Exam 11: Eyes

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The retinal structures viewed with an ophthalmoscope are the optic disc, the retinal vessels, the general background, and the macula. Fibers from the retina converge at the optic disc to form the optic nerve. The color of the disc (optic papilla) varies from creamy yellow-orange to pink. It is round or oval, has margins that are distinct and sharply demarcated, especially on the temporal side, and has a physiologic cup where blood vessels exit and enter.

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The anterior compartment, behind the cornea and in front of the iris and lens, has two chambers-anterior and posterior. It contains a clear liquid called aqueous humor, produced by the ciliary body. The continuous flow of fluid serves to deliver nutrients to the surrounding tissues and to drain metabolic waste. Intraocular pressure is determined by the balance between the amount of aqueous produced and resistance to its outflow at the angle of the anterior chamber. The posterior compartment is filled with a clear gel-like substance called vitreous humor.

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At birth, eye function is limited. Peripheral vision is intact in newborns. The macula is absent at birth but is mature by age 8 months. Eye movement is poorly coordinated but matures by age 3 to 4 months. The structure of the eyeball reaches adult size by age 8 years. With aging, the skin loses its elasticity, causing wrinkling and drooping; fat and muscles atrophy; and involution of the lacrimal glands causes decreased tear production and a feeling of dryness and burning. Pupil size decreases, and the lens loses elasticity, causing presbyopia. The normally transparent fibers of the lens begin to thicken and yellow, resulting in senile cataract. Visual acuity may diminish gradually after age 50 years.