Applicability of optical coherence tomography in blue-fronted parrots (Amazona aestiva)

Optical coherence tomography (OCT) measurement of adult blue-fronted parrots (Amazona aestiva), free from infectious, inflammatory or neoplastic systemic diseases and from any ophthalmological illness, aim at its characterization, as well as to standardize the examination technique for the species.

Pupillary dilation was achieved with rocuronium bromide (5 mg/mL) at 0, 2, 15, 17, 30, and 32 minutes. The animals were sedated with midazolam maleate (0.5 mg/kg/IM) and anesthetized with propofol (5.0 mg/kg/IV). Measurements were made to evaluate the thickness of the total retina (TR), sensorineural retinal (SR), and ganglion cell complex (GCC), 2 millimeters (mm) from the pecten toward the fovea. OCT data were compared to measurements of retinal histological slides from enucleated eyes of blue-fronted parrots, scanned in automatic fluorescence microscope and measured with by the VS-ASW^® software.

Averages of measurements from the 43 retinas evaluated by OCT were TR: 279.40 micrometers (μm), SR: 255.90 μm, and GCC: 138.60 μm, respectively, and the measurements of six retinas using fluorescence microscopy were 260.30 μm for TR, 238.20 μm for SR, and 129.30 μm for GCC, demonstrating a high correlation coefficient between all measurements (r = .8698, P < .0001). It is also possible to evaluate the anatomy of the retina and to identify its layers, variations and abnormalities using OCT images. Variations were found between the different areas of the retina, both in the images of the histological slides and in the images of the OCT.

Optical coherence tomography is a valuable technique for in vivo evaluation of retinal structures in blue-front parrots, providing detailed and accurate images. This method improves the understanding of retinal diseases, monitoring the beginning, progression and therapy of retinal diseases, in the same individuals during longitudinal studies. In comparison to histological investigations, OCT enables imaging in vivo, therefore reducing the number of euthanized animals or enucleated eyes.