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Journal of Biomedical Optics

Dynamics of retinal photocoagulation and rupture
Author(s): Christopher Sramek; Yannis M. Paulus; Hiroyuki Nomoto; Philip Huie; Jefferson Brown; Daniel V. Palanker
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Paper Abstract

In laser retinal photocoagulation, short (<20 ms) pulses have been found to reduce thermal damage to the inner retina, decrease treatment time, and minimize pain. However, the safe therapeutic window (defined as the ratio of power for producing a rupture to that of mild coagulation) decreases with shorter exposures. To quantify the extent of retinal heating and maximize the therapeutic window, a computational model of millisecond retinal photocoagulation and rupture was developed. Optical attenuation of 532-nm laser light in ocular tissues was measured, including retinal pigment epithelial (RPE) pigmentation and cell-size variability. Threshold powers for vaporization and RPE damage were measured with pulse durations ranging from 1 to 200 ms. A finite element model of retinal heating inferred that vaporization (rupture) takes place at 180-190°C. RPE damage was accurately described by the Arrhenius model with activation energy of 340 kJ/mol. Computed photocoagulation lesion width increased logarithmically with pulse duration, in agreement with histological findings. The model will allow for the optimization of beam parameters to increase the width of the therapeutic window for short exposures.

Paper Details

Date Published: 1 May 2009
PDF: 13 pages
J. Biomed. Opt. 14(3) 034007 doi: 10.1117/1.3130282
Published in: Journal of Biomedical Optics Volume 14, Issue 3
Show Author Affiliations
Christopher Sramek, Stanford Univ. (United States)
Yannis M. Paulus, Stanford Univ. School of Medicine (United States)
Hiroyuki Nomoto, Stanford Univ. Medical Ctr. (United States)
Philip Huie, Stanford Univ. Medical Ctr. (United States)
Jefferson Brown, Stanford Univ. (United States)
Daniel V. Palanker, Stanford Univ. Medical Ctr. (United States)


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