disease in the deeper parts of the eye. The modified epithelial
structure of which the lens is composed is always being added to
throughout life. The older portions of the lens are consequently
the more central. They are harder and less elastic. This
arrangement seems to predispose to difficulties of nutrition.
In many people, in the absence altogether of general or local
disease, the transparency of the lens is lost owing to degeneration
of the incompletely-nourished fibres. This idiopathic cataract
mostly occurs in old people; hence the term senile cataract.
So-called senile cataract is not, however, necessarily associated
with any general senile changes. An idiopathic uncomplicated
cataract is also met with as a congenital defect due to faulty
development of the crystalline lens. A particular and not
uncommon form of this kind of cataract, which may also develop
during infancy, is lamellar or zonular cataract. This is a partial
and stationary form of cataract in which, while the greater part
of the lens retains its transparency, some of the lamellae are
intransparent. Traumatic cataract occurs in two ways: by
laceration or rupture of the lens capsule, or by nutritional changes
consequent upon injuries to the deeper structures of the eye.
The transparency of the lens is dependent upon the integrity
of its capsule. Penetrating wounds of the eye involving the
capsule, or rupture of the capsule from severe blows on the eye
without perforation of its coats, are followed by rapidly developing
cataract. Severe non-penetrating injuries, which do not
cause rupture of the capsule, are sometimes followed, after a
time, by slowly-progressing cataract. Secondary cataract is
due to abnormalities in the nutrient matter supplied to the lens
owing to disease of the ciliary body, choroid or retina. In some
diseases, as diabetes, the altered general nutrition tells in the
same way on the crystalline lens. Cataract is then rapidly
formed. All cases of cataract in diabetes are not, however,
necessarily true diabetic cataracts in the above sense. Dislocations
of the lens are traumatic or congenital. In old-standing
disease of the eye the suspensory ligament may yield in part,
and thus lead to lens dislocation. The lens is practically always
cataractous before this takes place.
The Vitreous Humour.—The vitreous humour loses its transparency owing to exudation from the inflamed ciliary body or choroid. The exudation may be fibrinous or purulent; the latter only as a result of injuries by which foreign bodies or septic matter are introduced into the eye or in metastatic choroiditis. Blood may also be effused into the vitreous from rupture of retinal, ciliary or choroidal vessels. The pathological significance of the various effusions into the vitreous depends greatly upon the cause. In many cases effusion and absorption are constantly taking place simultaneously. The extent of possible clearing depends greatly upon the preponderance of the latter process.
Diseases of the Iris and Ciliary Body.—Inflammation of the iris, iritis, arises from different causes. The various idiopathic forms have relations to constitutional disturbances such as rheumatism, gout, albuminuria, tuberculosis, fevers, syphilis, gonorrhoea and others, or they may come from cold alone. Traumatic and infected cases are attributable to accidents, the presence of foreign bodies, operations, &c. In addition, iritis may be secondary to keratitis, scleritis or choroiditis. The beginning of an attack of inflammation of the iris is characterized by alterations in its colour due to hyperaemia and by circumcorneal injection. Later on, exudation takes place into the substance of the iris, causing thickening and also a loss of gloss of its surface. According to the nature and severity of the exudation there may be deposits formed on the back of the cornea, attachments between the iris and lens capsule (synechiae), or even gelatinous-looking coagulations or pus in the anterior chamber.
The subjective symptoms to which the inflammation may give rise are dread of light (photophobia), pain, generally most severe at night and often very great, also more or less impairment of sight. Along with the pain and photophobia there is lacrymation. An acute attack of iritis usually lasts about six weeks. Some cases become chronic and last much longer. Others are chronic from the first, and in one clinical type of iritis, in which the ciliary body is also at the same time affected, viz. iritis serosa, there is usually comparatively little injection of the eye or pain, so that the patient’s attention may only be directed to the eye owing to the gradual impairment of sight which results. In some cases, and more particularly in men, there is a tendency to the recurrence at longer or shorter intervals of attacks of iritis (recurrent iritis). In these cases, as well as in all cases of plastic iritis which have not been properly treated, serious consequences to sight are apt to follow from the binding down of the iris to the lens capsule and the occlusion of the pupil by exudation.
Inflammation of the ciliary body, cyclitis, is frequently associated with iritis. This association is probable in all cases where there are deposits on the posterior surface of the cornea. It is certain where there are changes in the intra-ocular tension. Often in cyclitis there is a very marked diminution in tension. Cyclitis is also present when the degree of visual disturbance is greater than can be accounted for by the visible changes in the pupil and anterior chamber. The exudation may, as in iritis, be serous, plastic or purulent. It passes from the two free surfaces of the ciliary body into the posterior aqueous, and into the vitreous, chambers. This produces, what is a constant sign of cyclitis, more or less intransparency of the vitreous humour. Where there has been excessive exudation into the vitreous, subsequent shrinking and liquefaction take place, leading to detachment of the retina and consequent blindness.
The treatment of iritis necessarily differs to some extent according to the cause. The general treatment applicable to all cases need only be here considered. What should be aimed at, at the time of the inflammation, is to put the eye as far as possible at rest, to prevent the formation of synechiae and alleviate the pain. An attempt should be made to get the pupil thoroughly dilated with atropine. The dilatation should be kept up as long as any circumcorneal injection lasts. If a case of iritis be left to itself or treated without the use of a mydriatic, posterior synechiae almost invariably form. Some fibrinous exudation may even organize into a membrane stretching across, and more or less completely occluding, the pupil. Synechiae, though not of themselves causing impairment of vision, increase the risk that the eye runs from subsequent attacks of iritis. It should however be remembered that as the main call for a mydriatic is to prevent synechiae, the raison d’être for its use no longer exists when, having been begun too late, the pupil cannot properly be dilated by it. Under these conditions it may even do harm. The eyes should also be kept shaded from the light by the use of a shade or neutral-tinted glasses. During an attack any use of the eyes for reading or sewing or work of any kind calling for accommodation must be prohibited. This applies equally to the case of inflammation in one eye alone and in both.
Pain is best relieved by hot fomentations, cocain, and in many cases the internal use of salicin or phenacetin. The treatment sometimes required for cases of old iritis is iridectomy. The operation is called for in two different classes of cases. In the first place, to improve vision where the pupil is small, and to a great extent occluded, though the condition has not so far led to serious nutritive changes; and in the second place, with the object as well of preventing the complete destruction of vision which either the existing condition or the danger of recurrence of the inflammation has threatened. Iridectomy for iritis should be performed when the inflammation has entirely subsided. The portion of iris excised should be large. The operation is urgently called for where the condition of iris bombans exists.
Iris tumours, either simple or malignant, are of rare occurrence.
A frequent result of a severe blow on the eye is a separation of a portion of the iris from its peripheral attachment (iridodialysis). Of congenital anomalies the most commonly met with are coloboma and more or less persistence of the foetal pupillary membrane. The most serious form of irido-cyclitis is that which may follow penetrating wounds of the eye. Under certain
