Abstract
Purpose :
It is assumed that progressive lens(PPL) users tends to mostly use the corridor area of the lens for reading at intermediate distances. But, other areas designed for distance or near vision can also be used depending on prescribed addition, accommodation amplitude(AA) and working distances. Using previously reported data on AA and prescribed addition vs age, the regions of the PPL that are usable for a given working distance can be predicted. The purpose of this study is to experimentally check these predictions when using computer screens.
Methods :
9 PPL presbyopic subjects were asked to use PPL glasses that were marked with a template having 2 color lines located at 10% and 90% of the addition that separated the distance (D), intermediate (I) and near (N) areas of the lens. The subjects were asked to read text in both a computer and a laptop screen located at 65cm and 80cm. Reading texts had letter sizes of 7, 9 and 12 points and were composed of 3 paragraphs located at the top, medium and bottom of the screens. For each of the 36 reading situations, the subjects indicated the lens area used for reading: distance (over first line), near (under second line) or corridor (between both lines). Correlation between theoretical and experimental data was analyzed.
Results :
The theoretical model predicts that subjects with Add≤1.25D can use the whole lens for seeing at distances between 65-80cm. Experimentally, the percentage of use of each area were D=33%, I=67%, C=0% at 65cm and D=25%, I=75%, C=0% at 80cm. Subjects with Add=1.50D will theoretically use the corridor and near areas for reading at 65cm but they will use the distance and corridor area for seeing at 80cm. Experimental data were D=0%, I=89% ,C=11% at 65cm and D=2% ,I=98% ,C=0% at 80cm. Subjects with Add≥1.75D should theoretically be forced to use the corridor for tasks between 65-80cm. Experimental results were: D=0%, I=94%, C=6% at 65cm and D=0%, I=100%, C=0% at 80cm Theoretical predictions and measurements agreed up to 99.1%. Differences in reading behavior were found depending on letter size and vertical position of the text; for example, the PPL near regions were only used with the lower-positioned laptop screen.
Conclusions :
The experiment suggests that PPL wearers indeed use the distance and near regions of their lenses for reading on computer screens, depending on their AA and prescribed addition, as theoretically predicted.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.