Visual field testing is central to the diagnosis and monitoring of glaucoma. However, as perimetry is subject to considerable test-retest variability, a large number of tests are often needed to be confident that changes are genuine.1 Novel technologies designed for use at home may improve access to testing whilst also providing improved statistical power by increasing the number of tests available. Previous authors have investigated the potential of self-tonometry, 2 home visual field testing3 and even home optical coherence tomography. 4
In this paper, Tsapakis and colleagues introduce a supra-threshold visual field test and propose its use for home-based glaucoma screening. The method, which uses a personal computer, involves presentation of stimuli on an LCD screen, with the patient registering a response by clicking a mouse button. Fifty-two test locations across the central 24 degrees were evaluated. Novel aspects of the test include using a web camera as a photometer to measure room luminosity, the ability to automatically e-mail test results to the clinician, and a function to allow test results to be combined to improve accuracy, although exactly how this is done was not described.
ROC curves were used to evaluate the ability of the new test to classify individual test points as seen or not seen compared to Humphrey perimetry. Area under the curves (AUCs) ranged from 0.762 to 0.837 depending on the threshold used. The Youden indices, which summarize the ROC curve, so giving a measure of effectiveness, ranged from 0.63 to 0.94 for sensitivity and from 0.73 to 0.49 for specificity. The screening test was easy to use, quick, and did not require specialized equipment. However, while home visual field testing may have an important role to play in future glaucoma care, this pilot study has significant limitations. Only 10 patients were evaluated, and their clinical characteristics were not described. The study was also limited by lack of a control group and lack of clarity as to whether patients were able to operate the test without supervision. There is limited explanation of what training was provided and it is not clear whether testing was performed in patients' homes or in the clinic setting. Also, the test requires the patient to find the optimal distance of their eyes from the screen, by locating their own blind spot, which many are likely to find difficult. There are also concerns regarding calibration of the LCD computer screen used to display stimuli, particularly given the variable quality of monitors and the proposal that patients use their own personal computer equipment.
To summarize, although home-based visual field testing is an attractive prospect, larger studies involving participants with a range of disease severities and including evaluation of ease of use, are needed before home-testing can be recommended for widespread practice.