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The Distribution of Near Point of Convergence in an Iranian Rural Population: A Population-Based Cross-Sectional Study Publisher



Hashemi H1, 2 ; Pakzad R2 ; Yekta A3 ; Asharlous A4 ; Aghamirsalim M5 ; Ostadimoghaddam H6 ; Valadkhan M1 ; 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. Department of Optometry, Iran University of Medical Sciences, Tehran, Iran
  5. 5. Eye Research Center, Tehran University of Medical Sciences, Tehran, Iran
  6. 6. Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
  7. 7. Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Source: Saudi Journal of Ophthalmology Published:2019


Abstract

Objective: To determine the distribution of near point of convergence (NPC) according to age, sex, and refractive error in a rural population above 1 year of age in 2015. Methods: In this population-based cross-sectional study, multistage cluster sampling was applied to randomly select two underserved areas from the north and southwest of Iran and all individuals above 1 year living in these areas were invited to participate in the study. All participants underwent ocular examinations including visual acuity measurement, refraction, binocular vision testing including cover test and measurement of NPC, and slit lamp biomicroscopy. Results: Of 3851 who were invited, 3314 participated in the study (response rate: 86.5%). The NPC was 8.42 ± 2.94 cm in the whole population, 8.59 ± 3.07 cm in men, and 8.30 ± 2.84 cm in women. Subjects above 70 years of age had the most remote NPC (mean: 10.44 ± 3.07 cm). The mean NPC was 7.79 ± 2.93, 8.83 ± 2.72, and 9.63 ± 2.70 cm in emmetropic, myopic, and hyperopic participants, respectively. According to the results of a multiple linear regression model, NPC had a positive correlation with age (b: 0.058, p < 0.001), male sex (b: 0.336, p: 0.005), and hyperopia (b: 0.044, p: 0.011). Among the evaluated variables, age had the greatest effect on NPC (Standardized coefficient: 0.402). Conclusion: The distribution of NPC in the Iranian population is different from other populations. Since NPC is influenced by age more than any other variable and presented normal values according to age in this study, the results can be used to interpret clinical measurements for diagnosis and treatment purposes. © 2019 The Authors
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