Foreign bodies within the Eyeball are unfortunately very common among workers in coal, iron, steel, &c. Striking with sufficient force, the chip of steel, &c., pierces the coats of the eyeball and passes to the inside. The piece may lodge in the iris, from which it may some times be removed with the wounded part of the iris by the operation of iridectomy (p. 481). If it lodge in the lens this body speedily loses its transparency, and may be removed with the foreign body by the operation for cataract. It may lodge in the back chamber among the vitreous humour, or in other situations from which it cannot he removed. Sometimes it may be seen by means of the ophthalmoscope and removed by a magnet. In many cases the person is not sure whether the foreign body that struck him passed in or simply wounded the eye in flying past. In such cases, if press ing over the eyelids in one particular spot produces a sudden sharp pain, the probability is the body is within the ball. Inflammation arises, severe pain is felt, the sight grows dim, &c. The danger is of sympathetic ophthalmia arising. This is inflammation occurring in the sound eye through nervous communication with the injured one. It is extremely serious. if the slightest sign of it inise, the injured eye should lie removed without delay, even though it be yet a seeing eye, in order to save its fellow.
Rolling Eyeballs ( Ng stag nuts).- -This is a continuous rolling movement of the eyeballs, which are constantly shifting about. It is seen in children the cornea; of whose eyes have lost all their transparency owing to inflammation, and perhaps is due to their seeing the light and continually endeavouring to gain clearer vision. Various other diseases of the eyes affecting vision produce it. Among miners cases of it arise by no means seldom. In them it appears to be induced by long-continued work under ground in the dim obscurity of a flickering lamp. It gradually becomes associated with nervous disease of the eyeball. Little can be done for it. But a young lad who has already worked some years underground, and shows signs of it, should at once be persuaded to change his occupation and take to something above-ground in the ordinary light.
Squint (Cross- Eyes — Strabimus) has been mentioned on p. 455. It is usually due to one muscle having a greater pull than another, so that the balance between them is lost. It may, however, result from paralysis of one muscle, by a blow, for example, the opposite muscle thereby gaining the advantage. There are several kinds of squint, the two chief being inward or convergent, and outward or diver gent. It has been shown that inward squint, in a large majority of cases, is dependent on long-sightedness, and outward squint on short sightedness. • Outward squint, however, is not so common as the other variety. Of convergent or inward squint Stcllwag, one of the greatest of authorities on eye affections, says it "is frequently developed at a very early age in children, whose attention is often and contitm ally attracted to small objects situated near the eyes, to whom picture-books and similar playthings are offered for amusement, which demand clear and distinct vision at short distances. As a rule, however, inward squint
first makes its appearance at the commence ment period when children go to school, when children are compelled for hours to read, write, and engage in similar occupations. . . .
"Everything that increases the necessity for focussing also increases the tendency to squint. In so far insufficient illumination, dark rooms, bad care of the child during the occupation, &c., may favour an occurrence of the strabismus." Now when squint exists, whether in one eye or both, the two eyes cease to act in harmony, and one of the chief benefits of seeing with two eyes--binocular vision (p. 458)—no longer exists. Moreover, supposing one eye only to squint, it invariably happens that the sight of that eye is largely discounted, is disregarded. Were that not so, seeing that the two eyes do not agree, objects would appear double, but by disregarding the sight of the squinting eye single vision is retained. The result of con tinued disregard, however, is that the squint ing eye loses its sharpness of sight, its vision becomes blunted. Anyone may learn this for himself by causing a person with a squinting eye to look at an object first with one eye and then with the other, and he will find how dialled the squinting eye has become.
The treatment for squint is twofold. In the first place, with children the causes leading to squinting must be done away with. They should ea be required to look loug at objects so small as to require much focussing of the eyes; their reading, writing, &c., should he taught in well-lighted rooms. If the child is quite young when the tendency shows itself it will be well to cease instruction of such kinds, of knitting, &c., for a time. When the child is old enough, glasses to correct the long sight should be obtained. It is also a good thing, when there is but one squinting eye, to have the sound eye closed up by means of a bandage for fifteen minutes several times each day, in order to compel the use of the erring one. Of course such procedure is useless unless the other steps already described have been taken. Should these measures fail, an eye surgeon would probably propose an operation. It con sists in cutting the muscle of the side to which the eye is pulled. It is a simple operation, not requiring chloroform in grown-up persons. It is desirable to do it early, if it is certain other measures fail, before the eye has been blunted from disuse. The muscle is, by the operation, detached from its position. It slips backwards for a little distance, and in course of time attaches itself to a new part of the eyeball. In effect the muscle is lengthened, so that it no longer has the pull over its fellow on the opposite side. Even when this has been done, providing spectacles to correct any long or short sight that may be present ought not to be neglected. In grown-up persons its main benefit is the correction of an unpleasant feature. To girls this is always of moment.