Control of myopia using diffusion optics spectacle lenses: 4-year results of a multicentre randomised controlled, efficacy and safety study (CYPRESS).

Aims: To evaluate the myopia control efficacy of Diffusion Optics Technology (DOT) spectacle lenses in children over a 4-year treatment period.

Methods: CYPRESS Part 1 (NCT03623074) was a 3-year multicentre, randomised, controlled, double-masked trial comparing two investigational spectacle lens DOT designs (Test 1, Test 2) and standard single vision Control lenses in 256 North American children aged 6-10 years. Children completing Part 1 (n=200) were invited to enrol in CYPRESS Part 2 (NCT04947735) for an additional 1-year period. In Part 2, Test 1 (n=35) and Control groups (n=42) continued with their original lens assignment and the Test 2 group (n=21) were crossed over to Test 1 (DOT 0.2) lenses. The co-primary endpoints were change from baseline in axial length (AL) and cycloplegic spherical equivalent refraction (cSER).

Results: Test 1 spectacle lenses demonstrated superiority to the Control in both co-primary endpoints: with a difference between means (Test 1-Control) of -0.13 mm for AL (p=0.018) and 0.33 D for cSER (p=0.008) in Part 1 and -0.05 mm for AL (p=0.038) and 0.13 D for cSER (p=0.043) in Part 2. Comparing treatment effects in Part 1 and 2 suggests that COVID-19 public health restrictions negatively impacted treatment efficacy in study years 2 and 3.

Conclusion: DOT 0.2 spectacle lenses are safe and effective at reducing myopia progression, with additional benefit evident in year 4 of wear. These results support the hypothesis that a mild reduction in retinal contrast can slow myopia progression in young children. The unprecedented disruption in participant schooling and lifestyle during the COVID-19 pandemic may have depressed treatment efficacy in Part 1.