Clinical usefulness of the Aniseikonia Inspector: a review

In the literature several articles have appeared which describe the accuracy and repeatability of direct-comparison aniseikonia tests, such as the New Aniseikonia Test and the aniseikonia test of the Aniseikonia Inspector. In these articles a discussion on the clinical relevance of the results is often missing. Therefore, this article discusses the clinical usefulness of direct-comparison aniseikonia tests, in particular that of the Aniseikonia Inspector.

Review of the literature shows that an aniseikonia test is usually evaluated by inducing aniseikonia in normal subjects using size lenses. The range of induced aniseikonia differs. Some investigations evaluated from appr. -8% to +8%, while other investigations evaluate a (too) small range from appr. -3% to +3%.

In general direct-comparison aniseikonia tests have a repeated measurement accuracy of approximately 0.5% standard deviation (this also includes actual aniseikonia fluctuations). A direct-comparison aniseikonia test with free eye rotation seems to underestimate the amount of aniseikonia. However, converting these underestimations into clinically applicable values shows that vertically the 'error' is on average smaller than only 0.5% and horizontally the 'error' is smaller than 1%. This may be statistically significant but clinically less relevant underestimation seems to disappear in tests without free eye rotation (as in the newer versions of the Aniseikonia Inspector).

Because aniseikonia does not seem to give any clinical symptoms until the aniseikonia has a value of 3-5%, the accuracy and repeatability of direction-comparison tests, such as that of the Aniseikonia Inspector, is sufficient for effective aniseikonia management.