Abstract
Purpose: :
Current vision science adaptive optics systems rely on near-infrared wavefront sensing beacons that are visible to subjects and interfere with perception of visual stimuli (Hofer et, al. ARVO 2010). Our purpose was to enable effective adaptive optics correction without impacting visual perception.
Methods: :
We made a number of modifications to an existing adaptive optics system to allow less obtrusive wavefront correction, including: 1. replacing the original 5 μW, 840 nm beacon (a typical wavelength) with a 12 μW and 980 nm beacon, 2. offsetting the beacon from the system axis and co-locating with a chromatically neutral fixation spot, and 3. shuttering the beacon when not actively wavefront sensing. We assessed the impact of these modifications by having 5 subjects use a hue-scaling method to report the appearance of small (~1 arcminute), brief (30 ms), 580 nm stimuli presented to the dark adapted fovea with and without the presence of the wavefront sensing beacon.
Results: :
Effective adaptive correction was obtained after these modifications, as determined by the measured residual wavefront and images of the photoreceptor mosaic. At the minimum power required for effective wavefront correction the 980 nm beacon was typically below threshold in photopic conditions and slightly above threshold when dark adapted, i.e. nearly invisible. Although the presence of the beacon could be effectively masked in most subjects by co-locating with a neutral fixation spot, it still significantly impacted color appearance for one subject in this condition, despite not being subjectively visible. However, the addition of a shutter to block the beacon when not actively wavefront sensing effectively eliminated this impact.
Conclusions: :
Extending the wavelength in combination with sensibly locating and shuttering the wavefront sensor beacon allows effective correction of the eye’s higher order aberrations without perceptual interference, even for threshold stimuli in the dark adapted fovea.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • perception • color appearance/constancy