GHT, OR AMAUROSIS.

_Causes._--The causes of this affection are tumors or other disease of
the brain implicating the roots of the optic nerve, injury to the nerve
between the brain and eye, and inflammation of the optic nerve within
the eye (retina), or undue pressure on the same from dropsical or
inflammatory effusion. It may also occur from overloaded stomach, from a
profuse bleeding, and even from the pressure of the gravid womb in
gestation.

_Symptoms._--The symptoms are wide dilatation of the pupils, so as to
expose fully the interior of the globe, the expansion remaining the
same in light and darkness. Ordinary eyes when brought to the light have
the pupils suddenly contract and then dilate and contract alternately
until they adapt themselves to the light. The horse does not swerve when
a feint to strike is made unless the hand causes a current of air. The
ears are held erect, turn quickly toward any noise, and the horse steps
high to avoid stumbling over objects which it can not see.

_Treatment_ is only useful when the disease is symptomatic of some
removable cause, like congested brain, overloaded stomach, or gravid
womb. When recovery does not follow the termination of these conditions,
apply a blister behind the ear and give one-half dram doses of nux
vomica daily.

TUMORS OF THE EYEBALL.

A variety of tumors attack the eyeball--dermoid, papillary, fatty,
cystic, and melanotic--but perhaps the most frequent in the horse is
encephaloid cancer. This may grow in or on the globe, the haw, the
eyelid, or the bones of the orbit, and can be remedied, if at all, only
by early and thorough excision. It may be distinguished from the less
dangerous tumors by its softness, friability, and great vascularity,
bleeding on the slightest touch, as well as by its anatomical structure.

STAPHYLOMA.

This consists in a bulging forward of the cornea at a given point by the
sacculate yielding and distention of its coats, and it may be either
transparent or opaque and vascular. In the last form the iris has become
adherent to the back of the cornea, and the whole structure is filled
with blood vessels. In the first form the bulging cornea is attenuated;
in the last it may be thickened. The best treatment is by excision of a
portion of the rise so as to relieve the intraocular pressure.

PARASITES IN THE EYE.

Acari in the eye have been incidentally alluded to under inflammation of
the lids.

_Filaria palpebralis