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Jason A. Croskrey, Brett Schroeder, Jungtae Rha, Adam M. Dubis, Joseph Carroll, Dennis P. Han; In Vivo Imaging of Human Photoreceptors with Adaptive Optics and SD-OCT After Short Duration PascalTM Macular Grid and Panretinal Laser Photocoagulation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2883.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the effects of short duration (20 ms) PascalTM grid and panretinal (PRP) laser photocoagulation on human photoreceptors using adaptive optics (AO) and spectral domain optical coherence tomography (SD-OCT).
High-speed AO ophthalmoscopy and SD-OCT were used to image macular grid laser and extramacular PRP laser photocoagulation lesions placed for the clinical indications of macular edema from hemicentral vein occlusion and of proliferative diabetic retinopathy, respectively. Using the PascalTM laser system (532 nm), grid treatment consisted of 100 µm diameter, 100 mW, 20 ms spots placed 100 µm apart in 3 x 3 grid arrays, in diffusely edematous retina to obtain minimally visible and consistent fundus lesions. PRP consisted of 200 µm diameter, 425 mW, 20 ms spots placed in 4 x 4 grid arrays, 200 µm apart, to obtain clinical lesions of moderate intensity. Laser lesions were imaged at 25, 49, and 175 days post grid laser treatment, and 82 days and 122 days post PRP laser treatment.
AO imaging showed absence of detectable photoreceptors within all imaged laser lesions, and showed intact photoreceptor mosaic between lesions. In one patient, cone density measured in an area adjacent to a PRP lesion was 6,940 cones/mm2, which is within normal values for that specific retinal location. Photoreceptor nonvisualization on AO correlated with obliquely-oriented hyperreflective opacities in the outer retina and focal interruption of the IS/OS line on SD-OCT. Rapid sequence images showed unidirectional choroidal blood flow through depigmented areas of the lesions. Diameter of photoreceptor non-visualized areas in the AO images were measured to be 105 µm and 284 µm for grid and PRP lesions, respectively. Poor photoreceptor AO imaging signal to noise ratio (SNR) was observed at macular thicknesses of 400-452 µm at 25 days post grid laser, and better SNR at thicknesses of 348-378 µm, 49 days post grid laser.
AO imaging of short duration (20 ms) PascalTM laser lesions of both threshold and moderate intensity shows apparent photoreceptor loss limited to areas of ophthalmoscopically visible RPE changes without evidence of surrounding loss. Retinal edema adversely affects the ability to use AO to image the photoreceptor layer in proportion to its severity. However, after resolution of edema, AO may provide a sensitive means of assessing the in vivo response of human photoreceptors to laser photocoagulation.
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