Corneal transplant surgery has undergone numerous modifications over the years with improvements in technique, instrumentation and eye banking. The main goals of corneal transplantation are achieving excellent optical clarity with long-term graft survival. Penetrating, anterior and posterior lamellar surgery along with femtosecond laser technology have partially met these goals, but outcomes are often unpredictable and surgeon dependent. Technology to predictably separate stroma from Descemet's membrane, techniques to minimize endothelial cell loss, improvements in imaging technology and emerging techniques like laser welding that might replace suturing, eventually making corneal transplantation a refractively predictable procedure are on the wish list of the cornea surgeon.

We report the use of optical reflectometry technique for evaluation of water film on contact lens. The water film can be measured through the spectral dependent reflectance evaluation, which is carried out by illuminating the contact lens with a white light and collecting the returning light with an optical fiber coupled to a spectrometer. Water film thinning process has been observed on different soft contact lenses and minimum measurable thickness is about 0.85 μm. The measurement is fast and accurate. The water film measurement can be valuable for contact lens design to improve its hydrophilic properties. The technique can be extended for the study of tear film dynamics in an eye.

Dry eye syndrome is a common irritating eye disease. Current clinical diagnostic methods are invasive and uncomfortable to patients. A custom designed noncontact infrared (IR) thermal image system was developed to measure the spatial and temporal variation of the ocular surface temperature over a 6-second eye-opening period. We defined two parameters: the temperature difference value and the compactness value to represent the degree of the temperature change and irregularity of the temperature distribution on the tear film. By using these two parameters, in this study, a linear discrimination result for the dry eye and the normal eye groups; the sensitivity is 0.9, the specificity is 0.86 and the receiver operating characteristic (ROC) area is 0.91. The result suggests that the custom designed IR thermal image system may be used as an effective tool for noncontact detection of dry eye.

Live imaging of an eye during embryonic development in mammalian model is important for understanding dynamic aspects of normal and abnormal eye morphogenesis. In this study, we used Swept Source Optical Coherence Tomography (SS-OCT) for live structural imaging of mouse embryonic eye through the uterine wall. The eye structure was reconstructed in mouse embryos at 13.5 to 17.5 days post coitus (dpc). Despite the limited imaging depth of OCT in turbid tissues, we were able to visualize the whole eye globe at these stages. These results suggest that live in utero OCT imaging is a useful tool to study embryonic eye development in the mouse model.

This research is aimed at characterizing in vivo differences between healthy and pathological retinal tissues at the microscopic scale using a compact adaptive optics (AO) retinal camera. Tests were performed in 120 healthy eyes and 180 eyes suffering from 19 different pathological conditions, including age-related maculopathy (ARM), glaucoma and rare diseases such as inherited retinal dystrophies. Each patient was first examined using SD-OCT and infrared SLO. Retinal areas of 4°x4° were imaged using an AO flood-illumination retinal camera based on a large-stroke deformable mirror. Contrast was finally enhanced by registering and averaging rough images using classical algorithms. Cellular-resolution images could be obtained in most cases. In ARM, AO images revealed granular contents in drusen, which were invisible in SLO or OCT images, and allowed the observation of the cone mosaic between drusen. In glaucoma cases, visual field was correlated to changes in cone visibility. In inherited retinal dystrophies, AO helped to evaluate cone loss across the retina. Other microstructures, slightly larger in size than cones, were also visible in several retinas. AO provided potentially useful diagnostic and prognostic information in various diseases. In addition to cones, other microscopic structures revealed by AO images may also be of interest in monitoring retinal diseases.

We recently developed several versions of a multimodal adaptive optics (AO) retinal imager, which includes highresolution scanning laser ophthalmoscopy (SLO) and Fourier domain optical coherence tomography (FDOCT) imaging channels as well as an auxiliary wide-field line scanning ophthalmoscope (LSO). Some versions have also been equipped with a fluorescence channel and a retinal tracker. We describe the performance of three key features of the multimodal AO system including: simultaneous SLO/OCT imaging, which allows SLO/OCT co-registration; a small animal imaging port, which adjusts the beam diameter at the pupil from 7.5 to 2.5 mm for use with small animals ubiquitous in biological research or for extended depth-of-focus imaging in humans; and slow scan Doppler flowmetry imaging using the wide field auxiliary LSO imaging channel. The systems are currently deployed in several ophthalmology clinics and research laboratories and several investigations have commenced on patients with a variety of retinal diseases and animals in vision research.

