How do you read Humphrey visual field?
Use this order to interpret your Humphrey visual field every time:
- Confirm it’s the right patient with name and date of birth.
- Confirm it’s the right/left eye.
- Look at the reliability indices.
- Look at the pattern.
- Look at the GHT, mean deviation, VFI, and pattern standard deviation.
- Compare to the previous visual fields.
What is a false positive on a visual field test?
False positives occur when the patient responds when no stimulus has actually been seen. A high number of false positive responses will make a field look better than it actually is and may mask shallow depressions. A false positive rate of 15% or more indicates an unreliable test that should be repeated.
What is VFI on Humphrey visual field?
On the Humphrey Field Analyzer, the visual field index (VFI)—a value similar to the MD—was added to the printout several years ago. The VFI is a staging index for the total amount of field loss. It is reported to be less sensitive to cataracts. Values range from 100% (normal) to 0% (perimetrically blind).
Is Humphrey visual field test accurate?
Reliability criteria were established by Humphrey Instruments, Inc. as less than 20% fixation losses or less than 33% false negative errors or false positive errors. Results: Overall, patients performed reliably in 52% of visual field tests.
What is threshold in perimetry?
The limits of the visual field are mapped to lights of different sizes and brightness. With threshold static automated perimetry, a computer program is selected. The most commonly used one tests the central 30° of the visual field using a six degree spaced grid.
What is VFI percentage?
VFI is expressed in percentage, where 100% represents a normal visual field and 0% represents a perimetrically blind field, and is plotted versus patient age.
What VFI is legally blind?
In the United States, statutory (legal) blindness continues to be defined as best-corrected visual acuity of 20/200 or worse, but also includes a definition based on VF limitation. In particular, the widest diameter of the VF, in the better eye, must subtend an angle at least 20 degrees.
What is right visual field deficit?
For example: a complete loss of visual field to the right (hemianopia) means that a person will be unable to see objects on their right hand side or communicate effectively with people positioned to their defective side.
Are perimetry tests accurate?
There are many ways to evaluate the visual field; a standard automated perimetry is only one of them. The tests are subjective, however, and they are often difficult for patients to perform. As a result it is not rare to have false positives or false negatives.
Can you have normal eye pressure and still have glaucoma?
Another form of glaucoma is called normal-tension glaucoma. If someone has normal-tension or normal-pressure glaucoma, their eye pressure has never been recorded above 21 mmHg, yet they still have optic nerve damage.