Assessment of types of phorias in myopic patients before and after refractive correction

Abstract

Purpose: To assess the types of phorias in different degrees of myopic patients and different age groups before and after refractive correction. Study design: Descriptive cross-sectional study. Material and methods: This was a comparative cross-sectional study that included 100 patients. Types of phorias in myopic patients were assessed before and after refractive correction. Patients involved are 15-35 years of age groups. Data was collected from the University of Lahore Teaching Hospital. Results: A total of 100 subjects were participated out of which 52% were males and 48% were females. 38% were 15-20 years, 42% were 21-25 years, 9% were 26-30 years, and 11% of participants were31-35 years of age. Visual acuity before the correction of refractive error was also recorded 42% of participants were observed with 6/6-6/12 visual acuity, 6/18-6/36 visual acuity was reported in 42% subjects and 16% subjects had <6/60 visual acuity. After the correction of myopic error 87% subjects had 6/6-6/12 and 13% subjects had 6/18-6/36 best corrected visual acuity. Degree of myopia was recorded mild in 42% participants, moderate in 42% subjects and severe in 16% subjects. Before the correction of myopia 21% participants were observed with esophoria, 54% had exophoria and 25% subjects were orthophoric. After refractive correction 13% participants were esophoric, 28% were exophoric and 59% were orthophoric while measuring horizontal phoria at distance. In vertical phoria before correction 14% participants were hyperphoria, 1% were hypophoria and 85% were orthophoric. After best correction 5% participants were recorded as hyperphoria, 1% were hypophoria and 94% were orthophoric. Conclusion: Horizontal and vertical phorias were evaluated at distance with Maddox rod. It is concluded that after correction the frequency of horizontal phorias is high than vertical phorias. In horizontal phorias exophoric pattern has significant frequency. Exophoria can also result due to weak fusional reserves. Fusional convergence eliminates the disparity of retinal images and maintain exophoria in myopic patients. So, convergence weakness and excess of divergence leads to exophoria in myopic patients. Mostly exophoric participants are reported from age range of 15 to 20 years. After refraction if patient still have asthenopia symptoms proper evaluation and management should be made for latent squint. By treating and managing the latent squint the chances of phorias to convert in manifest squint will be minimize.