We summarize the performance of an AO-OCT system with reference arm phase shifting for complex conjugate artifactfree imaging of in vivo retinal structures. As a complex conjugate artifact removal (CCR) method we used a previously reported technique requiring constant phase shifts between consecutive A-scans. In our system these shifts were generated by continuous beam path-length changes from offsetting the pivot point of the scanning mirror placed in the system reference arm. In order to reconstruct the complex spectral fringe pattern we used Fourier transformation along the transverse axis and a filtering algorithm. The suppression ratio of mirror complex artifact images was assessed based on acquired in vivo CCR AO-OCT images. Finally, potential problems and limitations connected with this acquisition scheme and data processing algorithms are discussed.

Optical coherence tomography with adaptive optics (AO-OCT) is a highly sensitive, noninvasive method for 3D imaging of the microscopic retina. The purpose of this study is to advance AO-OCT technology by enabling repeated imaging of cone photoreceptors over extended periods of time (days). This sort of longitudinal imaging permits monitoring of 3D cone dynamics in both normal and diseased eyes, in particular the physiological processes of disc renewal and phagocytosis, which are disrupted by retinal diseases such as age related macular degeneration and retinitis pigmentosa. For this study, the existing AO-OCT system at Indiana underwent several major hardware and software improvements to optimize system performance for 4D cone imaging. First, ultrahigh speed imaging was realized using a Basler Sprint camera. Second, a light source with adjustable spectrum was realized by integration of an Integral laser (Femto Lasers, λ_c=800nm, ▵λ=160nm) and spectral filters in the source arm. For cone imaging, we used a bandpass filter with λ_c=809nm and ▵λ=81nm (2.6 μm nominal axial resolution in tissue, and 167 KHz A-line rate using 1,408 px), which reduced the impact of eye motion compared to previous AO-OCT implementations. Third, eye motion artifacts were further reduced by custom ImageJ plugins that registered (axially and laterally) the volume videos. In two subjects, cone photoreceptors were imaged and tracked over a ten day period and their reflectance and outer segment (OS) lengths measured. High-speed imaging and image registration/dewarping were found to reduce eye motion to a fraction of a cone width (1 μm root mean square). The pattern of reflections in the cones was found to change dramatically and occurred on a spatial scale well below the resolution of clinical instruments. Normalized reflectance of connecting cilia (CC) and OS posterior tip (PT) of an exemplary cone was 54±4, 47±4, 48±6, 50±5, 56±1% and 46±4, 53±4, 52±6, 50±5, 44±1% for days #1,3,6,8,10 respectively. OS length of the same cone was 28.9, 26.4, 26.4, 30.6, and 28.1 ìm for days #1,3,6,8,10 respectively. It is plausible these changes are an optical correlate of the natural process of OS renewal and shedding.

Eye movements present during acquisition of a retinal image with optical coherence tomography (OCT) introduce motion artifacts into the image, complicating analysis and registration. This effect is especially pronounced in highresolution data sets acquired with adaptive optics (AO)-OCT instruments. Several retinal tracking systems have been introduced to correct retinal motion during data acquisition. We present a method for correcting motion artifacts in AOOCT volume data after acquisition using simultaneously captured adaptive optics-scanning laser ophthalmoscope (AOSLO) images. We extract transverse eye motion data from the AO-SLO images, assign a motion adjustment vector to each AO-OCT A-scan, and re-sample from the scattered data back onto a regular grid. The corrected volume data improve the accuracy of quantitative analyses of microscopic structures.

Laser Doppler flowmetry (LDF) is a technique used to measure relative average velocity, number and flux (number times velocity) of red blood cells in vessels or capillaries. In this study, the effect of topical timolol on the choroidal circulation was investigated in 12 healthy subjects. Maximum velocity of red blood cells and volumetric blood flow rate in sub-foveal choroids are determined in each eye just before instillation of drops and then every 30 min upto 2 hours. Average intraocular pressure (IOP) decreased significantly in the timolol-treated eyes compared to that of placebo-treated eyes. Nevertheless no significant differences in choroidal blood hemodynamic between timolol and placebo-treated eyes were observed.

We propose an algorithm to extract the angles of vessels for the correction of flow measurements in circumpapillary Doppler OCT scans. Firstly, we register a volume to two reference scans in order to determine the physiologically correct structure of the volume. Then, vessels are segmented in the volume and the angles are calculated and stored in a look-up table. After having registered the circular scan to the volume by using the projection along the z-axis, the angles can be extracted from the look-up table. Repeatability measurements of flow parameters on 5 vessels of a healthy subject are presented.

