A novel approach to wavefront-guided contact lenses: Aberrations exceeding manufacturing tolerances resulting from a generic anterior surface fitting model

Abstract

Purpose : This project aims to develop a method allowing wavefront correction on any commercial contact lens. This method requires the surface of a lens be known in order to apply correction. To achieve this, the lens surface is scanned and the scan fit to a model, resulting in a digital map of the surface, here referred to as a digital lens surface (DLS). A previous study established manufacturing tolerances for this method under conditions that the DLS of the lens is explicitly known. This study examines aberrations exceeding those tolerances as a result of using a generic fitting model to determine the DLS.

Methods : A conic model defining the surface of a scleral reference lens was used to produce a reference DLS with 64 radials, each radial a copy of the conic model. A scleral lens (Lens 1) incorporating the reference DLS was lathed and then scanned with a contact 3D scanner. Scans were fit to a generic 4^th-order polynomial and the fit used to generate a 2^nd DLS with 64 radials. To assess applicability of the fit, the difference between the reference and the 2^nd DLS was calculated. Among the 64 radials, the best- and worst-matching to the reference radial, and the mean radial, were identified and used to design 3 new DLSs. A 4^th new DLS was defined using all 64 radials. The 4 new DLSs were used to manufacture 4 new scleral lenses (Lenses 2-5) and the differences in aberrations between Lens 1 and Lenses 2-5 compared to prior established manufacturing tolerances: total dioptric difference (TDD) = 0.11±0.07 D and difference in higher order aberrations (ΔHOA) = 0.136±0.055 µm RMS (7 mm pupil).

Results : Differences between the reference DLS and the 4 new DLSs derived from the generic fit resulted in TDD between Lens 1 and Lenses 2-5 of 2.8x, 2.3x, 15.7x, and 7.3x the manufacturing tolerance. Also, the ΔHOA between Lens 1 and Lenses 2-5 were 1.01x, 1.51x, 2.03x, and 4.28x the manufacturing tolerance.

Conclusions : The generic fitting model produced no lenses within manufacturing tolerances of TDD. A lens within tolerances for ΔHOA was manufactured in only the ideal case: a DLS derived from the best-matching radial; a case requiring prior knowledge of the lens surface. The novel approach must result in TDD and ΔHOA near manufacturing tolerances given no prior knowledge of the lens surface, necessitating alternatives to a generic surface fitting model.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.