THE RATE OF BLUR ADAPTATION IN EMMETROPES AND MYOPES

ABSTRACT

Studies have shown that visual acuity defocused using convex lenses (myopic defocus) tend to improve after blur adaptation. This study examined how visual acuity changes immediately after defocus (using the myopic defocus method) is introduced, and in particular when blur adaptation first causes a significant improvement in the defocused VA in emmetropes and myopes. Participants were 30 normally sighted individuals (15emmetropes and 15myopes; 18females and 12males) who agreed to partake in this study. All participants wore their full refractive correction throughout the duration of the experiment. A +1.00DS was used to confirm the accuracy of each participant’s full refractive correction. A +3.00DS lens was used as the defocusing lens. Visual acuity was measured with the defocusing lens using the LogMAR letters on Bailey-Lovie visual acuity chart at baseline and at 2minutes interval over a period of 20minutes and a post-adaptation VA was also further measured at 2minutes interval over a period of 10minutes. Using the repeated measures of analysis of variance (ANOVA), a statistically significant increase was observed in defocused VA over time for emmetropes [starting at 6minutes (p=0.008) till 18minutes (p=0.034)] and myopes [starting at 4minutes (p=0.027) till 20minutes (p=0.003)] but there was no statistically significant difference (p>0.50) between emmetropes and myopes over time when compared. In conclusion, this emphasizes the importance of optimum refractive correction to avoid inducing blur amongst patients. Keywords: Blur adaptation, myopic defocus, visual acuity, optical blur