Chemically-induced pupil contraction may soon emerge as an alternative treatment for patients with presbyopia, reports a new study in the September 2015 Eye & Contact Lens.1 The research accompanies other recent attempts to manage the age-related condition using topical drops.2 

External methods like pinhole spectacles and multifocal contact lenses are current treatments for presbyopia; however, these must be removed regularly. Patients can also opt for surgical options like intraocular lens implantation and refractive lens replacement, but face complex recovery processes with the potential for procedure failure or infection. 

In this study, researchers in Egypt investigated the use of a parasympathomimetic drug (carbachol) and an alpha agonist (brimonidine) in a double-masked, randomized placebo-controlled clinical trial involving 48 naturally emmetropic and presbyopic subjects. A treatment group (n=30 eyes) received a single dose of carbachol 2.25% plus brimonidine 0.2% eye drops, and a control group (n=18) received placebo drops. Pupil size at both near and distance visual acuities was evaluated before and after treatment at one-, two-, four-, eight- and 10-hour increments. 

Mean near visual acuity in patients older than 50 improved from J-7.68±1.62 pre-treatment to J-3±1.6 at one hour, J-3.4±1.4 at two hours, J-4±1.26 at four hours, J-4.75±1.09 at eight hours and J-5.6±1.3 at 10 hours. Mean pupil size decreased significantly from 4.77±0.47mm pre-treatment to 2.5±0.51mm at one hour, 2.8±0.7mm at two hours, 3.13±0.6mm at four hours, 3.48±0.36mm at eight hours and 3.881±0.35mm at 10 hours. 

No statistically significant difference was found in mean near visual acuity and pupil size between initial application and one month and three months later, as well as between patients older than 50 and those younger than 50. There were no serious adverse ocular effects reported from carbachol plus brimonidine application; however, one patient did experience a mild burning sensation, and another reported temporary visual difficulty in low light. 

The protocol “permits acceptable reading vision for many presbyopes, even in older subjects,” the researchers conclude. “Because of increased depth of focus from the smaller pupil, it does not blur distance vision or immediate vision as does typical monovision therapy, and the perception of normal brightness in the untreated eye eliminates symptoms of dimming from the smaller pupil of the treated eye.” 

1. Abdelkader A. Improved presbyopic vision with miotics. Eye & Contact Lens. Sept 2015;41(5):323-327.
2. Is a topical treatment for presbyopia on the horizon? Review of Cornea & Contact Lenses. Jun. 2014;5.