To use or not to use the refractive correction along with hand-held magnifiers.
Equivalent viewing power (EVP), field of view, and working distance (WD) were calculated for 4 different magnifier equivalent powers, four magnifier-to-eye distances, and for uncorrected spherical ametropias varying from +20.00 to -20.00 D in 0.25 D steps. Results show that the various viewing conditions which arise (depending on whether or not the refractive correction is worn) can differ considerably. The uncorrected unaccommodating myope has a greater EVP than the equivalent power of the magnifier if he chooses a magnifier-to-eye distance shorter than the focal length of the magnifier. In this situation, field of view is also enhanced. The uncorrected unaccommodating hyperope using a magnifier-to-eye distance longer than the focal length of the magnifier achieves a stronger EVP than the equivalent power of the magnifier. However, field of view is then reduced. For the uncorrected unaccommodating spherical ametrope, the use of a magnifier-to-eye distance corresponding to the focal length of the magnifier seems to be a good compromise between EVP, field of view, and working distance.
Bolduc
M
M
Centre Louis-Hebert, Québec, Canada.
Simonet
P
P
Gresset
J
J
Melillo
M
M
D005139:Eyeglasses; D006801:Humans; D006956:Hyperopia / Q000628:therapy; D008433:Mathematics; D009216:Myopia / Q000628:therapy; D009988:Orthoptics; D012682:Sensory Aids; D014785:Vision, Ocular / Q000502:physiology*