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Vivek Labhishetty, Steven Cholewiak, Martin S Banks; Peripheral stimulation can override foveal stimulation in driving accommodation. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1402.
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© ARVO (1962-2015); The Authors (2016-present)
Experiments suggest that hyperopic focus in the peripheral retina increases the risk of developing myopia. This implies that signed defocus can trigger eye growth. But does this mean blur in the periphery affects other oculomotor mechanisms such as accommodation? Stimulation of the human peripheral retina when no foveal stimulus is present elicits accommodation. But in natural viewing, the fovea and periphery are nearly always both stimulated. We investigated accommodative responses when the fovea and periphery are both stimulated, but with different signs of defocus.
10 participants (18-25 yrs) viewed black-white textures monocularly. The stimuli varied in depth (±1.5D) sinusoidally (0.1, 0.2, 0.5, or 1.0Hz). Three conditions were tested: Real Blur, Defocus+LCA, and Defocus+LCA Conflict. In Real Blur, the optical distance of the textures (disks subtending 1, 2, 4, 6, 8, or 14°) was varied using a focus-tunable lens. For Defocus+LCA, the textures (again 1, 2, 4, 6, 8, or 14°) were rendered using simulated defocus with color-correct longitudinal chromatic aberration (LCA), a cue that drives accommodation. For Defocus+LCA Conflict, stimuli were split into two abutting regions, a variable sized central disk (1, 2, 4, 6, or 8°) and a peripheral annulus (14° outer radius), both rendered using defocus blur with LCA. The central and peripheral regions had equal magnitudes but opposite signs, signaled by LCA. Accommodative responses were measured at 30Hz with an open-field autorefractor. The data were fit with sinusoids to estimate response gain and phase.
Gains for the Real Blur and Defocus+LCA conditions were similar and consistent across stimulus sizes. Gain for Defocus+LCA Conflict were significantly lower when the central stimulus was smaller than 6°. Phase was consistent with the peripheral stimulus, not the foveal stimulus when the central stimulus was smaller than 4°.
When a small foveal stimulus (4° or smaller) was presented in conflict with a peripheral stimulus, response was dominated by the peripheral signal. Thus accommodation is determined by both foveal and peripheral stimulation when both are present. This observation has important implications for myopia prognosis and treatment and for computer-graphics techniques like foveated rendering.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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