GLAUCOMA DROPS CONTROL INTRAOCULAR-PRESSURE AND PROTECT OPTIC NERVES IN A RAT MODEL OF GLAUCOMA

PURPOSE. To determine whether chronic topical glaucoma therapy can con trol intraocular pressure (IOP) and protect nerve fibers in a rat mode l of pressure-induced optic nerve damage. METHODS. Sixteen adult Brown Norway rats were administered unilateral episcleral vein injections o f hypertonic saline to produce scarring of the aqueous humor outflow p athways. Twice daily applications of either artificial tears (n = 6), 0.5% betaxolol (n = 5), or 0.5% apraclonidine (n = 5) were delivered t o both eyes, and awake pressures were monitored with a TonoPen XL tono meter for 17 days before the rats were killed. RESULTS. For animals ad ministered artificial tears, the mean IOP of the experimental eyes was 39 +/- 2 mm Hg compared with 29 +/- 1 mm Hg for the control eyes. Thi s difference was statistically significant (P < 0.001). Mean IOPs in t he experimental eyes of animals administered betaxolol and apraclonidi ne were 29 +/- 7 and 29 +/- 4 mm Hg, respectively, whereas the mean IO P in the control eyes was 28 +/- 1 mm Hg for both groups. There was no statistically significant difference among these values. The mean IOP for the experimental eyes in the betaxolol and apraclonidine groups w as lower than that in animals administered artificial tears (P = 0.003 ). Quantitative histologic analysis of optic nerve damage in experimen tal eyes showed that four of the six animals administered artificial t ears had damage involving 100% of the neural area. This degree of dama ge appeared in only 3 of 10 animals administered glaucoma therapy. Opt ic nerve protection was closely correlated with IOP history because da mage was limited to less than 10% of the cross-sectional area in all a nimals in which the maximal IOP was less than or equal to 39 mm Hg, mo re than 2 SD below the mean value for eyes administered artificial tea rs. CONCLUSIONS. Topical glaucoma therapy in this model can prevent IO P elevation and protect optic nerve fibers.