gms | German Medical Science

Background: New clinical high resolution imaging technologies like spectral domain OCT and Fundusautofluorescence are useful tools in the evaluation of GA due to ARMD. The GA junctional zone includes changes in RPE-Bruch’s membrane (BrM) complex that are difficult to interpret. We measured and evaluated characteristic RPE cell changes in histological sections of GA eyes to provide a better basis for interpreting clinical GA imaging data.

Methods: In 7 GA eyes, 3 complete section sets through GA atrophy were analyzed in RPE morphology zones: 0/1 = uniform/ non-uniform morphology and pigmentation; 2A = heaped RPE; 2B = RPE posterior migration into basal deposits; 2L = RPE leaflets; 3 = RPE migration into retina; 4/5 = loss of pigmentation with/ without persisting basal deposits. Within zones, parameters were assigned semi-quantitative descriptors. The sum of AF intensity along lines perpendicular to BrM, measured with laser confocal microscopy, served as a surrogate for fundus AF.

Results: From the outer macula towards the central atrophic area we defined zones in which the RPE grades passed almost steadily upward, indicating increased pathology. AF sum intensity was both highest and most variable in grades 2A,B, and L. Sharp increases in AF sum intensity in grades 2–3, near atrophy, were frequently due to vertical superimposition of orthotopic and ectopic RPE.

Conclusions: Our histological measurements provide information about GA typical alterations of the RPE-Bruch’s membrane complex and are useful for interpreting clinical imaging data. High AF at GA borders is not reliably attributable to increased lipofuscin within individual cells, casting doubt on lipofuscin’s cytotoxicity in vivo.