Archive | April 2010

Most important :-)

Second only to the science, at ARVO this year I’m going to try and complete my State quarters collection! None of those Eagles, thank you, but if you have quarters with States on them, especially the recently minted Dependencies ones (Guam and the like), I’ll swop you!

Do people with Autistic Spectrum Disorder have better visual acuity?

Here’s the abstract I will be presenting at ARVO on Monday coming. I look forward to lots of discussion!

Normal clinical visual function in individuals with Autism Spectrum Conditions

K. Latham 1A,1B, T. Tavassoli 2, S. Baron-Cohen 2, S.C. Dakin 3, M. Bach 4. A Vision & Hearing Sciences, B Vision & Eye Research, 1 Anglia Ruskin University, Cambridge, United Kingdom; 2 Autism Research Centre, University of Cambridge, Cambridge, United Kingdom; 3 UCL Institute of Ophthalmology, University College, London, United Kingdom; 4 University Eye Hospital, Freiburg, Germany.

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 work 1 indicated superior visual acuity in ASC subjects, but methodological issues have been raised with this study 2, 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 FrACT 4 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.

Revised Nottingham Adjustment Scale

I’ve been struggling somewhat with the technology to link to pdfs of the ARVO abstracts. There being more than one way to skin a cat, here is the abstract that Daryl will be presenting at ARVO on Sunday.

Using Rasch Analysis to Refine the Nottingham Adjustment Scale (NAS) in the Visually Impaired

D.R. Tabrett1A,1B, K. Latham1A,1B.
A Vision & Hearing Sciences, B Vision & Eye Research, 1 Anglia Ruskin University, Cambridge, United Kingdom.

Purpose: The Nottingham Adjustment Scale (NAS) 1 is an existing self-report instrument that attempts to assess the degree of adjustment to visual impairment. Some of its psychometric properties have been tested previously; this study evaluates the NAS using Rasch analysis in a sample of visually impaired adults.

Methods: The original 55-item NAS was administered to 62 individuals with visual impairment during face to face interviews. Habitual binocular distance visual acuity (VA) was measured as was the level of depressive symptoms using the Geriatric Depression Scale (GDS). Using Rasch analysis, a revised instrument was developed. The properties of the revised instrument were then explored.

Results: Response scale and item function were sub-optimal in the original NAS. Performance was improved by altering the response scale and conducting systematic item reduction. The revised 28-item NAS has high person (0.87) and item (0.94) reliabilities and a person separation of 2.57. Items were better targeted to the less well-adjusted in this sample. Person measures derived from the revised NAS did not correlate with VA (r=-0.16, p=.20) and correlated moderately with GDS scores (r=0.73; p<.001), indicating good discriminant and convergent validity, respectively.

Conclusion: The NAS instrument can be improved by editing the response scale and removing misfitting items. The resultant 28-item instrument is a reliable and valid measure of adjustment to vision loss in this visually impaired study sample. Scale function may be improved further by the formulation of items targeted towards the better adjusted.

References: 1. Dodds AG, et al., J Vis Imp Blindness 1991;85:306-310.

Pre-ARVO

Now that the ash cloud is lifting, or at least the planes have been deemed able to fly through it, next week’s trip to the ARVO meeting is thankfully looking much more likely. I’ve got 2 poster presentations at the meeting:

First is on Sunday 2nd, 10.15-11.15 and 2.45-4.30. Daryl will be presenting ‘Using Rasch analysis to refine the Nottingham Adjustment Scale (NAS) in the visually impaired’. The poster will be in Hall B/C, Program #940 and poster #A274. 

My poster is on Monday 3rd, 11.00-12.00 and 1.45-3.30. I will be presenting  ‘Normal clinical visual function in individuals with Autism Spectrum Disorders’. Program #1845, poster #D697. 

I’m really looking forward to seeing lots of familiar faces, and meeting lots of people whose work I’ve read but our paths have not so far crossed. Please do drop by the posters and say hello!

Meet the team

And this is Daryl and myself (posed casually at a Humphrey). The pic was taken for the Vision and Eye Research Unit.

New Blog

Thanks for visiting my web page! I hope to be using this blog to update on what’s new in my research, and any other related bits that may be of interest.

There is quite a bit going on just now. Daryl Tabrett (final year postgrad student) is presenting one of the preliminary analyses from his PhD work at the College of Optometrists’ Research Symposium in York on Sunday. Please go along and say hello if you are there!

The ARVO meeting in Fort Lauderdale is also coming up fast, and both Daryl and myself will be presenting posters. Its my first ARVO since 1999, so I’m really looking forward to it! More on that one soon.