Anatomical, Histological Study Eye of the Bird Corncrake crex crex

The present study carried out to investigate the anatomical and histological structure of eye components in the Corncrake crex crex which it is omnivorous to correlate the eye structure with nutrition nature.
The results showed, anatomically, that the eye ball spherical and compressed some thing at the anterioposterior axis, on the other hand the posterior segment larger than the anterior segment the eyes set on the side of the head top. The eye ball composed of three tunics: Outer sclera and it is extension cornea, middle uvea (choroid, ciliary body and iris ) and inner retinal layer.
Histologicaly cartilages surround the eye ball as well as Os nervi optici present near the optic nerve. The cornea concaved and differ in its thickness. The stroma of cornea appeared as three subdivitions layer differ in their density. Pigmented cells appeared at the root of the cornea. The lens some what flattened at the anterior and spherical at the posterior portion. The annular pad appeared at both side of equatorial.
The choroids had lymphatic vessels and the other components resemble that of other vertebrates. The iris showed variations in the thickness and skeletal muscles appeared in it. The Ciliary body very obvious and concave, at the central region, to ward the vitreous humour.
The retina appeared avascular and duplex (with rods and cones). On the other hand the dorsal and central portion of the retina more thicker than that of ventral and peripheral respectively. One dorso temporal fovea also appeared, and visual streak upper to the fovea. The pigment epithelial layer cells cuboidal. There were one type of rods and two types of cones (double and single) in the retina which differ in their density. Other structures were observered such as oil droplets in the cones and parabloid in both rods and cones, The other layers of the retina resemble that other birds but their thickness differ at various portions of the eye ball.
The pecten oculi appeared as fan like vascular structure with 12 folds which originate from optic disc area processes extended from transverse pigmented bridge and then one process folded lateraly as well as upper bridge was noted.
We can conclude that the Crex crex bird have avery well acute vision because the cornea covexed and the lens flatted anteriory. On the other hand the retina contain temporal fovea, visual streak, oil droplets, Parabloid, Pecten oculi, these structures enable the bird to see it is various nutrients in the environment easly.