Spectral-domain optical coherence tomography imaging of normal foveae: A pilot study in 17 diurnal birds of prey.

Abstract

To describe and to establish normative data for the foveae of diurnal birds of prey using spectral-domain optical coherence tomography (SD-OCT). All animals (9 red-tailed hawks, 3 Cooper's hawks, 3 American kestrels, 1 sharp-shinned hawk, and 1 broad-winged hawk) had an ophthalmic examination performed with slit lamp biomicroscopy and indirect ophthalmoscopy. Following ophthalmic examination, SD-OCT was performed in each eye that had a visible fundus and normal fovea on SD-OCT. Temporal foveae depth, central foveae depth, pecten-temporal foveae distance, and pecten-central foveae distance (PCFD) were measured using SD-OCT. Differences in measured outcomes between species were determined using generalized linear mixed effects models. The central foveae (mean±SD) displayed a small but significant depth variation between species (P=.002) and was deepest in red-tailed hawks (293±16µm), followed by American kestrels (260±12µm), broad-winged hawks (256±16µm), Cooper's hawks (250±9µm), and sharp-shinned hawks (239±16µm). The temporal foveae were shallower than the central foveae in all species tested, and there was a significant variation between species (P<.001). The temporal foveae (mean±SD) were deepest in American kestrels (137±8µm), followed by red-tailed hawks (129±3µm), broad-winged hawks (59.5±3.5µm), Cooper's hawks (20.3±6.4µm), and sharp-shinned hawks (17.5±0.7µm). Pecten-temporal foveae distance was approximately 30% shorter than PCFD in all species. There were no differences in the parameters tested between the eyes within each species (P≥.47). Normative foveae SD-OCT data were obtained in four species of diurnal birds of prey. Further studies are warranted to provide structural and functional information regarding normal and pathologic changes that can affect the foveae.