Sympathetic amblyopia.-It sometimes happens that when one eye has been lost from injury or disease and is constantly inflamed and painful, the sight of the other becomes much impaired without any visible change taking place in its structure. This condition is known as "sympathetic amblyopia," and is generally cured by removing the blind and painful eye.

DISEASES OF THE VITREOUS HUMOUR.

The vitreous can be thoroughly examined by direct ophthalmoscopic examination.

Disease of the vitreous is often associated with disease of the retina or choroid.

It may be the seat of acute or chronic inflammation, its consistence may be altered so that it becomes more fluid than normal, and it may shrink in bulk in which case it will probably drag away the retina from its attachments. The changes which can be seen in the vitreous whilst the eye remains in the orbit, are loss of transparency caused by opacities of various size and shape, moving freely or slowly, or in rare instances. fixed. An idea may be formed of the consistence of the vitreous by noticing the rapidity of the movement of any particles seen floating in it; if their movements are rapid the vitreous is too fluid, but if they move sluggishly it is of normal consistence.

Acute inflammation of the vitreous alone sometimes occurs, it is probably syphilitic. The ophthalmoscope shows diffuse haze of the vitreous, vigorous antisyphilitic treatment will effect a cure.

Chronic inflammation.-Much more common is a chronic inflammation of the vitreous, secondary to

choroiditis, cyclitis or retinitis. The ophthalmoscope shows more or less diffuse haze, mingled with which, are large shreds or webs.

The treatment is as that of choroiditis, retinitis, (see Diseases of Choroid and Retina).

Opacities in the vitreous may be large dense masses, so large as barely to admit of any normal reflex from the fundus, muddy clouds stirred up from below on movement of the globe, membranes dense or gauzy; and beads, shreds, or threads, glistening scales, or numerous sandy dots, so numerous as to give the idea of general opalescence. Opacities in the vitreous are easily detected by direct ophthalmoscopic examination at a distance of 12" to 18", but if the eye is approached quite near they will not be seen so clearly as they lie too near the back of the lens. If the patient is directed to move his eye up and down quickly two or three times and then look straight in front of him, the opacities will be seen to pass across the illuminated fundus as dark figures on a red ground, showing that their movements are independent of those of the eyeball which is not the case with opacities situated in the cornea, lens or retina. In some cases only one or two small opacities exist and are found with difficulty and then lost again. Opacities near the outer surface of the vitreous are often attached to the retina or optic disc -more commonly the latter-they appear ill-defined and hazy and have no movement; they are single and are often first detected by indirect ophthalmoscopic examination as a circumscribed haze covering some part of the optic disc or its neighbourhood. By careful direct examination from different distances aided if necessary by convex lenses behind the sight hole of the ophthalmoscope, such an opacity can be accurately de

fined.

In sympathetic ophthalmia, as already stated, opacity appears in the vitreous; it is inflammatory.

In some cases though no definite opacity can be made out by the most careful examination, a diffuse haziness of the vitreous occurs, which blurs the outlines of the disc and retinal vessels, or indeed obscures them entirely, though a bright red reflex is returned from the fundus. The same appearance may be caused by diffuse corneal or lenticular haze, but in either case oblique illumination will show its position, whilst, if the opacity is in the vitreous, this method of examination will give only negative results. Crystals of cholesterine sometimes form in the vitreous they are the glistening opacities already mentioned. They may be very numerous and when the eye is moved appear like a number of dancing golden spangles or minute stars; the appearance is called sparkling synchysis, and may occur in eyes the vision of which is quite normal. Opacities from blood or lymph close to the back of the lens may be seen in their natural colour by oblique illumination.

Disease of the vitreous occurs in the higher degrees of myopia; the humour becomes fluid and opacities form in it which may be the result of former hæmorrhage. A foreign body, small piece of iron for instance may sometimes lodge in the vitreous and be visible. Bleeding into the vitreous may be caused by severe blows on the eye; the hæmorrhage may be so abundant as to entirely darken the interior of the eye and if near the back of the lens may-as already stated-be seen by oblique illumination. If only in small quantity and situated deep in the eye it is seen with the ophthalmoscope as a dark ragged cloud stirring up from below when the eye is moved and settling slowly down again. Penetrating wounds of the eyeball cause hæmorrhage into the vitreous which may be followed later on by the

formation of lymph or pus, giving a greenish yellow colour when the eye is examined by oblique illumination or by daylight. In some cases of pyæmia the vitreous becomes infiltrated with pus.

Spontaneous hæmorrhage.-Hæmorrhage into the vitreous may take place spontaneously, usually to only a small extent; the blood becomes absorbed to a greater or less extent in the course of time, but very commonly some permanent opacity remains. In some rare cases, however, repeated attacks of hæmorrhage take place so that after a time the chamber becomes filled with blood. This may occur in two classes of cases. I. In women about the climacteric. 2. In young adult males subject to bleeding from the nose and constipation. The sight of one or both eyes may be entirely destroyed, secondary cataract may form, the tension of the globe diminish, detachment of the retina take place and even shrinking of the eyeball follow.

The treatment of hæmorrhage into the vitreous depends on its cause. If traumatic, the eye should be kept bandaged, the pupil dilated with atropine, the patient kept at rest, on low diet without stimulants, and absorption promoted by the use of frequent blisters to the temple or behind the ear.

In the idiopathic form, the eyes must be kept at rest, and guarded from bright light by protectors; the patient should go about quietly, avoid straining, attention should be paid to the general health, uterine trouble should be treated if it exists. In the case of hæmorrhage associated with obstinate constipation some means should be taken to ensure a pretty free daily action of the bowels, by no means an easy task.

Cysticercus is occasionally seen in the vitreous.

CHAPTER X.

GLAUCOMA.

By Glaucoma we understand "a series of morbid changes of the eyeball; the most prominent of which, and apparently the one which causes all the others, being an increase of tension of the globe," (Bader). The cause of the increase of tension is unknown, but it is supposed to result from undue accumulation of the intra-ocular fluids dependent on hypersecretion or deficient removal. Glaucoma is said to be simple when the increase of tension progresses slowly and continuously without inflammatory outbreaks. Acute or chronic when attended by attacks of inflammation.

Simple glaucoma presents no very marked symptoms its onset being most insidious. It is characterised by gradual decrease of acuteness of vision, with narrowing of the visual field, impairment of the power of accommodation, causing rather rapid increase of presbyopia, sluggishness in movements of the iris, some dilatation of the pupil, and some apparent haziness of the crystalline lens. Increase of tension is probably one of the earliest symptoms, but is very liable to be overlooked until the disease is far advanced and considerable hardness of the globe has taken place. With the ophthalmoscope spontaneous pulsation of the retinal arteries may be seen, or pulsation may be produced by very slight pressure upon the globe. The vessels, especially the veins, are thinner on the surface of the optic disc than in the surrounding retina, and the disc itself may be more or less cupped. The cup of glaucoma is characterised by a bluish or dusky appearance of the