Doppler OCT is a functional extension of OCT that provides information on flow in biological tissues. We present a novel approach for total retinal blood flow assessment using ultrahigh speed Doppler OCT. A swept source / Fourier domain OCT system at 1050 nm was used for 3D imaging of the human retina. The high axial scan rate of 200 kHz allowed measuring the high flow velocities in the central retinal vessels. By analyzing en-face images extracted from 3D Doppler data sets, absolute flow for single vessels as well as total retinal blood flow can be measured using a simple and robust protocol.

We present recent developments from a phase variance based motion contrast method of retinal vascular OCT imaging, called phase variance contrast optical coherence tomography (PV-OCT). Using a 25 kHz spectral domain optical coherence tomography (SDOCT) system, the vascular visualization capabilities of this contrast method are demonstrated with composite images created from multiple data sets. Wide field vascular images extending over the fovea and optic nerve head are presented as well as microvascular retinal images over the fovea to demonstrate the trade-offs between imaging speed and vascular visualization.

Conclusion: The current data imply that the performance index as defined herein is a valid measure of the performance of a trainee using the virtual reality phacoemulsification simulator. Further, the performance index increase linearly with measurement cycles for less than five measurement cycles. To fully use the learning potential of the simulator more than four measurement cycles are required. Materials and methods: Altogether, 10 trainees were introduced to the simulator by an instructor and then performed a training program including four measurement cycles with three iterated measurements of the simulation at the end of each cycle. The simulation characteristics was standardized and defined in 14 parameters. The simulation was measured separately for the sculpting phase in 21 variables, and for the evacuation phase in 22 variables. A performance index based on all measured variables was estimated for the sculpting phase and the evacuation phase, respectively, for each measurement and the three measurements for each cycle were averaged. Finally, the performance as a function of measurement cycle was estimated for each trainee with regression, assuming a straight line. The estimated intercept and inclination coefficients, respectively, were finally averaged for all trainees. Results: The performance increased linearly with the number of measurement cycles both for the sculpting and for the evacuation phase.

Nowadays UV-cross-linking is an established method for the treatment of keraectasia. Currently a standardized protocol is used for the cross-linking treatment. We will now present a theoretical model which predicts the number of induced crosslinks in the corneal tissue, in dependence of the Riboflavin concentration, the radiation intensity, the pre-treatment time and the treatment time. The model is developed by merging the difussion equation, the equation for the light distribution in dependence on the absorbers in the tissue and a rate equation for the polymerization process. A higher concentration of Riboflavin solution as well as a higher irradiation intensity will increase the number of induced crosslinks. However, performed stress-strain experiments which support the model showed that higher Riboflavin concentrations (> 0.125%) do not result in a further increase in stability of the corneal tissue. This is caused by the inhomogeneous distribution of induced crosslinks throughout the cornea due to the uneven absorption of the UV-light. The new model offers the possibility to optimize the treatment individually for every patient depending on their corneal thickness in terms of efficiency, saftey and treatment time.

Optimal keratoplasty (Opti-^K®) is an improved method of laser thermal keratoplasty (LTK) that is performed using a continuous wave (cw) laser for anterior stromal heating together with a sapphire applanation window for epithelial protection. Opti-K^K® has been used to improve uncorrected near visual acuity (UNVA) in emmetropic presbyopes while retaining or even improving uncorrected distance visual acuity (UDVA) - a truly optimal result that is linked to corneal multifocality produced by optimal keratoplasty. Opti-K^K® has also been used to improve both UDVA and UNVA in hyperopic presbyopes. The safety and effectiveness of Opti-K^K® have been evaluated in a Nassau clinical study and in an ongoing U.S. Clinical Trial. The procedure is noninvasive, simple, rapid, comfortable and repeatable. Although Opti-K^K® VA improvements are temporary, treatments can be repeated whenever needed to maintain "vision rejuvenation^K®".

