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E Banin, LA Sarrazin, A Obolensky, E Averbukh, I Hemo; Foveal Cone Electroretinography in Patients With Neovascular AMD Treated by Photodynamic Therapy . Invest. Ophthalmol. Vis. Sci. 2002;43(13):598.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:1. To assess foveal cone function by focal electroretinography (FERG) in patients with sub-foveal choroidal neovascularization (CNV) due to age-related macular degeneration (AMD). 2. In a subset of patients, FERG was repeated after photodynamic therapy (PDT) was performed. Methods:Twenty patients (twenty-one eyes) with recent development of subfoveal choroidal neovascularization (CNV) due to neovascular AMD were included. All patients underwent a baseline evaluation including a complete clinical eye examination and fluorescein (and in some cases also ICG) angiography. The nature of the CNV membrane (predominantly classic or occult) was determined. Foveal cone FERG was performed using Burian-Allen contact lens electrodes and the MaculoScope system. A 42Hz flickering stimulus subtending 4° on the retina within a 12° annulus of bright light (to suppress stray activation) was directed upon the fovea or parafoveally using a Maxwellian view hand-held system. At least four sets of foveal responses (each averaging 2500 waveforms) were collected in each eye. In thirteen patients, testing was repeated 4-8 months following first PDT treatment. Results:Subfoveal CNV was associated with reduced amplitudes and delayed implicit times on foveal cone FERG testing. Mean amplitude in eyes with recent CNV (+/-SEM) was 0.115+/-0.008µV (lower limit of normal 0.18µV) and mean implicit time 39.08+/-0.29msec (upper limit of normal 38msec). No correlation with the type of CNV membrane (classic vs. occult) was evident. However, large amounts of sub-retinal fluid were associated with lower amplitudes. In the subgroup undergoing PDT the mean pre-treatment amplitude (+/-SEM) was 0.105+/-0.01µV and mean implicit time 38.99+/-0.39msec. Following 1-2 PDT treatments, mean amplitude was 0.099+/-0.01µV and mean implicit time 39.19+/-0.59msec. In this small group of patients, no correlation was found between FERG amplitude or implicit time and visual acuity before or after PDT. Conclusion:Subfoveal CNV in patients with AMD is associated with abnormal foveal cone electrophysiologic function. PDT did not significantly affect FERG responses. Further studies are needed to determine whether baseline foveal cone FERGs could assist in better patient selection for PDT treatment.
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