Recent research has found that early glaucoma results in central visual field sensitivity loss, an especially important finding given the fact that field defects in this region usually contribute to decreased vision-related quality of life more than peripheral visual field defects. Glaucoma standard of care mandates primary visual field testing with the 24-2 testing protocol. The 10-2 test is key for detecting central visual field defects, but adding this second test isn’t always practical for clinics due to the longer time requirement.

A new study published in the Journal of Glaucoma assessed the agreement between these two pivotal tests for detecting defects in the central 10° of the visual field. The team found substantial agreement between the Humphrey 24-2C and 10-2 protocols and suggested that combining the tests by adding central test points to the 24-2 test grid may obviate the need for two tests.

The researchers analyzed visual fields from 165 eyes of 18 healthy individuals, 12 glaucoma suspects and 62 glaucoma patients who completed 24-2C and 10-2 testing protocols within six months. The researchers defined a central visual field defect on 10-2 and 24-2C within the central 22 points as a cluster of three contiguous points with P-values less than 5%, equal to 5% and equal to 1% or less than 5%, equal to 2% and equal to 2% within a hemifield on the total deviation or pattern deviation plot. They found moderate to substantial agreement between the two testing grids for detecting central visual field defects, including high specificity in healthy eyes ranging from 94% to 100% for both testing protocols.

“In the current study, more central visual field defects were identified by the 10-2 test protocol in the superior and inferior hemifields than by the 24-2C test protocol,” the researchers wrote in their paper. “The larger number of central visual field defects detected with the 10-2 test likely is attributable in part to the increased number of test points on the 10-2 test grid (n=64) compared with the central 10° of the 24-2C test grid (n=22). Despite the larger number of central visual field defects detected by the 10-2 protocol, agreement with the 24-2C protocol for detecting any central visual field defects based on the total deviation and pattern deviation criteria was still moderate to substantial.”

The researchers acknowledged a false positive rate of ≤6% in their study. “We do acknowledge, however, that our specificity test set was small,” they wrote.

They concluded that the 24-2C test’s faster threshold algorithm and shorter test time may reduce the need to complete 10-2 testing. “Longitudinal studies are needed to determine how well the 24-2C identifies central visual field defects over time,” they wrote.