Timolol lowers intraocular pressure but does not inhibit the development of experimental myopia in chick

Schmid, Katrina L., Abbott, Meredith, Humphries, Michelle, Pyne, Kylie, & Wildsoet, Christine F. (2000) Timolol lowers intraocular pressure but does not inhibit the development of experimental myopia in chick. Experimental Eye Research, 70(5), pp. 659-666.

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Reports of intraocular pressure (IOP) being higher in myopes than emmetropes and of myopes being over-represented in glaucoma statistics, are consistent with a role of IOP in the excessive eye growth typically associated with myopia. We tested the hypothesis, based on these observations, that ocular hypotensive drugs would slow myopia progression using the chick as an animal model and timolol as an example of such a drug. To induce myopia, chicks (n = 56) were fitted with either monocular translucent diffusers or -15 D spectacle lenses from day 8. The drug treatment protocol comprised topical applications of 0.4% benoxinate, a local anaesthetic (to improve drug absorption), followed either by 0.5% timolol or distilled water (control), either daily (1000 hr) or twice daily (1000, 1600 hr). Refractive errors and ocular dimensions were measured on days 12 and 17. We also verified the ocular hypotensive effect of timolol in both normal (n = 8) and myopic (n = 12 diffusers; n = 12-15 D lenses) chicks. Here, we took baseline IOP measurements, instilled timolol and then monitored IOP over a further 5-9 hr. We found no difference in the amount of myopia produced in the timolol and control groups at either measurement time point (e.g. day 17, once per day application, diffusers: -26.9 +/- 3.3 D vs -22.7 +/- 9.1 D; lenses: -14.9 +/- 3.8 D vs -14.9 +/- 3.6 D). This was in spite of the fact that timolol did lower IOP in both normal and myopic chicks (27 and 18% reduction, respectively) While timolol does have an ocular hypotensive effect in the chick, it does not inhibit the development of myopia in this animal model.

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12 citations in Web of Science®
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ID Code: 4192
Item Type: Journal Article
Refereed: Yes
Additional Information: For more information, please refer to the journal’s website (see link) or contact the author. Author contact details: schmid.k@qut.edu.au
Keywords: Antihypertensive Agents/, pharmacology, Intraocular Pressure/, drug effects, Myopia/, prevention & control, Timolol/, pharmacology, Analysis of Variance, Animals, Chickens, Disease Models, Animal, Male, Research Support, Non, U, S, Gov't, Time Factors, Treatment Failure
DOI: 10.1006/exer.2000.0834
ISSN: 0014-4835
Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300)
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Copyright Owner: Copyright 2000 Elsevier
Deposited On: 14 Jun 2006 00:00
Last Modified: 15 Jan 2009 07:04

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