Abstract
Purpose :
Blur perception is influenced by the eye’s optical quality during emmetropization. We measured sensitivity to different types and levels of simulated optical blur and optical quality across the visual field in young children with normal vision.
Methods :
Children (n=27, 7.86±0.91yrs) with functional emmetropia (SE OD +0.94±0.55D) participated in 2 tests. (1) Blur discrimination thresholds were measured with an adaptive 4AFC task previously used in adults. Dead leaves stimuli were blurred with different pedestal levels and increments of Defocus (DEF) or Spherical Aberration (SA) kernels beyond 0°, 6°, or 12° eccentricity at 40cm. Participants chose which quadrant appeared blurriest. Blur discrimination thresholds were fit with a 2-parameter (Intrinsic Blur, Blur Criteria) dipper function. (2) Optical quality across the central horizontal ±30° was assessed using a scanning aberrometer at 4m and 40cm viewing distances. Strehl ratios, defocus and primary SA were computed for 4mm pupils. Outcomes were analyzed with One-way ANOVAs and correlations with axial length (AXL, 22.78±0.74mm).
Results :
(1) Intrinsic blur showed an overall effect of eccentricity (DEF & SA, p<0.001), significantly decreasing for 12° vs. 6° (DEF p=0.003, SA p=0.001) and 0° (DEF p<0.001, SA p=0.001), but no differences between 6° and 0°. Blur Criteria showed no general effect of eccentricity. Longer eyes showed lower Intrinsic Blur (DEF p=0.040, SA p=0.014) and Blur Criteria (SA p=0.032). (2) Strehl ratios also showed eccentricity-dependence (p=0.006), with better quality in the central 12° (p=0.014) and nasal retina (p=0.004) that increased with AXL (p=0.003). Defocus was more negative (hyperopic) peripherally (p<0.001). Primary SA showed no effect of eccentricity but was smaller in longer eyes (p<0.001). (3) For 0° (p=0.009) and 6° (p=0.020), Blur Criteria for DEF was correlated with the eye’s defocus. For 12°, Blur Criteria for SA was correlated with the eye’s SA (p=0.050).
Conclusions :
Elevated Intrinsic Blur at 12° but not between 0° and 6° indicate a critical role of the 6-12° retinal area in blur decoding. A similar pattern was observed of eccentricity dependence for optical quality. These correlations indicate a possible relationship of defocus within the central 12° and SA beyond 12°. Less positive SA was found in longer eyes with less hyperopia, these eyes (at higher risk of developing myopia later) also show lower sensitivity to blur.
This is a 2021 ARVO Annual Meeting abstract.