Of the lagophthalmus.
Sometimes from this operation, when too much of the skin is cut away, it happens, that the eye cannot be covered. And this sometimes proceeds from another cause. The Greeks call the disorder lagophthalmos[ HB ]. When too much of the eye-lid is wanting, there is no remedy for it; if but a small part, it may be cured. An arched incision must be made in the skin a little below the eye-brow, with its horns pointing downward. The wound ought to go as deep as the cartilage, but without injuring it: for if that be cut, the eye-lid falls down, and cannot afterwards be raised. Let the skin then be only divided, so as to allow it to descend a little in the lower part of the eye; which will be the consequence of the wound’s gaping above. Let lint be put into it to prevent the union of the divided skin, and to generate a little flesh in the middle: and when this has filled up the part, the eye is afterwards properly covered by the eye-lid.
Of an ectropium.
As it is a disorder of the upper eye-lid not to descend far enough to cover the eye, so there is a disease of the lower, in which it is not raised high enough, but hangs down, and cannot be brought close to the other. And this also sometimes proceeds from a similar fault in the cure, sometimes even from old age. The Greeks call it ectropium[ HC ]. If it happens from a faulty cure, the treatment is the same as in the foregoing case: only the horns of the wound are turned towards the cheeks, and not to the eye. If it proceed from old age, the whole of it must be cauterized externally with a thin plate of iron; then anointed with honey; and from the fourth day fomented with hot water, and anointed with medicines to bring on a cicatrix.
Of the staphyloma.
These then are the general disorders, that commonly occur in the parts about the eye, the angles, and eye-lids. In the eye itself the external coat is sometimes raised, either from the rupture or relaxation of some of the internal membranes; and it resembles a raisin stone in its form, whence the Greeks call it a staphyloma[ HD ]. There are two methods of cure for it. One is to pass through the middle, at the root of it, a needle with a double thread; then to tie tight the ends of one of the threads above, and of the other below; which by cutting it gradually may bring it off. The other is, to cut out from its surface about the bigness of a lentil; then to rub in spodium or cadmia. When either of these is done, the white of an egg must be spread upon wool and applied; and afterwards the eye must be fomented with the steam of hot water, and anointed with mild medicines.
Of clavi.
Callous tubercles in the white of the eye are called clavi; which name is given them from their figure. The best method is to pierce them at their very roots with a needle; and below that to cut them off, and then to anoint with mild medicines.
Description of the eye.
I have already elsewhere mentioned a cataract, because when recent, it is often removed by medicines. But when it is of long standing, it requires a manual operation, and one, which may be reckoned amongst the nicest. Before I treat of this, I shall give a short account of the nature of the eye; the knowledge of which, as it is of importance in several other parts, so it is peculiarly necessary here. The eye then has two external coats; the exterior of which by the Greeks is called ceratoides[ HE ]; and this, where it is white, is pretty thick, but before the pupil is thinner. The interior coat is joined to this, in the middle where the pupil is, and is concave, with a small aperture; round the pupil it is thin, but at a distance from it, something thicker; and by the Greeks is called chorioides[ HF ]. As these two coats surround the internal part of the eye, they again join behind it, and becoming finer, and uniting together, pass through the opening, which is between the bones, to the membrane of the brain, and are fixed to it. Under these, in the part where the pupil is, there is a void space; then again below, is an exceeding fine coat, which Herophilus called arachnoides[ HG ], the middle part of which subsides, and in that cavity is contained somewhat, which from its resemblance to glass the Greeks call hyaloides[ HH ]. This is neither liquid, nor dry; but seems to be a concreted humour; from the colour of which, that of the pupil is either black, or grey, though the external coat be white. This is inclosed by a small membrane, which proceeds from the internal part of the eye. Under these is a drop of humour resembling the white of an egg, from which proceeds the faculty of vision. By the Greeks it is called chrystalloides.