[RPE morphometry in geographic atrophy due to AMD]

Area of Science:

• Ophthalmology
• Histopathology
• Retinal Imaging

Background:

• Geographic atrophy (GA) involves complex changes in the retinal pigment epithelium (RPE) and Bruch's membrane.
• Interpreting these junctional zone changes is challenging with current high-resolution imaging.
• Histological evaluation of RPE cell degeneration in GA eyes is crucial for understanding disease progression.

Purpose of the Study:

• To measure and evaluate degenerative RPE cell changes in histological sections of GA eyes.
• To correlate RPE alterations with specific grades of degeneration.
• To assess the potential for visualization of these changes with modern imaging technologies.

Main Methods:

• Evaluation of seven GA eyes using light microscopy.
• Grading of RPE alterations in three eye sections (0=normal, 1=irregular, 2=enlarged/heaped, 3=migrating, 4=absent).
• Measurement of total RPE height, individual RPE cell height, and basal deposit height in graded zones.

Main Results:

• RPE pathology increased progressively from the outer macula towards the central GA zone.
• Zone 2 showed highly variable total RPE height (16.9 ± 5.6 µm) with mixed cell morphologies.
• Basal deposits increased in continuity and thickness with RPE degeneration, reaching 9.5 ± 4.3 µm in the atrophic zone.

Conclusions:

• Degenerative RPE phenomena, particularly grade 2/3, are substantial.
• These changes are often large enough for detailed visualization.
• Modern imaging technologies (e.g., SD-OCT) can likely detect these significant RPE alterations.