Moorfields Acuity Chart: Novel Sight Test Detects Early Age-Related Macular Degeneration
An international team of scientists, led by Prof. Roger Anderson from the University of Ulster at Coleraine and the NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, has designed a test that can spot the first stages of sight loss in age-related macular degeneration.
Left: conventional chart. Right: Moorfields Acuity Chart. Image credit: Nilpa Shah et al.
Age-related macular degeneration (AMD) is the leading cause of sight loss in industrialized countries.
Worldwide, AMD affects 8.69 percent of the adult population – almost double the prevalence of dementia.
AMD affects the macula – the central part of the light-sensitive layer of the eye (the retina) that we use for reading and recognizing faces.
Most sight loss from AMD happens in the later stages. But, until now, there has been no quick and reliable sight test that can detect the earliest changes in the retina in AMD.
Standard letter charts are not consistent or sensitive enough to give an early diagnosis accurately or to monitor AMD’s progress.
To address the problem, Prof. Anderson and co-authors invented a new test chart — called the Moorfields Acuity Chart — that uses letters built up from fine black-and-white stripes.
Their previous work showed that these ‘high-pass’ letters are more equally readable than standard letters and that they seem to vanish altogether at the point when they are too small to be recognized.
In the current study, published in the British Journal of Ophthalmology , the scientists compared the sensitivity of the Moorfields Acuity Chart with the standard test used to measure clarity of visual perception in 80 AMD patients and 38 people with normal vision.
The participants were asked to read the letters from two versions of each type of chart, shown in random order.
They were then given a visual acuity score based on the number of letters they could read before making 4 mistakes on one line.
Results showed that Moorfields Acuity Charts produced more reliable results from one test to the next than using the standard charts for people with AMD. This was not the case for participants with normal vision.
Importantly, the difference between the Moorfields Acuity Chart and standard chart scores was approximately 4.5 lines in people with AMD and better visual acuity compared to people without AMD who had similar visual acuity, where the difference was 1.5 lines.
The Moorfields Acuity Chart will be produced commercially under license by Peter Allen and Associates.
Prof. Anderson and co-authors are currently preparing to assess the chart’s performance in a larger clinical trial.