Patient Age, Presbyopia, and Monovision
The age of a patient is a consideration in predicting postoperative patient satisfaction. The loss of near vision with aging should be discussed with all patients. Before 40 years of age, individuals with emmetropia generally do not require reading adds to see a near target. After this age, patients need to understand that if their eyes are made emmetropic through refractive surgery, they will require reading glasses for near vision. They must also understand that “near vision” tasks include all tasks performed up close, such as applying makeup, shaving, or seeing the computer or cell phone screen—not just “reading.” These points cannot be overemphasized for patients with myopia who are approaching 40 years of age. Before refractive surgery, these patients can read well with and without their glasses. Some may even read well with their contact lenses. If their eyes are made emmetropic after surgery, many will not read well without reading glasses. The patient needs to understand this phenomenon and must be willing to accept this result before undergoing any refractive surgery that aims for emmetropia. In patients who wear glasses, a trial with contact lenses will simulate vision following refractive surgery, and approximate the patient’s reading ability after surgery.
A discussion of monovision (ie, 1 eye corrected for distance and the other eye for near/intermediate vision) often fits well into the evaluation at this point. The alternative of monovision correction should be discussed with all patients in the age groups approaching or affected by presbyopia. Many patients have successfully used monovision in contact lenses and want it after refractive surgery. Others have never tried it but would like to, and still others have no interest. If a patient has not used monovision before but is interested, the attempted surgical result should first be demonstrated with glasses or temporary contact lenses at near and distance. Generally, the dominant eye is corrected for distance, and the nondominant eye is corrected to approximately –1.50 to –1.75 D. For most patients, such refraction allows good uncorrected distance and near vision without intolerable anisometropia. Some surgeons prefer a “mini-monovision” procedure, whereby the near-vision eye is corrected to approximately –0.75 D, which allows some near vision with better distance vision and less anisometropia. The exact amount of monovision depends on the desires of the patient. Higher amounts of monovision (up to –2.50 D) can be used successfully in selected patients who want excellent postoperative near vision. However, in some patients with a higher degree of postoperative myopia, improving near vision may lead to unwanted adverse effects of loss of depth perception and anisometropia. It is advisable to have a patient simulate monovision with contact lenses before surgery (generally about 5 days to 1 week, but practices are variable) to ensure that distance and near vision, as well as stereovision, are acceptable and that no muscle imbalance is present, especially with higher degrees of monovision.
Although typically the nondominant eye is corrected for near, some patients prefer that the dominant eye be corrected for near. Of several methods for testing ocular dominance, one of the simplest is to have the patient point to a distant object, such as a small letter on an eye chart. Alternatively, the patient can make an “okay sign” with 1 hand and look at the examiner through the opening, and then close each eye to determine which eye he or she was using when pointing; this is the dominant eye.
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.