Abstract
Purpose :
Myopia, the dominant form of the ocular disorder, is believed to be heavily influenced by viewing distance (VD) and eye-received illuminance (EI). However, the precise roles of the two factors during the development of myopia are unknown due to the lack of quantification methods. This study proposes a quantification method that shows the relationship between the progression of refractive error (RE) and the visual behavior (VD-EI) space measured by a novel device Clouclip.
Methods :
Clouclip was developed to be attached on the spectacle and to continuously measure VD and EI every 5 and 20 seconds respectively. 145 children aged between 10 and 13 were recruited from 3 primary schools. The measurements were taken in 5 sessions during 1.5 years with an interval of 3 months and RE was also recorded 3 times during the period. The time series of VD-EI measurements were denoised by a lowpass filter. The gradient of VD-EI series was thresholded to segment the subseries in which the VD-EI measurement is locally stable. The mean of each local subseries represents the average stable visual behavior and the length of the subseries is calculated as the percentage of stable time (PoST). The VD-EI space is divided into a 7-by-7 grid. For each person, the total PoST of all stable subseries falling in each cell is associated with the progression of RE. The relationship between the total PoST and the change of RE is estimated in an ordinary linear regression.
Results :
The mean (standard deviation [SD]) RE change is -0.921±0.469 diopter and all 145 students progressed negatively. The mean of stable subseries (average stable visual behavior) for the 5 subjects with the largest and lowest RE progression is plotted in Figure 1 with the color coded by the corresponding PoST. The total PoST in each VD-EI cell and the RE progression together with the regression line is plotted in Figure 2. Twenty-nine out of 49 areas were significantly related to the RE progression (p<0.05 in red line). Negative slope indicates protective behavior while positive slope represents harmful behavior. 90% (25 out of 28) cells above 30cm have negative slope and 71% (15 out of 21) cells below 30cm have positive slope.
Conclusions :
This is the first time to show quantitatively the association between myopic refractive change and visual behavior. The approach applied in the study provides a valuable tool to illustrate the myth of myopia.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.