What is Visual Field Test (VFT) or Perimetry Test? Why is it needed for Glaucoma patients?
Visual Field Test (VFT), which is also referred to as Perimetry Test, is a key diagnostic test for Glaucoma. It also helps in determining the severity and progression of Glaucoma over time. This test measures the Central as well as Peripheral vision (side vision) which together constitute our Visual Field (hence the name Visual Field Test) and is used for diagnosis of Glaucoma since Glaucoma often starts by affecting the peripheral vision. Although Imaging studies like OCT , HRT etc are available now to guide doctors in Glaucoma treatment, Perimetry Test is still the gold standard for Glaucoma diagnosis. It evaluates vision loss due to Glaucoma, damage to the visual pathway of the brain and other optic nerve diseases. The stage of Glaucoma indicated by the test is useful to choose the target / desired Intra-Ocular Pressure (IOP) and to determine the follow up requirements.
How is the Visual Field Test done?
At Krishna Netralaya, VFT is conducted on the advanced Octopus automated Visual Field Analyser (VFA) from Haag-Streit Switzerland. During the test, patient is required to look at a central point on a hemispherical screen and not move the eyes during the test (known as central fixation). The machine lights up a random spot on the screen and the patient is required to press a button if he/she saw the light spot while maintaining central fixation. The light spot is repeatedly presented in different areas on the screen. The light stimulus increases and decreases in intensity too. The test takes roughly 20 minutes per eye. At the end of the test a report is generated which shows defects in the visual field of the patient. There is a learning curve when taking the test so sometimes it is repeated to get more accurate results. It is performed on one eye at a time.
When is Perimetry Test done?
Perimetry Test is done as soon as Glaucoma is suspected. Follow up tests are required to monitor progression of the Glaucoma disease / any worsening of the disease. Follow up tests can be done at intervals of 3-12 months, depending on the severity of Glaucoma.
Dr Smriti Jain, Glaucoma specialist at Krishna Netralaya, says “It is important to properly explain the test and the results to the patient. In my experience once a Perimetry Test is performed correctly and the results are explained to the patients, their understanding about the need for a regular treatment and follow up is much better. It’s like working together after that hand-in-hand. We see much better adherence to the advice given”.
Have more questions about #Glaucoma? Schedule a consultation with our Glaucoma specialist Dr. Aditi Agarwal
Advanced Glaucoma Care at Krishna Netralaya includes Complete Diagnostics (Applanation Tonometry, Gonioscopy, Perimetry/Visual Field Test, Pachymetry/Central Corneal Thickness Test, OCT/Retinal Nerve Fibre Layer Analysis etc.), Medical and Laser Treatments, as well as Surgical Treatments (Trabeculectomy, Ahmed Glaucoma Valve Implantation etc.)
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