Rate of change and predictive factors for increasing minus contact lens powers in young myopes.

Background: Understanding the factors associated with myopic progression is critical to properly recruit subjects into clinical trials for control of myopia. The purpose of this study is to describe the rate of change in soft contact lens (SCL) power and the associated predictive factors in a young clinical population from the Contact Lens Assessment in Youth study.

Methods: Data from a retrospective chart review of myopic SCL wearers aged eight to 22 years were analysed for rate of progression of myopia and associated characteristics using multivariate methods.

Results: Myopic subjects (n = 912) with at least six months of follow-up were observed (4,341 visits, mean follow-up 25 months, 37 per cent hydrogel and 63 per cent silicone hydrogel SCLs). During observation, 36 per cent of subjects experienced a change in soft contact lens power of -0.50 D or more. Significant predictors of future increase in minus lens power were: ages eight to 13 years, shorter time to the first increase in minus power and hydrogel soft contact lens material. The mean annualised increase in minus decreased with age (-0.31D per year for eight to 13 year olds to -0.10 D per year for 20 to 22 year olds, p < 0.0001). Increases in minus were less common among users of silicone hydrogel materials than hydrogel daily disposable lenses after controlling for age (p = 0.039).

Conclusion: In this retrospective chart review of young soft contact lens wearers, the mean annualised rate of increase in minus soft contact lens power decreased with age, longer time to first increase in power and was greater with hydrogel soft contact lenses. The rates observed were similar to progression rates in prospective myopia clinical trials that employed cylcoplegic autorefraction.