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Nathan Doble, Elaine Wells-Gray, Colleen M Cebulla, Stacey S Choi; Integrity of individual cone photoreceptors over drusen in early stage dry AMD. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5104.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the changes in the inner (IS) and outer segments (OS) of individual cones located over drusen of various sizes in patients with early stage dry age-related macular degeneration (AMD). It is known that with an increase in drusen size, vision continues to deteriorate, eventually leading to scotoma.
Early stage dry AMD patients with diffusely located drusen in the posterior pole were imaged with an adaptive optics (AO) - optical coherence tomography (OCT) - scanning laser ophthalmoscopy (SLO) system. Retinal locations with different drusen size (≤ 80 µm in height) were selected for AO imaging to determine when the druse begins to alter the IS and OS. All patients had undergone comprehensive eye examinations to rule out any conditions other than dry AMD. IS and OS lengths (ISL and OSL) were measured over, around, and in between drusen across the AO-OCT B-scan. Drusen were grouped based on their heights in 10 µm increments and correlation between the drusen height (including the region without drusen) and IS and OS lengths were investigated.
No statistically significant differences in ISL between all groups were measured for drusen <60 µm in height. For drusen higher than this, the ISL became significantly shorter (p<0.05). Between the 2 highest groups (60.1-70 µm and 70.1-80 µm drusen height), the difference in ISL was not found to be statistically significant. The difference in OSL between the areas without drusen and up to drusen <30 µm in height was not statistically significant, but >30 µm showed significant OSL shortening (p<0.05) until the drusen height was >60 µm. Again, between the 2 highest drusen groups (60.1-70 µm and 70.1-80 µm drusen height), the difference in OSL was not found to be statistically significant. Correlation coefficient (Pearson) for the OSL change as a function of drusen height was -0.75 whereas for the ISL, r = -0.65. The cut-off drusen height that started to shorten the ISL was 60 µm while for the OSL, it was the half the height i.e. 30 µm.
The OS is more vulnerable to drusen than the IS, and the results potentially provide an earlier time point when treatments for dry AMD could be applied to circumvent any damage to cone photoreceptors.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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