The common procedures used to seal the scleral or conjunctival injuries are based on the traditional suturing techniques, that may induce foreign body reaction during the follow up, with subsequent inflammation and distress for the patient. In this work we present an experimental study on the laser welding of biocompatible patches onto ocular tissues, for the closure of surgical or trauma wounds. The study was performed ex vivo in animal models (porcine eyes). A penetrating perforation of the ocular tissue was performed with a surgical knife. The wound walls were approximated, and a biocompatible patch was put onto the outer surface of the tissue, in order to completely cover the wound as a plaster. The patches were prepared with a biocompatible and biodegradable polymer, showing high mechanical strength, good elasticity, high permeability for vapour and gases and rather low biodegradation. During preparation, Indocyanine Green (ICG) was included in the biopolymeric matrix, so that the films presented high absorption at 810 nm. Effective adhesion of the membranes to the ocular tissues was obtained by using diode laser light emitted from an 810 nm diode laser and delivered by means of a 300 μm core diameter optical fiber, to produce spots of local film/tissue adhesion, due to the photothermal effect at the interface. The result is an immediate closure of the wound, thus reducing post-operative complications due to inflammation.

Focussed femtosecond laser pulses are applied in ophthalmic tissues to create an optical breakdown and therefore a tissue dissection through photodisruption. The threshold irradiance for the optical breakdown depends on the photon density in the focal volume which can be influenced by the pulse energy, the size of the irradiated area (focus), and the irradiation time. For an application in the posterior eye segment the aberrations of the anterior eye elements cause a distortion of the wavefront and therefore an increased focal volume which reduces the photon density and thus raises the required energy for surpassing the threshold irradiance. The influence of adaptive optics on lowering the pulse energy required for photodisruption by refining a distorted focus was investigated. A reduction of the threshold energy can be shown when using adaptive optics. The spatial confinement with adaptive optics furthermore raises the irradiance at constant pulse energy. The lowered threshold energy allows for tissue dissection with reduced peripheral damage. This offers the possibility for moving femtosecond laser surgery from corneal or lental applications in the anterior eye to vitreal or retinal applications in the posterior eye.

Retinal photocoagulation is a long time established treatment for a variety of retinal diseases, most commonly applied for diabetic macular edema and diabetic retinopathy. The damage extent of the induced thermal coagulations depend on the temperature increase and the time of irradiation. So far, the induced temperature rise is unknown due to intraocular variations in light transmission and scattering and RPE/choroidal pigmentation, which can vary inter- and intraindividually by more than a factor of four. Thus in clinical practice, often stronger and deeper coagulations are applied than therapeutically needed, which lead to extended retinal damage and strong pain perception. The final goal of this project focuses on a dosimetry control, which automatically generates a desired temperature profile and thus coagulation strength for every individual coagulation spot, ideally unburden the ophthalmologist from any laser settings. In this paper we present the first realtime temperature measurements achieved on patients during retinal photocoagulation by means of an optoacoustic method, making use of the temperature dependence of the thermal expansion coefficient of retinal tissue. Therefore, nanosecond probe laser pulses are repetitively and simultaneously applied with the treatment radiation in order to excite acoustic waves, which are detected at the cornea with an ultrasonic transducer embedded in the contact lens and then are processed by PC.

Selective retina treatment (SRT) is a laser based method to treat retinal diseases associated with disorders of the retinal pigment epithelium (RPE) while preserving photoreceptors and choroid. Applying microsecond laser pulses to the 100- 200 strongly absorbing melanin granules inside the RPE cells induces transient micro bubbles which disrupt the cells. Aim of this work is to understand bubble dynamics in clusters with respect to the influence of the adjacent retina. Bubble dynamics were investigated in vitro on porcine RPE. An about 200 μm thick layer of agarose gel was applied to the RPE layer in order to simulate the mechanical properties of retina. Different laser pulse durations from 1 ns (532 nm, Nd:YAG) to 1.7 μs (527 nm, Nd:YLF) were used. The bubbles were investigated interferometrically (fiber interferometer @ 830 nm) and with fast flash photography (25 ns flash duration). Bubble lifetimes were measured. The results show that with retina phantoms the bubble formation threshold was reached at 2.5 times higher irradiation than without retina phantom for 1.7 μs laser pulses. The microbubbles generated with 1 ns laser pulses were almost not influenced by the agarose layer. Irradiation twofold over bubble formation threshold resulted in 3.5 times longer bubble lifetimes for μs and 2 times longer for ns pulse durations, respectively.

