Principles of Accommodation and Technology Update of Presbyopia Corrections using IR and UV Lasers

Purpose: To update and review the technology and principles of laser presbyopia reversal (LAPR) via sclera ablation and thermal shrinkage using infrared and UV lasers. Recent clinical data and new methods are also summarized. Study Design: LAPR using laser sclera ablation for increased accommodation of presbyopic eyes. Place and Duration of Study: New Taipei City, Taiwan, between June, 2021 and July, 2021. Methodology: Accommodation gain was obtained by laser scleral ablation of an eye using Er:YAG laser (at 2.94 um) using either line-pattern or dots-pattern outside the limbus in the oblique quadrants of an eye. The principles of accommodation and the key factors influencing the outcomes are discussed. The accommodation gain (AG) after the surgery is mainly due the change in anterior curvature and anterior shift of the lens. The effectiveness of ciliary body contraction for lens relaxation (or accommodation) may be influenced by the combined aging factors, including lens property changes (index, size, thickness and curvature), tissue elastic changes (in sclera and ciliary) and the zonular tension change. Classical theories of accommodation include Helmholtz and Schachar hypothesis. The key issues and new directions to overcome the drawbacks of the existing LAPR procedure (based on scleral ablation) are proposed. Clinical outcomes from two major groups, SurgiLight and Ace Vision, with two years follow are summarized. Results: Clinical outcomes during 2000 to 2020 are summarized showing an average Accommodation gain about 2.0 D, and postoperative egression about 0.25 D (after two years). Conclusion: Laser presbyopia reversal (LAPR) via sclera ablation using infrared laser is safe and effective, but suffers drawbacks of being invasive and procedures are too slow. New directions are required for improved outcomes.