Purpose: The Adaptation to Age-related Vision Loss (AVL) scale was developed to measure the adjustment of older adults who are adapting to late-life vision loss. The purpose of this study was to assess whether the AVL scale satisfies the Rasch model in a cataract population

Methods: The 24-item AVL scale (18 negatively and 6 positively coded) was mailed to 436 cataract patients for self-administration whilst they were on the waiting list for cataract surgery at the Flinders Eye Centre, Adelaide, South Australia. Rasch analysis was performed to determine whether the items were measuring a single construct (unidimensionality) as examined with fit statistics and principal components analysis (PCA) of the residuals. The ability of the scale to distinguish between the levels of adaptation of the participants (person separation) was investigated, with a value ≥2.0 established as the minimum acceptable.

Results: The AVL scale was unable to differentiate sufficiently between participants’ levels of adaptation, indicating poor person separation. One item did not fit the construct, causing misfit. Furthermore, the five positively worded items did not appear either to measure the same construct as other items, resulting in lack of unidimensionality evidenced by PCA. Following the deletion of these items, the AVL scale was one-dimensional but a single item continued to misfit, so it had to be deleted, resulting in an 18-item AVL scale. Even so, the discriminating abilities of the scale continued to be poor.

Conclusions: The AVL scale is not an appropriate measure of adaptation to vision loss in a cataract population.

Key Words: Rasch analysis; adaptation to Age-related Vision Loss Scale; cataract; Australia.

J Optom, Vol. 2, No. 3, July-September 2009
Accepted: 6 July 2009

Article is in both English and Spanish.

Vijaya K Gothwal^1,2, Thomas A Wright¹, Ecosse L. Lamoureux^3,4,5 and Konrad Pesudovs1^1
1NH&MRC Centre for Clinical Eye Research, Department of Ophthalmology, Flinders Medical Centre and Flinders University of South Australia, Bedford Park, South Australia, Australia
²Meera and L B Deshpande Centre for Sight Enhancement, Vision Rehabilitation Centres, L V Prasad Eye Institute, Hyderabad, India
³Centre for Eye Research Australia, Department of Ophthalmology, University of Melbourne, Victoria, 8002, Australia
⁴Vision CRC, Sydney, New South Wales, Australia
⁵Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.