RELATION OF OPTICAL COHERENCE TOMOGRAPHY TO MICROANATOMY IN NORMAL AND RD CHICKENS

PURPOSE. To elucidate the relation between optical coherence tomograph y (OCT) scans and retinal histology in normal and retinal degeneration (rd) chickens. METHODS. Retinas from adult normal and rd chickens wer e examined in vivo with OCT at 850 nm and compared quantitatively with stained cryosections of unfixed retinas from the same locations. RESU LTS. The nerve fiber layer (NFL) and inner plexiform layer (IPL) show homogeneous backscatter throughout their thicknesses. NFL reflectivity is similar to 0.6 log units higher than that of the IPL. The inner nu clear layer shows a low reflectivity the properties of reflections fro m ganglion cell and outer nuclear layers are indeterminate. The outer retina and choroid form a large reflective complex. Photoreceptor inne r segments produce the highest of these reflections in normal chicken retinas, similar to 1.5 log units higher than that of the IPL. The ret inal pigment epithelium also has a relatively large backscatter coeffi cient and is the dominant reflector in rd retinas that lack photorecep tors. Choroidal pigment produces an intermediate level of backscatter and is the largest attenuator of signal at 850 nm. CONCLUSIONS. Quanti fied OCT signals have a predictable relationship to histology and path ology in chicken retinas. The results from rd retinas represent a firs t step toward in vivo quantitation of retinal structure in retinal deg enerative disease.