Functional vision research: measuring vision-related outcomes in orientation and mobility - VROOM

Abstract

Retinal implants and other vision-restoration treatments are being developed for people with very low vision, and translational research is needed to show whether or not these interventions are effective. Clinical trials can investigate outcomes in controlled conditions, but functional vision research is needed to measure the changes in vision that matter to participants in their lived environments. This project considers functional vision in the context of orientation and mobility (O&M) assessment.

At the commencement of this study, there were no established methods of measuring very low vision that is useful for O&M. The aim of this doctoral project was to devise an instrument for use in vision-restoration research to measure functional vision for mobility, capturing meaningful changes resulting from a retinal implant.

Whereas vision for reading and other sedentary tasks can be measured in the clinic, functional vision for mobility is a complex, dynamic, social phenomenon, and social research methods are needed to deal with this complexity. In this study, initial consultation with functional vision experts helped to scope what is meant by effective mobility and to identify visual behaviours evident in people with very low vision who are often referred to as blind.

A substantial part of this doctoral study involved the design and implementation of a research protocol called LoVADA (Low Vision Assessment of Daily Activities). This protocol was trialled in a cross-sectional study with adults who had advanced retinitis pigmentosa (n=40), and then with three people who had a prototype retinal implant. None of the O&M tasks in the protocol succeeded in directly measuring functional vision for mobility. However, the LoVADA studies generated a rich, embedded mixed-methods data-set about the lived experience of people with very low vision. From this data-set, emergent theories about functional vision for mobility were developed. These theories interpret complex relationships between vision, O&M and personal mobility choices, providing a client-centred framework for a novel instrument that measures functional vision for mobility.

The VROOM instrument is a constructivist measure of Vision-Related Outcomes in Orientation and Mobility. It quantifies shared knowledge about functional vision, which is co-constructed during a typical O&M assessment session comprised of interview and observed travel. The VROOM instrument is portable and reduces qualitative data to a score out of 50 on the spot, through the use of behaviourally anchored rating scales. The client can confirm or contest findings, and contribute to interpretation. This constructivist measure gives more authentic data than an objective measure that can be misinterpreted by researchers, and more robust data than a subjective measure derived from unsubstantiated self-report.

The VROOM instrument embraces any level of functional vision from bare light perception through to vision for driving, which means it has the potential for wide application beyond the context of vision-restoration research. It shows promise of being able to measure subtle variations in functional vision, even light perception, to compare different people, eye conditions, levels of spatial cognition, times, places, lighting conditions, and life circumstances, with and without a retinal implant.