Accommodative Gain in Relation to Perceived Target Clarity

Abstract

Purpose The purpose of this study is to determine the relationship between target clarity and the magnitude of accommodative lag using the metric accommodative gain (AG). Methods Monocular accommodative responses were measured with Grand Seiko autorefraction using both proximal and minus lens techniques in 139 subjects 5–35 years old. Subjects viewed a 1.5mm letter at 13 discrete distances (range = 40 – 3.33cm) for the proximal technique and fixed at 33cm through minus lenses of increasing power for the lens technique. Subjects were instructed to keep the target clear and report when it blurred. The AG was calculated (accommodative response / accommodative demand) for the four greatest consecutive demands perceived clear (termed conditions 1–4) and the first demand perceived blurry (termed condition 5). Results Multivariate planned contrast, including age as a predictor, revealed mean AG was significantly larger when the target was clear (range = 0.71 to 0.77 for conditions 1–4 across techniques) versus blurry (0.59 and 0.68 for condition 5 across techniques) (p<0.001 for proximal and p<0.036 for lens). Age was only a contributing factor for the proximal technique with youngest subjects having the largest decrease in AG when the target changed from clear to blurry (p=0.017). Conclusions These data suggest that across age and technique, the AG is relatively constant when the target is perceived clear, but drops below ~70%, on average, once the target is perceived as blurry for subjects ranging from 5 to 35 years of age. The AG may be a useful metric to compare accommodative responses across a range of demands and to identify accommodative responses which may not be sufficient to perceive a clear target.

Blur Detection, Depth of Field, and Accommodation in Emmetropic and Hyperopic Children

“…The magnitude of lag does not always correlate to levels of perceived blur (Figure 3). 17 Additionally, it has also been shown that there is a “dipper” effect in which the threshold for blur detection slightly improves when the reference blur (e.g. : the clear letter) is also out of focus.…”

“…Additionally, increased accommodative lag may occur due to an increased depth-of-focus which is associated with an increase in accommodative effort. 7, 17…”

Impact of Visual Cues on the Magnitude and Variability of the Accommodative Response in Children With Emmetropia and Uncorrected Hyperopia and Adults

“…2, Table 2), which supports the afferent pathway hypothesis for an increase in accommodative microfluctuations. Greater accommodative demands have been associated with larger accommodative lags in children and adults 43–47. Higher accommodative demands, also have been associated with increases in the depth-of-focus 42.…”

Effects of Optical Correction Method on the Magnitude and Variability of Accommodative Response: A Test-retest Study

“…In the present study, we used the WAM-5500 autorefactor, which has been demonstrated to be an accurate tool for quantifying accommodation in both static and dynamic modes, and in different contexts and experimental conditions. 34,35,[43][44][45] The WAM-5500 can acquire continuous recordings of accommodation and pupil size in the dynamic mode (high-speed), with a sensitivity of 0.01 D and 0.1 mm, respectively, and a temporal resolution of approximately 5…”

“…Interestingly, we found a lower variability, although significant between both correction methods (see figure 2), at 40 cm distance. This length is considered as the habitual distance for near tasks in the vast majority of nonpresbyopic adults, 45,61 and it is also the normalized distance used in optometric examinations for near tests. 40 We support the contention that the visual functioning may be adapted to the habitually used distance in the real life.…”