Agreement between Optical Coherence Tomography and Histology Derived Retinal Thickness Measures

Abstract

Abstract: : Purpose: To determine the agreement between optical coherence tomography (OCT2) and histology derived retinal thickness measures in the rabbit. Methods: Retinal thickness was evaluated in 10 pigmented Dutch Belted rabbits. Rabbits were prepared 3 weeks prior to imaging by placing 3 argon laser burns (100mW, 150µm spot width, 0.1ms duration) in the left eye, forming an equilateral triangle with one side in apposition and inferior to the optic nerve head (ONH). The laser burns were used to facilitate image acquisition with the OCT and subsequent comparison of thickness measures derived from histological preparations. OCT2 imaging was performed with a minimum of 3 crosshair scans spanning the horizontal distance between the burns apposite to the ONH were obtained. Retinal thickness values were determined automatically by the OCT2 . The rabbits were euthanized, anterior poles removed and a calibrated tissue punch was used to mark the retina to evaluate tissue shrinkage. Ocular tissues were fixed, dehydrated and embedded in JB-4 plastic resin. Histological sections were analyzed using a quantitative computer image analysis system attached to the microscope. Results: Mean retinal shrinkage due to histological preparation in the x-y dimension was 3.4%. The OCT2 data in the lateral plane was scaled to that of the histology. The mean retinal thickness across rabbits was 131.0±12.5µm (range 112-156) by histology and 116.7±11.0µm (range 105-146) by OCT2. The mean difference in retinal thickness was 14.29µm (SEM 5.04). The magnitude of the difference varied across individual sections and between rabbits. Conclusions: Retinal thickness was on average 10% greater when measured histologically than with OCT2. The most likely source of variation between techniques is that OCT2, by definition, measures the optical properties of the retina rather than absolute thickness per se.

Keywords: imaging/image analysis: clinical • retina • animal model