In simple glaucoma operative interference is anything but satisfactory; the most favourable result is, that the disease may be stayed at the stage at which it has arrived, but no gain of sight is to be expected. We must also bear in mind the possibility of the eye going quite to the bad after an operation. On the whole an operation in simple glaucoma should not be rashly undertaken. The course of the disease is very slow, and if our patient is advanced in years we may well leave him alone, hoping that his sight may last as long as he does. If, however, he has a prospect of living for many years, we have no alternative but to advise him to take his chance of an operation, and having decided to perform one, to do it with as little delay as possible. The operative treatment of inflammatory, especially of acute, glaucoma is much more satisfactory; as a rule, however, no good is likely to result from an operation in cases where vision has been reduced to bare perception of light; but in glaucoma fulminans much improvement may take place even though all perception of light has been lost for some days.

In performing iridectomy for glaucoma we must take care to remove the iris well down to its insertion and to excise a good broad piece (see Iridectomy), merely cutting away a portion of the iris near the margin of the pupil does no good. The operation is easy enough in cases of acute glaucoma, but in those of old standing, where the structures are rotten or the pupils so widely dilated that the iris has become a thin rim at the periphery of the anterior chamber, it is anything but simple. In such cases sclerotomy is to be preferred to iridectomy.

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In cases of glaucoma where for any reason operation does not seem advisable we must do our best to give relief by medical treatment. The means which will be found most useful are the instillation of solutions

of sulphate of eserine (gr. ii. to iv. to water 3j.), application of sedative fomentations, administration ot opium, and the local abstraction of blood by leeches or the artificial leech, with perfect rest of the eyes.

Atropine should not be used in glaucoma, as it causes increase of tension of the eyeball. Its application is recommended in some works on ophthalmic subjects, but it does more harm than good; eserine, however, has a contrary effect and is often of great benefit.

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CHAPTER XI.

THE RETINA AND OPTIC NERVE.

DISEASES of the retina and optic nerve can be diagnosed by the ophthalmoscope alone. Before the introduction of this instrument all cases of want of sight arising without cause apparent to the unaided eye were collected together under the names of "Amblyopia" and "Amaurosis." To the former were referred all cases where vision was much impaired, but not entirely lost; to the latter cases in which no perception of light remained. But now that the ophthalmoscope has come generally into use, making the interior of the eyeball as accessible to our sight as the exterior, we have come to refer "amblyopia" and "amaurosis" to their proper causes, and the terms have fallen into comparative disuse. For instance, if in a case of want of sight we find on ophthalmoscopic examination that there is haziness of the vitreous, inflammation of the retina, or choroid, etc., we do not say, as formerly, that the patient is amblyopic, but that he is suffering from disease of the vitreous, retinitis, choroiditis, etc. Again, in cases of total blindness the ophthalmoscope will detect atrophy of the optic nerve, and instead of saying that the patient is " amaurotic," we say that he is suffering from optic nerve atrophy. The terms “amblyopia" and "amaurosis" may, however, still be used in some cases to be presently described, where there is partial or complete loss of sight, with an apparently healthy condition of the ocular structures.

Hyperæmia of the retina occurs from over-strain of the eyes, in doing near work (especially in hypermetropic or astigmatic eyes), or from constantly looking at bright light; the disease is not uncommon amongst engine-drivers and others who work over a blazing fire. Symptoms.-The symptoms are dimness of vision, and a feeling of fullness and discomfort about the eyes; in hypermetropic or astigmatic individuals there will be the usual complaints of pain in the eyes, headache and inability to read or work for any length of time. The ophthalmoscope shows redness of the optic disc, engorgement and twisting of the retinal vessels both arteries and veins, with increase in the visible number of each. This form of hyperæmia may be described as active, another form affecting only the veins, which are found enlarged tortuous and sometimes varicose, depending on interference with venous circulation being looked upon as passive hyperæmia.

Hyperæmia of the retina, especially the active form, is not easily recognised, as the limits between health and disease fade almost imperceptibly into each other, and considerable experience is required in order to judge with certainty where one ends and the other begins.

Treatment.-Active hyperæmia must be treated by insuring perfect rest to the eyes. To this end all near work must be prohibited, the accommodation must be paralysed by using a solution of sulphate of atropine, (gr. ii. to iv., to 3j.) three times a day or oftener; the eyes must be shielded from light by protective spectacles or shades. Leeches or the artificial leech should be applied to the temples from time to time, and purgatives given if necessary.

After subsidence of the hyperæmia any anomaly of refraction must be carefully neutralised, the eyes being

well under the influence of a mydriatic during the examination.

Passive hyperæmia is generally an indication of some more serious disease and requires no special treatment. (See ISCHEMIA).

INFLAMMATION OF THE RETINA-RETINITIS.

Causes. Retinitis most frequently depends on some constitutional condition, as albuminuria, diabetes, gout, or syphilis; it may also arise from embolism of the vessels of the retina, hæmorrhage into its substance, or from cerebral disease; from tumours or entozoa within the globe, exposure to sudden flashes of bright light, or wounds of the eyeball. It may also be secondary to choroiditis, iritis, or cyclitis, and is a part of sympathetic ophthalmia.

Symptoms.-Retinitis is characterised by hyperæmia of the retina, associated with more or less dense and extensive opacity of its structure, either diffuse or in spots or patches, and frequently with extravasations of blood in its substance.

Disturbance of vision may be a prominent symptom, or the patient may hardly be aware that anything is amiss with his eyes. The degree of impairment of vision depends upon the situation and extent of the inflamed portion of the retina; for instance, a small patch of inflammatory exudation in the region of the yellow spot will cause much loss of sight, whereas a considerable amount of opacity situated peripherally will give rise to scarcely any symptoms.

Pain, photophobia, coloured vision, and flashes of