2016 IGA/College of Optometrists Research Grant Award
Pam McClean - Princess Alexandra Eye Pavilion, Edinburgh
Project title: Evaluation of a novel method of visual field testing Saccadic Vector Optokinetic Perimetry (SVOP) for the diagnosis of glaucoma
Purpose and background of proposed investigation
Diagnosis of glaucoma includes a test of the peripheral vision or visual field test also called standard automated perimetry (SAP). This type of test is subjective and difficult to complete as the patient has to keep very steady, concentrate looking at a central fixation point for a few minutes and press a button when a light is seen. Usually 1 in 5 people cannot manage the visual field test properly. Partly because of this, many people referred to hospital eye services because of possible glaucoma turn out to not have the disease. We also know that some people with glaucoma are not diagnosed because of the limitations of current tests.
Our research team has developed a new visual field tester called Saccadic Vector Optokinetic Perimetry (SVOP) that makes use of a person’s natural eye movements and reactions. When a small light appears in the periphery, if seen, the person will look directly at the light. The new visual field tester has a camera that records this eye movement and a computer programme decides whether the eye movement was correct, i.e., directed to the small light. A correct eye movement indicates the person could see the light. This process is repeated for several stimuli to assess the peripheral vision.
This study will evaluate the performance of this new test, SVOP, and compare it with SAP to diagnose people with glaucoma, and to correctly identify those who are normal. To find out how accurate the test is we will compare the test results with a reference standard (to determine if a person has the disease).
The reference standard for this study will be provided by masked readers who will evaluate if there are glaucoma changes in the back of the eye using pictures of the optic disc and a scanning imaging test, optical coherence tomography. Our team has successfully tried this new SVOP technology in children and we have done pilot studies in adults with glaucoma. We will study if SVOP is a better test than SAP to detect people with glaucoma and reduce the number of people with glaucoma missed and the number of normal people referred unnecessarily to the hospital.
We have some funding to collect normative data but are seeking funding from IGA to complete this. We then plan to apply for funding for a large study examining the diagnostic performance of the new device. This study will aim to recruit 634 participants to two large NHS units (Belfast and Edinburgh) supported by a registered clinical trials unit (Belfast). The study will involve patients referred to the hospital from the community with possible glaucoma. The research team includes glaucoma experts, ophthalmologists, optometrists, statisticians, and engineers.
Patients and patient representatives have greatly contributed to the project by informing us about their difficulties with the standard visual field tests, and their preference for an easier and better visual field test to diagnose glaucoma. Patients and patient representatives will continue to play an important role in the conduct and dissemination of the project. The project will last 24 months.
This study will evaluate the diagnostic accuracy of an intervention (SVOP) for glaucoma diagnosis. It will test a novel way of detecting visual field loss by recording and analyzing natural saccadic eye movements when a light appears in the periphery. There is already proof of clinical efficacy of this technology for evaluating the visual field in children and SVOP has been commercialized for this purpose. Pilot studies on glaucoma patients have been successful.