The motion sensitivity screening test in clinical practice in Abuja, Nigeria: affordable automated perimetry for the third world?"

Abstract

Perimetry is essential in the clinical management and evaluation of glaucoma patients and other patients with diseases impacting on visual fields, but automated equipment may be too expensive for many practitioners in the developing world. I have used the Wu-Jones automated motion sensitivity system in a medium sized practice in Nigeria, a developing country, and hereby present an audit of our experience with it. The Wu-Jones Motion Sensitivity screening test is a lap-top computer-based test which integrates a number of components including a test program and reporting facility, a self-organizing neural network, a database management mechanism, and a menu-mouse-windowing user interface. T h e test is available on the public domain and is small enough (194mb) to fit into a diskette. This test has been used at the Rachel Eye Center in Abuja since 1998, and has been applied to 339 individuals, 2 9 8 of whom are included in this analysis. Patients tested fell into four main groups: those with clinical glaucoma (intraocular pressure > 20mmH g on at least one occasion and optic cup/disc ratio of 0.5 or more), glaucoma suspects, (i.e., ocular hypertensives >20mmHg or c/d ratio of 0.5 or mor e and first-degree relatives of glaucoma patients) patients undergoing routine tests for pre-employment (‘normals'), and 'others’. These 'normals' were used as controls. Records are available for 531 eyes. It took an average of t wo minutes to complete the test. Significant field defects (Motion sensitivity less than 50%) were detected overall in 15.6% of tested eyes, 7.2% of normals but in 32.6% of glaucoma eyes. Using the 'normals' as controls, the sensitivity of the test in our hands varied from 33% to 72% and specificity from 57% to 9 3 % at motion sensitivity cut off points from 5 0% to 97%. At the 83% cut off point, positive and negative predictive values were 86.0 % and 47.5% respectively. Reliability averaged 70%. I find the test easy to administer and understand by patients. Results can be recalled without difficulty, facilitating the longitudinal follow up process. This test will be of value to practices in the third world unable to afford more expensive equipment in the third world. The main investment would be in form of a laptop computer and a diskette. It can also be a useful adjunct for office practice in the western world.