested for pupil diameters of 2 to 5mm and for various spectral illuminations. The MTF charts demonstrate uniform performance of the lens for up to 3.00D at various illumination wavelengths and pupil diameters while preserving a continuous contrast of above 25% for spatial frequencies of up to 25 cycles/mm. Capability of correcting astigmatism of up to 1.00D was measured. Conclusions: The proposed EDOF IOL technology was tested by numerical simulations as well as experimentally characterized on an optical bench. The new lens is capable of solving presbyopia and astigmatism simultaneously by providing focus extension of 3.00D under various illumination conditions, wavelengths and pupil diameters of the implanted lens without loss of energy at any of the relevant distances.

Refilling the lens capsule while preserving capsular integrity offers the potential to restore ocular accommodation. There are two persisting problems in capsular bag refilling for possible clinical application: Leakage of the injectable material through the capsular opening and capsular opacification. Numerous attempts for solving these cardinal problems have not been proven to be clinically applicable. Recently, we developed a novel capsular bag refilling procedure using a novel accommodative intraocular lens that serves as an optic as well as a plug for sealing the capsular opening. The procedure and the results of monkey experiments will be presented.

A rapid line-scan confocal imager was developed for reflected light measurement of fast IOSs correlated with retinal activation. This functional imager provides two, i.e., frame-by-frame and line-by-line, imaging modalities. While frame-by-frame imaging allows dynamic visualization of IOSs over a two-dimensional retinal area at a frame speed > 100 Hz; line-by-line recording can provide ultrafast (> 10 KHz) monitoring of a fixed line area of the retina. A series of experiments was conducted to characterize reflected IOSs in frog retinas, and simultaneous electrophysiological responses were measured. Our experiments indicated that reflected IOSs were tightly correlated with retinal stimuli. Because of effective rejection of out-of-focus background light, rapid confocal imaging typically disclosed fast IOSs with magnitude peak > 30% ▵I/I, where ▵I was dynamic optical change and I was background light intensity. We anticipate that further development of the IOS imaging technology will pave the way toward noninvasive, high resolution evaluation of retinal function.

Wide-field and high-sensitive Doppler optical coherence angiography of the posterior human eye has been demonstrated. High-sensitive phase-resolved spectral-domain optical coherence tomography using the superluminescent diode with the central wavelength of 840 nm and bandwidth of 50 nm (FWHM) is developed. Two OCT signals with a time separation are acquired simultaneously with double sampling beams divided by using a Wollaston prism and a polarization-sensitive spectrometer consisting of two line scan cameras. The total power of two beams on the cornea is 700 μW. The line scan rate of cameras is 27 kHz and each OCT channel has the sensitivity of 93 dB. The two sampling beams are separated by approximately 162 um on the retina. The scanning of the beams is applied along the plane consisting of them. A single position on the sample is scanned twice with these two beams. High-contrast and high-sensitive phase-resolved blood flow image is obtained with these two OCT signals. Since the two signals are highly correlated, the decorrelation noise is small. In addition to that, this method does not require dense lateral sampling comparing to the lateral resolution which is demanded for previous phase-sensitive flow imaging. High-speed and high-sensitive blood flow imaging is enabled. The retinal and choroidal vasculature images with the area of 7.7 × 7.7 mm (512 × 256 axial scans) are obtained within 5 s.

We developed a high speed Doppler tomography system together with flow extraction algorithms that provide a flexible tool to assess retinal perfusion. The aim of the present study is to stimulate perfusion by flickering with light of adjustable color and to measure changes depending on light frequency and flicker location. We observed relative changes in arterial flow velocity during flicker stimulation up to 50%. We found in arteries close to the optic nerve head the highest flicker response at a frequency of 8Hz. We believe that a multimodal functional imaging concept is of high value for an accurate and early diagnosis and understanding of retinal pathologies and pathogenesis.

We present both axial and transverse components estimation using joint Spectral and Time domain Optical Coherence Tomography (STdOCT) method. Whereas axial component of velocity vector can be determined from the time-dependent Doppler beating frequency, the transverse component can be assessed by the analysis of the broadening of flow velocity profiles (Doppler bandwidth). This enables us to quantitatively determine the absolute value of the velocity vector. The accurate analyses are performed using well-defined flow of Intralipid solution in the glass capillary. This enables performing in vivo imaging and allows to calculate velocity maps of the retinal vasculature.

Movies acquired from fundus imaging using Indocyanine Green (ICG) and a scanning laser ophthalmoscope provide information for identifying vascular and other retinal abnormalities. Today, the main limitation of this modality is that it requires esoteric training for interpretation. A straightforward interpretation of these movies by objective measurements would aid in eliminating this training barrier. A software program has been developed and tested that produces and visualizes 2D maps of perfusion measures. The program corrects for frame-to-frame misalignment caused by eye motion, including rigid misalignment and warp. The alignment method uses a cross-correlation operation that automatically detects the distance due to motion between adjacent frames. The d-ICG movie is further corrected by removing flicker and vignetting artifacts. Each pixel in the corrected movie sequence is fit with a least-squares spline to yield a smooth intensity temporal profile. From the dynamics of these intensity curves, several perfusion measures are calculated. The most effective of these measures include a metric that represents the amount of time required for a vessel to fill with dye, a metric that represents the diffusion of dye, and a metric that is affected by local blood volume. These metrics are calculated from movies acquired before and after treatment for a neovascular condition. A comparison of these before and after measures may someday provide information to the clinician that helps them to evaluate disease progression and response to treatment.

A novel optical scanning method for an anterior segment optical coherence tomography (AS-OCT) system has been described. This method has been designed for imaging the entire anterior segment of the eye (from cornea to posterior surface of the crystalline lens) at a time. The ability to image the entire anterior segment is crucial in understanding the mechanism of human accommodation and the efficacy of accommodative intraocular lenses. In a conventional scanning system the beam is shined straight into the eye parallel to the optical axis. For anterior segment imaging, large lateral scan area leads to an increase in the angle of incidence on each of the four ocular surfaces. This causes significant reduction in signal reflected from regions further from the optical axis. This reduction combined with loss in signal due to coherence makes it difficult to image the entire anterior segment of the eye, where optical depth penetration of 10mm is required. To overcome this limitation, we have designed a new OCT scanning system, which achieves close to normal incidences across all the lateral locations on the ocular surfaces within a 6 mm clear aperture. This provides an increase in the amount of light scattered back to the system resulting in higher signal-to-noise ratio (SNR). The scanning system consists of two different custom designed lenses, one of them optimized for cornea and the anterior surface of the crystalline lens, while the other for the posterior surface of the crystalline lens. Two semicircular halves of each lens were glued together to form a single optical system. To evaluate the performance of our design we constructed and imaged a model eye and compared it with images obtained by conventional telecentric scanning method. SNR improvement by a factor of 3.71 was observed for the front surface of the lens and 18.83 for the back surface of the lens.

