Page 1324 - Problem-Based Feline Medicine

1316 PART 15 CAT WITH EYE PROBLEMS

in pupil shape. Pigment deposition on the anterior ally obviously smaller than the opposite side, but the
capsule may be seen. cornea does not have a significantly smaller radius of
● Pupillary membranes, which are membranous curvature than the scleral coat. In contrast, a pthisical
structures spanning the pupil space. Immobility of globe will usually have an obviously smaller corneal
the pupil often results. radius of curvature than the scleral coat, causing the
appearance of a bulging cornea.
Diagnosis
There is unusual coverage of the globe by the nictitat-
Diagnosis is based on the appearance of a small ing membrane because of the small globe size.
globe with low intra-ocular pressure and signs of
Other ocular abnormalities are sometimes present,
previous inflammation.
for example:
Tonometry will usually reveal unusually low intraocu- ● Persistent pupillary membranes (PPM), which are
lar pressure (usually < 10 mmHg). small strands of tissue arising from the iris sur-
face. They connect either to other points on the
iris surface, the posterior surface of the cornea
MICROPHTHALMOS
where they form gray focal opacities, or the ante-
rior lens capsule. Persistent pupillary membranes
Classical signs
are unassociated with other signs of intra-ocular
● Small globe unassociated with signs of inflammation.
previous inflammation. ● Congenital cataract resulting in opacity of the lens.
● ± Other ocular abnormalities such as Congenital cataracts are more likely to be nuclear in
congenital cataract or persistent pupillary location, with the surrounding cortex clear.
membranes.
● Rare in cats.
Diagnosis
Diagnosis is based on the clinical signs of a small, but
Clinical signs
relatively normal looking eye.
Rare in cats.
If intra-ocular pressure can be measured, is usually nor-
The globe is small, and there is no history or signs of mal (15–25 mmHg). In contrast, pressure is usually low
previous inflammation. The corneal diameter is usu- in a pthisical globe.

RECOMMENDED READING
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Gilger BC, Hamilton HL, Wilkie DA, et al. Traumatic ocular proptoses in dogs and cats: 84 cases (1980–1993).
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Glaze MB, Gelatt KN. Feline ophthalmology. In: Gelatt KN (ed) Veterinary Ophthalmology, 3rd edn. Baltimore,
Maryland, Lippincott, Williams & Wilkins, 1999, pages 998–999.
Hampson ECGM, Smith RIE Bernays ME. Primary glaucoma in Burmese cats. Aust Vet J Nov 2002; 80(11):
672–680.
Ramsay DT, Marretta SM, Hamor RE, et al. Ophthalmic manifestations and complications of dental disease in dogs
and cats. J Am Anim Hosp Assoc 1996; 32: 215.