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Arunkumar Krishnan, Nimesh Bhikhu Patel, Harold E Bedell; Relating structural and functional changes at the preferred retinal locus in macular degeneration. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© ARVO (1962-2015); The Authors (2016-present)
Subjects with bilateral central field loss (CFL) usually fixate with a non-foveal preferred retinal locus (PRL). Retinal structure at the PRL has not been investigated thoroughly and investigating the structure-function correspondence at the PRL is important for understanding visual performance. In this study we relate localized sensitivity changes in the vicinity of the word-fixation PRL of subjects with bilateral CFL (as previously reported) to structural measures of their outer retina.
Twelve subjects (20-89yrs) with bilateral CFL due to age-related macular degeneration or Stargardt’s disease participated. The word-fixation PRL for a 3-letter word at each subject’s critical print size was determined with NIDEK MP1 micro-perimeter. Supra-threshold screening to detect micro-scotomas (MSs) was performed using Goldmann Size II targets (13 arc min, L spot =127 cd/m2, L BG = 1.27 cd/m2) with a sampling density of 12 arc min in a grid region centered on the PRL.The PRL region was imaged using a high-density optical coherence tomography scan with averaging of 9 B-scan frames. After offline image registration, regions of interest in the OCT image (496 by 154 pixels) corresponding to the MP1 test locations were identified and manually segmented using a custom MATLAB program. The outer and inner margins of retinal pigment epithelium (RPE), inner margins of outer nuclear layer (ONL) and internal limiting membrane (ILM) were traced to determine the thickness of RPE, ONL + photoreceptor layer and the total retinal thickness. These thicknesses were compared between the MS and Non-MS locations in each subject.
Three subjects with no MSs and 1 subject with a poor quality OCT scan were excluded from thickness analysis. A total of 165 B-Scans were analyzed, 52 (32%) from locations with MSs. The range of thickness ratios (layer thickness in the location of a MS / average layer thickness in same eye in Non-MS locations) for RPE, ONL + photoreceptor and total retina were: 0.26–2.13, 0.31–1.6 and 0.78–1.1 respectively. Mean thicknesses of all 3 layers did not differ significantly in MS and Non-MS locations (t (7), p = 0.47, 0.43 and 0.09).
Structure-function correlation in regions of MS at the PRL in subjects with bilateral CFL was poor. This may be attributable to disease diversity and/or functional changes preceding structural changes at the PRL.
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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