The morphology of the pecten oculi in the common buzzard (Buteo buteo)

The pecten oculi are an intraocular, vascular, and pigmented structure peculiar to the avian eye. In this study, we investigated the pecten oculi of the common buzzard (Buteo buteo) using stereomicroscopy and light and scanning electron microscopy (SEM).

Twenty eyes from 10 adult buzzards were studied. Specimens from each buzzard were preserved in 10% buffered formalin and observed stereomicroscopically before being embedded in paraffin, sectioned, and stained with three stains: Mallory's triple staining technique as modified by Crossman, Hematoxylin-Eosin (HE), and Safranin O, and for examination by light microscopy. Specimens from two buzzards were also prepared for SEM.

Stereomicroscopy and SEM examination showed the pecten oculi in the common buzzard to be pleated-consisting of 17-18 100 μm thick folds. These folds are connected to one another by bands of connective tissue extending vertically between the plications. Blood vessels, approximately 30-40 μm in diameter, were seen on the surface of the each fold. These vessels arise from the base of pecten, becoming thinner toward the apical end of the structure. A network of capillary vessels at the base of the plicated structure resembles contour lines. At high amplification, melanin granule accumulations were observed around the vascular structures of the plica on SEM images. Light microscopy supported the SEM observations.

These findings reveal that the pecten oculi in the common buzzard are plicated and are remarkably similar to that of the other diurnal raptors.