Monovision survives as a strategy to compensate for presbyopia because binocular approaches have not yet succeeded. The significant disadvantages of monovision include asymmetric visual correction and reduced binocular function (eg, reduced binocular visual acuity, reduced stereo acuity, and reduced binocular contrast sensitivity). The advantages of surgical monovision include patients' greater freedom from their glasses or contact lenses for both distance and near, excellent visual results at distance and near, and a high degree of patient satisfaction.1-6
Success with LASIK monovision depends on proper patient selection and education, excellent binocular visual results, and patients' postoperative adaptation and feelings of support.5,6PATIENT SELECTION
Amblyopia or a strong sighting preference such as a monofixation syndrome are contraindications for LASIK monovision. The patients most likely to succeed with monovision are presbyopic and therefore approximately 43 years of age or older. Interestingly, male patients show a significant preference for full distance correction, whereas female patients choose monovision and full distance correction equally.5,6 Table 1 compares the occupations, sports, hobbies, and need for depth perception of individuals who favor full distance versus monovision correction.
Patients with a type-A personality may be better suited to full distance correction. Those who are willing to accept visual compromises and are most interested in freedom from their glasses or contact lenses for both distance and near are the best candidates for monovision.
Myopes Versus Hyperopes
I conducted a retrospective study of 388 patients over the age of 40 who underwent LASIK and were offered a choice between monovision and full distance correction. I found significant differences in the success rates of LASIK monovision between myopes and hyperopes.6 The visual results and satisfaction scores were excellent in both groups. All monovision patients achieved a UCVA of 20/30 or better in their distance eye and J2 or better in their near eye. Nevertheless, statistical analysis indicated that (1) the visual results for distance were better in myopes than in hyperopes (P=.043), (2) the number of enhancement procedures was higher in patients corrected for monovision (P=.04) and in hyperopes (P=.08), and (3) the level of satisfaction was higher among myopes (P=.012) and patients corrected for full distance (P=.002). Of most concern, hyperopic patients who received monovision correction had the most difficulty with side effects (light-related and depth perception; P=.00).
It is important to recognize that monovision is a more problematic means of correcting presbyopia in hyperopes than in myopes. The former group is at a higher risk in terms of enhancements (number and predictability) and side effects, so careful patient selection is especially important with these individuals.6
A monovision trial can aid patient selection. Although some practitioners use a spectacle demonstration, this method has not achieved scientific validity. The best option is a contact lens trial, which should be conducted for 3 weeks.1,2 The trial may not be required in myopic patients for whom the conversion to full distance correction involves adding to the correction, whereas hyperopic patients' conversion to full distance entails a reversal of correction and the additional loss of corneal tissue. It is also important to remember that the results of LASIK monovision may be superior to those of contact lens monovision because it provides constant optical correction, eliminates the astigmatism that may remain with contact lens wear, and frees the patient from his contact lenses.
Surgeons should educate patients preoperatively about accommodation, presbyopia, and the rationale for monovision. The informed consent process needs to acknowledge that monovision reduces binocular function, and surgeons should advise patients who choose this treatment option to wear distance correction for their near eye when driving.
Postoperative adaptation may last for several months and provoke great anxiety in patients, so ophthalmologists must be willing to provide reassurance. Surgeons should allow several months for adaptation before making a decision about converting the patient to full distance correction. The expected dropout rate for LASIK monovision is approximately 5%.5,6
Although some practitioners advocate limited monovision, I have achieved excellent results with full monovision of up to 2.50 D of anisometropia. Monovision patients desire optimal reading vision, so the goal of full monovision should be J1. Despite the concern that higher levels of anisometropia will reduce patients' stereo acuity, clinical studies of monovision have thus far failed to document any subjective complaints. It is worth bearing in mind that, the higher the patient's myopia in his reading eye, the longer his reading ability will last as he ages.
Successful monovision procedures require excellent visual outcomes. These patients will insist upon enhancements until their distance visual acuity is at least 20/30 or better and their near visual results are J2 or better. In especially demanding patients, the surgeon may have to perform a higher number of enhancements.
LASIK monovision remains a viable and valuable option for managing presbyopia. With proper patient selection and education, careful surgical planning, and a willingness to support patients and perform enhancements, surgeons will achieve success with this treatment modality.
1. Jain S, Arora I, Azar DT. Success of monovision in presbyopes: review of the literature and potential applications to refractive surgery. Surv Ophthalmol. 1996;40:6:491-499.
2. Sippel KC, Jain S, Azar DT. Monovision achieved with excimer laser refractive surgery. Int Ophthalmol Clin. 2001;412:91-101.
3. Wright, KW, Guemes A, Kapadia MS, Wilson SE. Binocular function and patient satisfaction after monovision induced bimyopic photorefractive keratectomy. J Cataract Refract Surg. 1999;25:177-182.
4. Jain S, Ou R, Azar DT. Monovision outcomes in presbyopic individuals after refractive surgery. Ophthalmology. 2001;108:1430-1433.
5. Goldberg DB. Laser in situ keratomileusis monovision. J Cataract Refract Surg. 2001; 27:1449-1455.
6. Goldberg DB. Comparison of myopic and hyperopic patients after LASIK monovision. J Cataract Refract Surg. In press.