Retinal laser photocoagulation is an established treatment method for many retinal diseases like macula edema or diabetic retinopathy. The selection of the laser parameters is so far based on post treatment evaluation of the lesion size and strength. Due to local pigment variations in the fundus and individual transmission the same laser parameters often lead to an overtreatment. Optoacoustic allows a non invasive monitoring of the retinal temperature increase during retinal laser irradiation by measuring the temperature dependent pressure amplitudes, which are induced by short probe laser pulses. A 75 ns/ 523 nm Nd:YLF was used as a probe laser at a repetition rate of 1 kHz, and a cw / 532 nm treatment laser for heating. A contact lens was modified with a ring-shaped ultrasonic transducer to detect the pressure waves at the cornea. Temperatures were collected for irradiations leading to soft or invisible lesions. Based on this data the threshold for denaturation was found. By analyzing the initial temperature increase, the further temperature development during irradiation could be predicted. An algorithm was found to calculate the irradiation time, which is needed for a soft lesion formation, from the temperature curve. By this it was possible to provide a real-time dosimetry by automatically switching off the treatment laser after the calculated irradiation time. Automatically controlled coagulations appear softer and more uniformly.

We describe a high-speed long-depth range optical frequency domain imaging (OFDI) system employing a long-coherence length tunable source and demonstrate dynamic full-range imaging of the anterior segment of the eye including from the cornea surface to the posterior capsule of the crystalline lens with a depth range of 12 mm without removing complex conjugate image ambiguity. The dependence of the whole anterior segment change on time following abrupt relaxation from the accommodated to the relaxed status was measured for a healthy eye and that with an intraocular lens.

The effect of using collimator lenses with different focal lengths on the performance of a spectral-domain adaptive optics optical coherence tomography (AO-OCT) system has been studied. In vivo OCT scans of a healthy human retina were taken separately with different collimator lenses. Although shorter focal length lenses provide a smaller beam diameter at the pupil of the eye, and therefore a larger diffraction-limited spot size, on the return path the shorter focal length collimators demonstrate a better performance focusing the sinc-function-like intensity distribution returning from the eye on the fiber tip. The results might have applications in the OCT imaging of challenging cases.

We present the concept, optical design, and first proof of principle experimental results for a telescopic contact lens intended to become a visual aid for age-related macular degeneration (AMD), providing magnification to the user without surgery or external head-mounted optics. Our contact lens optical system can provide a combination of telescopic and non-magnified vision through two independent optical paths through the contact lens. The magnified optical path incorporates a telescopic arrangement of positive and negative annular concentric reflectors to achieve 2.8x - 3x magnification on the eye, while light passing through a central clear aperture provides unmagnified vision.

The realism of an ocular prosthesis is limited by the immobility of the pupil. Our method to solve this problem is to use a liquid crystal display (LCD) to control the pupil size as a function of the ambient light. This study demonstrates the first LCD to our knowledge surviving the ocular prosthetic manufacturing steps. The dynamic pupil is controlled by a novel, entirely autonomous and self-powered passive electronic circuit using photodiodes in a high voltage configuration. Future work for a complete prosthesis with a dynamic pupil is discussed. Finally, a standard device for the mass production of ocular prostheses is presented.

Electronic retinal prostheses seek to restore sight to patients suffering from retinal degenerative disorders. Implanted electrode arrays apply patterned electrical stimulation to surviving retinal neurons, producing visual sensations. All current designs employ inductively coupled coils to transmit power and/or data to the implant. We present here the design and initial testing of a photovoltaic retinal prosthesis fabricated with a pixel density of up to 177 pixels/mm². Photodiodes within each pixel of the subretinal array directly convert light to stimulation current, avoiding the use of bulky coil implants, decoding electronics, and wiring, and thereby reducing surgical complexity. A goggles-mounted camera captures the visual scene and transmits the data stream to a pocket processor. The resulting images are projected into the eyes by video goggles using pulsed, near infrared (~900 nm) light. Prostheses with three pixel densities (15, 55, and 177 pix/mm²) are being fabricated, and tests indicate a charge injection limit of 1.62 mC/cm² at 25Hz. In vitro tests of the photovoltaic retinal stimulation using a 512-element microelectrode array have recorded stimulated spikes from the ganglion cells, with latencies in the 1-100ms range, and with peak irradiance stimulation thresholds varying from 0.1 to 1 mW/mm². With 1ms pulses at 25Hz the average irradiance is more than 100 times below the IR retinal safety limit. Elicited retinal response disappeared upon the addition of synaptic blockers, indicating that the inner retina is stimulated rather than the ganglion cells directly, and raising hopes that the prosthesis will preserve some of the retina's natural signal processing.

