A Randomized Trial Using Progressive Addition Lenses to Evaluate Theories of Myopia Progression in Children with a High Lag of Accommodation

PURPOSE. To compare the effect of wearing, then ceasing to wear, progressive addition lenses (PALs) versus single vision lenses (SVLs) on myopia progression in children with high accommodative lag to evaluate accommodative lag and mechanical tension as theories of myopia progression. METHODS. Eighty-five children (age range, 6‐11 years) with spherical equivalent (SE) cycloplegic autorefraction between 0.75 D and 4.50 D were randomly assigned to wear SVLs or PALs for 1 year; all children wore SVLs a second year. Children had high accommodative lag and also had near esophoria if their myopia was greater than 2.25 D SE. The primary outcome after each year was the previous year’s change in SE. RESULTS. When the children were randomly assigned to SVLs or PALs, the adjusted 1-year changes in SE were 0.52 D (SVL group) and 0.35 D (PAL group; treatment effect 0.18 D; P 0.01). When all children wore SVLs the second year, there was no difference in myopia progression between SVL and former PAL wearers (0.06 D; P 0.50). Accommodative lag was not associated with myopia progression. CONCLUSIONS. The statistically significant, but clinically small, PAL effect suggests that treatments aimed at reducing foveal defocus may not be as effective as previously thought in myopic children with high accommodative lag. Finding no evidence of treatment loss after discontinuing PAL wear supports hyperopic defocus-based theories such as accommodative lag; however, not finding an association between accommodative lag and myopia progression is inconsistent with the PAL effect being due to decreased foveal blur during near work. (Clinical Trials.gov number, NCT00335049.) (Invest Ophthalmol Vis Sci. 2012;53:640‐649) DOI:10.1167/iovs.11-7769 T he prevalence of myopia in the United States may be increasing 1 ; one-third of US adults are myopic. 2 Elucidation of the mechanism underlying the progression of myopia in children could yield more effective treatments. Although progressive addition lenses (PALs) have generally yielded modest reductions in myopia progression that were not clinically meaningful, 3‐8 subgroup analyses from a previous large, wellexecuted clinical trial found that PALs may be more effective in children with high lag of accommodation. 9 Positive results from PAL treatment in children with high lag of accommodation could provide insight into the mechanism responsible for juvenile-onset myopia progression. The Study of Theories about Myopia Progression (STAMP) is a 2-year clinical trial designed to evaluate two theories of myopia progression using the previously reported PAL treatment effect. The first theory hypothesizes that high accommodative lag during near work produces hyperopic retinal blur that causes accelerated axial eye growth. 10‐13 The ability of hyperopic retinal blur to accelerate eye growth is well documented in animals. 14‐17 The effect of hyperopic retinal blur may be greatest in the fovea because constant, full-field hyperopic defocus can alter eye shape to create relative peripheral hyperopia (a more prolate eye shape) in monkeys. 18 However, the effect of hyperopic retinal blur is completely negated by short periods of clear vision. 19‐21 The potent effect of clear vision calls into question whether transient hyperopic retinal blur during periods of near work can cause juvenile-onset myopia progression. Although the Correction of Myopia Evaluation Trial (COMET) reported a 3-year reduction in myopia progression of 0.20 D for myopic children wearing PALs, 6 subgroup analyses found a greater treatment effect when children had high accommodative lag and either near esophoria or low myopia. 9 Two other PAL trials have also reported that