there is otherwise always a loss of tissue resulting from the
inflammation and this loss is made up for by more or less densely
intransparent connective tissue (nebula, leucoma). These according
to their site and extent cause greater or less visual disturbance.
Primary keratitis may be ulcerative or non-ulcerative,
superficial or deep, diffuse or circumscribed, vascularized or
non-vascularized. It may be complicated by deeper inflammations
of the eye such as iritis and cyclitis. In some cases the
anterior chamber is invaded by pus (hypopyon). The healing
of a corneal ulcer is characterized by the disappearance of pain
where this has been a symptom and by the rounding off of its
sharp margins as epithelium spreads over them from the surrounding
healthy parts. Ulcers tend to extend either in depth or
superficially, rarely in both manners at the same time. A deep
ulcer leads to perforation with more or less serious consequences
according to the extent of the perforation. Often an eye bears
permanent traces of a perforation in adhesion of the iris to the
back of a corneal scar or in changes in the lens capsule (capsular
cataract). In other cases the ulcerated cornea may yield
to pressure from within, which causes it to bulge forwards
(staphyloma).
The principal causes of primary keratitis are traumata and infection from the conjunctiva. Traumata are most serious when the body causing the wound is not aseptic or when micro-organisms from some other source, often the conjunctiva and tear-sac, effect a lodgment before healing of the wound has sufficiently advanced. In infected cases a complication with iritis is not uncommon owing to the penetration of toxines into the anterior chamber.
Inflammations of the cornea are the most important diseases of the eye, because they are among the most frequent, because of the value of the cornea to vision and because much good can often be done by judicious treatment and much harm result from wrong interference and neglect. The treatment of primary keratitis must vary according to the cause. Generally speaking the aim should be to render the ulcerated portions as aseptic as possible without using applications which are apt to cause a great deal of irritation and thus interfere with healing. On this account it is important to be able to recognize when healing is taking place, for as soon as this is the case, rest, along with frequent irrigation of the conjunctiva with sterilized water at the body temperature, and occasionally mild antiseptic irrigation of the nasal mucous membrane is all that is required. It is a common and dangerous mistake to over treat.
Of local antiseptics which are of use may be mentioned the actual cautery, chlorine water, freshly prepared silver nitrate or protargol, and the yellow oxide of mercury. These different agents are of course not all equally applicable in any given case; it depends upon the severity as well as upon the nature of the inflammation which is the most suitable. For instance, the actual cautery is employed only in the case of the deeper septic or malignant ulcers, in which the destruction of tissue is already considerable and tending to spread further. Again the yellow oxide of mercury should only be used in the more superficial, strumous forms of inflammation. Many other substances are also in use, but need not here be referred to.
Secondary keratitis takes the form of an interstitial deposit of leucocytes between the layers of the cornea as well as often of vascularization, sometimes intense, from the deeper network of vessels (anterior ciliary) surrounding the cornea. The duration of a secondary keratitis is usually prolonged, often lasting many months. More or less complete restoration of transparency is the rule, however, eventually.
No local treatment is called for except the shading of the eyes and in most cases the use of a mydriatic to prevent synechiae when the iris is involved. Often it is advisable to do something for the general health. In young people there is probably nothing better than cod-liver oil and syrup of the iodide of iron. Inherited syphilis, tuberculous and other inflammations are the causes of secondary keratitis.
Neuro-paralytic Keratitis.—When the fifth nerve is paralysed there is a tendency for the cornea to become inflamed. Different forms of inflammation may then occur which all, besides anaesthesia, show a marked slowness in healing. The main cause of neuro-paralytic keratitis lies in the greater vulnerability of the cornea. The prognosis is necessarily bad. The treatment consists in as far as possible protecting the eye from external influences, by keeping it tied up, and by frequently irrigating with antiseptic lotions.
Certain non-inflammatory and degenerative changes are met with in the cornea. Of these may be mentioned keratoconus or conical cornea, in which, owing to some disturbance of vitality, the nature of which has not been discovered, the normal curvature of the cornea becomes altered to something more of a hyberboloid of revolution, with consequent impairment of vision: arcus senilis, a whitish opacity due to fatty degeneration, extending round the corneal margin, varying in thickness in different subjects and usually only met with in old people: transverse calcareous film, consisting of a finely punctiform opacity extending, in a tolerably uniformly wide band, occupying the zone of the cornea which is left uncovered when the lids are half closed.
Tumours of the cornea are not common. Those chiefly met with are dermoids, fibromata, sarcomata and epitheliomata.
Scleritis.—Inflammation of the sclera is confined to its anterior part which is covered by conjunctiva. Scleritis may occur in circumscribed patches or may be diffused in the shape of a belt round the cornea. The former is usually more superficial and uncomplicated, the latter deeper and complicated with corneal infiltration, irido-cyclitis and anterior choroiditis. Superficial scleritis or, as it is often called, episcleritis, is a long-continued disease which is associated with very varying degrees of discomfort. The chronic nature of the affection depends mainly upon the tendency that the inflammation has to recur in successive patches at different parts of the sclera. Often only one eye at a time is affected. Each patch lasts for a month or two and is succeeded by another after an interval of varying duration. Months or years may elapse between the attacks. The cicatricial site of a previous patch is rarely again attacked. The scleral infiltration causes a firm swelling, often sensitive to touch, over which the conjunctiva is freely movable. The overlying conjunctiva is always injected. The infiltration itself at the height of the process is densely vascularized. Seen through the conjunctiva its vessels have a darker, more purplish hue than the superficial ones. The swelling caused by the infiltration gradually subsides, leaving a cicatrix to which the overlying conjunctiva becomes adherent. The cicatrix has a slaty porcellanous-looking colour. Superficial scleritis occurs in both sexes with about equal frequency. No definite cause for the inflammation is known. The treatment on the whole is unsatisfactory. Burning down the nodules with the actual cautery, and subsequently a visit to such baths as Harrogate, Buxton, Homburg and Wiesbaden, may be recommended.
Deep scleritis with its attendant complications is altogether a more serious disease. Etiologically it is equally obscure. Both eyes are almost always attacked. It more generally occurs in young people, mostly in young women. Deep scleritis is more persistent and less subject to periods of intermission than episcleritis. The deeper and more wide-spread inflammatory infiltrations of the sclera lead eventually to weakening of that coat, and cause it to yield to the intra-ocular pressure. Vision suffers from extension of the infiltration to the cornea, or from iritis with its attendant synechiae, or from anterior choroiditis, and sometimes also from secondary glaucoma. The treatment is on the whole unsatisfactory. Iridectomy, especially if done early in the process, may be of use.
The Aqueous Humour.—Intransparency of the aqueous humour is always due to some exudation. This comes either from the iris or the ciliary processes, and may be blood, pus or fibrin. An exudation in this situation tends naturally to gravitate to the most dependent part, and, in the case of blood or pus, is known as kyphaema or hypopyon.
The Crystalline Lens Cataract.—Intransparency of the crystalline lens is technically known as cataract. Cataract may be idiopathic and uncomplicated, or traumatic, or secondary to