This paper describes a compact adaptive optics scanning laser ophthalmoscope (AO-SLO) for high-resolution retinal imaging. The key features of this system are: (1) incorporation of a dual liquid crystal on silicon spatial light modulator (LCOS-SLM) as a wavefront compensation device and (2) sequential processing of aberration measurement/compensation and SLO imaging. The dual LCOS-SLM can compensate higher order aberration with high stabilization and realizes high-efficiency wavefront correction without polarization dependence. The sequential processing can fully utilize the power of the light to a retina only for the imaging, so the system produces high-contrast SLO images. The sequential processing also enables the use of lenses in ocular optics, giving a compact optical system with focus correction lenses for an eye with high reflective error. The optical system occupies only 500 mm x 370 mm, which is achieved by axially symmetric aspherical mirrors arranged off-axis and lenses in ocular optics. With this system, it is possible to observe photoreceptors at the parafoveal region of human healthy subjects at 32 or 64 frames per second.

Adaptive optics ophthalmic imaging systems that rely on a standalone wave-front sensor can be costly to build and difficult for non-technical personnel to operate. As an alternative we present a simplified wavefront sensorless adaptive optics laser scanning ophthalmoscope. This sensorless system is based on deterministic search algorithms that utilize the image's spatial frequency as an optimization metric. We implement this algorithm on a NVIDIA video card to take advantage of the graphics processing unit (GPU)'s parallel architecture to reduce algorithm computation times and approach real-time correction.

A compact retinal camera with adaptive optics which was designed for clinical practice was used to test a new adaptive optics control algorithm to correct for the angular ray deviations of a model eye. The new control algorithm is based on pupil movements rather than the measurement of the slopes of the wavefront with an optoelectronic sensor. The method for the control algorithm was based on the hypothesis that majority of the changes of the aberrations of the eye are due to head and eye movements and it is possible to correct for the aberrations of the eye by shifting the paraxial correction according to the new position of the pupil. Since the fixational eye movements are very small, the eye movements are assumed to be translational rather than rotational. Using the new control algorithm it was possible to simulate the aberrations of the moving model eye based on pupil tracking. The RMS of the residual wavefront error of the simulation had a magnitude similar to the RMS of the residual wavefront error of the adaptive optics correction based on optoelectronic sensor for angular ray deviations. If our hypothesis is true and other factors such as the tear film or the crystalline lens fluctuations do not cause changes in the aberrations of the eye as much as motion does, the method is expected to work in vivo as it did for a model eye which had no intrinsic factors that cause aberration changes.

Volumetric scans of current SD-OCT devices can contain on the order of 50 million pixels. Due to this size and because quantitative measurements in these scans are often needed, automatic segmentation of these scans is required. In this paper, a fully automatic retinal layer segmentation algorithm is presented, based on pixel-classification. First, each pixel is augmented by intensity and gradient data from a local neighborhood, thereby producing a feature vector. These feature vectors are used as inputs for a support vector machine, which classifies each pixel as above or below each interface. Finally, a level set method regularizes the result, producing a smooth surface within the three-dimensional space. Volumetric scans of 10 healthy and 8 glaucomatous subjects were acquired with a Spectralis OCT. Each scan consisted of 193 B-scans, 512 A-lines per B-scan (5 times averaging) and 496 pixels per A-line. Two B-scans of each healthy subject were manually segmented and used to train the support vector machine. One B-scan of each glaucomatous subjects was manually segmented and used only for performance assessment of the algorithm. The root-mean-square errors for the normal eyes were 3.7, 15.4, 15.0 and 5.5 μm for the vitreous/retinal nerve fiber layer (RNFL), RNFL/ganglion cell layer, inner plexiform layer/inner nuclear layer and retinal pigment epithelium/choroid interfaces, respectively, and 5.5, 11.5, 9.5 and 6.2 μm for the glaucomatous eyes. Based on the segmentation, retinal and RNFL thickness maps and blood vessel masks were produced.

The measurement of central corneal thickness (CCT) is vastly useful for diagnostic and therapeutic evaluation. The ultrasound pachymetry is currently the most common CCT technique. This study was undertaken to determine the precision and correlation of measurements obtained by mechanical and ultrasound pachymetry. The ultrasound pachymetry was determined using an A-scan ultrasonic pachymeter. The probe tip was held perpendicular on the central cornea by a support that goes down smooth to avoid excessive pressure and instability. The mechanical pachymetry was determined using a micrometer with a tip of 2mm of diameter. The tip of the micrometer was held perpendicular on the central cornea by a support that keeps stabilized. A 10x optics increase and a digital video camera shows real time image of approach and full contact of the tip with the cornea. Eight human corneas were obtained from cadaveric eyes. Measurements in both systens were taken for three different users, each one performed five readings. The results for both systems has an average SD of 33 microns refers to the systematic error between users (for positioning, center, pinching). But the difference between systems was 120 microns, possibly refers to the imprecision of ultrasound pachymetry in measuring in vitro corneas.

