Shorter Viewing Distance Reduces Contrast in Man-Made Environments.

Purpose: Myopia is associated with increased near-work, time spent indoors, and urban environments. This may in part stem from the spatial frequency (SF) composition of the visual environment in such scenarios compared to nature. We investigated the SF content of natural and man-made environments and how the relative contrast experienced may be affected by viewing distance. Design: Experimental study of environmental contrast. Subjects Participants and Controls: Digital images (n = 594) from natural, mixed-urban, urban, and indoor environments across Singapore. Methods: The fast Fourier transform was computed and radially averaged, and the slope of the amplitude spectra with SF was determined. The total contrast energy within each SF octave ( Main Outcome Measures: Environment differences in SF gradient, total contrast, and scale invariance. Results: As expected, indoor environments displayed the steepest SF gradients at -1.36 ± 0.1, more than urban (-1.22 ± 0.1, Conclusions: The SF content of natural environments is consistent regardless of viewing distance, signifying scale invariance. This does not apply in man-made environments where contrast at all SFs directly depends on viewing distance. This implies that shorter viewing distances in man-made environments further exacerbate inherent deficits in middle and higher SF contrast, and thus these environments may fail to stimulate the eye with sufficient contrast compared to natural environments, possibly explaining why such environments induce myopia. Financial Disclosures: The authors have no proprietary or commercial interest in any materials discussed in this article.