"
messages[2]="Vitreous cavity: is filled with the vitreous humor, a transparent gel that maintains the structure of the globe. It is made up of hyaluronic acid, collagen fibers, and a dilute salt water solution. The collagen is thickest in its peripheral portion, the vitreous cortex, which has firm attachments to the anterior retina and the border of the optic disc. With aging (or inflammation, high myopia, and trauma), the vitreous degenerates into lakes of water that place stress on its attachments to the retina. Eventually, the vitreous detaches itself from the optic disc, leaving a floater. If the peripheral vitreous cortex detaches from the retina, it may tear a hole in the retina. If fluid seeps under the hole, the retina may detach, and vision is lost. The retina must be emergently reattached surgically to preserve vision.
"
messages[3]="Ganglion cell: conveys visual signals through the optic nerve to the lateral geniculate body in the thalamus.
"
messages[4]="Bipolar cell: way station in neural pathway from rods and cones to ganglion cells.
"
messages[5]="Rod: the photoreceptor that transduces light into neural signals responsible for vision in low light situations.
"
messages[6]="Cone: the photoreceptor that transduces light into neural signals responsible for high resolution and color vision.
"
messages[7]="Retinal pigment epithelium: a single layer of hexogonal cells that provides metabolic support to the rods and cones (photoreceptors). The tight junctions between retinal pigment epithelial cells form the outer blood-retinal barrier, which prevents macromolecules that escape from choroidal vessels from entering the retina.
"
messages[8]="Macula: retinal region containing a high density of cones and ganglion cells specialized in visual acuity and color vision.
"
messages[9]="Choroid: the vascular nutrient layer of the outer retina.
"
messages[10]="Sclera: the collagenous outer wall of the eyeball. Its outermost portion, called the episclera, has a rich vascular network. It is here that bilirubin accumulates to stain the superficial sclera yellow (\"icterus\"). The sclera becomes inflamed in connective tissue diseases, usually forming a nodule with a tangle of hyperemic episcleral and conjunctival vessels. The episclera is covered by the conjunctiva, a vascular mucous membrane.
"
messages[11]="Optic nerve: contains the retinal ganglion cell axons that are travelling to the optic chiasm and on to the lateral geniculate body.
"
messages[12]="Retina: the neural inner layer of the posterior part of the eye. It has a nutrient retinal pigment epithelial outer portion and a sensory inner portion.
"
messages[13]="Retinal artery & vein: these vessels travel in the innermost retinal layer, and are visible through the ophthalmoscope. The arteries nourish only the retinal ganglion cells and their axons. The deeper layers of the retina get their blood from the choroid.
"
messages[14]="Fovea: central depression within the macula in which the retina consists only of cones. All other retinal layers are pushed aside to the surrounding area so that light can travel unimpeded directly to the cones.
"
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