Myopia Control by Optical Means: Past and Present

Myopia is in epidemic proportion in China and many Asian cities. The prevalence of myopia is well beyond 80% in these cities. Since high myopia increases the risk of sight-threatening diseases such as glaucoma, retinal degeneration and detachments, it is important to decrease the prevalence of myopia and in particular the high myopia population. In fact, China has identified myopia as a national concern in 2018 and different ministries are joining hands in leading major initiatives to combat myopia in China. From animal studies, we now know that eye growth is modulated by optical inputs received during the early developmental phase. Apparently, optically defocused images formed behind the eye (called hyperopic defocus) would accelerate eye growth; whereas defocused image formed in front (called myopic defocus) would slow down eye growth. This feedback mechanism is universal in many different animal species. In addition, our studies have shown that the eye can integrate simultaneously presented optical defocus and that myopic defocus is a power stop signal to eye growth. Using the principle, we have attempted to incorporate and project myopic defocus in novel optical devices for controlling myopia progression in children. The Centre for Myopia Research of the PolyU has successfully produced special contact lenses as well as spectacle lenses that have incorporated myopic defocus for myopia control. They are Defocus Incorporated Soft Contact lenses (DISC) and Defocus Incorporated Multiple Segments (DIMS) spectacle lenses. Randomised control clinical trials have been conducted in schoolchildren using these lenses and they have shown to effectively slow down the myopia progression by 60%. These new optical devices could significantly decrease the high myopia population and will be useful in controlling myopia in children clinically. Acknowledgement: The research was supported by the Edwin Leong Endowed Professorship, and industrial grants from Hoya Lens Ltd (H-ZG3B; H-ZG5N); Dean Reserve Fund (1-ZVN2), RGC/GRF PolyU 151033/15M; PolyU 151051/17M.