First demonstration of human visual performance through refractive-index modified ophthalmic devices written in hydrogels

Abstract

Purpose : We previously showed that femtosecond laser-induced refractive index (RI) change can be used to create high quality, customized, optical devices in hydrogels and cornea (Gandara-Montano et al., 2015; Savage et al., 2014). Here, we investigated human visual performance through such devices written in hydrogel phase plates.

Methods : A scanning system consisting of a pair of X-Y galvanometer scanning mirrors, relay optics, and a microscope objective (field of view: 88x245 µm) was used to focus a 400 nm wavelength femtosecond laser into plano hydrogel phase plates (Contamac). RI change was inscribed to produce a -1.5 D sphere over a 6 mm diameter optical zone, in the form of a phase-wrapped Fresnel lens consisting of a mosaic of ~1400 stitched segments (limited by the scanner field of view). For vision testing, an adaptive optics vision simulator was used to correct native aberrations in 5 cyclopleged, visually-intact subjects (2 female, average age: 25±5 years) over a 6 mm pupil, while they viewed a white-light stimulus through a 5.8 mm artificial pupil. We then measured through-focus visual acuity (VA) and contrast sensitivity (CS) at subjective best focus with hydrogel phase plates in a plane optically relayed to the subjects’ pupil. Performance was assessed in two double-masked conditions: viewing through an untreated phase plate (UPP) or through a treated phase plate (TPP) containing the -1.5 D Fresnel lens.

Results : The average difference in subjective best focus between the UPP and TPP was -1.55±0.17 D, matching closely the intended change in refractive power. Peak VA with the UPP and TPP was -0.22±0.06 and -0.16±0.06 logMAR, respectively (p=0.047, paired Student t-test). At the peak spatial frequency (3.4 cycles/deg), CS was 73.7±42.5 and 65.3±38.0 with the UPP and TPP, respectively (p=0.478, paired Student’s t-test). From 1 to 30 cycles/deg, CS with the TPP was degraded by 7.7±8.8% as compared to the UPP, however this difference was not statistically significant (p=0.089, paired Student’s t-test).

Conclusions : Femtosecond laser-induced RI change is a promising method for correcting the eye’s refractive error and creating high quality visual devices. Future work will focus on larger field of view laser scanning systems with fewer stitched zones and expanding the ophthalmic devices towards more complex customized wavefront and presbyopia corrections.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.