Abstract
Purpose: :
There is currently debate as to whether superior performance (e.g. on visual search) by individuals with autistic spectrum conditions (ASC) reflects a difference in low-level processing or in higher-level cognitive factors. Our purpose was to determine whether subjects with ASC differ in basic clinical visual function from unaffected observers. Previous work1 indicated superior visual acuity in ASC subjects, but methodological issues have been raised with this study2, 3.
Methods: :
17 adult observers with a clinical diagnosis of ASC (age 31.2±10.2yrs; 9 male, 8 female; Autism Spectrum Quotient (AQ) 39.1±6.6) and 19 controls (age 28.9±6.6yrs; 13 male, 6 female; AQ 16.6±4.0) participated. Habitual distance visual acuity (VA) was measured with an EDTRS chart. Observers were refracted by an Optometrist (KL) and best corrected VA assessed with the EDTRS chart, and with the FrACT4 at a 4m working distance. Clinical contrast sensitivity was assessed with Mars charts.
Results: :
Refracting observers improved mean binocular EDTRS VA from -0.13 to -0.17logMAR. This difference was statistically significant (F(1,34)=18.6, p<.001), but not group dependent (F(1,34)=0.7, p=.42). We report no significant difference between ASC and control groups’ best corrected monocular (t=1.56, df 70, p=.12) or binocular (t=0.94, df 34, p=.35) acuity assessed by EDTRS chart, or binocular acuity assessed with FrACT (t=0.27, df 34, p=.79). Clinical contrast sensitivity did not differ between groups (t=0.28, df 34, p=.78).
Conclusions: :
There is no evidence for differences in basic clinical visual functions between young adults with ASC diagnoses and controls. Superior performance by observers with ASC on other visual tasks does not appear to arise from differences in low-level visual function.
References: :
1. Ashwin, E et al., Biol Psychiatry, 2009. 65:17-21. 2. Bach, M & Dakin, SC. Biol Psychiatry, 2009. 66:e19-20. 3. Ashwin, E et al., Biol Psychiatry, 2009. 66:e23-24. 4. Bach, M. Optom Vis Sci, 1996. 73:49-53.