Page 1222 - Problem-Based Feline Medicine

1214 PART 15 CAT WITH EYE PROBLEMS

● Cytology may reveal small basophylic inclusion ● Trifluorothymidine (Viroptic, Glaxo Wellcome)
bodies at the level of the basement membrane. has the best in vitro effect of all available topical
● The organism can be readily cultured. agents. Use q 6–8 h.
● Acyclovir (Zovirax ophthalmic ointment, Glaxo-
Neoplasia.
SmithKline) may be the only commercially available
● Squamous cell carcinoma, particularly of the lower
drug in some countries. The efficacy against FHV-1
lid in depigmented eyelids, may present with
has been reported as poor. Use q 6–8 h.
swollen red eyelids and a mucopurulent discharge.
● Dilute povidine iodine (diluted 50% in saline) has
● Cytology or fine-needle biopsy will confirm this
been used, but there is only anecdotal evidence of
condition.
its efficacy in clinical situations, and at this strength
● Lesions are frequently ulcerated.
can be very irritating to eyes.
Bacterial conjunctivitis.
Oral antiviral agents include:
● Not common as a primary ocular disease, but is
● Acyclovir (Zovirax) appears very effective, even at
seen secondary to viral infection.
doses far below the in vitro ED . The usual dose is
● The inflammation is less intense than the acute 50
50 mg/kg q 6–12 h, but watch for toxic signs of bone
herpesvirus presentation, but in chronic herpesvirus
marrow suppression even at this dose. Often used in
cases, bacterial infection is frequently misdiagnosed
conjunction with oral α interferon, and the resulting
as the cause of conjunctivitis and ocular discharge.
synergism significantly reduces ED of acyclovir.
● Bacterial conjunctivitis causes a mucopurulent dis- 50
● Valacyclovir (Valtrex, GlaxoSmithKline) is an acy-
charge.
clovir prodrug but rapid absorption of this drug in
Hemorrhage. cats appears to make it more readily able to cause
● Hemorrhage may be seen as a diffuse or focal area toxicity, especially in sick, acutely infected cats.
of redness, but there is usually little hyperemia or ● Interferon α: α interferon is a cytokine produced nat-
no inflammation. urally by leukocytes. It may prevent spread if given in
● It is not common to have an ocular discharge with the very early stages of infection in acutely infected
conjunctival hemorrhage. cats. There are no specific dosage recommendations
but commonly used dosage is 30 IU daily. This dose
is made up in 1ml syringes and frozen. Each day, one
Treatment
syringe is thawed and two drops placed topically in
Topical and probably systemic corticosteroids are the eye, the remainder given orally for absorption
contraindicated in all cases of ocular herpesvirus across oronasal mucus membranes. The dose is com-
infections. The effect of topical NSAIDs has produced monly given for 7 days on 7 days off.
equivocal results experimentally.
Other therapies that are used include:
A variety of topical ocular antiviral agents are ● Oral lysine: Lysine has been used in human medi-
available. However, not all treatments are commercially cine to suppress clinical signs of herpes simplex
available worldwide. infections. Lysine competes with arginine for incor-
● Idoxuridine inhibits DNA synthesis by competing poration in the viral genome. Arginine is necessary
with thymidine for incorporation into viral DNA. It for the replication of the FHV-1 virus, and incorpo-
is no longer in production, but has been the most ration of lysine produces a non-infective virus par-
commonly used topical agent for treating FHV-1 ticle. It may be more effective in cats with corneal
infection. Check with your “compounding phar- disease than those with conjunctivitis alone. The
macist”, as topical drops are frequently made to recommended dose is 250 mg daily.
order. Idoxuridine 0.1% drops most commonly ● Topical and/or systemic tetracycline antibacteri-
used, and produce excellent results. Drops need to als are commonly used because of their specific
be used at least three to four times daily. effect on Chlamydophila felis and Mycoplasma
● Vidarabine (adenine arabinoside. Vira-A, Parke- organisms, which may be present together with her-
Davis) interferes with DNA polymerase and may be pesvirus infections.
effective in cases that are resistant to idoxuridine. – Tetracyclines have a mild anti-inflammatory
Use q 6–8 h. effect on ocular tissue. They suppress antibody