Archive | October 2010

Depression and Vision Loss

Daryl and I have a CET piece in Optician today, on the topic of depression and vision loss. You can answer the MCQs here. Emotional support for VIPs (visually impaired people) is an important area: even as Optometrists / Opticians mostly dealing with the optical requirements of our patients, I think we need to be aware of the range of support that people need to help them come to terms with vision loss. Emotional support services are starting to become more widely available: the work of VINCE (Vision Impairment Network for Counselling and Emotional support) as part of Vision 2020 has been particularly helpful in raising awareness. Whether the progress can continue is another matter though. I’m just reeling from the suggested cuts to the Higher Education budget likely to come out of the Spending Review. Could services for VIPs possibly remain unaffected?


Vision 2011, Kuala Lumpur

The triennial ‘Vision’ conference on visual impairment is coming up soon, to be held in Kuala Lumpur in February 2011. Abstract acceptances have just been announced. I have 2 presentations, and a hand in 2 more courtesy of Daryl:

K Latham, DR Tabrett, C Usherwood, J Schaitel, S Waller. ‘Reading medicine labels with impaired vision’. Invited presentation in the ‘New developments in R&R’ session.

K Latham, DR Tabrett. ‘Reading function with and without low vision aids’. Paper presentation.

DR Tabrett, K Latham. ‘Factors influencing self-reported visual function in the visually impaired’. Paper presentation.

DR Tabrett, K Latham. ‘Evaluation of the geriatric depression scale (GDS) in the visually impaired using Rasch analysis’. Poster presentation.

I’ve never been to Malaysia before, so am really looking forward to the meeting. Especially if it is as good as the previous meeting in Montreal was in 2008: there was almost too much interesting stuff going on there!

Derivation of the Acceptance and Self-Worth Adjustment Scale

The paper is now available from Optometry and Vision Science, published ahead of print here. Here’s the abstract for a taster:

Derivation of the Acceptance and Self-Worth Adjustment Scale.

Daryl R. Tabrett and Keziah Latham.

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.