The iris (a rainbow) has received its name from the varied color it presents. It is a thin, circular shaped, contractile curtain suspended in front of the lens, being perforated by an aperture, the pupil, for the transmission of light.

The perfection of the eye is very much increased by the action of this curtain. In a strong light the pupil contracts and shuts out the superfluous rays; in a feeble light it dilates in order to admit into the eye all the light which can be received.

The iris is liable to inflammation. While the name iritis is used to indicate a distinct affection, it is rarely that inflammation is confined to the iris alone, but parts anterior to it, and the deeper structures behind it are involved.

Causation

The affection may be the result of injuries, over-exertion, or caused by various morbid states of the blood.

Symptoms

The white of the eye changes to a bright pink hue. The iris at first becomes indistinct, losing its color; the pupil is contracted, and its inner edges are irregular. In the next stage, one of effusion, the surface appears in some cases rusty; in others a film closes the pupil. In very acute cases the conjunctiva becomes affected by the inflammation. Pain, restlessness, intolerance of light, and excessive flow of tears are the common associate symptoms.

Prognosis

If the disease is of recent origin the prognosis is favorable. If it has existed for a long time and came on slowly and insidiously, the chances of recovery without impairment of sight are doubtful.

Treatment

To allay pain,and quiet restlessness, paregoric in teaspoonful doses can be given. To subdue inflammation,the bowels should be moved freely by epsom salts, and the diet be restricted to milk, broths, raw eggs, etc.

To preserve the pupil entire, it should be kept well dilated by means of a solution of the sulphate of atropine (gr. i ad. aquae distil. 3i). Of this a few drops should enter the eye morning and night.

If the animal is full blooded, strong and hardy, " Gray powder" in one grain doses may properly be given three times a day between the feedings. This mercurial should only be continued for four or five days. After the acute inflammation has subsided, the iodide of potassium may be given three times daily in three grain doses. If the animal is debilitated the syrup of the iodide of iron is advised in ten drop doses at each feeding. If the need is apparent cod liver oil may also be added to the treatment. The tonics should be persisted in until the film disappears, leaving the pupil clear.