Disparity between central and peripheral refraction inheritance in twins

Abstract

The last decades have witnessed a sudden increase in myopia incidence among youngsters that have been related to modern lifestyle along with the use of emerging technologies affecting visual exposure. Increasing exposures to known risk factors for myopia, such as time spent indoors, close-distance work, or low-light conditions are thought to be responsible for this public health issue. In most cases, development of myopia is secondary to a vitreous chamber enlargement, although the related mechanisms and the potential interaction between central and peripheral retinal area remain unclear. For a better understanding, we performed a classical twin study where objective refractive error along 70° of horizontal retinal arc was measured in 100 twin pairs of university students, 78% of which showed manifest myopia. We found the variance of shared environmental origin (range 0.34 to 0.67) explained most of the objective refractive error variance within central 42° of the retina (22° temporal to 19° nasal), whereas additive genetic variance (range 0.34 to 0.76) was predominant in the peripheral retinal areas measured. In this sample of millennial university students, with a large prevalence of myopia, environmental exposures were mostly responsible for inter-individual variation in the retinal horizontal area surrounding the macula, while their relative weight on phenotypic variance was gradually descending, and replaced by the variance of genetic origin, towards the retinal periphery.

Impact of Peripheral Refractive Errors in Mobility Performance

“…Myopic eyes tend to be relatively hyperopic in the periphery due to the elongated shape of the eye, whereas hyperopic and emmetropic eyes are more myopic in the periphery. 12 , 13 Many optical treatments to slow the progression of myopia rely on the introduction of peripheral myopic defocus to compensate for the intrinsic hyperopic blur and slow axial growth. 14 , 15 On the other hand, intraocular lenses (IOLs) implanted in cataract surgery to replace the crystalline lens, induce peripheral myopia and astigmatism.…”