We develop a compact polarization sensitive corneal and anterior segment swept-source optical coherence tomography (PS-CAS- OCT) for evaluating the usefulness of PS-OCT, and enabling large scale studies in the tissue properties of normal and diseased eyes using the benefits of the PS-OCT, which provides better tissue discrimination compared to the conventional OCT by visualizing the fibrous tissues in the anterior eye segment. Our polarization-sensitive interferometer is size reduced into a 19 inch box for the portability and the probe is integrated into a position adjustable scanning head for the usability of our system.

A tissue discrimination algorithm of polarization sensitive optical coherence tomography (PS-OCT) based on optical properties of tissue was developed. We calculated three dimensional (3D) feature vector (intensity, extinction coefficient, birefringence) obtained by PS-OCT. The tissue types of each pixel were discriminated according to positions of the feature vectors in 3D feature space. This algorithm was applied for discrimination of human anterior eye chamber. Conjunctiva, selera, trabecular meshwork (TM), cornea and uvea were well separated in the 3D feature space and discriminated in good contrast.

Segmentation of retinal structures is an important step for quantitative diagnostic applications of optical coherence tomography (OCT) in ophthalmology. Contrary to previous segmentation algorithms that are based on intensity images, we use the tissue specific contrast provided by polarization sensitive (PS) OCT for segmentation of retinal layers and lesions. Our algorithms exploit the polarization scrambling property of the retinal pigment epithelium (RPE) in a first step to segment the RPE. The RPE is then used as a "backbone" to identify further structures like the normal RPE position (indicating Bruch's membrane) or the posterior tips of the photoreceptors. In a final step, lesions like drusen, RPE atrophies, and subretinal fluids are segmented.

The aim was to evaluate a method for visualizing fs laser pulse induced microincisions inside crystalline lens tissue. Porcine lenses were modified ex vivo by fs laser pulses to create defined planes at which lens fibers separate. Lens fiber orientation and fs laser-induced micro-incisions were examined using a confocal laser scanning microscope. Micro-incision visualization revealed different cutting effects depending on fs laser pulse energy, ranging from altered tissue scattering properties with all fibers intact to definite fiber separation with a wide gap. CLSM permits visualization and analysis and thereby control of fs laser pulse induced microincisions inside crystalline lens tissue.

Shorter pulse durations help confine thermal damage during retinal photocoagulation, decrease treatment time and minimize pain. However, safe therapeutic window (the ratio of threshold powers for rupture and mild coagulation) decreases with shorter exposures. A ring-shaped beam enables safer photocoagulation than conventional beams by reducing the maximum temperature in the center of the spot. Similarly, a temporal pulse modulation decreasing its power over time improves safety by maintaining constant temperature for a significant portion of the pulse. Optimization of the beam and pulse shapes was performed using a computational model. In vivo experiments were performed to verify the predicted improvement. With each of these approaches, the pulse duration can be decreased by a factor of two, from 20 ms down to 10 ms while maintaining the same therapeutic window.

This study evaluates the effects of exposure duration, beam diameter, and power on the safety, selectivity, and healing of retinal lesions created using a continuous line scanning laser. A 532 nm laser (PASCAL^TM) with retinal beam diameters of 40 and 66 μm was applied to 60 eyes of 30 Dutch-Belted rabbits. Retinal exposure duration varied from 15 to 60 μs. Lesions were acutely assessed by ophthalmoscopy and fluorescein angiography (FA). RPE flatmounts were evaluated with live-dead fluorescent assay (LD). Histological analysis was performed at 1 hour, 1 and 3 days, 1 and 2 weeks, and 1 and 2 months following laser treatment. Ophthalmoscopic visibility (OV) of the lesions corresponded to photoreceptor damage on histological analysis at 1 hour. In subvisible lesions, FA and LD yielded similar thresholds of RPE damage. The ratios of the threshold of rupture and of OV to FA visibility (measures of safety and selectivity) increased with decreasing duration and beam diameter. Above the threshold of OV, histology showed focal RPE damage and photoreceptor loss at one day without inner retinal effects. By one week, continuity of photoreceptor and RPE layers was restored. By 1 month, photoreceptors appeared normal while hypertrophy and hyperpigmentation of the RPE persisted. Retinal therapy with a fast scanning continuous laser achieves selective targeting of the RPE and, at higher power, of the photoreceptors. The damage zone in the photoreceptor layer is quickly filled-in, likely due to photoreceptor migration from adjacent zones. Continuous scanning laser can treat large retinal areas within standard eye fixation time.

Purpose: It is hypothesized that 6.1 μm produced by a portable laser would be useful for incising tissue layers such as performing a retinectomy in detached retina with extensive anterior proliferative vitreoretinopathy. Methods: An alexandrite laser system, which provides a high-intensity Q-switched pulse (780 nm, 50-100 ns duration, 10 Hz), is wavelength-shifted by a two-stage stimulated Raman conversion process into the 6-7 μm range (Light Age, Inc.). Fresh cadaver porcine retinas were lased with 6.1 μm using a 200 μm diameter spot at 0.6 mJ after removal of the vitreous. Specimens were examined grossly and prepared for histological examination. Results: The Raman-shifted alexandrite laser produced a smooth Gaussian profile. A narrow spectrum was produced at 6.1 μm. A full-thickness retinal incision with minimal thermal damage was obtained at a low energy level of 0.6 mJ in the retinas. However, the depth of the incision did vary from an incomplete incision to a full-thickness incision involving the underlying choroidal layer in attached retinas. Conclusions: The 6.1 μm mid-infrared energy produced by a portable laser is capable of incising detached retinas with minimal thermal damage.

