Overview
There are several problems with the standard test used in UK glaucoma clinics to measure how much of the world people can see at once (their ‘visual field’). It was designed for people in the condition’s early stages and so doesn’t work as well for people who have already lost a substantial part of their visual field. The results for these patients vary a lot, which makes it hard to monitor whether treatment is working well enough to prevent sight loss. The test doesn’t give much information about side (peripheral) vision, which is important for getting about independently, for example when crossing the street. Plus, the current test can be frustrating for the person being tested because many of the test points will be in their ‘blind’ areas.
So in this project the student and team will develop a more patient-friendly test that can give a reliable and detailed picture of what vision people still have. They will build a computer programme and test a group of people with glaucoma to work out the most useful and reliable test measures and procedure. They will also relate the results to people’s mobility with the aim of ending up with a test that’s a good measure of glaucoma’s effects on day-to-day living.
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Scientific summary
Improving visual field tests for moderate and advanced glaucoma
Aim: To establish and evaluate a visual field test for patients with moderate/advanced glaucoma.
Methods and Analyses, Main Outcome Measures: Stimulus-response functions will are being measured in 15 patients with moderate and advanced glaucoma, in the central and peripheral visual field, with stationary (static) as well as moving (kinetic) stimuli.
Based on this model, computer simulations are being performed to establish efficient sampling strategies for the central and peripheral field. Key ideas are to use kinetic perimetry to measure the outer boundaries of the field as a “region of interest” (ROI), and then to combine threshold and suprathreshold stimuli to obtain an optimal balance between high spatial resolution and depth-of-damage information. Outcome measures: retest variability, test duration and “frustration factor” (ratio of seen/presented stimuli).
Patients with moderate and advanced glaucoma will be examined repeatedly to compare with current clinical tests (e.g. Humphrey Field Analyzer 24-2/10-2 test). In addition patients will perform tests of static and dynamic balance and two standard mobility tasks, and complete questionnaires on previous falls and fear-of-falling. Outcome measures: retest variability, relationship with falls history, patient preference.
Anticipated Findings:The team anticipates that reproducible “full field” data, obtained within a few min/eye, provide clinically important information not currently available from standard perimetry (e.g. extent of far peripheral inferior-temporal field) and will relate more closely to real-world visual problems experienced by individual patients with moderate and advanced glaucoma (e.g. mobility and balance).