Tehran University of Medical Sciences

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Enantiomorphism and Rule Similarity in the Astigmatism Axes of Fellow Eyes: A Population-Based Study; [Enantiomorfismo Y Similitud De La Regla En Los Ejes Del Astigmatismo En Ojos Contralaterales: Estudio Poblacional] Publisher Pubmed



Hashemi H1 ; Asharlous A2 ; Yekta A3 ; Ostadimoghaddam H4 ; Mohebi M5 ; Aghamirsalim M6 ; Khabazkhoob M7
Authors
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Authors Affiliations
  1. 1. Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
  2. 2. Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
  3. 3. Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
  4. 4. Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
  5. 5. Farabi Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
  6. 6. Eye Research Center, Rassoul Akram Hospital, Iran University of Medical Sciences, Tehran, Iran
  7. 7. Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Source: Journal of Optometry Published:2019


Abstract

Purpose: To evaluate the relationship patterns between astigmatism axes of fellow eyes (rule similarity and symmetry) and to determine the prevalence of each pattern in the studied population. Methods: This population-based study was conducted in 2015 in Iran. All participants had tests for visual acuity, objective refraction, subjective refraction (if cooperative), and assessment of eye health at the slit-lamp. Axis symmetry was based on two different patterns: direct (equal axes) and mirror (mirror image symmetry) or enantiomorphism. Bilateral astigmatism was classified as isorule if fellow eyes had the same orientation (e.g. both eyes were with-the-rule) and as anisorule if otherwise. Results: Of the total cases of bilateral astigmatism, 80% were isorule, and in the studied population, the prevalence of isorule and anisorule astigmatism was 14.89% and 3.53%, respectively. The prevalence of isorule increased with age (p < 0.001). The prevalence of both isorule and anisorule increased at higher degrees of spherical ametropia (p < 0.001). Median inter-ocular axis difference was 10° in mirror symmetry and 20° in direct symmetry with no significant difference between two genders (p > 0.288). Both symmetry patterns reduced with age (p < 0.001). Among cases of bilateral astigmatism, 15.5% and 19.8% had exact direct and mirror symmetry, respectively. Conclusion: Bilateral astigmatism is mainly isorule in the population and anisorule astigmatism is rare. The enantiomorphism is the most common pattern in the population of bilateral astigmatism. © 2018 Spanish General Council of Optometry