In the United States, monovision is the technique used most frequently for the nonspectacle correction of presbyopia. In this approach, the refractive power of 1 eye is adjusted to improve near vision. Monovision may be achieved with contact lenses, laser in situ keratomileusis (LASIK), surface ablation (photorefractive keratectomy [PRK]), conductive keratoplasty (CK), or even lens surgery. Historically, the term monovision typically referred to the use of a distance contact lens in 1 eye and a near contact lens in the other. A power difference between the eyes of 1.25–2.50 diopters (D) was targeted on the basis of near visual acuity demands. Many refractive surgeons target mild myopia (–0.50 to –1.50 D) for the near-vision eye in the presbyopic and prepresbyopic population. The term modified monovision, or mini-monovision, is more appropriate for this lower level of myopia for the near-vision eye. Mini-monovision is associated with only a mild decrease in distance vision, retention of good stereopsis, and a significant increase in the intermediate zone of functional vision. The intermediate zone is where many visual functions used in daily life occur (eg, looking at a computer screen, store shelves, or a car dashboard). For many patients, this compromise is an attractive alternative to constantly reaching for reading glasses. Selected patients who want better near vision may prefer greater monovision correction (–1.50 to –2.50 D) despite the accompanying decrease in distance vision and stereopsis. The clinician should counsel the patient that leaving 1 eye undercorrected may lead to glare and halos when driving at night. This can be corrected with driving glasses.
Appropriate patient selection and education are fundamental to the overall success of monovision treatment. Although monovision can be demonstrated with trial lenses in the examination room, a contact lens trial period at home is often more useful. Patients whose vision is neither presbyopic nor approaching presbyopia are typically not good candidates for monovision, as they are usually seeking optimal bilateral distance visual acuity. However, patients in their mid- to late 30s should be counseled about impending presbyopia and the option of monovision.
The best candidates for monovision are patients with myopia who are older than 40 years and who, because of their current refractive error, retain some useful uncorrected near vision. These patients have always experienced adequate near vision simply by removing their glasses and therefore understand the importance of near vision. Patients who do not have useful uncorrected near vision (ie, patients with myopia worse than –4.50 D, high astigmatism, or hyperopia; or contact lens wearers) may be more accepting of the need for reading glasses after refractive surgery. For most patients, refractive surgeons routinely aim for mild myopia (–0.50 to –0.75 D, occasionally up to –1.50 D) in the nondominant eye. It is prudent to give the patient a trial with contact lenses to ascertain patient acceptance and the exact degree of near vision desired. Patients should understand that loss of accommodation is progressive and that, as a result, monovision may not be permanent and corrective glasses may eventually be required.
Reinstein DZ, Carp GI, Archer TJ, Gobbe M. LASIK for presbyopia correction in emmetropic patients using aspheric ablation profiles and a micro-monovision protocol with the Carl Zeiss Meditec MEL 80 and VisuMax. J Refract Surg. 2012;28(8):531–541.
Rocha KM, Vabre L, Chateau N, Krueger RR. Expanding depth of focus by modifying higher-order aberrations induced by an adaptive optics visual simulator. J Cataract Refract Surg. 2009;35(11):1885–1892.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.