Lens magnification affects the estimates of refractive error obtained using eccentric infrared photorefraction

Abstract

Positive- and negative-powered ophthalmic lenses are used in eccentric infrared photorefraction to calibrate the device, correct the subject's baseline refractive error before an experimental manipulation, or stimulate blur-driven accommodation. Through theoretical modeling of luminance gradients formed across the pupil and empirical measurements of the eye's refractive error using a commercial photorefractor, this study shows that image magnification by positive lenses and image minification by negative lenses under- and overestimates the refractive error, respectively, all independent of image defocus. The impact of image magnification/minification therefore appears non-trivial in experimental paradigms involving ophthalmic lenses to manipulate the eye's optics during photorefraction.

Correction of Low-Moderate Hyperopia Improves Accommodative Function for Some Hyperopic Children During Sustained Near Work

“…46 A recent study reported that photorefractive estimates of refractive error/accommodation made through spectacle lens correction could underestimate the magnitude of refractive error due to image magnification of the luminance profile in the pupils. 48 The authors further report that this effect is compounded by large vertex distances. However, in the present study, constant vertex distance (12 mm) while wearing spectacles was checked and maintained by fixing adhesive nose pads on the spectacles of each participant, thus minimizing effects from variable vertex distance.…”

Two‐dimensional simulation of eccentric photorefraction images for ametropes: factors influencing the measurement

“…The simulations with −8D to +8D trial lenses at three vertex distances ( Figure ) suggest that both their effective power at the pupil plane and magnification effects impact the refractive error estimates . For example, moving a +7D lens between the spectacle plane (e.g.…”