Visual Field Assessment
Strategy and interpretation
Automated static perimetry (Humphrey 24-2 or 30-2, SITA Standard or Fast) is standard for glaucoma. The 24-2 tests 54 points within the central 24 degrees at 6-degree spacing; the 10-2 is used for advanced or macular disease. Read the reliability indices first: fixation losses under 20%, false positives under 15%, false negatives under 15%. Then interpret mean deviation (overall depression), pattern standard deviation (focal loss), the glaucoma hemifield test, and the pattern deviation plot, which adjusts for cataract and other media opacity.
Patient instructions
Explain that the patient should look straight at the fixation target, keep the eye still, and press the button whenever a light is seen, even if faint or peripheral. Correct near vision with the appropriate add for the 30-2; an uncorrected presbyope generates lens-rim artifact. Offer rest breaks.
Worked example
A 24-2 shows mean deviation −4.2 dB, pattern standard deviation 3.6, glaucoma hemifield test "outside normal limits," and an inferior arcuate defect on pattern deviation that respects the nasal horizontal meridian. That pattern is classic for glaucoma; cataract would depress mean deviation but usually leave pattern deviation relatively intact.
Traps
Ignoring reliability indices. Missing lens-rim artifact at the periphery. Not repeating an abnormal field before calling it glaucomatous. Testing without near correction. Failing to compare with prior fields when judging progression.