We describe results of retinal imaging with a novel instrument that combines adaptive optics - Fourier-domain optical coherence tomography (AO-OCT) with an adaptive optics scanning laser ophthalmoscope (AO-SLO). One of the benefits of combining Fd-OCT with SLO includes automatic co-registration between the two imaging modalities and the potential for correcting lateral and transversal eye motion resulting in motion artifact-free volumetric retinal imaging. Additionally this allows for direct comparison between retinal structures that can be imaged with both modalities (e.g., photoreceptor mosaics or microvasculature maps). This dual imaging modality could provide insight into some retinal properties that could not be accessed by a single imaging system. Additionally, extension of OCT and SLO beyond structural imaging may open new avenues for diagnostics and testing in ophthalmology. In particular, non-invasive vasculature mapping with these modalities holds promise of replacing fluorescein angiography in vascular identification. Several new improvements of our system are described, including results of testing a novel 97-actuator deformable mirror and AO-SLO light intensity modulation.

Ultrahigh speed line scan detectors based on CMOS technology have been recently demonstrated in ultrahigh resolution spectral-domain optical coherence tomography (UHR-SD-OCT) for retinal imaging. While successful, fundamental tradeoffs exist been image acquisition time, image sampling density, and sensitivity, all of which impact the extent of motion artifacts, visualization of fine spatial detail, and detection of faint reflections. Here we investigate these tradeoffs for imaging retinal nerve fiber bundles (RNFBs) using UHR-SD-OCT with adaptive optics (AO). Volume scans of 3°x3° and 1.5°x1.5° were acquired at retinal locations of 3° nasal and 6° superior to the fovea on a healthy subject. Dynamic AO compensation across a 6 mm pupil provided near-diffraction-limited performance. The acquisition rates were 22.5k lines/s and 125k lines/s with A-lines spaced at 0.9 μm and 1.8 μm and B-scans at 1.8 μm and 9 μm. Focus was optimized for visualizing the retinal nerve fiber bundles (RNFBs). En face projection and crosssectional views of the RNFBs were extracted from the volumes and compared to images acquired with established conventional CCD-based line-scan camera. The projection view was found highly sensitive to eye motion artifacts, yet could only be partially compensated with coarser sampling, since fine sampling was necessary to observe the microscopic features in the RNFBs. For the cross-sectional view, speckle noise rather than eye motion artifacts limited bundle clarity. The highest B-scan density (1.8 μm spacing) coupled with B-scan averaging proved the best combination. Regardless of view, the higher line rate provided better RNFB clarity.

We developed a multimodal adaptive optics (AO) retinal imager for diagnosis of retinal diseases, including glaucoma, diabetic retinopathy (DR), age-related macular degeneration (AMD), and retinitis pigmentosa (RP). The development represents the first ever high performance AO system constructed that combines AO-corrected scanning laser ophthalmoscopy (SLO) and swept source Fourier domain optical coherence tomography (SSOCT) imaging modes in a single compact clinical prototype platform. The SSOCT channel operates at a wavelength of 1 μm for increased penetration and visualization of the choriocapillaris and choroid, sites of major disease activity for DR and wet AMD. The system is designed to operate on a broad clinical population with a dual deformable mirror (DM) configuration that allows simultaneous low- and high-order aberration correction. The system also includes a wide field line scanning ophthalmoscope (LSO) for initial screening, target identification, and global orientation; an integrated retinal tracker (RT) to stabilize the SLO, OCT, and LSO imaging fields in the presence of rotational eye motion; and a high-resolution LCD-based fixation target for presentation to the subject of stimuli and other visual cues. The system was tested in a limited number of human subjects without retinal disease for performance optimization and validation. The system was able to resolve and quantify cone photoreceptors across the macula to within ~0.5 deg (~100-150 μm) of the fovea, image and delineate ten retinal layers, and penetrate to resolve targets deep into the choroid. In addition to instrument hardware development, analysis algorithms were developed for efficient information extraction from clinical imaging sessions, with functionality including automated image registration, photoreceptor counting, strip and montage stitching, and segmentation. The system provides clinicians and researchers with high-resolution, high performance adaptive optics imaging to help guide therapies, develop new drugs, and improve patient outcomes.

In ophthalmology, femtosecond laser transections (photodisruption) in the vicinity of the retina need to be performed with minimized threshold energy to not harm peripheral retinal tissue. However, the aberrations of the anterior eye elements cause a distortion of the wavefront and therefore a raised threshold energy when focussing into the posterior segment. We present an optical system that allows for correcting aberrations in eyes using adaptive optics consisting of a deformable mirror and a Hartmann-Shack-Sensor with a novel light source. If combined with femtosecond laser pulses this system offers the possibility for minimally invasive laser surgery in the posterior eye segment.

Purpose: To evaluate the clinical benefit of using an adaptive optics visual simulator (AOVS) and its impact in different clinical settings. Methods: An adaptive optics visual simulator performed the experimental procedure and was used to optically introduce aberrations in 9 normal eyes for visual acuity (VA) change, and in 10 cyclopleged eyes for enhancing depth of focus (DoF). AOVS was also used to correct 20 highly aberrated eyes. Results: The correction/induction of high order aberrations (HOA) alters the best-corrected visual acuity (BCVA) by a mean of ~1 to 1.5 lines compared to the best spectacle correction. The depth of focus (DoF) was most enhanced (~2.0 D) with the introduction of negative and positive spherical aberration of 0.6 μm magnitude. The correction of HOAs in highly aberrated eyes improved BCVA by a mean of ~1.5 to 2 lines in two groups of pathological eyes. Conclusions: Aberrations have differing effects according to their clinical use. The AOVS defines the clinical response of HOAs on VA, visual perceptions and DoF.

