Myopic LASIK with monovision boosts reading vision, preserves distance UCVA

Am J Ophthalmol. 2010;150(3):381-386.

Issue: November 25, 2010

LASIK-induced monovision increased spectacle independence in myopic eyes with presbyopia, a study found.

"The goal of monovision is to increase both the distance and near vision without wearing glasses," the authors said. "Our results indicate that using monovision, the ability to read without spectacles at a normal reading distance while maintaining good uncorrected distance visual function is achieved."

The prospective study included 37 presbyopic patients who had monovision induced from bilateral myopic LASIK.

Inclusion criteria included age older than 45 years, myopia less than 6 D and corneal astigmatism less than 3 D. Patients with unstable refraction, previous ocular surgery, suspected keratoconus, ocular or systemic disease, or history of amblyopia or other conditions affecting ocular motility were excluded.

Preoperatively, mean spherical defect was –3.14 D and mean cylindrical defect was –0.98 D.

Non-wavefront ablation was performed in all cases. Investigators assessed visual, refractive and anatomic outcomes at 1 day, 1 week, and 1, 3 and 6 months after surgery.

Study data showed that induction of a mean residual spherical equivalent defect of –0.97 D in the nondominant eye yielded a mean near binocular uncorrected visual acuity of 0.74. A reading test showed mean binocular UCVA of 0.88 at a mean distance of 48 cm, which was sufficient to read newsprint without glasses. Mean binocular distance UCVA was 1.08.

Distance binocular contrast sensitivity diminished somewhat more with monovision than with full-distance correction. However, the difference was statistically significant only at greater spatial frequencies (P = .001), the authors said.

Monovision remains a good option for the presbyopic patient who desires functional vision without spectacles at all distances. This approach has been shown to work with contact lenses, IOLs, and corneal refractive surgery, including LASIK. This study again confirms that for most patients neuroadaptation occurs, allowing tolerance to the anisometropia. Personal experience and the literature suggest that an anisometropia of 1.5 D or less allows good function with retention of some stereopsis while reducing the chance for development of a relative amblyopia in the near eye.

In this study, a near target of slightly less than 1 D was associated with a high degree of tolerance in a younger group with mild to moderate presbyopia. Usually we target the dominant eye for distance, but some patients prefer the opposite. This can be tested for in the clinic by simply placing the appropriate add in front of a patient while wearing distance correction and seeing which is better tolerated. Many teach a contact lens trial is indicated, but some studies suggest this approach can also yield confounding outcomes as a dislike for contact lenses can be interpreted as a poor tolerance of monovision and as much as a month of contact lens wear may be required to be certain that monovision is tolerated. The enhancement rate, especially in the distance eye, is higher for monovision as the demands on the single eye for distance are high. I offer all patients glasses for use as needed for distance tasks like night driving and long periods of reading, but as many as 50% of my patients find them unnecessary.

Fortunately, for the small number of patients where neuroadaptation does not occur, a PRK or LASIK enhancement can generate symmetrical distance vision and a happy patient. As a final caveat, both my 92-year-old mother following cataract surgery and much younger wife are set up with monovision and delighted. For me, I remain dependent on readers because of the long hours behind binocular microscopes used by multiple doctors, but I remain highly annoyed by my dependence on readers and am looking forward to the day a surgical approach can give me back quality distance and near vision like I enjoyed before age 45.

– Richard L. Lindstrom, MD
OSN Chief Medical Editor