Interocular astigmatic symmetry: A systematic review

Abstract

Purpose: The objective of this investigation was to consolidate the extant data pertaining to interocular astigmatic symmetry, with a view to discerning any patterns that may emerge from the research.

Methods: A systematic literature review was conducted in accordance with the PICO framework. The search, conducted through September 2024, included three databases (PubMed, Web of Science, and Scopus) and the reference list of the selected articles, which were identified from inception. The articles were selected based on the inclusion criteria of population-based studies with data on interocular astigmatic symmetry.

Results: A total of 65 articles were retrieved, of which 13 met the inclusion criteria. The thirteen studies included a total of 329,747 subjects from ten different countries. The prevalence of interocular astigmatic symmetry according to axis orientation was isorule in most of the articles (i.e., both eyes having the same pattern: with-the-rule astigmatism, against-the-rule astigmatism, or oblique astigmatism), except for those pertaining to the geriatric population. Regarding the classification according to axis orientation, mirror symmetry was demonstrated to be the most prevalent pattern in interocular astigmatism. Genetic and individual factors, such as age, sex, and refractive error, did not exhibit a discernible influence on interocular astigmatic symmetry.

Conclusion: The findings of this study indicated a clear trend through the isorule pattern and mirror symmetry in a population.

Keywords: Astigmatic symmetry; Astigmatism symmetry; Interocular symmetry; Mirror symmetry; Rule symmetry; Systematic review.