CORNEAL STAPHYLOMA.
Bulging corneal scar with adherent iris: from perforation, escape of aqueous, intraocular pressure, vascularization of cornea. Diagnosis by central cicatrix, vascularisation, pigmentation. Oblique illumination. Treatment: iridectomy, eserine. Suture. Enucleation.
This is a bulging forward of a corneal scar with the iris adherent to its internal surface. It may originate in perforation of the cornea and escape of the aqueous humor, or in intraocular pressure that advances the iris until it comes in contact with the cornea, which becoming adherent and receiving an abnormally large supply of blood or plasma, softens and bulges outward. It may grow out to a great length in some cases, Eck has seen it two inches in the horse, and somewhat smaller in an ox. May records a case affecting both eyes in the dog.
Diagnosis is not usually difficult. The scar in the midst of a granulating projection of the cornea is nearly conclusive, but the recognition of pigmentation of the growth and the adherent iris often revealed by oblique illumination will nearly always show the true nature of the case.
Treatment is by iridectomy and eserin if the disease can be recognized in its earliest stages, but it is rarely satisfactory. Later the choice may be between excision of the staphyloma and coaptation of the edges of the wound by suture, and the enucleation and removal of the eyeball. The last resort is preferable to the continued irritation of the staphyloma by the lids and cilia under the ocular movements.
ECTASIA CORNEÆ. KERATOCONUS. CONICAL CORNEA.
This consists in a thinning and protrusion of the cornea in the form of a blunt cone, without loss of transparency. It has accordingly been called staphyloma pellucida. There is a gradual attenuation and distension of the corneal tissue from some unknown cause. It has been seen mainly in the young and is manifestly due to a trophic defect. Stockfleth records a case in a foal and Bayer in a cow. No satisfactory treatment has been proposed, but as the trouble usually comes to a standstill without perforation, it can be left to take its course. With rapid increase and manifest tension antiseptic puncture of the cornea or even iridectomy might be tried.
KERATOGLOBUS.
This is a variety of ectasia in which the clear, pellucid, protruding cornea is more globular and less conical in outline. It is seen especially with enlargement of the entire eyeball (buphthalmus).