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Abstract #6093 Published in IGR 2-2
Timolol lowers intraocular pressure but does not inhibit the development of experimental myopia in chick
Schmid KL; Abbott M; Humphries M; Pyne K; Wildsoet CFExperimental Eye Research 2000; 70: 659-666
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. The authors 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 hours). Refractive errors and ocular dimensions were measured on days 12 and 17. The authors 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, they took baseline IOP measurements, instilled timolol and then monitored IOP over a further five to nine hours. They 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 versus -22.7 ± 9.1 D; lenses: -14.9 ± 3.8 D versus -14.9 ± 3.6 D). This was despite 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.
Dr. K.L. Schmid, Centre for Eye Research, School of Optometry, Queensland University of Technology, Brisbane, Australia. k.schmid@qut.edu.au
Classification:
8.1 Myopia (Part of: 8 Refractive errors in relation to glaucoma)
11.3.4 Betablocker (Part of: 11 Medical treatment > 11.3 Adrenergic drugs)
