Clinical evaluation of multisampling supra-threshold perimetry in glaucoma
Mr Mike Horler
Visual field tests are used in the management of glaucoma to establish whether or not the condition is progressing and its current and likely future affect upon the patient's quality of life. Current visual field tests produce variable results and repeat (confirmatory) tests are often neglected. This places large demands upon both patients and the NHS that are difficult to meet.
The research will clinically evaluate a new visual field test that has shown considerable promise in pilot studies (fast, less demanding for the patient and less variable). The project involves testing a group of glaucoma patients with both the new and a standard visual field test.
Confirmation of the pilot data findings should lead to earlier detection of any progressive deterioration, more efficient management strategies with better outcomes for patients and a more cost-effective service.
Each patient will attend twice. At each visit the patient will undergo:
- Central visual field testing with the HFA, SITA standard program 24-2
- Central visual field testing with the multisampling supra-threshold strategy using a pass criterion of 3 seen out of a maximum of 5 presentations.
This strategy will be run on the Henson Pro perimeter with software specifically written for the research project. The software will have a false positive trial rate of 25%, use the HEART algorithm to establish the supra-threshold test intensity and use a 24-2 stimulus distribution. The software will monitor response times and selectively remove responses that fall outside of the patient's normal response window. The number and location of the stimuli removed in this way will be recorded to allow the benefits of this adaptation to be quantified.
The order in which the tests are conducted will be randomised to avoid order effects. Optimal, wide field refractive correction will be worn during both visual field tests and the time taken to complete each test will be recorded.
Subjects will be asked to fill in a structured questionnaire (to reduce bias and allow quantitative data analysis). The questionnaire will be designed to measure their preference (SITA or multisampling) and the basis for their preference, e.g. easier task, shorter test time (timing information will be collected for comparison with perceived test times), stimulus presentation rate, ergonomic design of perimeter etc.
Outcome
It is hoped that the new visual field test would produce less variable results and be fast and less demanding for patients. These attributes could make the test a valuable tool in the detection of glaucoma and participation in monitoring established cases of glaucoma in primary care.