Development of Item Banks to Measure the Impact of Amblyopia and Strabismus on Quality of Life

Author: Sheela Kumaran

Kumaran, Sheela, 2020 Development of Item Banks to Measure the Impact of Amblyopia and Strabismus on Quality of Life, Flinders University, College of Nursing and Health Sciences

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Amblyopia (lazy eye) and strabismus (cross eyes or ocular misalignment) are common developmental disorders of childhood. When not diagnosed or treated successfully, these endure as chronic conditions into adulthood and are associated with a range of visual and motor deficits. However, it is not clear how these conditions impact Quality of life (QoL). Understanding the patient’s perspectives of the QoL implications of these conditions is important to evaluate its burden and the effectiveness of interventions provided. But these evaluations are limited by the lack of valid and comprehensive patient reported outcome measures (PROMs). Moreover, the existing PROMs, being paper based are limited in content and fall short of desired psychometric qualities. Most of them have been developed for high income countries. Therefore, the aim of this doctoral research was to develop amblyopia and strabismus specific QoL item banks that can be implemented via a computer adaptive testing (CAT) system for adults in Australia and India. The study comprised of two phases and was carried out independently in Australia and India to enable development of country-specific measurement systems. This thesis encompasses complete phase 1 (content identification) and phase 2 (psychometric validation and calibration) of the Indian item bank construction and the phase 1 of the Australian item bank construction. Phase 2 Australia is work in progress beyond this doctoral study.

In phase 1, the content for the item banks were identified by a systematic review of the existing PROMs (n=22), published qualitative studies (n=5) and extensive qualitative studies in Australia (n=49) and India (n=30). The pool of items underwent a systematic process of binning and winnowing (item reduction and classification) and optimal sets of representative items addressing all important aspects of QoL such as activity limitations, emotional impact and social impact were devised. The pilot item banks for Australia and India had 386 and 341 items respectively.

In phase 2, the Indian item banks were administered to adults with amblyopia and strabismus in India (n=304). Rasch analysis, a modern psychometric method, was used to validate and optimise the psychometric properties (e.g. rating scale functioning, measurement precision) of the Indian item banks and establish item calibrations for the CAT simulation. Phase 2 in Australia is ongoing; an interim psychometric analysis with the data collected (n=55) was performed.

The psychometric analysis of the Indian data resulted in twelve valid amblyopia and strabismus specific item banks: symptoms – frequency (n=32), symptoms - severity (n=32), symptoms - bothersome (n=32), activity limitations (n=43), driving (n=18), mobility (n=12), concerns (n=58), emotional impact (n=35), social impact (n=19), convenience (n=24), economic impact (n=13) and coping (n=20). The CAT simulations of these item banks indicated that an average of 7 and 15 items are required to measure these QoL constructs with moderate and high precision respectively.

The item banks developed in this doctoral research show promising ability to measure the QoL impacts of amblyopia and strabismus precisely. Implementing these item banks via a CAT system will greatly reduce the respondent burden of answering long paper-based questionnaires. Incorporating these in routine clinical settings would enable real time measurement and monitoring of QoL parameters. This would be useful to substantiate the effectiveness of novel amblyopia treatments and the benefits of strabismus correction for adults.

Keywords: amblyopia, strabismus, quality of life, patient reported outcome measures, item banks, questionnaire, rasch analysis


Thesis type: Doctor of Philosophy
Completed: 2020
School: College of Nursing and Health Sciences
Supervisor: Dr Paul Constable