IXMUS - Colour field charts for macular assessment

OPTICIAN looks at a recent addition to the simple yet effective card based methods of vision screening

All eye care practitioners and increasing numbers of patients are familiar with the Amsler chart for screening and monitoring of central vision changes related to macular disease. Its very simplicity of use and interpretation has led to its widespread popularity, but some concerns have been raised regarding its sensitivity.

The conventional black and white Amsler test grid fails to detect 87 per cent of early and small size (less than six degrees) macular field defects and 45 per cent of all macular field defects. Only one out of every three cases with wet macular degeneration and choroidal neovascularisation may be detected by the conventional grid. As the new treatment options become available for the treatment of choroidal neovascularisation, the earliest possible detection of such lesions is now even more important than before for timely delivery of vision-saving care. The red-on-black version of the Amsler grid is too difficult to be seen (very low contrast) by many patients and creates an unacceptably high false alarm rate.^1,2

US optometrist Dr Erik Mutlukan has developed three further cards, the Ixmus Color Visual Field Test Cards, which exploit contrast and colour to enhance their sensitivity, compared with traditional Amsler cards, when screening central vision. Each is designed to be viewed monocularly at 30cm in good light and with fixation maintained upon a central target on the cards.