A novel adaptive optics system is presented for the study of vision. The apparatus is capable for binocular operation. The binocular adaptive optics visual simulator permits measuring and manipulating ocular aberrations of the two eyes simultaneously. Aberrations can be corrected, or modified, while the subject performs visual testing under binocular vision. One of the most remarkable features of the apparatus consists on the use of a single correcting device, and a single wavefront sensor (Hartmann-Shack). Both the operation and the total cost of the instrument largely benefit from this attribute. The correcting device is a liquid-crystal-on-silicon (LCOS) spatial light modulator. The basic performance of the visual simulator consists in the simultaneous projection of the two eyes' pupils onto both the corrector and sensor. Examples of the potential of the apparatus for the study of the impact of the aberrations under binocular vision are presented. Measurements of contrast sensitivity with modified combinations of spherical aberration through focus are shown. Special attention was paid on the simulation of monovision, where one eye is corrected for far vision while the other is focused at near distance. The results suggest complex binocular interactions. The apparatus can be dedicated to the better understanding of the vision mechanism, which might have an important impact in developing new protocols and treatments for presbyopia. The technique and the instrument might contribute to search optimized ophthalmic corrections.

We have developed a hybrid adaptive optics visual simulator, combining two different phase manipulation technologies: an optically-addressed liquid crystal phase modulator, with a relatively slow temporal response but capable of producing abrupt or discontinuous phase profiles with high fidelity; and a membrane deformable mirror, restricted to smooth profiles but with a temporal response allowing close-loop compensation of the eye's aberration fluctuations. As proof of concept, objective results as a function of defocus are presented for a phase element structured as discontinuous radial sectors, generated with the liquid crystal modulator while the deformable mirror was used to correct the system aberrations and, further, to introduce the aberrations of two real subjects. The hybrid adaptive optics visual simulator is specially intended as a tool for developing new ophthalmic optics elements, where it opens the possibility to explore designs with irregularities and/or discontinuities.

A custom-built OCT system was used to obtain images of the whole mouse eye. We developed a semi-automated segmentation method to detect the boundaries of the anterior and posterior corneal, lens and retinal surfaces as well as the anterior surface of the iris. The radii of curvature of the surfaces were calculated using a conic section fit of each boundary. Image distortions due to refraction of the OCT beam at the successive boundaries were corrected using a ray-tracing algorithm. Corrected ocular distances, radii of curvature of the cornea and lens surfaces, and anterior chamber angle were obtained on 3 C57BL/6J mice. In vivo imaging of the whole eye, segmentation, conic function fits and correction were successful in all three animals. The posterior lens surface of one mouse could not be fit accurately with a conic section. Biometric parameters of C57BL/6J mice compared well with previous published data obtained from histological sections. The study demonstrates the feasibility of quantitative in vivo biometry of mouse models.

We performed OCT imaging of the rat retina at 70,000 axial scans per second with ~3 μm axial resolution. Three-dimensional OCT (3D-OCT) data sets of the rat retina were acquired. The high speed and high density data sets enable improved en face visualization by reducing eye motion artifacts and improve Doppler OCT measurements. Minimal motion artifacts were visible and the OCT fundus images offer more precise registration of individual OCT images to retinal fundus features. Projection OCT fundus images show features such as the nerve fiber layer, retinal capillary networks and choroidal vasculature. Doppler OCT images and quantitative measurements show pulsatility in retinal blood vessels. Doppler OCT provides noninvasive in vivo quantitative measurements of retinal blood flow properties and may benefit studies of diseases such as glaucoma and diabetic retinopathy. Ultrahigh speed imaging using ultrahigh resolution spectral / Fourier domain OCT promises to enable novel protocols for measuring small animal retinal structure and retinal blood flow. This non-invasive imaging technology is a promising tool for monitoring disease progression in rat and mouse models to assess ocular disease pathogenesis and response to treatment.

In vivo retinal imaging is an outstanding tool to observe biological processes unfold in real-time. The ability to image microstructure in vivo can greatly enhance our understanding of function in retinal microanatomy under normal conditions and in disease. Transgenic mice are frequently used for mouse models of retinal diseases. However, commercially available retinal imaging instruments lack the optical resolution and spectral flexibility necessary to visualize detail comprehensively. We developed an adaptive optics scanning laser ophthalmoscope (AO-SLO) specifically for mouse eyes. Our SLO is a sensor-less adaptive optics system (no Shack Hartmann sensor) that employs a stochastic parallel gradient descent algorithm to modulate a deformable mirror, ultimately aiming to correct wavefront aberrations by optimizing confocal image sharpness. The resulting resolution allows detailed observation of retinal microstructure. The AO-SLO can resolve retinal microglia and their moving processes, demonstrating that microglia processes are highly motile, constantly probing their immediate environment. Similarly, retinal ganglion cells are imaged along with their axons and sprouting dendrites. Retinal blood vessels are imaged both using evans blue fluorescence and backscattering contrast.

Congenital abnormalities are often caused by genetic disorders which alter the normal development of the eye. Embryonic eye imaging in mouse model is important for understanding of normal and abnormal eye development and can contribute to prevention and treatment of eye defects in humans. In this study, we used Swept Source Optical Coherence Tomography (SS-OCT) to image eye structure in mouse embryos at 12.5 to 17.5 days post coitus (dpc). The imaging depth of the OCT allowed us to visualize the whole eye globe at these stages. Different ocular tissues including lens, cornea, eyelids, and hyaloid vasculature were visualized. These results suggest that OCT imaging is a useful tool to study embryonic eye development in the mouse model.

Raman spectroscopy (RS) and Optical Coherence Tomography (OCT) are powerful tools for optical analysis of tissues with complimentary strengths. OCT excels and visualizing tissue microstructure while RS can relay tissue biochemical composition. Both instruments have significant potential to serve as valuable tools in non-invasive characterization of the rodent models of retinal disease. In this abstract we present the design and application of a common detector combined RS-OCT instrument for evaluating the morphological and biochemical differences in a rat model for oxygen induced retinopathy. Rat pups that have undergone a variable oxygen treatment are compared to rats raised in room air. Images and spectra collected at an age of 26 days postnatal demonstrate differences in both the thickness of the inner and outer nuclear layers, but also in the biochemical composition.

The aim of the study was to produce two-dimensional reconstruction maps of the living corneal sub-basal nerve plexus by in vivo laser scanning confocal microscopy in real time. CLSM source data (frame rate 30Hz, 384x384 pixel) were used to create large-scale maps of the scanned area by selecting the Automatic Real Time (ART) composite mode. The mapping algorithm is based on an affine transformation. Microscopy of the sub-basal nerve plexus was performed on normal and LASIK eyes as well as on rabbit eyes. Real-time mapping of the sub-basal nerve plexus was performed in large-scale up to a size of 3.2mm x 3.2mm. The developed method enables a real-time in vivo mapping of the sub-basal nerve plexus which is stringently necessary for statistically firmed conclusions about morphometric plexus alterations.

