Contralateral effect of topical β-adrenergic antagonists in initial one-eyed trials in the Ocular Hypertension Treatment Study

Effects of brimonidine 0.2%-timolol 0.5% fixed-combination therapy for glaucoma

“…18 According to the previous literature, timolol can have a crossover effect that causes lowering of IOP by 1.5 mmHg in the untreated eye. [19][20][21] In our fi rst study, the diurnal IOP at baseline and at 6 months after treatment was not signifi cantly different in the untreated fellow eye, but trough IOP and mean IOP showed a tendency to decrease (Table 4). Therefore, we speculate that timolol had a crossover effect.…”

“…22 Notwithstanding the possibility that we underestimated the diurnal variation of IOP, the comparison between the instilled eye and the untreated fellow eye under the same conditions may be meaningful, given the diurnal variation of IOP. [19][20][21][22] In our third study, we confi rmed that brimonidine/ timolol fi xed-combination therapy had signifi cant effects on pupil size but observed no signifi cant changes in corneal curvature or ACD. Timolol causes beta-adrenergic inhibition or alpha-adrenergic activation of the iris sphincter muscle.…”

Pressure Lowering Medications

“…Prostaglandin analogue is slightly but not significantly better than timolol in pressure-lowering effectiveness. Similar reduction of pressure by timolol was also reported in the contralateral, untreated eye (Dunham et al, 1994;Piltz et al, 2000). Absorption of timolol by the nasopharyngeal mucosa has raised concerns of potentially life-threatening side effects following topical administration (Passo et al, 1984;Diggory and Franks, 1997).…”

Clinical implications of pharmacogenetics for glaucoma therapeutics

“…8 Also of interest was the OHTS finding that African Americans who were treated with calcium-channel blockers did not respond as well as Caucasians in the beta blocker treated eye. 17 An explanation for this statistical observation is not clear, but the use of a systemic medication would be considered an 'environmental variable' that can impact the effectiveness of a drug. Neither of these aforementioned studies reported on an analysis based on iris color, regardless of race, to test whether iris pigmentation and possible nonspecific binding of the drug may be a factor in the response analysis.…”

“…Such a distribution in response is clearly evident in aqueous humor flow in normal subjects 21 and in the IOP response of the contralateral eye to topical beta blockers in patients enrolled in OHTS. 17 Given these response distributions for aqueous humor flow and IOP response to topical beta blockers, it is reasonable to hypothesize that SNPs in candidate genes contribute to these ocular response variations.…”