EYE, DISEASES OF.—The various diseases affecting the organ of sight may be conveniently discussed as external and internal, or those which affect the outer parts of the eye—the conjunctiva and the cornea ; and those which have their seats in the interior of the eye—the choroid, the crystalline lens, the various media, the retina, and the optic nerve. These diseases are here discussed under their several headings.
Conjunetivitis.—An inflammation of the conjunctiva, or the mucous membrane of the eyelid, and that portion of the mucous membrane of the eyeball which is united with the eyelid. It may be a simple catarrhal process—catarrhal conjunctivitis ; a granular process—trachoma ; or a puru lent process—suppurative conjunctivitis or blennorrhcea.
Catarrhal Conjunctivitis is an extraordinarily frequent disease, met with in the larger cities. It is for the most part comparatively harmless, although not always so. As a rule it is due to external irritants, such as dust, smoke, and bad air, and manifests itself as a reddening of the eyelids, the profuse flow of tears, a burning pain, and some irritability of the eves. Very often, on awakening in the morning, both lids be found glued together. especially at the inner angle. In children, the inner surfaces of the lids often become the seats of small blisters as large as the head of a pin. The disease may not be the cause of any definite symptoms, and is sometimes discovered only by accident.
Very often the condition may continue for years, and in obstinate cases it may resist every form of treatment. As a rule, however, the disease sub sides under appropriate therapeutic measures. All secret remedies a:nd eye-washes should be zealously avoided, as they are liable to do great harm.
It is better to resort to timely medical advice. Ordinarily, the introduction of eye-drops prescribed by the doctor, together with cooling applications, arc sufficient. In obstinate cases it may be necessary to resort to mild cauterisation of the mucous membranes of the eye. Sometimes the disease may be traced to some visual defect, such as near or far sightedness, or to an irregular curva ture of the cornea. In such cases the wearing of suitable glasses will cause the trouble to disappear. Persons whose occupation exposes their eves to continual irritation should wear a pair of protecting glasses (see Figs. 135, 136), and in
some instances the abstention from smoking and drinking also has a very beneficial effect.
Granular Conjunctivitis is a contagious disease which runs a chronic course with occasional exacerbations. It appears as a violent inflammation of the mucous membranes of the eye, which become covered with numerous oval, transparent nodules (see Plate XII., Fig. 4). The severity of the disease depends in the first place upon its chronic course, and secondly upon the complications and sequelie. When the disease has been present for some time, cloudiness and ulceration of the cornea may develop, result ing in the more or less complete loss of sight. This may be accompanied also by a scar-like contraction of the connective tissue of the lids, adhesion between the latter and the eyeball, and inversion of the eyelids and the eye lashes. During its entire course the disease is marked by the discharge of more or less mucous and pus, by pain, and by a morbid intolerance of light (photophobia). The severity of these symptoms depends upon the extent to which the cornea has been involved.
This form of conjunctivitis is usually met with among the unclean, poorly domiciled lower classes ; and is found also in institutions, where its spread is favoured by the use in common of towels and other objects. Certain localities (such as Arabia and Egypt) arc especially afflicted ; and in eastern Europe (Russia, Poland, Hungary) the disease is more prevalent than in the western part of the Continent. In low countries (as Holland and Belgium) the disease is of more frequent occurrence than in mountainous countries like Switzerland. The disease, which has been endemic in Europe from the earliest times, became epidemic in that continent after the return of Napoleon I. from his Egyptian campaign. At that time hundreds of thousands were afflicted ; but since then the virulence has declined, although it is to be noted that lately it has again extended itself in Prussia. The disease is being brought to the United States through the great arteries of immigration, although attempts—more or less successful—arc being made to prevent its entrance.