More about Vision Assessment in Multiple Sclerosis

In my blog post from last September, I discussed a questionnaire that is being studied to evaluate the visual quality of life in people living with MS, the “NEI-VFQ-25.” This questionnaire, along with vision function tests and tests of optic nerve and visual pathway health, are being used increasingly to assess the quality of vision and vision’s impact on the function and quality of life of those with MS.

Another vision-related test that is being studied in people with MS is called the King-Devick (K-D) test, which is more of a visual performance test than a test of vision itself. The K-D test involves the person reading aloud a list of numbers on three separate cards in order as quickly as possible. The numbers on each successive card become progressively more crowded, making it increasingly harder to read them quickly. The amount of time it takes to read all three cards is the K-D time score. The whole test takes less than two minutes.

Unlike more simple tests of vision (visual acuity, low contrast acuity, color vision, peripheral vision) that are used in evaluating MS, performing well on the K-D test requires far more widespread brain function, including good vision and intact eye movements, as well as attention, concentration and level of fatigue. As a result, the K-D test may be a very sensitive way of determining in one test if there are problems in many of the pathways that may be affected by MS that result in visual problems.

To date, there is limited but compelling data that show that people with MS perform more poorly on the K-D test than people without MS. These data show that poor performance on the K-D test in people with MS is correlated with worse vision (poorer high and low-contrast acuity), optic nerve health (history of optic neuritis, thinning of the optic nerve layer on OCT) and tests of global brain function (MS Functional Composite and EDSS). In addition, people with MS who score more poorly on the K-D test are more likely to have a low Visual Quality of Life score and are more likely to be out of work due to disability.

More study is needed to confirm the utility of the K-D test in the MS population. For now, however, it is a promising predictor of widespread neurologic dysfunction in MS. It therefore may be a useful tool in the future to assess visual performance in MS longitudinally in patients in the outpatient setting and as an outcome measure in treatment trials.

Note: The visual function of people living with MS is currently being evaluated in our MS Eye Clinic in collaboration with the MS Center at the Swedish Neuroscience Institute. We will consider performing K-D testing routinely when further data are available.