AUTHORS:

Kaczkos O., Grochalski M., Vinas Pena M., Zielinska A., Wojtkowski M.D., Pniewski J., Komar K.

ABSTRACT:

Purpose : Retinal-projection systems must cope with the eye’s accommodation, which is individual, influenced by multiple factors, and varies over time posing a challenge for accurate retinal image formation. Here, we objectively assess accommodation in two-photon vision and examine the role of aberration correction, outlining its potential for augmented-reality (AR) applications.

Methods : The study involved 6 healthy volunteers (3W, 3M; aged 25-47) with no diagnosed visual system pathologies. Ethical approval was obtained from the Bioethics Committee of the Collegium Medicum, Nicolaus Copernicus University. The experimental flower-shaped stimulus (4.5 arcmin size) was projected onto the retina using a MEMS scanner with a 520 nm cw laser for one-photon (1P) stimulation or a 1028 nm pulsed laser for two-photon (2P) stimulation, both perceived as green. The optical system also included an adaptive optics path with a Hartmann-Shack wavefront sensor and a deformable mirror (DM140A-35-P01), operating with an 880 nm beacon beam. Accommodative demand was provided by changing defocus in a Badal system, alternating from 0 D to 2 D, with each step lasting 5 seconds for eight repetitions. The accommodative response was calculated based on changes in the measured defocus. The procedure was performed for 1P and 2P stimulation, with and without static correction of higher-order aberration and astigmatism (HOA+ast) of the subject’s eye. Ocular aberrations of the subjects were obtained for all conditions.

Results : The measured accommodative lag for 2P vision with natural aberrations was larger than for 1P vision (0.77 ± 0.13 D and 0.48 ± 0.08 D, respectively, p-value 0.04). After correction of HOA+ast, this effect was still present: 0.56 ± 0.11 D for 2P vision and 0.35 ± 0.07 D for 1P vision (p-value 0.04). Correction of HOA+ast reduced the accommodative lag by 40.5 ± 13.9% for 2P vision (p-value 0.01) and by 46.18 ± 17.28% for 1P vision (p-value 0.02).

Conclusions : Two-photon vision is associated with a higher accommodative lag, both with natural aberrations and after HOA+ast correction, demonstrating a reduced accommodative response despite preserved image quality. Combined with previous evidence of high visual quality over a broader defocus range (IOVS 2025;66(8):1551), these results suggest that 2P stimulation may reduce accommodative fatigue, providing a functional advantage for AR displays.

Investigative Ophthalmology & Visual Science, 2026, vol. 67(7), art. 4218, doi: