Significance
The determination of aniseikonia tolerance may aid in developing optimal treatment plans for cataract surgery, refractive surgery, and refractive correction with glasses and contact lenses.
Purpose
This study aims to measure aniseikonia tolerance.
Methods
We included 33 patients (mean age ± standard deviation, 28.9 ± 6.4 years; male:female, 12:21) with anisometropia ≤1.0 D and best spectacle-corrected visual acuity of 20/20 or more in both eyes, with no ophthalmologic disease other than refractive errors and no history of ocular surgery. The exclusion criteria were anisometropia >1.0 D, axial length difference > 0.5 mm, corneal refractive power difference > 0.5 D, astigmatism >3.0 D, stereoacuity threshold >100 sec arc according to the Titmus Stereo Test, and > 0 % aniseikonia according to the New Aniseikonia test. Aniseikonia tolerance was assessed using Eyemark Hello, a haploscope using gaze-detection technology. While the optotype of one eye was enlarged or reduced at a speed of 2%/sec, the patients were instructed to press a button on the controller to indicate blurring, flickering, and diplopia. The value at which the patient responded was considered the aniseikonia tolerance value and assessed thrice per eye, five times if the values were highly variable, and then averaged.
Results
The mean aniseikonia tolerance was approximately 3%; the median value was approximately 2% (range, 1.0%–11.5%; dominant eye, 3.3 ± 2.6%; non-dominant eye, 2.9 ± 1.8%). No significant difference in aniseikonia tolerance between the dominant and non-dominant eyes was observed for the enlarged optotypes. No case showed changes in the ocular alignment before discomfort occurred. No significant correlation was observed between aniseikonia tolerance and anisometropia, axial length difference, corneal power difference, and ocular deviation.
Conclusions
Aniseikonia should be maintained at <2% for a comfortable visual environment. Aniseikonia tolerance may be an important indicator for cataract surgery, refractive surgery, and spectacle correction.
