Relationship between visual field severity and response to fixed combination dorzolamide/timolol or timolol alone.

Purpose: To examine the response to intraocular pressure (IOP)-lowering medications as a function of glaucoma severity represented by visual field defects.

Methods: Post hoc analysis of a multicenter, double-masked, parallel study comparing the 24-h efficacy of the dorzolamide/timolol fixed combination (N = 117) versus timolol alone (N = 115) in patients with open-angle glaucoma or ocular hypertension. Visual field scoring was performed independently by three glaucoma specialists. Two scoring systems were used: the Advanced Glaucoma Intervention Study (AGIS) scoring system and a classical visual field scoring system. Patients were divided into three groups based on their visual field scores. The changes from baseline daytime and nighttime mean IOP, and 24-h IOP fluctuation after 8 weeks of treatment by baseline glaucoma severity, were compared across treatments using a simple linear regression analysis.

Results: Most (approximately 73%) patients had no visual field damage at baseline. With either dorzolamide/timolol or timolol alone, there was no significant difference in IOP response from baseline over 24 h based on the level of visual field damage, as measured by either the AGIS or the classic visual field scoring systems. The Pearson's rho correlations between the baseline AGIS score and the change in daytime IOP, nighttime IOP, and 24-h IOP range were 0.0024 (P = 0.97), -0.086 (P = 0.21), and 0.076 (P = 0.26), respectively. Correlations by classic score were 0.024 (P = 0.72), -0.074 (P = 0.28), and 0.061 (P = 0.37), respectively.

Conclusions: This analysis showed no significant relation between the severity of baseline visual field defects and the ocular hypotensive efficacy of the dorzolamide/timolol fixed combination and timolol alone.