The 24-2C test grid offers a means to assess more points within the central visual field compared with the 24-2, but many researchers are curious whether it can identify central visual field defects as frequently as the 10-2. A team from the Centre for Eye Health at the University of New South Wales in Australia compared the usefulness of the test grids in assessing central visual field defects. While the 24-2C can identify the presence of a clustered central visual field defect, the study proposed that the 10-2 may be more useful in comprehensively characterizing the defect and predicting central visual function.
The study was particularly interested in whether the resolution of the 24-2C was sufficient in characterizing the shape, extent and depth of central scotoma, according to Jack Phu, OD, PhD, a lead researcher of the study.
“The 10-2 undoubtedly covers more visual space compared with the 24-2C, and offers a slight advantage in determining structure-function concordance because of the increased sampling, but it remains a distinctly separate test, requiring additional clinical time,” he says. “Thus, its deployment should be carefully considered for the appropriate patient.”
The researchers assessed 131 glaucoma patients and 57 suspects. Each participant underwent perimetric testing using 24-2C SITA-Faster and 10-2 SITA-Fast and OCT macular imaging for structure-function correlations.
The 24-2C and 10-2 test grids returned similar global indices of visual field performance and proportionally similar amounts of central visual field loss. The differences were more pronounced when the study considered the absolute number of defects, reflecting the greater resolution of the 10-2 grid. The additional points in the 10-2 grid returned more clusters of defects and a greater rate of structure-function concordance compared with the 24-2C test grid. Still, the 10-2 took a median of 201 seconds, and the 24-2C a median of 154 seconds, corresponding to the different threshold algorithms.
“The increased test resolution [of the 10-2 test grid] provides a more comprehensive description of central vision loss, relevant for the clinician to develop an appropriate management plan, and the patientʼs quality-of-life and activities of daily living,” the researchers concluded in their paper.
“If a clinician sees or suspects a central visual field defect in their patient, they should decide on the importance of characterizing that defect carefully,” Dr. Phu notes.
Phu J, Kalloniatis M. Comparison of 10-2 and 24-2C test grids for identifying central visual field defects in glaucoma and suspect patients. Ophthalmology. March 12, 2021. [Epub ahead of print].