Pe. Miller et Dl. Panciera, EFFECTS OF EXPERIMENTALLY-INDUCED HYPOTHYROIDISM ON THE EYE AND OCULAR ADNEXA OF DOGS, American journal of veterinary research, 55(5), 1994, pp. 692-697
Schirmer tear test (STT), intraocular pressure (IOD) measurement, slit
-lamp biomicroscopy, and indirect ophthalmoscopy were performed on 8 d
ogs with I-131-induced hypothyroidism and 4 euthyroid control dogs at
weeks 0, 9, 13, 17, immediately prior to treatment with levothyroxine,
after 5 weeks of levothyroxine administration (0.022 mg/kg of body we
ight, PO, q 12 h), and at euthanasia 7 weeks after discontinuation of
replacement therapy. Although the control group had higher baseline ST
T values than the hypothyroid group after randomization of dogs into t
he 2 groups (P < 0.01), STT values remained unchanged from their respe
ctive baseline values at all time intervals for both groups. Hypothyro
id and control dogs had significant (P < 0.05) reduction in IOP from b
aseline values at all subsequent time points, but differences were not
observed when hypothroid dogs were compared with controls. Goblet cel
l indices determined from biopsy samples of the inferior-nasal conjunc
tival fornix obtained before induction of hypothyroidism (baseline), i
mmediately prior to and at conclusion of levothyroxine therapy, and at
euthanasia were not significantly different when values for hypothyro
id dogs were compared with their own baseline values or with values fo
r control dogs. Histologic examination of the globes and adnexa at eut
hanasia also failed to indicate consistent qualitative differences bet
ween hypothyroid and control dogs. Marked reduction in serum thyroid h
ormone concentrations had little effect on the eye and ocular adnexa o
ver the course of the study.