Effects of mydriatics on intraocular pressure and pupil size in the normal feline eye.
OBJECTIVE
To determine the effect of various mydriatics (1% atropine, 1% cyclopentolate, 0.5% tropicamide, 10% phenylephrine) on intraocular pressure (IOP) and pupil size (PS) in normal cats.


METHODS
The mydriatics were tested in 10 adult ophthalmoscopically normal European Domestic Short-haired cats. Procedure Single-dose drug studies were divided into placebo (vehicle of phenylephrine), 10% phenylephrine, 0.5% tropicamide, 1% cyclopentolate and 1% atropine. After measurement of IOP and pupil size (PS) at 8 a.m. on the first day, one drop of the tested drug was applied to one randomly selected eye. The IOP and PS were measured for a minimum of 36 h until the pupil returned to pretest size.


RESULTS
Ten per cent phenylephrine had no significant effect on IOP, and the effect on the pupil size was minimal (<or= 1 mm difference). One per cent atropine showed a maximal mean difference of 4.3 mmHg +/- 4.1 mmHg in IOP compared to the untreated eye. These differences were statistically significant at 1, 3, 6, 12 and 16 h post-treatment. At 1, 1.5 and 2 h after unilateral application of 1% cyclopentolate, the IOP in the treated eye was significantly higher than the IOP in the untreated eye with a maximal mean difference of 4.1 mmHg +/- 4.5 mmHg. With 0.5% tropicamide, IOP of the treated eye was significantly higher than IOP of the untreated eye at 1 and 1.5 h after treatment with a maximal mean difference of 3.5 mmHg +/- 3.3 mmHg. One per cent atropine caused the greatest increase in IOP, followed by 1% cyclopentolate and 0.5% tropicamide. The dilating effect of atropine, cyclopentolate and tropicamide lasted longer than the effect on intraocular pressure.


CONCLUSIONS
The parasympatholytics 1% atropine, 1% cyclopentolate and 0.5% tropicamide caused a statistically significant elevation of IOP and produced mydriasis in the treated eye in normal cats, while the sympathomimetic 10% phenylephrine had no significant effect on IOP or pupil size.
Stadtbäumer
Katrin
K
Clinic for Surgery and Ophthalmology, Veterinärplatz 1, 1210 Vienna, Austria. katrinstadtbaeumer@hotmail.com
Frommlet
Florian
F
Nell
Barbara
B
D000287:Administration, Topical; D000818:Animals; D001285:Atropine / Q000008:administration & dosage / Q000494:pharmacology; D002415:Cats / Q000502:physiology*; D003519:Cyclopentolate / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D007429:Intraocular Pressure / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009184:Mydriatics / Q000008:administration & dosage / Q000494:pharmacology*; D009883:Ophthalmic Solutions; D010656:Phenylephrine / Q000008:administration & dosage / Q000494:pharmacology; D011680:Pupil / Q000187:drug effects* / Q000502:physiology; D014065:Tonometry, Ocular / Q000662:veterinary; D014331:Tropicamide / Q000008:administration & dosage / Q000494:pharmacology
D009184:Mydriatics; D009883:Ophthalmic Solutions; D010656:Phenylephrine; D001285:Atropine; D003519:Cyclopentolate; D014331:Tropicamide