Abstract
Purpose:
285 million people are visually impaired worldwide. 90% of the world's visually impaired live in developing countries. One of the major causes of visual impairment is glaucoma. The Moorfields Motion Displacement Test (MMDT) is a novel glaucoma screening device, designed specifically for community based screening in developing countries. The current study was designed to determine the effect of education level and computer experience on MMDT repeatability.
Methods:
164 participants, from Nampula, Mozambique, were recruited to the study. Participants were stratified according to education level (primary vs tertiary) and experience of computer use (no experience vs experience). The subject’s task was to indicate the presence of horizontal displacement of the white line stimuli using a computer mouse. Threshold was determined using the minimum displacement perceived. Variables measured were global probability of true damage (PTD), testing time (TT) false positives (FP). PTD measured in percentage is calculated between each field location and the number of unseen responses. Global PDT is the sum of PDT of each location. The visual field test was conducted twice, and results compared device repeatability.
Results:
The mean age of the study group was 31 ± 11 (range = 15 - 56). 54 % of participants reported experience of computer use, while 46% participants reported university level education. Independent samples t test revealed no difference in PTD between computer subgroups for either the initial or repeat test (P = 0.84 and 0.97 respectively), or for education subgroups (P = 0.25 and 0.57 respectively). Paired T test analysis reveals no difference between PTD1 and PTD2 for any subgroup (P = 0.06 to 0.79). A statistically significant positive correlation was found between repeat PTD measures for all subgroups (r 0.91 to 0.98; P < 0.01 for all). Bland Altman analysis reveals good repeatability for all subgroups.
Conclusions:
The MMDT is a repeatable visual field device that could be implemented in community glaucoma screening programmes. The device has many advantages including its portability, affordability, and short testing time. It is easy to understand and to perform, robust to optical blur and to cataract, and therefore can be performed without near correction. The current results validate its general repeatability for all sectors of society likely to be encountered in developing communities.
Keywords: 758 visual fields •
642 perimetry •
759 visual impairment: neuro-ophthalmological disease