What do the numbers on a visual field test mean?

What do the numbers on a visual field test mean?

The visual threshold is the intensity of stimulus seen 50% of the time at each location. The threshold values of each tested point are listed in decibels in the sensitivity plot. Higher numbers mean the patient was able to see a more attenuated light, and thus has more sensitive vision at that location.

What is mean deviation in visual fields?

The mean deviation (MD) of the visual field is a statistical index used to determine the average difference in visual field sensitivity compared to the mean sensitivity of a normal observer of the same age. MD has also been used to monitor overall visual field change over time.

What are the normal range of visual field?

A normal visual field is an island of vision measuring 90 degrees temporally to central Fixation, 50 degrees superiorly and nasally, and 60 degrees inferiorly. Visual acuity increases from movement discrimination in the extreme peripheral vision to better than 20/20 in the center of vision.

How do you read visual field test results?

Use this order to interpret your Humphrey visual field every time:

1. Confirm it’s the right patient with name and date of birth.
2. Confirm it’s the right/left eye.
3. Look at the reliability indices.
4. Look at the pattern.
5. Look at the GHT, mean deviation, VFI, and pattern standard deviation.
6. Compare to the previous visual fields.

What is normal VFI?

The VFI can range from 100% (normal visual field) to 0% (perimetrically blind field). 1. The VFI has been shown to be less susceptible than the MD to the effects of cataract or diffuse media opacities. 1,2. VFI is intended for use in calculating rates of progression and staging glaucomatous functional damage.

How do you read Hvf?

SEQUENCE OF HVF PRINTOUT INTERPRETATION

1. Confirm patient’s name, ID number, and date of examination.
2. Identify which testing algorithm (24-2, 30-2, etc) is being used.
3. Confirm that the appropriately sized target was used for the test.
4. There is a section that lists the pupil diameter at the time of testing.

What is a normal person’s field of view?

In human vision, the field of view is composed of two monocular FOVs which our brains stitch together to form one binocular FOV. Individually, our eyes have a horizontal FOV of about 135 degrees and a vertical FOV of just over 180 degrees. These measurements are based on the FOV during steady fixation of the eyes.

What is a 20 degree visual field?

A person with a visual field of 20 degrees can see things straight ahead but wouldn’t be able to see things to either side without moving their eyes.

What is normal MD in visual field test?

The mean deviation or mean defect (MD) gives an overall value of the total amount of visual field loss, with normal values typically within 0dB to -2dB.

What is normal peripheral vision degrees?

A normal visual field for a person covers 170 degrees around, while peripheral vision covers 100 degrees of this field.

What do the deviations on a visual field test mean?

Pattern deviation (PD): This shows more localized deviation results and the degree to which the shape of a patient’s field differs from normal controls. Pattern deviation charts can be useful in tracking changes in a glaucoma-related deficit. Visual field index (VFI): This is similar to the mean deviation and gives a percentage for overall vision.

What does below-2db mean on visual field test?

Below -2dB may indicate a visual deficit. Total deviation (TD): These charts show all portions of a person’s visual field that differ from age-matched controls. The numbers show the difference in decibels between the patient’s test results and those values expected for the person’s age.

How are the degrees of the visual field measured?

Your visual field is measured in degrees from the central fixation in four quadrants: temporal (toward your ear), nasal (toward your nose), superior (upper, or above center), and inferior (lower, or below center). A normal visual field measures about 90 degrees temporally, 50 degrees superiorly and nasally, and 60 degrees inferiorly. 

When to use the pattern standard deviation ( PSD )?

For patients with a localized visual field defect, the pattern standard deviation (PSD) best quantifies the amount of loss as well any progression of glaucoma in the early stages. Note that the PSD is not helpful in tracking advanced glaucomatous defects.