The corneal endothelium serves as the posterior barrier of the cornea. Factors such as clarity and refractive properties of the cornea are in direct relationship to the quality of the endothelium. The endothelial cell density is considered the most important morphological factor of the corneal endothelium. Pathological conditions and physical trauma may threaten the endothelial cell density to such an extent that the optical property of the cornea and thus clear eyesight is threatened. Diagnosis of the corneal endothelium through morphometry is an important part of several clinical applications. Morphometry of the corneal endothelium is presently carried out by semi automated analysis of pictures captured by a Clinical Specular Microscope (CSM). Because of the occasional need of operator involvement, this process can be tedious, having a negative impact on sampling size. This study was dedicated to the development and use of fully automated analysis of a very large range of images of the corneal endothelium, captured by CSM, using Fourier analysis. Software was developed in the mathematical programming language Matlab. Pictures of the corneal endothelium, captured by CSM, were read into the analysis software. The software automatically performed digital enhancement of the images, normalizing lights and contrasts. The digitally enhanced images of the corneal endothelium were Fourier transformed, using the fast Fourier transform (FFT) and stored as new images. Tools were developed and applied for identification and analysis of relevant characteristics of the Fourier transformed images. The data obtained from each Fourier transformed image was used to calculate the mean cell density of its corresponding corneal endothelium. The calculation was based on well known diffraction theory. Results in form of estimated cell density of the corneal endothelium were obtained, using fully automated analysis software on 292 images captured by CSM. The cell density obtained by the fully automated analysis was compared to the cell density obtained from classical, semi-automated analysis and a relatively large correlation was found.

Researchers have sought to gain greater insight into the mechanisms of the retina and the optic disc at high spatial resolutions that would enable the visualization of small structures such as photoreceptors and nerve fiber bundles. The sources of retinal image quality degradation are aberrations within the human eye, which limit the achievable resolution and the contrast of small image details. To overcome these fundamental limitations, researchers have been applying adaptive optics (AO) techniques to correct for the aberrations. Today, deformable mirror based adaptive optics devices have been developed to overcome the limitations of standard fundus cameras, but at prices that are typically unaffordable for most clinics. In this paper we demonstrate a clinically viable fundus camera with auto-focus and astigmatism correction that is easy to use and has improved resolution. We have shown that removal of low-order aberrations results in significantly better resolution and quality images. Additionally, through the application of image restoration and super-resolution techniques, the images present considerably improved quality. The improvements lead to enhanced visualization of retinal structures associated with pathology.

Fundus imaging has become an essential clinical diagnostic tool in ophthalmology. Current generation scanning laser ophthalmoscopes (SLO) offer advantages over conventional fundus photography and indirect ophthalmoscopy in terms of light efficiency and contrast. As a result of the ability of SLO to provide rapid, continuous imaging of retinal structures and its versatility in accommodating a variety of illumination wavelengths, allowing for imaging of both endogenous and exogenous fluorescent contrast agents, SLO has become a powerful tool for the characterization of retinal pathologies. However, common implementations of SLO, such as the confocal scanning laser ophthalmoscope (CSLO) and line-scanning laser ophthalmoscope (LSLO), require imaging or multidimensional scanning elements which are typically implemented in bulk optics placed close to the subject eye. Here, we apply a spectral encoding technique in one dimension combined with single-axis lateral scanning to create a spectrally encoded confocal scanning laser ophthalmoscope (SECSLO) which is fully confocal. This novel implementation of the SLO allows for high contrast, high resolution in vivo human retinal imaging with image transmission through a single-mode optical fiber. Furthermore, the scanning optics are similar and the detection engine is identical to that of current-generation spectral domain optical coherence tomography (SDOCT) systems, potentially allowing for a simplistic implementation of a joint SECSLO-SDOCT imaging system.

The performance and imaging characteristics of ultrahigh speed ophthalmic optical coherence tomography (OCT) are investigated. In vivo imaging results are obtained at 850nm and 1050nm using different configurations of spectral and swept source / Fourier domain OCT. A spectral / Fourier domain instrument using a high speed CMOS linescan camera with SLD light source centered at 850nm achieves speeds of ~91,000 axial scans per second with ~3μm axial resolution in tissue. A spectral / Fourier domain instrument using an InGaAs linescan camera with SLD light source centered at 1050nm achieves ~47,000 axial scans per second with ~7μm resolution in tissue. A swept source instrument using a novel wavelength swept laser light source centered at 1050nm achieves 100,000 axial scans per second. Retinal diseases seen in the clinical setting are imaged using the 91kHz 850nm CMOS camera and 47kHz 1050nm InGaAs camera based instruments to investigate the combined effects of varying speed, axial resolution, center wavelength, and instrument sensitivity on image quality. The novel 1050nm swept source / Fourier domain instrument using a recently developed commercially available short cavity laser source images at 100,000 axial scans per second and is demonstrated in the normal retina. The dense 3D volumetric data sets obtained with ultrahigh speed OCT promise to improve reproducibility of quantitative measurements, enabling early diagnosis as well as more sensitive assessment of disease progression and response to therapy.

We used second harmonic generation (SHG) microscopy to image and quantify the structural changes of bovine corneal edema. Forward SHG (FWSHG) and backward SHG (BWSHG) signals were simultaneously collected from normal and edematous bovine corneas to reveal their morphological differences. In SHG imaging, edematous corneas can be characterized by uneven expansion in the lamellar interspacing and increased lamellar thickness in posterior stroma (depth > 200 μm), while the anterior stroma composed of interwoven collagen architecture remained unaffected. Our work demonstrate the capability of SHG imaging in providing morphological information for the investigation of corneal edema biophysics and its potential application in the in vivo evaluation of advancing corneal edema.

