Design of multizone soft contact lens to slow myopia progression

This paper presents a design of multizone soft contact lens (SCL) to correct myopia and slow its progression in children and young adults. The SCL anterior surface was a multizone spherical surface, being divided into five concentric zones with diameters of 3.5, 4.5, 6, 8.6, and 14.2 mm respectively. The first zone is for distance correction surrounded by alternating plus power treatment zone and distance correction zone. The outmost zone was a connecting carrier for fixing the SCL. Based on an established myopic model eye, the multizone SCL was designed employing Zemax software. The relative peripheral myopic shift of the designed SCL was analyzed by the mean sphere M at eight peripheral positions from 0° to 35° in steps of 5° under 3 and 6 mm pupil diameters. A -3 diopter (D) multizone SCL with a central thickness of 0.0659 mm and a diameter of 14.2 mm was obtained. The refractive error at 0° field of view (FOV) is fully corrected for 3 mm pupil. The mean sphere M of the myopic model eye fitted with the designed SCL is up to -5.45 D at 20° under 3 mm pupil (photopic vision), and nearly -6 D at 35° under 6 mm pupil (scotopic vision), showing significant peripheral myopic shift. Besides, the modulation transfer function (MTF) values remain above 0.56 at 50 c/mm for distance vision under 3 mm pupil for the full ±15° FOV. The above shows that the designed multizone SCL is able to correct myopic refractive error in photopic vision. In addition, it produces a large peripheral myopic defocus in both photopic and scotopic conditions, exhibiting excellent potential to slow the myopia progression.