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Derivation of the Acceptance and Self-Worth Adjustment Scale

Tabrett, Daryl R.; Latham, Keziah

Optometry & Vision Science:
doi: 10.1097/OPX.0b013e3181f6f760
Original Article
Abstract

Purpose. The original 55-item Nottingham Adjustment Scale (NAS) is a first generation self-report instrument constructed using classical test theory to evaluate adjustment to vision loss. This study assesses the function of the NAS using Rasch analysis in a sample of adults with visual impairment and presents a revised second-generation instrument.

Methods. Ninety-nine subjects with established vision loss (median onset 5 years) were administered the NAS. Rasch analysis was performed to: (1) determine optimum response scale function, (2) aid item reduction, (3) determine reliability indices and item targeting, (4) assess unidimensionality using Rasch-based principal component analysis, (5) assess differential item functioning (notable defined as >1.0 logit), and (6) formulate person measures to correlate with Geriatric Depression Scale scores and distance visual acuity to indicate convergent and discriminant validity, respectively.

Results. Response categories exhibited underutilization, which when repaired improved response scale functioning and ordered structural calibrations. Misfitting items were removed iteratively until all items had mean-square infit and outfit values of 0.70 to 1.30. However, principal component analysis confirmed insufficient unidimensionality (two contrasts identified, eigenvalues 2.4 and 2.3). Removal of these contrasts and two further iterations restored unidimensionality. Despite item mistargeting (1.58 logits), the revised 19-item instrument demonstrated good person (0.85) and item (0.96) reliability coefficients, good convergent and discriminant validity, and no systematic differential item functioning. The resultant 19-item instrument was termed the Acceptance and Self-Worth Adjustment Scale (AS-WAS).

Conclusions. In those with established vision loss, the 19-item Acceptance and Self-Worth Adjustment Scale is a reliable and valid instrument that estimates the level of adjustment concerned with acceptance, attitudes, self-esteem, self-efficacy, and locus of control. An additional measure of depression and anxiety is recommended to assess adjustment in a broader sense. Confirmation of item ordering is required if to be used in those with newly acquired vision loss.

Author Information

*BOptom, MCOptom

PhD, MCOptom

Vision and Eye Research Unit, Postgraduate Medical Institute, Anglia Ruskin University, Cambridge, United Kingdom (DRT, KL), and Department of Vision & Hearing Sciences, Anglia Ruskin University, Cambridge, United Kingdom (DRT, KL).

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.optvissci.com).

Received December 1, 2009; accepted July 7, 2010.

Keziah Latham; Department of Vision and Hearing Sciences; Anglia Ruskin University; East Road; Cambridge CB1 1PT, United Kingdom; e-mail: Keziah.latham@anglia.ac.uk

© 2010 American Academy of Optometry