This multicenter, prospective cross-sectional study compared the prevalence of abnormal 24-2 and 10-2 visual field (VF) test results in patients with various stages of glaucoma.
Study design
Investigators used data from the African Descent and Glaucoma Evaluation Study (AD-AGES), where participants underwent 24-2 and 10-2 VF testing at standardized intervals. Of 775 eyes, 364 were classified as early glaucoma (glaucomatous optic neuropathy [GON], abnormal 24-2 VF, mean deviation under 6dB), 303 were glaucoma suspects (GON, normal VF), and 108 had ocular hypertension (normal disc and VF, IOP >22mmHg).
Outcomes
In all 3 groups, investigators noted a significant proportion of eyes were classified as normal based on 24-2 tests, but abnormal on the 10-2 test (35%, 39% and 61% for ocular hypertensives, glaucoma suspects and early glaucoma patients, respectively). Even when using a range of criteria to define VF defects, a large proportion of eyes within the glaucoma continuum had an abnormal 10-2 despite a normal 24-2.
Of note, patients of African descent were significantly more likely to have abnormal 10-2 results compared to those without African ancestry (67.3 vs. 56.8%, P=0.009).
Limitations
Although patients had extensive experience with perimetry, false-positives remain a possible confounding factor. While this study demonstrates that central VF damage seen on the 10-2 test is often missed with the 24-2 test, there are no precise guidelines on when and how often 10-2 VF should be performed.
Clinical significance
This study underscores that patients currently classified as suspects or pre-perimetric may in fact have established glaucomatous functional damage.
Despite the lack of established guidelines, the presence of abnormalities in the central 10 degrees of a 24-2 may indicate significant macular damage and should prompt physicians to consider obtaining a 10-2 VF. Patients of African descent should also have a lower threshold for obtaining a 10-2 VF.