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Peripheral depth cues for accommodation stimulation

Compartir 23/05/2016 Publicaciones Científicas

C. Otero1,2, M. Aldaba1,2, B. Martínez-Navarro3, J. Pujol1,2

1Davalor Research Center - Universitat Politècnica de Catalunya, Terrassa, Barcelona, Spain; 2 Centre for Sensors, Instruments and Systems Development, Universitat Politècnica de Catalunya, Terrassa, Barcelona, Spain; 3 Image and Multimedia Technology Center, Universitat Politècnica de Catalunya, Terrassa, Barcelona, Spain

Purpose

To analyze the effect of realistic images that have peripheral depth cues on the accommodative response.

Methods

Monocular accommodative responses (AR) at 2 D and 5 D of Accommodation Stimulation (AS) were measured with PowerRef II (Plusoptix, Inc.) when subjects looked randomly at 4 different scenes: one real scene comprising well known objects at different depth planes (real); and three virtual scenes comprised by different 2dimensional pictures seen through a Badal lens. First image consisted on a fixation target and a white even surrounding (white); the second image consisted on a photography of the real scene taken in conditions that closely mimic a healthy standard human eye performance (peripheral blur); and finally the third image was the same previous photography but rendered with a depth of focus to infinite (peripheral sharpness). In all cases the field of view of the scene displayed was roughly 25° and the fixation target was a Maltese cross subtending 2°.

Results

30 right eyes from healthy young subjects were measured in this study. The achieved statistical power was of 0.99. At 2 D of AS the repeated measures ANOVA did not show statistically significant differences in the AR among the 4 scenes (p>0.07) and the mean AR differences were below 0.25 D in all cases. At 5 D of AS, the repeated measures ANOVA was statistically significant (p<0.05) and the corresponding Bonferroni posthoc tests showed the following mean AR differences ± SD (pvalue) between the real scene and the virtual ones: realwhite=+ 0.66 D ± 0.03 D (p<0.01); realperipheral sharpness=+0.43 ± 0.03 D (p=0.07); realperipheral blur=+0.25 ± 0.04 D (p=0.89).

Conclusions

It is clinically shown that accommodation is inaccurately stimulated in Badal optometers that display a stimulus poor in depth cues. Contrary, AS can be clinically accurate in the same Badal optometer when displaying a realistic image rich in peripheral depth cues, even though these peripheral cues (also referred to retinal blur cues) are shown in the same plane as the fixation target. These results have important implications in stereoscopic virtual reality systems that fail to represent retinal blur appropriately.

Peripheral depth cues for accommodation stimulation

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