Abstract
Low vision therapy, such as magnifiers or contrast enhancement, is widely used. Scientific evidence proving its efficacy is scarce however. The objective of this study was to investigate whether the benefits of magnification and contrast enhancement depended on the origin of low vision. For this purpose we measured reading speed with artificially induced low vision in 12 healthy subjects in conditions of a simulated central scotoma, blurred vision and oscillopsia. Texts were either blurred, set in motion or blanked at the gaze position by using eye tracking and gaze contingent display. The simulated visual impairment was calibrated such that all types of low vision caused equal reading impairment. We then tested the effect of magnification and contrast enhancement among the different types of low vision. We found that reading speed improved with increasing magnification and with higher contrast in all conditions. The effect of magnification was significantly different in the three low vision conditions: The gain from magnification was highest in simulated blur and least in central scotoma. Magnification eventually led to near normal reading speed in all conditions. High contrast was less effective than high magnification and the effect of contrast enhancement was similar in all low vision conditions. From these results we conclude that the type of low vision determines the benefit that can be expected from magnification. Contrast enhancement leads to similar improved reading speed in all low vision types. We provide evidence that supports the use of low vision aids.
Highlights
Reading impairment is a main complaint of patients suffering from low vision
We measured reading speed and we found that in all types of simulated low vision reading speed improved with magnification (oscillopsia: F(5,55)=82, p
At the second but lowest magnification and contrast condition reading speed was similar in all three conditions (magnification: F(2,33)=0.1, p=0.9, BIC=167; contrast: F(2,33)=1.0, p=0.4, BIC=154), indicating that all types of low vision led to a comparable impairment of reading at this particular contrast and magnification
Summary
Reading impairment is a main complaint of patients suffering from low vision. improving reading speedLow vision is defined as an uncorrectable loss of vision is the primary therapeutic goal (Elliott et al, 1997). Reading impairment is a main complaint of patients suffering from low vision. International Classification of Diseases assumes moderate provided. Its aim is it to enable and support low vision pato severe vision impairment with visual acuity below 6/18 tients in reading and other daily activities. In order to debut better than 3/60 in the better eye with the best possible cide which low vision aids are beneficial for an individual correction (World Health Organization, 1992). Near and distance visual acuity, contrast sensitivity to estimations of 2010, glMobiaclhlya1e9l1CmhirlilisotnenpeMopDle suffer andMvaistuhailafsieAldbaeregtgakMenDin,tPo HacDcount. It from low vision (SteveDnespaerttmal.e,n2t 0o1f3O).pMhthaajolmr ocalougseys, for is dDifefpicaurtlmt teonptroefdOicpt hwtheatlhmeorlaongdy,how much an individual vision loss are cataraIncst,elasgpeitrael,laBteedrnmUancuivlaerrsditeygeHnoesrpaittiaoln, Ipnasteielsnptitmala,yBberenneUfintivfreorsmityloHwosvpisitiaoln, therapy
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