Alphagan (brimonidine 0.1%, 0.15% and 0.2%, Allergan) has been used for diminishing or eliminating large pupil size related to night vision problems following refractive surgery. One study showed that Alphagan significantly decreased pupil size under nighttime conditions but not under daytime conditions. Many doctors tell patients to instill one drop 30 minutes before an anticipated need, such as night driving. The effect may last 6-8 hours.
In a study, patients instilled one drop of Alphagan in their eyes. Pupil measurements were taken at 30 minutes, and at four and six hours under different illuminations. Researchers compared these measurements with those of the patients baseline without the use of Alphagan.
Unlike the other drug pilocarpine which had been used for nighttime glare in the past and has many side effects, Alphagan maintains a normal pupil in bright and average room illumination. The drug also showed a significant decrease in pupil dilation in dark illumination at precisely when it is needed.
Data show an average decrease in pupil size of 2mm in dim light after Alphagan use. The effect occurs through stimulation of the alpha2 receptor that operates the gain-control feedback mechanism of the pupil dilator. This causes hyperpolarization and inhibits further norepinephrine release. Alphagan does not affect the parasympathetic pathway as pilocarpine does. So, Alphagan does not affect the ciliary muscle and will not induce brow ache or over-focusing.
It should be noted that using Alphagan for nighttime glare is off-label and that insurance will not pay for its use. Generic Alphagan (Brimonidine) can be obtained with an Rx and a coupon for about $12.00 per bottle.