Abstract
Purpose:
Determine thickness, volume, and topography of BlinD and pre-BlinD (“lipid wall” [1]) in nnAMD and age-matched control eyes.
Methods:
Short post-mortem donor eyes were post-fixed in osmium tannic acid paraphenylenediamine for macula-wide high-resolution sections [2]. nnAMD case ascertainment used histological criteria [3]. Thickness and type of sub-RPE lipid (BlinD, drusen, pre-BlinD) was determined at 25 locations in each of 2 sections that together included the fovea and nasal, temporal, and superior perifovea [3]. To estimate BlinD volume, regression lines fit to BlinD thicknesses pooled across eyes were used to generate a conical solid of rotation peaking at the fovea.
Results:
In 25 nnAMD eyes of 23 donors (82.7 ± 7.93 yr, 17F, 6M), median BlinD thickness was 3.9 ± 4.7 µm (Q3 = 5.9 µm). BlinD was thickest foveally, declining to near zero at 3 mm eccentricity. Median BlinD volume was 0.0146 mm3 (Q3= 0.0331 mm3). In 29 control eyes of 29 donors (78.9 ± 9.75 yr, 19F, 10M), any sub-RPE lipid was 2.5-4.3X, and pre-BlinD 2.1-3.6X, more abundant foveally than perifoveally.
Conclusions:
1) In some patients BlinD may be thick enough for detection by next-generation OCT. 2) The conical shape and foveal centration of biomechanically fragile BlinD may explain the tendency of choriocapillary neo-vessels to grow towards the fovea [4]. 3) BlinD volume falls in the middle range of druse volumes [5] and could elevate some eyes from low-risk into high-risk quintiles. 4) More sub-RPE lipid under the fovea in aged eyes supports the idea that soft drusen and BlinD arise from age-related lipoprotein accumulation in Bruch’s membrane (BrM) that fills in towards the RPE and creates pre-BlinD internal to the inner collagenous layer [6]. 5) RPE cell number is stable with aging yet perifoveal rod photoreceptors are selectively lost [7,8]. Because BrM lipoprotein accumulation can block LDL-mediated micronutrient transport [9], foveally centered BlinD could reduce micronutrients available for translocation to perifoveal photoreceptors by RPE. 1. Ruberti. IOVS. 2003;44:1753. 2. Curcio. IOVS. 2011;52:3943. 3. Curcio. Retina. 2012;accepted 11/13/12. 4. Bressler. Retina. 1983;3:7. 5. Yehoshua. Ophthalmology. 2011;118:2434. 6. Huang. Exp Eye Res. 2007;85:202. 7. Morgan. IOVS. 2009;50:1350. 8. Curcio. IOVS 1993;34:3278. 9. Cankova. Exp Eye Res. 2011;93:947.
Keywords: 412 age-related macular degeneration •
583 lipids •
504 drusen