Page 1207 - Problem-Based Feline Medicine

58 – THE CAT WITH A RED COLORATION OF THE GLOBE 1199

Affected eyes are hypotonic (low intra-ocular pres- Clinical signs
sure – below 100 mmHg), because inflammation in
Glaucoma causes deep episcleral vessel injection.
the ciliary body reduces aqueous humor production.
Deep vessels are usually straighter and larger, do not
move when the overlying bulbar conjunctiva is moved,
Diagnosis and do not blanch with the topical application of 1:1000
epinephrine. The signs of glaucoma are more subtle in
Diagnosis is based on clinical signs. Congested, red
cats than in dogs.
conjunctiva with a cloudy anterior chamber, miotic
pupil, and very soft eye are almost pathognomonic for The intra-ocular pressure (IOP) is high. In most cats
uveitis. with signs of glaucoma the IOP will be above 30
mmHg (normal 10–25 mmHg).
All cases should have a thorough clinical examination,
and a minimum data base obtained through laboratory An enlarged globe (buphthalmos) may or may not be
tests. present, depending on the chronicity of the increased
IOP.
Common causes of uveitis which need to be ruled out
based on diagnostic tests are FIV, FeLV, FIP, crypto- The pupil will be dilated or semi-dilated, with either
coccosis, other fungal infections and toxoplasmosis. absent or poor pupillary light reflexes. The increased
IOP causes paralysis of the iris sphincter muscle, reti-
Candida albicans is a rare cause of uveitis in cats.
nal damage, and often blindness within days.
Ocular lesions consist of conjunctival hyperemia and
chemosis, fibrin and flocculent material in all ocular The cornea may be slightly cloudy because of pres-
chambers, and small nodular lesions in the fundus. On sure changes in the endothelium. The cloudiness may
histological examination, organisms are evident that have a mottled appearance.
are free and phagocytized in the vitreal and retinal
Signs of chronic anterior uveitis may be present,
exudates.
especially abnormalities in the appearance of the iris
Any problem causing a bacteremia may cause uveitis. surface including pinkish discoloration associated
with fibrovascular membranes, or grayish discoloration
Many cases of uveitis are idiopathic, and no obvious
of the iris surface with iris melanoma.
cause is found.
Signs of lens instability may be present including:
● Aphakic crescent (crescent shape produced by the
GLAUCOMA* clear space between the edge of the displaced lens
and the adjacent pupillary margin).
Classical signs ● Anterior or posterior luxation (dislocation).
● Iridonesis (wobbling of the iris).
● Red eye caused by deep episceral vessel
injection. Signs of intra-ocular neoplasia are occasionally pres-
● Increased IOP above 25 mmHg. ent, seen as a change in the shape, thickness, color
● ± Enlarged globe (buphthalmos). and/or contour of the iris. Diffuse black irises may be
● Cornea may be cloudy. seen in older cats with melanosis and iris melanoma.
● Pupil mid-dilated to dilated and poorly
responsive to light. Diagnosis
● ± Signs of chronic uveitis (changes in the
Initial diagnosis is based on the appearance of buph-
appearance of the iris surface).
thalmos with any or all of the other related signs of
● ± Uveal neoplasia (change in iris color,
glaucoma, chronic anterior uveitis and lens instability.
size, shape and/or thickness).
● ± Lens instability or dislocation. Measurement of intra-ocular pressure (IOP) with
tonometry. Normal range for IOP in the cat is 10–25
See the main reference on page 1312 for details (The mmHg. Readings over 30 mmHg are supportive of
Cat With Abnormal Globe Position or Size). a diagnosis of glaucoma.