For a long time acute eye irritation has been assessed by means of the DRAIZE rabbit test, the limitations of which are known. Alternative tests based on in vitro models have been proposed. This work focuses on the "reconstituted human corneal epithelium" (R-HCE), which resembles the corneal epithelium of the human eye by thickness, morphology and marker expression. Testing a substance on R-HCE involves a variety of methods. Herewith quantitative morphological analysis is applied to optical microscope images of R-HCE cross sections resulting from exposure to benzalkonium chloride (BAK). The short term objectives and the first results are the analysis and classification of said images. Automated analysis relies on feature extraction by the spectrum-enhancement algorithm, which is made sensitive to anisotropic morphology, and classification based on principal components analysis. The winning strategy has been the separate analysis of the apical and basal layers, which carry morphological information of different types. R-HCE specimens have been ranked by gross damage. The onset of early damage has been detected and an R-HCE specimen exposed to a low BAK dose has been singled out from the negative and positive control. These results provide a proof of principle for the automated classification of the specimens of interest on a purely morphological basis by means of the spectrum enhancement algorithm.

We describe an efficient approach for the automated segmentation of pathological/morphological structures in ophthalmic Spectral Domain Optical Coherence Tomography (SDOCT) images. In this algorithm, image pixels are treated as nodes of a graph with edge weights assigned to associate pairs of pixels. The weights vary according to the distances, brightness differences, and feature variations between pixel pairs. Cuts through the graph with minimum accumulated weights correspond to morphological layer boundaries. This approach has been applied to SDOCT images with encouraging results and thus forms an adaptable framework for the segmentation of many different ophthalmic structures.

Bevacizumab (Avastin) has been used as one of the anti-VEGF therapies to manage neovascular age-related macular degeneration (AMD). The drug delivery system for bevacizumab needs to be improved in order to decrease the frequency of injection and reduce the adverse effects. In our study, bevacizumab was conjugated with poly (lactic-co-glycolic acid) (PLGA) microbubbles by activating carboxyl functional groups. The averaged size of microbubbles was estimated 1.055±0.258μm, allowing for ultrasound guided drug delivery. The binding efficiency between bevacizumab and microbubbles was evaluated in an enzyme-linked immunosorbent assay plate. The test results demonstrated the potential of using PLGA microbubbles to deliver bevacizumab with imaging guidance.

Optical-resolution photoacoustic microscopy (OR-PAM) provides superb optical absorption contrast for red blood cells (RBCs), which makes it ideal for in vivo microvasculature imaging. In comparison, optical coherence tomography (OCT), widely used for tissue microstructure imaging, provides high optical scattering contrast. The two contrast mechanisms are highly complementary. In this work, we combined OR-PAM and OCT into a single, dual-modality imaging instrument for in vivo mouse eye imaging. We demonstrated in vivo dual-modality imaging of the anterior segment of mouse eyes with laser pulse energy within the ANSI laser safety standard.

Dynamic light scattering (DLS) experimental data is statistical in nature and therefore requires a probabilistic analysis tool. The probabilistic sparse Bayesian learning (SBL) algorithm is introduced for analyzing DLS data from ocular lenses. The algorithm is used to reconstruct the most-relevant size distribution of the α-crystallins and their aggregates. The performance of the algorithm is evaluated by analyzing simulated data from a known distribution and experimental DLS data from the ocular lenses of several mammals.

A fundus camera is an optical system designed to illuminate and image the retina while minimizing stray light and backreflections. Modifying such a device requires characterization of the optical path in order to meet the new design goals and avoid introducing problems. This work describes the characterization of one system, the Topcon TRC-50F, necessary for converting this camera from film photography to spectral imaging with a CCD. This conversion consists of replacing the camera's original xenon flash tube with a monochromatic light source and the film back with a CCD. A critical preliminary step of this modification is determining the spectral throughput of the system, from source to sensor, and ensuring there are sufficient photons at the sensor for imaging. This was done for our system by first measuring the transmission efficiencies of the camera's illumination and imaging optical paths with a spectrophotometer. Combining these results with existing knowledge of the eye's reflectance, a relative sensitivity profile is developed for the system. Image measurements from a volunteer were then made using a few narrowband sources of known power and a calibrated CCD. With these data, a relationship between photoelectrons/pixel collected at the CCD and narrowband illumination source power is developed.

Ocular fundus reflectometry is a technique aimed at the in-vivo measurement of the reflectance of the tissues of the ocular fundus. Studies have demonstrated a correlation between optical and physiological properties of such tissues in humans and the existence of a control mechanism, called neuro-vascular coupling (NC), which adjusts local blood perfusion to support vision-induced neural activity. We developed an instrument for functional imaging of the neural tissues of the ocular fundus based on reflectance measurements to study the NC. The images acquired with the instrument needed processing to work out reflectance time-courses. The algorithm exploited previously requires long computational time, provides poor discrimination of objects and need manual intervention. We have developed a fully automatic algorithm based on differential multiscale framework for the processing of the images of the ocular fundus with reduced computational time. This algorithm is reasonably efficient to determine relative translational displacement (translation and rotation) between the images and also to remove the geometric distortion. Simulation results performed on the fundus images show that differential multiscale framework based image registration reduces computational times up-to one fourth of the time required by the general purpose algorithm, and provides better alignment precision.

The aim of this work was to study the effect of enzymes such as proteinase K, trypsin, collagenase with hyaluronidase, as well as a mixture of all these enzymes, on albumin and collagens incorporated in the vitreous body, using a cyanine dye as a spectral-fluorescent probe. We studied the vitreous body of the eyes of 19/20-week human fetuses, in which, as we showed earlier, the concentration of albumin in the vitreous body is sufficiently high. Proteinase K steeply decreased the albumin content in the vitreous body, whereas trypsin and hyaluronidase with collagenase had no effect on the albumin content. Collagen was not subjected to proteinase K. Enzymatic digestion of collagen occurred under the action of collagenase with hyaluronidase. The content of albumin and collagen sharply decreased in the system after treatment of the vitreous body with mixture of all enzymes. Hence, the results obtained showed that, even being in the mixture, these enzymes have a selective effect on albumin and collagens. The possibility to study the dose-dependent character of enzymatic vitreolysis using a cyanine dye probe has been shown. The spectral-fluorescent probe for albumin and collagens proved to be useful for experimental approaches at screening the enzymatic mixtures possessing the selective action. The study performed is considered as a preclinical trial, and the method presented as promising for the further research in this field. The effect of the enzymes used for therapeutic purposes on the functional conditions of the vitreous body should be studied.

