Aniseikonia Tolerance May Guide Surgical Procedures, Spectacle Correction

Maintaining aniseikonia at a level below 2% may be optimal for creating a visually comfortable environment, according to research published in Optometry and Vision Science. These findings should be considered when performing cataract or refractive surgery or manufacturing spectacles, as these treatments may sometimes induce aniseikonia, the report suggests.  

Researchers enrolled 33 participants (mean age, 28.9 years; 21 women; anisometropia ≤1 diopter [D]) in an investigation to determine aniseikonia tolerance. Study participants underwent assessment with a haploscope — the investigators enlarged the optotype of 1 eye at a speed of 2% per second while participants pressed a button to indicate diplopia, flickering, or blurring. The team repeated the assessment 2 additional times or 4 additional times in cases involving high variability and determined the mean values to be the patients’ aniseikonia tolerance.  

The mean aniseikonia tolerance was approximately 3.0% (median, ≈2%; range, 1%-11.5%) and there were no significant differences between dominant and nondominant eyes for the enlarged optotypes (3.3% vs 2.9%). No participants demonstrated ocular deviation prior to the induced discomfort and no significant associations were noted between aniseikonia tolerance and anisometropia, axial length difference, ocular deviation, or stereopsis, according to the report. 

“If the degree of aniseikonia tolerance can be determined prior to cataract surgery, it would aid in the development of optimal surgical plans and treatment options, leading to improved postoperative satisfaction,” according to the study authors. “This is true for cataract and refractive surgeries as well as refractive correction with glasses or contact lenses.” 

Study limitations include failure to examine patients with anisometropia greater than 1 D, and performing only near vision examinations.