Abstract
Purpose :
Normalized cumulative frequency progression data for treated and untreated eyes in myopia control trials produce lines with near equivalent gradients, strongly suggesting a consistent absolute reduction in axial elongation across the progression range.(Brennan & Cheng, 2018 Eye & Contact Lens, in press) A clinical trial where intervention was applied monocularly offers the opportunity to confirm this, using progression data from untreated eyes as proxies for propensity to progress in treated eyes.
Methods :
Axial elongation data for the initial 10-month period from Anstice & Phillips (Ophthalmology 2011:118:1152) were digitized using ImageJ (https://imagej.nih.gov/ij/). Significant correlation between treated and untreated eyes (R=0.54, P < 0.001) verifies that the untreated eye serves as a measure of the propensity of the treated eye to progress. Deming regression was performed to account for variance in measures of both treated and control eyes with equal variance in both measures assumed. A ‘Bland-Altman like’ (BAL) plot was also constructed to aid visualization.
Results :
Figure 1 reproduces the Anstice and Phillips plot with overlaid Deming regression line showing near parallel slope to the line of equivalence (p=NS), demonstrating constant absolute treatment effect across the progression range. This is further confirmed in figure 2 which shows the BAL plot with a best-fit line showing near zero gradient (p=NS). Apparent stochastic variation is considerable.
Conclusions :
This analysis corroborates the previous evidence that myopia control interventions provide a consistent absolute, and not relative, treatment effect across the progression range. Expressing myopia control treatment efficacy as a percentage is misleading as treatment effect is lower in percentage terms in faster progressors.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.