We have proposed a new automatic visualization procedure based the ratio of optical densities (ODs) obtained at two different wavelength for the oxygen saturation imaging in human retinal vessels. This method utilized the morphological processing and the line convergence index filter to estimate the reflection image of outside vessels and extract the vessel structure from retinal image, respectively. In the experimental measurement, clear difference between retinal arteries and veins has been observed. In this study, the data processing technique of the line convergence index filter was applied to a color fundus image to investigate the ability of vessel extraction. In addition, four-wavelength imaging was proposed to evaluate oxygen saturation of the retinal capillary vessels and to decrease the influence of the melanin pigmentation.

We present an application of the Joint Spectral and Time domain OCT (STdOCT) method for detection of wide range of flows in the retinal vessels. We utilized spectral/Fourier domain OCT (SOCT) technique for development of scan protocols for Doppler signal analysis. We performed retinal imaging in normal eyes using ultrahigh speed (200 000 axial scans/s) SOCT instrument with a CMOS camera. Various raster scan protocols were implemented for investigation of blood flow in the retina. Data analysis was performed using the method of joint Spectral and Time domain OCT (STdOCT). Detection of blood flow velocities ranging from several tens of mm/s to a fraction of mm/s was possible with scanning methods allowing for appropriate selection of time intervals between data taken for Doppler OCT analysis. Axial blood flow velocity measurement was possible in retinal vessels. Doppler OCT signal can be utilized as a contrast mechanism for visualization of retinal capillaries.

We will present research on the development of an optical receiver module with a wide frequency bandwidth and excellent response to near-infrared radiation. This module is being produced to promote new imaging modalities, allowing retinal specialist to utilize established diagnostic instruments, such as scanning laser ophthalmoscopes (SLO) in a unique or more effective manner. In particular, it can be applied towards more accurate visual threshold studies in both the healthy and diseased eye. With this goal in mind, measurements of the targeted receiver's performance with and without additional amplification are presented, as is a survey of available APD detectors.

Oxygen saturation measurements in the retina is an essential measurement in monitoring eye health of diabetic patient. In this paper, preliminary result of oxygen saturation measurements for a healthy patient retina is presented. The retinal oximeter used is based on a regular fundus camera to which was added an optimized optical train designed to perform aperture division whereas a filter array help select the requested wavelengths. Hence, nine equivalent wavelength-dependent sub-images are taken in a snapshot which helps minimizing the effects of eye movements. The setup is calibrated by using a set of reflectance calibration phantoms and a lookuptable (LUT) is computed. An inverse model based on the LUT is presented to extract the optical properties of a patient fundus and further estimate the oxygen saturation in a retina vessel.

Thermal modifications induced in the corneal stroma were investigated by means of second harmonic generation (SHG) imaging. Whole fresh cornea samples were heated in a water bath at temperatures in the 35-80 °C range for a 4-min time. SHG images of the structural modifications induced at each temperature were acquired from different areas of cross-sectioned corneal stroma by using an 880 nm linearly- and circularly-polarized excitation light emitted by a mode-locked Ti:Sapphire laser. The SHG images were then analyzed by means of both an empirical approach and a 2D-theoretical model. The proposed analyses provide a detailed description of the changes occurring in the structural architecture of the cornea during the thermal treatment. Our results allow us to depict a temperature-dependent biochemical model for the progressive destructuration occurring to collagen fibrils and nonfibrillar components of the stroma.

The corneal cross-linking is a method that associates riboflavin and ultraviolet light to induce a larger mechanical resistance at cornea. This method has been used for the treatment of Keratoconus. Since cross-linking is recent as treatment, there is a need to verify the effectiveness of the method. Therefore, the viability of the fluorescence spectroscopy technique to follow the cross-linking formation at cornea was studied. Corneas were divided in two measuring procedures: M1 (cornea + riboflavin), and M2 (cornea + riboflavina + light irradiation, 365nm). For fluorescence measurements, a spectrofluorimeter was used, where several wavelengths were selected (between 320nm and 370nm) for cornea excitation. Several fluorescence spectra were collected, at 10 min-interval, during 60 min. Spectra allowed one to observe two very well defined bands of fluorescence: the first one at 400nm (collagen), and the second one at 520nm (riboflavin). After spectra analyses, a decrease of collagen fluorescence was observed for both groups. For riboflavin, on the other hand, there was a fluorescence increase for M1, and a decrease for M2. Thus, it is possible to conclude that it this technique is sensitive for the detection of tissue structural changes during cross-linking treatment, encouraging subsequent studies on quantification of cross-linking promotion in tissue.

Low power diode laser welding is a recently developed technique used as a support tool for conventional suturing in ophthalmic surgery. The main application is in penetrating keratoplasty: in the last four years (2005-2009), clinical trials were performed at the Ophthalmic Department of Prato (Italy). In penetrating keratoplasty, diode laser welding is used to assure the transplanted corneal button in its final position. The donor tissue is positioned in the recipient eye and 8-16 single stitches are apposed. The surgical wound is then stained with a saturated (10% w/w) sterile water solution of Indocyanine Green (ICG), it is washed with sterile water and then a diode laser (810 nm, 13 W/cm²) is used to induce the sealing of the wound. The laser light induces a thermal effect, localized in the stained tissue. In vivo and ex vivo studies in animal models evidenced that welding induces a modification of the corneal collagen architecture through the wound walls, thus enabling a short healing time and a good restoration of the tissue. In this study on human subjects, we confirmed the results evidenced in animal models, by morphological observations. In two cases out of 60, transplant rejection was observed. It was thus possible to study the efficacy of laser welding in the closure of the wound one year after implant. Direct morphological observation evidenced good strengthens of the welded tissue. Histological analysis pointed out a good restoration of the regular collagen architecture at the external perimeter of the corneal button, where laser welding was performed, showing the occurrence of a correct and effective wound healing process.

