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The cornea

Categories: Diseases of The Eye and Ear

This is almost circular in shape. It is convex anteriorly and
projects forward from the sclerotic in the same manner that a watch glass

does from its case. This layer covers what we call the pupil.



The second tunic or coat (membrane) is formed from behind forward by the

Choroid, the ciliary body and the Iris. The choroid is the vascular and

dark coat covering the posterior five-sixths of the globe. The ciliary

b
dy connects the choroid to the circumference of the iris. The iris is

the circular muscular septum (division) which hangs vertically behind the

cornea, presenting in its center a large rounded opening, the pupil.



The choroid is a thin highly vascular membrane of a dark brown or

chocolate color and is pierced behind by the optic nerve and in this

situation is firmly adherent to the sclerotic.



The ciliary body comprises three muscles for its make-up and connects the

choroid to the circumference of the iris.



The Iris (rainbow) has received its name from its various colors in

different individuals. It is a thin, circular shaped, contractile curtain,

suspended in the aqueous (watery) humor behind the cornea and in front of

the lens, being perforated a little to the nasal (nose) side of its centre

by a circular opening, the pupil, for the transmission of light. By its

circumference it is continuous with the ciliary body, and its inner or

free edge forms the margin of the pupil. The anterior surface of the iris

is variously colored in different individuals and marked by lines which

converge toward the pupil.



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