Design and 3D Printing of Soft Orthokeratology Lenses

The effectiveness of hard orthokeratology (OK) lenses in controlling myopia has been confirmed in clinical practice. However, there exist defects including wear discomfort, limited regulation of mechanical properties and geometry, and effectiveness inconsistency with the expected efficacy. Herein, we analyze the relationship between the mechanical properties of OK lenses and the vertex displacement of the human cornea through the finite element model. It is noted that the expected corneal deformation of 15-20 μm can be achieved by soft OK lenses with an elasticity modulus above 9 MPa, which is far lower than the 2.7 GPa of commercial OK lenses. No obvious displacement difference occurred when the elasticity modulus of the OK lenses exceeded 200 MPa. Thus, we propose the hypothesis of soft OK lenses based on hydrogel materials for controlling myopia. The soft OK lenses are fabricated by a two-step 3D printing technology using a multicomponent bioink containing methyl methacrylate, hydroxyethyl methacrylate, polyethylene glycol diacrylate, and 3-(trimethoxysilyl)propyl methacrylate (KH-570). The printed OK lenses possess comfort wear, high light transmittance, smooth surface, regulated elasticity modulus (from 33 to 535 MPa) and geometry, and excellent biocompatibility. Additionally, the effectiveness of soft OK lenses is confirmed through a porcine corneal model with obvious corneal deformation comparable to that of the commercial ones. This study demonstrates the feasibility of soft OK lenses for controlling myopia and provides support for the design and fabrication of soft OK lenses for comfortable wear.