Through focus imaging with a non coaxial soft contact lens optical design for presbyopia

Abstract

Purpose : Non coaxial optical designs alter the light energy distribution reaching the retina and may offer visual performance benefits for a range of applications in ophthalmic lenses, including contact lenses. We aim to demonstrate through focus imaging of a novel presbyopic soft contact lens design incorporating non coaxial optics (NC) using a physical model eye and clinical visual acuity.

Methods : The NC was designed to correct presbyopia (low, medium and high additions) in a single lens by creating an axial depth of focus contributed to by divergent light from off axis focal points. Two versions of the NC lens were manufactured for clinical and benchtop measures, namely, a soft contact lens (Soft NC; lathed Hioxiflcon B, 49% hydrogel) and an exact geometrical and optical replica in polymethylmethacrylate (PMMA NC; geometrical design adjusted for refractive index). Using the PMMA NC, through focus images of a 36 arm Siemens star target was captured on an anatomically correct physical model eye (on-axis) over vergences from -0.2D to +2.6D (0.2D steps; 5mm pupil). Monocular high (90%) contrast visual acuity (VA; logMAR) was recorded for a high (+2.5D) addition presbyope at vergences corresponding to 600cm, 200cm, 100cm, 50cm and 40cm wearing Soft NC and 2 controls (Coopervision Clariti^TM single vision sphere (distance refractive error correction [SV] and Coopervision Clariti^TM Multifocal high addition [MF].

Results : Siemens star images for the PMMA NC in the model eye are shown in Figure 1. Good focus was demonstrated from 0.0 to +2.0D vergence indicating a continuous depth of field over 2.0D. VA with Soft NC was 0.0 logMAR or better from 600cm through 50cm and was 0.1 at 40cm (Figure 2) - significantly better than SV except at 600cm and comparable to MF at 50cm and 40cm.

Conclusions : A single parameter presbyopic contact lens designed with non coaxial optics demonstrated good through focus performance over 2.0D vergence in a physical model eye and with visual acuity (600cm to 50cm). Non coaxial optics may be configured with clinically meaningful depth of field and provide the lens designer with the potential to develop simultaneous vision based optical designs for presbyopia.

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

 

Fig 1: Siemens Star images formed by RGP NC in model eye at different vergences (0.0D to +2.2D)

 

Fig 2: Visual acuity measured at different vergences for soft NC, soft MF and soft SV