The definition of the term cataract is an opacity of the crystalline lens, or of its capsule, or of both.

To render this more intelligible it is necessary to briefly consider the anatomy of this portion of the eye. The crystalline lens is a transparent, double convex body, situated immediately behind the pupil. The function of this lens is to produce distinct perception of form and outline, and to accommodate the eye to vision at different distances.

The capsule of the lens is a transparent and highly elastic membrane which closely surrounds it.

Causation

Cataract, especially capsular, maybe caused by wounds and injuries to the lens, its capsule, or to the eye itself. It is attributed to inflammation, and has been produced artificially in animals by modifying the constitution of the blood. From this it is to be inferred that certain derangements of circulation and the general system may induce cataract.

Two forms of cataract are recognized, the soft and the hard; the latter is peculiar to advanced age.

Symptoms

In. cataract of the capsule, there will be seen behind the pupil a non-transparent body of a gray, dead white; if cataract of the lens exists, the body will be bluish-white or amber colored.

After a certain age an unaffected lens acquires a yellow color, then changes to an amber.

In hard cataract the cloudiness appears in this already discolored lens, and great impairment of vision may result before the grayness is plainly evident on a superficial examination.

Treatment

When the characteristic changes in the eye are detected, every means to improve the general health should be resorted to. Tonics if indicated are to be given, and selected as the need is manifest.

The employment of the most judicious methods can have no other influence on the disease than to possibly retard its progress. Nothing can exert a curative influence excepting the knife of a surgeon.

The writer recalls an interesting case in which the condition of the eye of a dog presented unusual appearances. The affection was confined to one side. On the first examination nothing abnormal could be detected. An hour later the animal was seen and the lens had become opaque and a bright red color. In a few hours the opacity disappeared and the eye again seemed unaffected. These peculiar changes the owner of the dog had observed for some months.

The general health of the animal was excellent, his usefulness in the field remained unimpaired.