Archive | May 2011

What factors influence self-reported difficulty?

The primary outcomes of Daryl’s thesis have just been accepted for publication in Investigative Ophthalmology and Visual Science. We wanted to know more about what factors influence the responses of someone with visual impairment when they are asked in questionnaires how much difficulty they have performing different daily tasks (often described as activities of daily living). Questionnaires representing the patient’s perspective (known as Patient Reported Outcomes, or PROs) are becoming an increasingly important part of evidence based medicine, so to understand what they are measuring is important.

For the PRO that we used (the Massof Activity Inventory), we found that much of the variance in responses could be explained (not that surprisingly) by visual function: the worse someone’s vision was, the more difficulty they reported in vision-related daily tasks.  More interesting was the specific visual functions best related to self-report: from a range of functions tested, acuity (distance or near), a measure of reading performance, and a measure of non-central visual fields were the most correlated measures. Also of interest was that it was the standard measures of function reflecting severity of vision loss, rather than function achieved with low vision aids, that best reflected self-report.

Beyond vision however, responses of difficulty were also significantly affected by subjects’ levels of depression and adjustment to their visual impairment, with more difficulty reported by those with more depressive symptoms and poorer adjustment. These results highlight the need for those with VI to receive the emotional support that they need to come to terms with their vision loss, and that receiving this support could improve their perceived visual function.

The study will be published soon under ‘early view’ at IOVS as: Tabrett DR & Latham K. Factors influencing self-reported vision-related activity limitation in the visually impaired.