Drops may be practical for pupil management after refractive surgery

Topical phentolamine mesylate may be an effective nonsurgical solution.

Issue: August 2011

Marguerite B. McDonald

Patients who are unhappy with their vision in low-light conditions after having cataract or LASIK procedures may be able to turn to an eye drop instead of additional surgery.

Marguerite B. McDonald, MD, FACS, a Refractive Surgery Board Member of Primary Care Optometry News sister publication, Ocular Surgery News, is the principal investigator of studies evaluating the use of topical phentolamine mesylate (Ocularis Pharma) and Varilux Physio Enhanced spectacle lenses (Essilor of America) for postsurgical pupil management.

Phentolamine mesylate

Pilocarpine, which constricts pupils, and brimonidine, which inhibits dilation, are the topical agents that have been used in the past for pupil management. Phentolamine mesylate (PM), a miotic drop, appears to last longer, about 12 hours, Dr. McDonald said, whereas the effects of pilocarpine and brimonidine last about half that. There are drawbacks to the need for more frequent instillations of pilocarpine and brimonidine, Dr. McDonald said. For example, with every drop of pilocarpine instilled, there is a nearsighted shift.

“That wears off just in time for the next drop, and you get another nearsighted shift, so your spectacle prescription is changing all day long,” Dr. McDonald said.

With brimonidine, the effect wears off with time and frequent dosing, “So as the days and weeks go by, people stop experiencing any effect from it,” she said. Furthermore, pilocarpine is known to cause headaches.

In a placebo-controlled study of PM that Dr. McDonald presented at the American Academy of Ophthalmology 2010 and Hawaiian Eye 2011, all patients were at least 6 weeks postop and reported severe night vision problems. They also had a score of at least two lines or better improvement on mesopic low-contrast visual acuity testing during contralateral illumination by flashlight. The 16 patients randomized to active treatment instilled one drop of PM mixed in Tears Naturale II (Alcon).

“Everyone seemed to respond to the treatment, and it was safe and well tolerated,” Dr. McDonald said. At 2 to 3 hours after treatment, PM did not increase either heart rate or blood pressure. Moreover, “PM significantly decreased mean pupil size, decreased the root-mean-square (RMS) error and improved visual acuity in a significant number of subjects. It also significantly improved contrast sensitivity in both the presence and absence of glare.”

The eye drop did cause a significant increase in eye redness, however.

Although PM is considered a twice-a-day drop, “most people won’t need to take a second drop. By that time, they’ll be headed to bed,” Dr. McDonald said.

Spectacle lens

The Varilux Physio Enhanced spectacle lens, another means of nonsurgical pupil management to enhance night vision, is an improved wavefront-corrected progressive lens that accounts for pupil dynamics, according to Dr. McDonald.

When the lenses are made, the software program considers pupil modeling in any lighting condition, pupil size and distance to the object of regard, which decreases the optical aberrations, especially coma, in each part of the lens.

“So no matter where you are looking, what lighting conditions, what direction, how far away – whether you are looking at something 12 inches away or 20 feet away – there will be the fewest possible aberrations,” she said. “The addition of the pupil modeling makes a huge difference, especially in dim light.” – by Bob Kronemyer

References:

McDonald MB, Essilor Study Group. Factoring pupil size changes into a wavefront-optimized progressive lens design improves vision in low light conditions. A poster presentation at the American Academy of Ophthalmology annual meeting. October 2010. Chicago.

McDonald MB, Pitlick WH, VanDevanter DR, et al. Phentolamine mesylate (PM) treatment of severe night vision complaints. A poster presentation at the American Academy of Ophthalmology annual meeting. October 2010. Chicago.

Marguerite B. McDonald, MD, FACS, can be reached at Ophthalmic Consultants of Long Island, 360 Merrick Road, Lynbrook, NY 11563; (516) 766-2519; margueritemcdmd@aol.com.

Disclosure: Dr. McDonald is a consultant to Ocularis Pharma.