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V. Sarup, G. McEwan, K. Patil, J.M. Castellano, S.C. Sharma; Effect of Cosopt and Trusopt on Retinal Ganglion Cell survival in Hypertensive eyes of Adult Rats. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2117.
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Purpose: Chronic elevated intraocular pressure (IOP) leads to Retinal Ganglion cell (RGC) death in adult rat retina. Cosopt [Dorzolamide 2% and Timolol 0.5%] and Trusopt [Dorzolamide2%] are drugs used to treat hypertensive eyes. In the present experiments, the effect of these two drugs was studied on RGC survival in hypertensive eyes of adult rats. Methods: IOP was elevated in the right eye of Adult female Wistar rats by episcleral venous occlusion method. Intraocular pressure was regularly monitored. Cosopt or Trusopt was applied twice daily in the experimental eye. In Group A, drug application began two weeks before surgery. In Group B, drug application began on the day of surgery. In Group C, drug application started two weeks after surgery and in Group D drug application started four weeks after surgery. RGCs were labeled five days before sacrifice with 5% Fluorogold. Animals were sacrificed one, two and three months after starting the drug and RGCs were counted in each group (n=5) to evaluate the effect of each drug. Results: Application of Cosopt and Trusopt increased the survival rate of RGCs when compared to the experimental untreated eyes. Cosopt was more effective than Trusopt at all the time points studied. RGC survival in Cosopt series was highest in Group A (96.4% at 1month) as compared to Group D (80% at 2 months). RGC survival in Trusopt series was highest in Group A (92.3% at 1month) as compared to Group D (77.5% at 2months). IOP of experimental eyes reduced by 1.5–2.5 mmHg in all groups studied. The percentage of RGC survival was however not directly related to the drop in IOP. Conclusions: Cosopt and Trusopt increased the survival rate of RGCs in hypertensive eyes consistently. Although the drugs reduced relatively little IOP in experimental eyes, the beneficial effect observed on RGC survival was more in relation to the reduction in IOP. The beneficial effect on RGC survival is perhaps due to the neuroprotective effect of these drugs. Future studies will be directed to evaluate the mechanism sub serving neuroprotection using these drugs. Supported in part by a Grant from Merck & Co., Inc.
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