Correlation of Fundus Autofluorescence and Histology of Laser-induced Choroidal Neovascularization in the Rat

Abstract

Purpose : To characterize and correlate the patterns of fundus autofluorescence (FAF) and histological features of laser-induced choroidal neovascularization (CNV) in Brown Norway (BN) rats.

Methods : CNV was induced by laser photocoagulation in BN rats. FAF images were obtained and the histological features of CNV lesions were evaluated by light microscopy (LM) at 10 min, 72 hr, 1 wk, 2 wk, and 3 wk after laser injury.

Results : The size of the laser injured area on FAF peaked at 72 hr and gradually decreased after 1 wk. The lesion on FAF exhibited a central punctate dark area surrounded by a discrete bright core with a dark rim 10 min after laser. The lesion boundaries became less distinct after 72 hr. After 1 wk, the lesion exhibited a bright core surrounded by a dark inner ring and a bright outer ring. The highest FAF intensity was observed 10 min after laser and significantly decreased 1 wk after laser. After acute laser injury (72 hr), LM revealed that the central core was composed of loose tissue with chronic inflammatory cells and marked loss of the photoreceptor inner segments (IS), outer segments (OS) and RPE. Pigment migration into the retina and Müller cell activation/proliferation were present. At the margin of the central core, disruption and loss of IS/OS were observed. In the peripheral aspect of the CNV lesion, disorganization of the IS/OS and RPE and rounding-up of pigment were present. In later laser injury (2 wk), LM revealed dense fibrovascular connective tissue with total loss of the IS/OS and RPE in the central core. A glial scar was present with pigment migration into the outer retina. At the margin of the central core, the IS/OS and RPE cell size and number were attenuated. In addition, a thin, loose fibrovascular layer was interposed between the RPE and Bruch membrane with focal RPE hypertrophy in the peripheral aspect of the CNV lesion.

Conclusions : The laser insult elicits a “target-like” configuration of FAF in CNV lesions. The intensity and area of FAF inversely change over time, with a distinct alteration in tissue morphology. FAF appears to correlate with the integrity of the photoreceptors and RPE overlying CNV lesions, and thus may serve as an in vivo, non-invasive assessment for photoreceptor and RPE morphology and function in rodent models of CNV.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.