Looking at the white of the eye, the first coat is the transparent
conjunctiva, which is reflected back on to the eyeball from the
eyelids. Next comes the sclerotic coat, formed of dense whitish tissue,
which seen through the transparent conjunctiva makes up the “white of
the eye.” The sclerotic coat covers the whole globe of the eyeball with
the exception of the transparent bulging cornea in front (which,
however, is practically a continuation of the sclerotic), and the back
of the eye where the optic nerve enters. The sclerotic is the thickest
and densest coat of the eye.
Within the sclerotic coat, and so to speak lining it, comes the choroid
coat. Countless blood vessels run through this coat, supplying both the
one above it and that beneath it. As this coat approaches the front of
the eye under the circumference of the cornea, it thickens into the
ciliary body, forming a dense ring of tissues underneath the junction of
the cornea and the sclerotic coat.