Abstract
Purpose :
Two-photon vision is associated with the perception of short pulses of near-infrared (NIR) laser radiation as a visible (VIS) light. It is caused by the nonlinear process of two-photon absorption by visual pigments. The longer wavelength of the stimulating radiation suggests that this phenomenon may be beneficial for functional visual examination in cataract patients compared to normal, one-photon based, perception of light. To verify this hypothesis, we performed measurements of the one-photon (VIS) and two-photon (IR) visual thresholds for a group of cataract patients before and 6 months after the intraocular lens (IOL) implantation.
Methods :
We used custom-built two-photon perimeter with NIR pulsed laser (λc = 1028.4 nm, τp = 12.2 ps, Frep = 19.17 MHz) and VIS continuous wave laser (λ = 520 nm) as a source of stimulating light. Due to two-photon vision effect both sources are perceived as green. The sensitivity of central part of the macula (10 deg diameter) was tested in 32 patients aged 53-84 years, under scotopic conditions. The examined patients were qualified for IOL surgery because of cataract with no diagnose of diabetes and retinal diseases. 6 months after the surgery 25 patients were tested again. The retinal sensitivity assessment was the same as described in [1] except smaller number of tested locations (17) to shorten examination time. The visual function of the patients before and after IOL implantation was also tested by commercial MAIA microperimeter (photopic version) on the same retinal area. The study was approved by the Ethics Committee of the Collegium Medicum, NCU.
1. BOE 12(1) pp. 462-479 (2021)
Results :
The mean difference of sensitivity after the cataract surgery was equal to: 6.6 ± 1.3 dB (SEM) for VIS laser, 2.8 ± 0.7 dB (SEM) for IR laser and 2.0 ± 0.6 dB (SEM) for MAIA. There is significant difference between VIS and IR result (p-value 0.014) and between VIS and MAIA result (p-value 0.004).
Conclusions :
The obtained results indicate that presence of cataract stronger affects the sensitivity of retina as measured by VIS- than IR-laser-based perimetry under scotopic conditions. It supports the hypothesis that two-photon visual sensitivity of cataract patients is limited less by the changes that occur in the lens than normal visual sensitivity. Surprisingly, the photopic visual sensitivity measured by MAIA also has changed slightly, which may be explained by wide spectral range of stimulus used in the device.
This is a 2021 ARVO Annual Meeting abstract.