Abstract
Purpose :
Multifocal contact lenses (MCLs) attempt to increase depth-of-focus in presbyopic patients and are an emerging method to halt myopia progression in young myopes. We measured optical aberrations in patients fitted with same MCLs designs and estimated through-focus optical performance to investigate the relative impact of native and MCL optics on their function.
Methods :
Ten young subjects (YS, 25±2yrs) and five presbyopic subjects (PS, 52±5yrs) were fitted with MCLs of same distance power (-2 D) and three different center-near adds (Low Add: +1.25D, Middle Add:+1.75D, High Add: +2.5D, LA, MA, HA, respectively). Ocular high order aberrations (HOAs) were measured under paralyzed accommodation, with no lens, and lenses LA, MA, HA, using a Hartmann-Shack wavefront sensor (HASO, 32x32 microlenses, Imagine Eyes). A Badal system corrected the patient’s spherical refractive error and the defocus introduced by the fixed power MCLs. Wave aberrations (eye, and eye with MCL) were fitted by 6th order Zernike polynomials on 4.57 mm pupils. Simulations of wave aberrations (eye w MCLs) were obtained by adding the eye’s wave aberrations with the phase map representing the MCLs, based on their theoretical power profiles. Through-Focus (TF) optical performance was calculated as Visual Strehl (VS) –from the measured/simulated wave aberrations- as a function of defocus. DOF was estimated as the dioptric range >0.1 VS
Results :
Average Root Mean Square error for native HOAs was 0.18±0.05 um (YS) & 0.17±0.06 um (PS), and average native 4th order spherical aberration (SA) was 0.04±0.04 um (YS) and 0.06±0.06 um (PS), for 4.57mm pupils. The measured average SA induced by the MCLs was: -0.04±0.03 (LA), -0.05±0.02 (MA), -0.06±0.03 (HA) um. The simulated TF VS showed an expansion of DOF with MCLs (not captured in the experimental HS-based data). VS at best focus (No Lens) was 0.45±0.15 (YS) and 0.40±0.16 (PS), and decreased on average by a factor of 1.10/1.68 (LA), 1.42/1.21(MA) and 2.35/2.43 (HA) in YS/PS. The average DOF with the MCLs was 1.67±0.08D (LA), 1.69±0.08D (MA), and 2.07±0.26 D (HA).
Conclusions :
MCLs increase DOF both in young and presbyopic subjects, at the expense of slight optical degradation at best focus. The increase is systematic in all subjects, only slightly affected by native aberrations, and with near add magnitude. Hartmann-Shack measurements may underestimate the optical effect of MCL if not sufficiently high order Zernike polynomials are used.
This is a 2020 ARVO Annual Meeting abstract.