Topically administered timolol and dorzolamide reduce intraocular pressure and protect retinal ganglion cells in a rat experimental glaucoma model.
OBJECTIVE
This study sought to elucidate the effects of timolol and dorzolamide on intraocular pressure (IOP) and retinal ganglion cell (RGC) death in an experimental model of glaucoma in rat.


METHODS
Mild elevation of IOP was induced in rats by intracameral injection of India ink and subsequent laser trabecular photocoagulation. IOP was measured before the surgical procedures and weekly thereafter. Timolol (0.5%), timolol XE (0.5%), dorzolamide (1%), and artificial tears (vehicle) were topically applied daily. Retinal sections were prepared for histology to determine RGC number.


RESULTS
Timolol, timolol XE, and dorzolamide induced a significant reduction in IOP (p<0.05) and counteracted the reduction in RGC number that occurred in vehicle treated glaucomatous eyes (p<0.05). The coefficient of correlation between RGC number and IOP was significant in the dorzolamide treated group (r = -0.908, p<0.005), but not in other groups (p>0.05).


CONCLUSIONS
Both timolol formulation and dorzolamide reduced IOP and protected RGCs in a rat model of experimental glaucoma. It cannot be ruled out that timolol might protect RGCs by additional mechanisms other than simply lowering of IOP.
Seki
M
M
Division of Ophthalmology and Visual Science, Graduated School of Medical and Dental Sciences, Niigata University, 1-757 Asahimachi, Niigata, Niigata 951-8585, Japan.
Tanaka
T
T
Matsuda
H
H
Togano
T
T
Hashimoto
K
K
Ueda
J
J
Fukuchi
T
T
Abe
H
H
D000818:Animals; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D002452:Cell Count; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection; D004195:Disease Models, Animal; D005901:Glaucoma / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D009883:Ophthalmic Solutions; D051381:Rats; D017208:Rats, Wistar; D012165:Retinal Ganglion Cells / Q000187:drug effects* / Q000473:pathology; D013449:Sulfonamides / Q000627:therapeutic use*; D013876:Thiophenes / Q000627:therapeutic use*; D013999:Timolol / Q000627:therapeutic use*
D000959:Antihypertensive Agents; D009883:Ophthalmic Solutions; D013449:Sulfonamides; D013876:Thiophenes; D013999:Timolol; C062765:dorzolamide