Tolerance to surgically induced anisometropia-A systematic review

Surgically induced anisometropia is well tolerated by some individuals, while others experience binocular visual complaints. Surgically induced anisometropia is a common treatment for presbyopia and may also intentionally or non-intentionally be the results after surgery for unilateral cataract with ametropia in the fellow eye. Research has shown significant variations in the tolerance of anisometropia. The aim of this systematic review was to examine the correlation between the degree of anisometropia, patient satisfaction and binocular visual complaints. We searched the databases: PubMed, EMBASE, Google Scholar, Cochrane and Web of Science for relevant reported studies. The search was supplemented with ongoing trials from www.clinicaltrials.gov. We searched for the following words: Anisometropia or monovision and satisfaction, aniseikonia, asthenopia, diplopia, headache, dizziness or fatigue. Our inclusion criteria encompassed all original studies, observational studies and randomized clinical trials that reported on clinical symptoms in patients with induced anisometropia. We included studies with induced anisometropia through cataract surgery or refractive surgery. Out of 1701 studies identified, 35 were included (N: 3186 patients): six randomized and 29 non-randomized studies. Six studies compared patients with surgically induced anisometropia to distance corrected emmetropic patients. Follow-up periods ranged from one to 32 months, with patient age from 22 to 96 years. Twenty-two studies reported on surgically induced anisometropia after cataract surgery, 13 after corneal refractive surgery and reported a combined mean anisometropia of 1.57 diopters (D). Overall, patient satisfaction with surgically induced anisometropia was generally high and comparable with emmetropia in four of six comparative studies. Independence from reading glasses was higher in anisometropic patients, while independence from glasses for distance vision was higher in emmetropic patients. Asthenopia was generally reported by few patients, and when it was reported, it was generally mild. In conclusion, this systematic review and meta-analysis of 35 studies involving 3186 patients suggests that surgically induced anisometropia just below 1 D is a viable approach to achieving high patient satisfaction with high degree of independence from reading glasses and minimal asthenopia. The majority of studies report high patient satisfaction and minimal incidence of asthenopia with no significant difference between anisometropic patients and distance-corrected emmetropic patients.