Macular degeneration: do conventional measurements of impaired visual function equate with visual disability?

Aims-To examine the relation between measures of vision and ability to perf orm daily living tasks in those visually impaired with macular degeneration . Methods-A visual functioning index (daily living tasks dependent on vision: DLTV) was used to evaluate patients' perception of their ability to perfor m vision dependent tasks. Distance visual acuity, near visual acuity, readi ng speed, and contrast sensitivity were measured in all patients. In additi on, a new measure of reading ability was derived, designated the reading in dex. This takes into account both the size of the text read and the time to read it and is equivalent to the reading speed in words per minute divided by text size in M. Results-The reading index was found to show best associations with the majo rity of items within the DLTV. Stepwise regression identified the combinati on of reading index and distance visual acuity as having the best associati ons with DLTV items. The present study also demonstrated that specific leve ls of vision as measured by acuity, reading index, and contrast sensitivity corresponded with different perceived amounts of difficulty in the perform ance of daily living tasks. Conclusions-This study showed that reading index is valuable in predicting the ability to perform daily living tasks and therefore may be useful in th e visual assessment of the visually impaired individual. In addition, this study identified specific levels of vision at which individuals reported di fferent degrees of difficulty in performing daily living tasks.