Retinotopic Accommodation Responses in Myopia

Abstract

The experiments demonstrate a reduction in retinotopic processing in LOMs, which results in an increased variability in their dynamic accommodation response to stationary near targets and reduced performance for dynamic step tasks. The results demonstrate a reduced blur appreciation under dynamic conditions in these refractive groups that may lead to periods of retinal image blur of varying magnitude during near work.

The relationship between object spatial profile and accommodation microfluctuations in emmetropes and myopes

“…If high SFs are below the detection threshold of the accommodation controller in myopes (MYOs), the contrast gradient available in the cortical image would be shallower than that found in non-myopic observers. This finding could explain the higher magnitude microfluctuations that have been reported in myopic observers (Day et al, 2009a;Day, Strang, Seidel, Gray, & Mallen, 2006;Seidel et al, 2003). In addition, a shallower perceptual contrast gradient would lead to a larger ocular depth of focus (Day et al, 2009a), which has also been reported in MYOs (Collins, Buehren, & Iskander, 2006;Rosenfield & Abraham-Cohen, 1999;Vasudevan, Ciuffreda, & Wang, 2006).…”

“…Differences in the magnitude of the accommodation microfluctuations have been found between MYOs and EMMs have been found (Day et al, 2009a;Day et al, 2006;Seidel et al, 2003), but none of the studies have made a detailed investigation of the effect of altering the contrast gradient in these subject groups. There is a suggestion from a recent paper that MYOs may be less sensitive to high SFs than EMMs (Radhakrishnan et al, 2004), and this needs to be investigated further.…”

“…Previous work suggests that information regarding image blur may be provided by modulation of the cortical image by the accommodation microfluctuations, which are small variations in dioptric power (within an envelope of about 0.50D) of the crystalline lens (Campbell, Robson, & Westheimer, 1959;Charman & Heron, 1988;Collins, 1937;Collins, Davis, & Wood, 1995;Denieul, 1982;Kotulak & Schor, 1986a;Seidel, Gray, & Heron, 2003;Winn, Pugh, Gilmartin, & Owens, 1990a). Computational modeling of the accommodation error detector proposed that the accommodation controller compares changes in lens power with the cortical image contrast over time (Kotulak & Schor, 1986a).…”

Near Work–Induced Contrast Adaptation in Emmetropic and Myopic Children

“…If the participants stayed accommodated at near for a protracted time, this could produce myopic defocus on the contrast-sensitivity test pattern. However, the reported time required to change the accommodation response from 2.5 to 1 D is typically 0.25 to 0.30 seconds [49][50][51] and is similar for emmetropes and myopes [52][53][54] ; thus this is unlikely to account for the observed findings. Moreover, the contrast-sensitivity test was performed at 1 m, a distance close to the tonic accommodation level and a distance considered to usually induce high focusing accuracy.…”

Dynamic Accommodation Responses Following Adaptation to Defocus

“…Seidel et al 20 observed that accommodation latency periods were significantly longer in a group of late onset myopes (LOM) in comparison with groups of EMMs and early onset myopes (EOM). Under binocular conditions the latencies were equivalent, but EOMs and LOMs produced significantly longer response times to a 2.00 D step change than EMMs.…”