The Tolerance Of Induced Anisometropia – A Systematic Review

Surgical induced anisometropia (SIA) is well tolerated by some individuals, while others may experience binocular visual issues. SIA is commonly employed as a treatment for presbyopia and is induced surgically in cases of unilateral cataract with ametropia in the fellow eye. Research has indicated significant variations in the tolerance of anisometropia. However, most studies have primarily focused on objective measurements such as stereopsis or visual acuity and not subjective visual complaints. The aim of this systematic review was to investigate the correlation between SIA and subjective symptoms.

Systematic review

We conducted a comprehensive search in the databases PubMed, EMBASE, Google Scholar, Cochrane databases and Web of Science to identify relevant reported studies. The search was supplemented with ongoing trials from www.clinicaltrials.gov. We searched with the following words: Anisometropia or monovision and aniseikonia, asthenopia, diplopia, headache, dizziness, or fatigue. Our inclusion criteria encompassed all original studies, including observational studies, case reports and randomized clinical trials, investigating clinical symptoms in patients with induced anisometropia. We included studies with induced anisometropia through cataract surgery or refractive surgery.

Of 1340 studies identified, 13 (651 patients) were included; three case studies, four retrospective studies, and six prospective studies. All studies were observational. Follow-up periods ranged from one to 17 months, age range: 36-94 years. Eight studies reported on SIA after cataract surgery, five used refractive surgery. SIA ranged from 0,5 to 11 diopters. Six studies found postoperative stereopsis worsens with anisometropia, although statistically insignificant. Four studies reported postoperative aniseikonia ranging from 0.9% to 18.9%. Patient satisfaction with SIA was generally high (>80% in six studies reporting a satisfaction level) and comparable to that of fully corrected patients in three studies comparing the two groups.

This systematic review of 13 studies indicate that SIA is well tolerated with high patient satisfaction, slightly diminished stereopsis and increasing aniseikonia. However, the studies were all observational and descriptive with large inter-variability in study design, method and outcome measures precluding meta-analysis and correlation analysis. Like other reviews, it is prudent to interpret the results with caution due to the inter-variability. Strong evidence from randomized, controlled clinical trials utilizing validated questionnaires would be beneficial.