A visual field test is a method of measuring an individual's entire scope of vision, that is their central and peripheral (side) vision. Visual field testing actually maps the visual fields of each eye individually. The visual field test is a subjective examination, requiring the patient to understand the testing instructions, fully cooperate, and complete the entire test in order to provide useful information. During the test lights are flashed on, and you have to press a button whenever you see the light. Your head is kept still. You have to rest your chin on a chin rest. The lights are bright or dim at different stages of the test. Some of the flashes are purely to check you are concentrating. Each eye is tested separately, and you should allow 15-45 minutes to have the whole test.
Visual field testing is most frequently used to detect any signs of glaucoma damage to the optic nerve. In addition, visual field tests are useful for detection of central or peripheral retinal disease, eyelid conditions such as ptosis or drooping, optic nerve disease, and diseases affecting the visual pathways within the brain. The visual pathways carry information from the eye to the visual or occipital cortex in the brain, where this information is processed into vision.
Normally the test is carried out by a computerised machine, a Humphrey. Occasionally the manual test has to be used, a Goldman. Again, for each test you have to look at a central point, and have to press a buzzer each time you see the light.
The majority of computerized perimeters are specialized pieces of hardware. They typically consist of a projection area, an embedded controller, an input device for an operating technician, an input device for the patient, and a method of printing results. These machines are built for physician's offices or hospitals. As a result they are, bulky; not portable, and usually require their own room. They are also expensive and may cost roughly INR 1.5lacs to INR 2lacs along with good maintenance. Hence this is not surprising to know that the charges of the test for a patient may range from INR 500 to INR 900 and hence it may not be affordable for different people for different reasons specially in a developing world like India.
All the above facts encourage developing some technique so that the test can be conducted at low cost without any specialised hardware but on computer screen. The first aim of this project will be developing algorithm for a visual test and implementing it on ImageJ so that a similar test can be conducted on a personal computer(but preferably with a large monitor conduct the test in good ergonomic conditions).
visual field test, glaucoma, retina, Humphrey, Goldman
Presenting author: Ashish Kumar Ram
Organisation: Samsung India Software Organisation