Assessment of the pigeon (Columba livia) retina with spectral domain optical coherence tomography

Background: To assess the normal retina of the pigeon eye using spectral domain optical coherence tomography (SD-OCT) and establish a normative reference. Methods: Twelve eyes of six ophthalmologically normal pigeons (Columba livia) were included. SD-OCT images were taken with dilated pupils under sedation. Four meridians, including the fovea, optic disc, red field, and yellow field, were obtained in each eye. The layers, including full thickness (FT), ganglion cell complex (GCC), thickness from the retinal pigmented epithelium to the outer nuclear layer (RPE-ONL), and from the retinal pigmented epithelium to the inner nuclear layer (RPE-INL), were manually measured. Results: The average FT values were significantly different among the four meridians (p < 0.05), with the optic disc meridian being the thickest (294.0 ± 13.9 ㎛). The average GCC was thickest in the optic disc (105.3 ± 27.1 ㎛) and thinnest in the fovea meridian (42.8 ± 15.3 ㎛). The average RPE-INL of the fovea meridian (165.5 ± 18.3 ㎛) was significantly thicker than that of the other meridians (p < 0.05). The average RPE-ONL of the fovea, optic disc, yellow field, and red field were 91.2 ± 5.2 ㎛, 87.7 ± 5.3 ㎛, 87.6 ± 6.5 ㎛, and 91.4 ± 3.9 ㎛, respectively. RPE-INL and RPE-ONL thickness of the red field meridian did not change significantly with measurement location (p > 0.05). Conclusions: Measured data could be used as normative references for diagnosing pigeon retinopathies and further research on avian fundus structure.