Eyes of myopic and emmetropic patients behave similarly at close accommodative targets. Photo: Getty Images.

Researchers in Portugal and Spain hypothesized that any change in peripheral refraction in the hyperopic direction with accommodation in myopia could lead to an increased risk of myopia progression in predisposed eyes due to their commonly recognized pattern of peripheral hyperopic refraction compared with axial refraction. However, they found that myopic eyes seem to behave similarly to emmetropic eyes for closer accommodative targets. Peripheral refraction during high accommodative levels is not significantly different between emmetropes and myopes.

The study measured axial and off-axis refraction patterns in 25 myopic patients with spectacle lens correction and 15 lens-free emmetropes at different target distances from 2.00m (0.50D) to 0.20m (5.00D) in terms of sphere, astigmatism and spherical equivalent refraction. Refraction was measured at the center and at 20º and 40º degrees from the line of sight both nasally and temporally. Fixation target was a Maltese cross set at 2.00m, 0.50m, 0.33m and 0.20m from the corneal plane.

Off-axis refraction in myopic eyes with spectacle lens correction was significantly more myopic in the temporal retina compared with lens-free emmetropes, except for the closest target distance. Relative off-axis refractive error changed significantly with accommodation when compared with axial refraction particularly in the myopic group. The researchers said they believe this change in the negative direction was due to changes in the spherical component of refraction that became more myopic relative to the center at the 0.20m distance as the J0 component of astigmatism was significantly reduced in both emmetropes and myopes for the closest target.

“Those differences in peripheral spherical equivalent refraction between both groups are attributable to peripheral astigmatism since results failed to show significant differences between myopic eyes with spectacle lenses and lens-free emmetropes in the spherical component for any accommodative level studied except for 40º temporally for the 3.00D stimulus,” they concluded.