Astigmatism: Prevalence; Distribution and Determinants in Owerri; Nigeria

ABSTRACT

Background: Astigmatism impairs focusing ability of the eyes at far and near distances. This causes distortion; blurred vision; eye strain; headache; makes difficult visual tasks such as reading; driving (especially at night); focusing on the classroom board and computer screen. This study determined the prevalence; distribution and determinants of astigmatism in Owerri; Imo State; Nigeria in order to establish a baseline data for the state. Materials and Methods: Three thousand; four hundred and fifty - one adults consisting of 2606 persons as test subjects and 845 persons as controls were randomly selected for the study. Structured - questionnaire was administered to the subjects and thereafter; the visual acuity at far and near including tonometry; ophthalmoscopy; perimetry; retinoscopy and subjective refraction were done. Astigmatic correction was prescribed in the minus cylinder format and astigmatism was defined as a cylindrical error less than -0.50 diopter cylinder in any axis. Astigmatism was classified by axis as with-the-rule (WTR); against-the-rule; and oblique astigmatism. Results: A prevalence of 20.9 and 22.5 of astigmatism was found in the study and control groups respectively. From the astigmatics; 59.4 and 61.1 of females in the study and control groups respectively (especially females aged 40-49) were mostly affected. WTR astigmatism of =1.00DC (P = 0.000) was statistically significant between study and control groups. A higher prevalence of astigmatism was found in subjects domiciled in the rural areas and caused by factors like environmental influences; poor nutrition and irrational first line drug use of chloroquine. Conclusion: To achieve the targets of vision 2020; we recommend periodic visual examination and health education on diet; drug use and safe environmental practises especially for people living in rural areas in low income economy like ours