The 24-2 visual field test was comparably worse than other tests in consideration to glaucoma patients' central vision.
Donald C. Hood, PhD
The most common visual field test used to assess severity of glaucoma—the 24-2 visual field (VF) test—may be underestimating the severity of vision loss in many patients, according to a recent study.
Study coauthor Donald C. Hood, PhD, James F. Bender Professor of Psychology and a professor of Ophthalmic Science at Columbia University, noted that early glaucoma typically involves the macula and the 24-2 test, which has now been found to either miss or underestimate damage to patients’ central vision.
“Patients should be tested with 10-2 VF patterns and optical coherence tomography (OCT) scans of both disc and macula,” he said in a statement.
Early on, patients may not even notice central visual loss, but catching it early and accurately, assessing the extent of damage, can help doctors treat glaucoma and slow its progression.
Hood and his team already knew that a 24-2 visual field test—a test in which patients use 1 eye to view 54 grid points—tends to underestimate problems with central vision, so the logical next step was to determine if the test also underestimated central damage. They compared the accuracy of the 24-2 visual field test and the 10-2 visual field test, which uses a grid of 68 dots.
They recruited 57 patients with glaucoma whose mean derivation on the 24-2 visual field test was -6 db or better. The patients then completed the 24-2 and 10-2 visual field tests, as well as spectral-domain optical coherence tomography of the optic disc and macula to visualize the extent of the damage to the eye. Patients were classified using the Hodapp-Parrish-Anderson system, the visual field index system and the Brusini system.
The team compared the participants’ results on the visual field tests with the extent of evidence of macular damage in each patient. Patients showed greater functional deficits on the 10-2 test than on the 24-2 tests which corresponded to the damage researchers observed. The mean score for patients on the 24-2 test was -2.5 dB, compared to -3.0dB on the On the 10-2.
“These findings suggest that current glaucoma staging systems based on 24-2 (or 30-2) visual fields underestimate disease severity and the presence of macular damage,” investigators wrote.
Hood noted in a statement that clinicians tend to focus on patients’ loss of peripheral vision, and not frequently the macula, when looking for signs of early glaucoma. This is counterintuitive, he noted—the central region of the retina is relied on for a person’s ability to read, drive, and distinguish faces, among so many other necessary tasks.
"Our work has shown that damage can and does occur in this area, and the most commonly used field test can fail to detect most of the damage,” Hood said. “It is important to detect this damage, because early diagnosis and treatment can prevent further vision loss."
Investigators advised that new systems be considered for implementation by clinicians, fellow investigators, and public health authorities tasked with diagnosing and addressing glaucoma.
The study, "Association of Macular Visual Field Measurements With Glaucoma Staging Systems," was published online in JAMA Ophthalmology.