Exposure to ultraviolet (UV) radiation, even in small quantity, can cause several damages to the human eye. Continuous exposure the ultraviolet rays may cause corneal swelling, lens opacity (cataract), harms to the retina and pterygium. The purpose of this work is the study of the alteration of the corneal tissue and its UV natural protection in different scenarios, using a device previously developed, which provides measurements of corneal transmittance in the UV range. The device consists of ultraviolet source and detector, digital processing and visualization of results in real time. The dual beam system provides tissue UV transmission with accuracy of 0.25%. A protocol has been established for testing the UV protection on the cornea, as well as performing the removal of the corneal tissue, simulating refractive keratotomy. We have observed that it's evident that each corneal layer has influence in the UV absorbance, the results show the influence of the epithelial layer (~50μm depth), the little endothelium influence (~10μm depth), and the stroma layer is responsible for the strongest influence (~350μm depth). Preliminary studies on 42 human corneas lead to demonstrate that as the stromal layer is reduced, there is significant loss of the natural UV protection of the cornea, sometimes presenting a very restricted protection.

A new technology of deformable mirror will be presented. Based on magnetic actuators, these deformable mirrors feature record strokes (more than +/- 45μm of astigmatism and focus correction) with an optimized temporal behavior. Furthermore, the development has been made in order to have a large density of actuators within a small clear aperture (typically 52 actuators within a diameter of 9.0mm). We will present the key benefits of this technology for vision science: simultaneous correction of low and high order aberrations, AO-SLO image without artifacts due to the membrane vibration, optimized control, etc. Using recent papers published by Doble, Thibos and Miller, we show the performances that can be achieved by various configurations using statistical approach. The typical distribution of wavefront aberrations (both the low order aberration (LOA) and high order aberration (HOA)) have been computed and the correction applied by the mirror. We compare two configurations of deformable mirrors (52 and 97 actuators) and highlight the influence of the number of actuators on the fitting error, the photon noise error and the effective bandwidth of correction.

We report on the development of a novel, low cost instrument that is capable of accurately measuring small, short and long term changes in the thickness of the cornea and tear film at high speed. The performance of the instrument was tested by measuring the influence of Allergan's OPTIVE^TM lubricating eye drops on the thickness of the cornea and tear film. Comparative measurements to quantify the performance were taken using Haag-Streit's LenStar. It was found that the newly developed instrument accurately measured a change in thickness of around 9 μm with an accuracy comparable to the LenStar, and with a standard deviation of less than 1 micrometer. Since the new instrument was not configured to resolve the tear film from the cornea, we are not yet able to distinguish the cause of the thickening.

Purpose: Testing whether the extended depth of focus technology embedded on non-toric contact lenses is a suitable treatment for both astigmatism and presbyopia. Methods: The extended depth of focus pattern consisting of microndepth concentric grooves was engraved on a surface of a mono-focal soft contact lens. These grooves create an interference pattern extending the focus from a point to a length of about 1mm providing a 3.00D extension in the depth of focus. The extension in the depth of focus provides high quality focused imaging capabilities from near through intermediate and up to far ranges. Due to the angular symmetry of the engraved pattern the extension in the depth of focus can also resolve regular as well as irregular astigmatism aberrations. Results: The contact lens was tested on a group of 8 astigmatic and 13 subjects with presbyopia. Average correction of 0.70D for astigmatism and 1.50D for presbyopia was demonstrated. Conclusions: The extended depth of focus technology in a non-toric contact lens corrects simultaneously astigmatism and presbyopia. The proposed solution is based upon interference rather than diffraction effects and thus it is characterized by high energetic efficiency to the retina plane as well as reduced chromatic aberrations.

In this work we present an image processing software for automatic astigmatism measurements developed for a hand held keratometer. The system projects 36 light spots, from LEDs, displayed in a precise circle at the lachrymal film of the examined cornea. The displacement, the size and deformation of the reflected image of these light spots are analyzed providing the keratometry. The purpose of this research is to develop a software that performs fast and precise calculations in mainstream mobile devices. In another words, a software that can be implemented in portable computer systems, which could be of low cost and easy to handle. This project allows portability for keratometers and is a previous work for a portable corneal topographer.

The shape of the surfaces of ex-vivo human crystalline lenses was measured using a shadow photography technique. From these data, the back-focal distance and the contribution of each surface to the main optical aberrations of the lenses were estimated. The aberrations of the lenses were measured separately with two complementary techniques: a Hartmann-Shack wavefront sensor and a point-diffraction interferometer. A laser scanning set-up was also used to measure the actual back-focal length as well as the phase aberration in one meridian section of the lenses. Measured and predicted back-focal length agreed well within the experimental errors. The lens aberrations computed with a ray-tracing approach from the measured surfaces and geometrical data only reproduce quantitatively the measured aberrations.

An accurate solid eye model (with volumetric retinal morphology) has many applications in the field of ophthalmology, including evaluation of ophthalmic instruments and optometry/ophthalmology training. We present a method that uses volumetric OCT retinal data sets to produce an anatomically correct representation of three-dimensional (3D) retinal layers. This information is exported to a laser scan system to re-create it within solid eye retinal morphology of the eye used in OCT testing. The solid optical model eye is constructed from PMMA acrylic, with equivalent optical power to that of the human eye (~58D). Additionally we tested a water bath eye model from Eyetech Ltd. with a customized retina consisting of five layers of ~60 μm thick biaxial polypropylene film and hot melt rubber adhesive.

Light flickering at a rate of 4- 20 cycles per second can produce unpleasant reactions such as nausea and vertigo. In this paper, the possibility of achieving an objective evaluation/prediction of the physiological effects induced by flicker is investigated using a new imaging method based on the pupil size determination. This method is also compared with the blood flow analysis in the choroid.

We have developed a high-resolution, multi-color retinal imaging system using liquid crystal adaptive optics. A liquid crystal on silicon (LCOS) spatial light modulator (SLM) is used to correct ocular aberrations. In order to compensate for the dependency of an LCOS SLM on optical wavelength and acquire aberration-corrected images at different color, we apply an open-loop technique. In the open-loop technique, the imaging light is separated from the sensing light and the optimal phase modulation is applied only to the imaging light while the sensing light is not phase-modulated. With the system, in vivo imaging of the human retina is achieved by using illumination light at wavelength of 655nm and 593nm and sensing light at 780nm. Photoreceptors are clearly revealed at each illumination wavelength with the liquid crystal adaptive optics.