A prototype was built to provide means for clinical studies of alterations on the cornea UV natural protection from current procedures, such as the refractive surgery and corneal crosslinking. The prototype consists of an optical dual beam UVA/UVB system, for measuring the transmittance of the cornea at the 300nm - 400nm range. The system performs 500 measurements/s (±0.25% precision for the transmittance). It has been correlated to spectrophotometer (0.985) for donated human corneas. Preliminary studies on human corneas demonstrate that as the stromal layer is reduced, there is significant loss of the cornea natural UV protection.

In this work we present the first attempt to close the anterior lens capsule bag by the use of chitosan patches, where Gold Nanorods (GNRs) are embedded. GNRs exhibit intense localized plasmon resonances at optical frequencies in the near infrared (NIR): upon excitation with a NIR laser, a strong photothermal effect is produced, which can be exploited to develop minimally invasive therapies. Here we use the chitosan-GNRs films as a novel NIR sensitive nanocomposite for the photothermal conversion of NIR laser light during surgical interventions of tissue welding. Chitosan is an attractive biomaterial due to its biodegradability, biocompatibility, antimicrobial and wound healing-promoting activity. Colloidal GNRs were embedded in chitosan based, highly stabilized, flexible and easy-to-handle films, which were stored in water until the time of surgery. In these preliminary tests, a capsulorhexis was performed in freshly enucleated porcine eyes. The lens was aspired, then the patch was put onto the capsule bag and welded: a diode laser (810 nm) was used to deliver single spots (200 μm core diameter optical fiber) of local capsule/patch adhesion. Then the bag was refilled with silicon oil. The result is an immediate closure of the capsular tissue, with high mechanical strength. The laser welded chitosan- GNRs films are an innovative and highly stable solution to be exploited for the treatment of capsular breaks and for the implementation of a lens refilling procedure.

Non-invasive imaging of retinal function based on the recording of spatially distributed reflectance changes evoked by visual stimuli has to-date been performed primarily using modified commercial fundus cameras. We have constructed a prototype retinal functional imager, using a commercial endoscope (Storz) for the frontend optics, and a low-cost back-end that includes the needed dichroic beam splitter to separate the stimulus path from the imaging path. This device has been tested to demonstrate its performance for the delivery of adequate near infrared (NIR) illumination, intensity of the visual stimulus and reflectance return in the imaging path. The current device was found to be capable of imaging reflectance changes of 0.1%, similar to that observable using the modified commercial fundus camera approach. The visual stimulus (a 505nm spot of 0.5secs) was used with an interrogation illumination of 780nm, and a sequence of imaged captured. At each pixel, the imaged signal was subtracted and normalized by the baseline reflectance, so that the measurement was ΔR/R. The typical retinal activity signal observed had a ΔR/R of 0.3-1.0%. The noise levels were measured when no stimulus was applied and found to vary between ± 0.05%. Functional imaging has been suggested as a means to provide objective information on retina function that may be a preclinical indicator of ocular diseases, such as age-related macular degeneration (AMD), glaucoma, and diabetic retinopathy. The endoscopic approach promises to yield a significantly more economical retinal functional imaging device that would be clinically important.

Neglecting pupil irradiance fluctuations using a Hartmann Shack wavefront sensor leads to phase reconstruction bias. This bias depends on the pupil irradiance profile, the Hartmann Shack geometry and the amplitude and structure of the aberrations. In order to quantify the impact on real eye aberrations measurement, pupil irradiance and ocular aberrations of three trained subjects have been acquired on the LESIA testbed at Hospital des Quinze-Vingts. The pure WFS error is quantified with these data sets, on various lenslet array geometries. The propagation of this pure WFS error on actual systems, namely a static aberro- meter and an AO imager, is addressed. We find that, for a large enough lenslet array and with a reasonably clean optical path, the induced error is negligible.

The stiffness of biological tissues could be assessed by measuring the propagation of mechanically induced waves on its surfaces that could help identifying various tissue pathologies. Here we present results for the volumetric assessment of mechanical waves propagating on both surfaces of the crystalline lens measured with the Phase-Sensitive Swept Source Optical Coherence Tomography (PhS-SSOCT) technique. The results indicate that the system could detect vibrations of as small as 0.03 μm in amplitude induced on the surface of crystalline lens, and hence, PhS-SSOCT could potentially be used to assess stiffness of a crystalline lens.

