Daryl and I have just had a paper accepted in ‘Ophthalmic and Physiological Optics’ regarding which areas of the binocular visual field are most important for representing self-reported functional ability in activities of daily living. The most central parts of the field are (unsurprisingly) best associated with self-reported difficulty in reading. For mobility, visual field function in paracentral areas from 10-30 deg eccentricity (especially 10-20 deg) best reflects self-reported difficulty. What is hopefully useful is that we provide equations to relate mean visual field thresholds to likely self-reported difficulty with particular mobility tasks (and vice versa). The abstract is below, and a link to the paper will follow in due course:
Important areas of the central binocular visual field for daily functioning in the visually impaired
Daryl R. Tabrett, Keziah Latham
Purpose: To determine the areas of the central binocular visual field which correspond best with self-reported vision related activity limitations (VRAL) in individuals with visual impairment using a clinically relevant and accessible technique.
Methods: 100 participants with mixed visual impairment undertook binocular threshold visual field testing using a Humphrey 30-2 SITA Fast program. The Activity Inventory (AI) was administered to assess overall, mobility related and reading related self-reported VRAL as part of a face-to-face clinical interview. Different eccentricities of the binocular field (central 5, 5 to 10, and 10 to 30 degrees) were compared to self-reported VRAL in bivariate analyses and further explored using multivariate analyses.
Results: All areas of the binocular visual field were significantly associated with self-reported VRAL in bivariate analyses, with greater field loss associated with increased VRAL (p <0.001). Multivariate analyses identified that function of the central 5 to 10 degrees best predicted overall self-reported VRAL, and function of the central 5 degrees (especially the right-hand-side) and the central 10 to 30 degrees (especially 10 to 20 degrees) best predicted self-reported VRAL in reading and mobility tasks, respectively.
Conclusions: The results highlight the association between central binocular visual fields and self-reported VRAL in people with visual impairment. Central binocular fields can be measured using a widely available threshold test in order to understand the likely functional limitations of those with vision loss, particularly in mobility tasks. Self-reported VRAL can be estimated using the regression equations and graphs provided and difficulty levels in specific tasks can be determined.