Axial length change with short-term exposure to visual stimuli with a limited range of spatial frequencies

Abstract

Purpose : Animals reared in environments with limited spatial frequency information can show changes in eye growth. The human eye shows short-term changes in axial length (AxL) in response to defocus, which limits the spatial information available to the eye. This study investigated the change in AxL with 60-minute exposure to videos filtered to present differing ranges of spatial frequencies, including full spectrum (FS), lowpass (≤ 1.5 cpd, LSF), bandpass (3 – 6 cpd, MSF) and highpass (≥ 10 cpd, HSF) (Figure 1), all viewed in the distance with no blur present.

Methods : Thirteen participants were tested on four separate days. Each session involved a 20-min washout (watching the FS video) and then 60-min exposure to a spatially filtered video (randomized order). Participants watched all videos binocularly, with optimum distance refractive correction. AxL of the RE was measured with Lenstar LS 900 at baseline (after washout), and then at 30 and 60 min. A still image was used as a fixation target when measuring the AxL and to measure the accommodation response with a binocular autorefractor WAM-5500. The ON- and OFF-retinal response stimulated by the videos was also analysed using the “Realtime ON OFF analysis of the visual world” software.

Results : A two-way repeated measures ANOVA showed that AxL did not change significantly by viewing the spatially filtered videos (F_3,33 = 0.71, p = 0.56). The AxL change with 60-min exposure to LSF (+3 ± 6 µm), MSF (+2 ± 7 µm) and HSF (+4 ± 6 µm) and FS videos (-0.5 ± 4 µm) were similar (Figure 2). The change in accommodation response (range: 0.03 D to 0.13 D) stimulated by the videos was minimal and not statistically significant (P>0.05). All four videos were found to result in a bias towards an ON-retinal pathway stimulation.

Conclusions : The spatial frequency detail of the visual stimulus did not cause significant short-term changes in axial length, when the eye was optimally corrected. This result does not support the hypothesis that the spatial frequency content of the retinal image is the primary factor in short-term defocus mediated changes in axial length.

This is a 2021 ARVO Annual Meeting abstract.

 

Figure 1: An example of the spatially filtered videos: (a) FS (b) lowpass, LSF (≤1.5 cpd) (c) bandpass, MSF (3 – 6 cpd) (d) high pass, HSF (≥10 cpd).

 

Figure 2: Mean Axl change (+/- SD) from baseline (µm) over the 60-minute viewing sessions with different spatially filtered videos (FS, LSF, MSF and HSF).