The effects of pupil motion on retinal imaging are studied in this paper. Involuntary eye or head movements are always present in the imaging procedure, decreasing the output quality and preventing a more detailed diagnostics. When the image acquisition is performed using an adaptive optics (AO) system, substantial gain is foreseen if pupil motion is accounted for. This can be achieved using a pupil tracker as the one developed by Imagine Eyes R®, which provides pupil position measurements at a 80Hz sampling rate. In any AO loop, there is inevitably a delay between the wavefront measurement and the correction applied to the deformable mirror, meaning that an optimal compensation requires prediction. We investigate several ways of predicting pupil movement, either by retaining the last value given by the pupil tracker, which is close to the optimal solution in the case of a pure random walk, or by performing position prediction thanks to auto-regressive (AR) models with parameters updated in real time. We show that a small improvement in prediction with respect to predicting with the latest measured value is obtained through adaptive AR modeling. We evaluate the wavefront errors obtained by computing the root mean square of the difference between a wavefront displaced by the assumed true position and the predicted one, as seen by the imaging system. The results confirm that pupil movements have to be compensated in order to minimize wavefront errors.

Patients with diabetic retinopathy (DR) may experience a reduction in retinal oxygen saturation (SO2). Close monitoring with a fundus ophthalmoscope can help in the prediction of the progression of disease. In this paper we present a noninvasive instrument based on structured illumination aimed at measuring the retina optical properties including oxygen saturation. The instrument uses two wavelngths one in the NIR and one visible, a fast acquisition camera, and a splitter system that allows for contemporaneous collection of images at two different wavelengths. This scheme greatly reduces eye movement artifacts. Structured illumination was achieved in two different ways, firstly several binary illumination masks fabricated using laser micro-machining were used, a near-sinusoidal projection pattern is ultimately achieved at the image plane by appropriate positioning of the binary masks. Secondarily a sinusoidal pattern printed on a thin plastic sheet was positioned at image plane of a fundus ophthalmoscope. The system was calibrated using optical phantoms of known optical properties as well as an eye phantom that included a 150μm capillary vessel containing different concentrations of oxygenated and deoxygenated hemoglobin.

Stimulation of retinal neuronal cells using optogenetics via use of chanelrhodopsin-2 (ChR2) and blue light has opened up a new direction for restoration of vision with respect to treatment of Retinitis pigmentosa (RP). In addition to delivery of ChR2 to specific retinal layer using genetic engineering, threshold level of blue light needs to be delivered onto the retina for generating action potential and successful behavioral outcome. We report measurement of intensity distribution of light reaching the retina of Retinitis pigmentosa (RP) mouse models and compared those results with theoretical simulations of light propagation in eye. The parameters for the stimulating source positioning in front of eye was determined for optimal light delivery to the retina. In contrast to earlier viral method based delivery of ChR2 onto retinal ganglion cells, in-vivo electroporation method was employed for retina-transfection of RP mice. The behavioral improvement in mice with Thy1-ChR2-YFP transfected retina, expressing ChR2 in retinal ganglion cells, was found to correlate with stimulation intensity.

Over the past 100 years medicine evolved continuously, which can clearly be seen in the rising average of life expectancy. But as the population becomes older and older the number of old age diseases increases. Cataract is such an old age disease and worldwide the number one reason for blindness. Implantation of IOL's is up-to-date the only possibility to restore vision. In this study we present novel polymers containing derivatized coumarins in the side chains as smart materials for IOL manufacturing. These materials enable tuning of the focal length of an already implanted IOL by 2 diopters via photo induced dimerization and cleavage of the coumarin side groups respectively. The advantages of these new polymers are increased dimerization rates while decreasing the energy dose needed for photochemical dimerization of the coumarin side groups.

In aberrometry, optical system of an eye plays a twofold role - as an object of measurement and as a part of aberrometer. It means that the aberrations to be measured are themselves the source of measurement errors. Simulation with ZEMAX demonstrated error dependencies for all Zernike components having an axial asymmetry. To compensate for the induced errors, the ray tracing procedure is proposed to be modified in a way to individually tilt the probing beam in each point where it enters the eye and to make it to cross the visual axis on the retina. One iteration makes the error less by about one order. Optical layout is proposed containing two sets of two-coordinate acousto-optic deflectors, the first one changing the height of the beam and the second one directing the laser beam into the same point that was designated in the initial measurement.