Binocular adaptive optics visual simulator with convergence control.

We present a new generation of binocular adaptive optics visual simulator (B-AOVS). As in earlier versions, the system optimizes hardware use by managing both eyes with a single intensity spatial light modulator for pupil control and a single phase modulator for aberration manipulation, both of them based on liquid-crystal-on-silicon (LCoS) technology. A single Hartmann-Shack sensor measures refraction and aberrations in both eyes, and a single tunable lens extends the correction and measurement range. Only the stimulus generation module is duplicated, using two HD microdisplays to ensure adequate resolution and field of view. The main improvement in this prototype is the addition of a motorized twin-periscope system that adjusts the vergence angle of the stimuli, enabling more realistic visual testing at multiple distances. Among other applications, this feature paves the way for studies requiring accommodative changes that would be otherwise unfeasible due to the vergence-accommodation conflict. For this particular reason, studies with past generations of B-AOVS were typically carried out in presbyopes or cyclopleged subjects, on the assumption that avoiding the conflict by preventing accommodation would render convergence irrelevant. To specifically test this assumption, our first use of the prototype was to measure defocus curves in one presbyopic and four cyclopleged subjects for varying levels of induced spherical aberration, with and without convergence control. In this non-accommodative situation, convergence showed minimal influence, as defocus curves remained similar, and therefore the validity of previous studies with B-AOVS under fixed convergence conditions remains unchallenged. Beyond this case, the new vergence control system enables accurate 3D stimulus presentation for visual simulation and opens avenues to study the impact of aberrations on the vergence-accommodation conflict.