THE EFFECTS OF PROGRESSIVE CONTACT LENSES ON PERIPHERAL REFRACTIVE ERROR
Ithar. M. Beshtawi1. PhD, Hema Radhakrishnan2, PhD
1 Optometry Department, Faculty of Medicine and Health Sciences, An-Najah National University, Nablus, State of Palestine.
2 Faculty of Life Sciences, The University of Manchester, Manchester, UK
Introduction: Myopia has a high prevalence throughout the world. It is caused by multi-factorial aetiologies, but generally the genetic and the environmental factors are the main causes. Recently, it has been proved that the relative hyperopic refractive error, at the periphery of the cornea, interferes with ocular emmetropization & axial length of the eye which in turn leads to the development and progression of central myopia. The conventional minus lenses used to correct myopia, induce more relative peripheral hyperopia, and therefore lead to central myopic progression. The purpose of this study was to assess the influence of progressive contact lenses on correcting the peripheral refraction.
Methods. Peripheral refraction was measured using the Shin-Nippon autorefractor. The participants were asked to look at seven targets with the same size and shape, and the spherical and cylindrical refractive measurements were then taken in 10° intervals up to ±30° in horizontal meridian firstly without any lens then with four progressive contact lenses (Acuvue Bifocals (Johnson and Johnson) – Centre Distance, Magni Vue (David Thomus) – Centre Distance, Pure vision multifical (Bausch and Lomb) – Centre Near and Acuvue Oasys for Presbyopia (Johnson and Johnson) – Centre near) in a random order.
Results. The majority of the sample showed a relative hyperopic shift in the periphery compared with the central axial refraction. The progressive contact lenses showed a significant effect on altering the peripheral astigmatic components (J180 and J45; P<0.05). Only the Acuvue bifocal contact lenses (centre distance) showed a significant impact on altering all the refractive components measured at the periphery in relative to the central refraction (P<0.05).
Conclusion. Progressive multifocal and bifocal contact lenses did not show any significant impact in altering the myopic central refraction. Only one of the central distance lenses, the Acuvue bifocal showed a significant effect in altering the peripheral spherical equivalent as well as the astigmatism component (J180 and J45) at the periphery. The effect of custom made progressive contact lenses on correcting the peripheral and central refraction in myopes needs further investigation.
Key words: Myopia, Peripheral Refraction, Cornea, Multifocal Contact Lenses.