Abnormal Effective Threshold to Blur in Graduate Students with Clinical Accommodative Disorders

Abstract

Purpose : The purpose of this study was to examine the differences in accommodative response control between subjects with normal or abnormal accommodative function, using Jiang's modified control model for steady-state accommodation that incorporate a sensory component.

Methods : 36 graduate students between age of 18 and 30 participated. Based on the standard clinical accommodative testing procedures and diagnostic criterion, the sample was divided into normal accommodation (NA) and abnormal accommodation (AA) groups with 18 subjects in each group. AA group consists of subjects with accommodative insufficiency, access and/or infacility. All accommodative responses (AR) were objectively measured using an open-field autorefractor monocularly. Accommodative stimulus-response function was assessed at 5 different stimulus distances. Baseline tonic accommodation was recorded after 5 min of dark adaptation. Accommodative error (AE) was continuously recorded during a 10 min monocular reading task at 3 diopter distance.

Results : Accommodative stimulus-response function (Fig 1A) and accommodative controller gain (ACG), representing a motor controller, showed no significant difference between groups (NA: 5.8±8.3; AA: 2.5±7.4; p=0.22) (Fig 1B). However, effective threshold to blur (ET), a parameter incorporating accommodative sensory gain (ASG) and depth-of-focus, showed a statistically significant difference (NA: 0.46±0.86; AA: -0.06±0.65; p=0.047) (Fig 1C). A positive association was found between AE and ET (Y=0.62+0.44*X; R²=0.42; p<0.001), but not AE and ACG (Y=0.66+0.02*X; R²=0.05; p=0.167) (Fig 2).

Conclusions : Our results suggest a possible association between abnormal effective threshold to blur with abnormal accommodative response in graduate students with clinically significant accommodative dysfunction. The abnormal sensory gain control might help us to understand the potential mechanism underlying clinical accommodative disorders.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Fig 1. Accommodation parameters for normal (NA) and abnormal accommodation (AA) groups: 1A, accommodative stimulus-response function. 1B, accommodative controller gain (ACG). 1C, effective threshold to blur (ET). Error bar represents standard error; * represents statistical significance (p<0.05).

 

Fig 2. Scatterplot of the correlation between accommodative error (AE) and effective threshold to blur (ET). Linear regression line is plotted as solid line.