With the selection of appropriate criteria, visual field (VF) examinations with additional macular locations can modestly improve the detection of macular defects in glaucomatous optic neuropathy (GON) without loss of specificity, according to findings published in Ophthalmology. 

Researchers evaluated this subject matter using a prospective, cross-sectional study that included 440 control participants and 499 patients with GON. Participants were tested with a fundus tracker permieter using a 24-2 grid with 12 additional macular locations (24-2+). 

Researchers identified the presence of GON in participants, defining macular defects as locations with measurements outside the 5% and 2% normative limits on total deviation (TD) and pattern deviation (PD) maps within the VF’s central 10 degrees.


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Defects were classified based on the total number of affected macular locations (overall detection) or on the largest number of affected macular locations connected in a contiguous cluster (cluster detection). Equivalent specificity between the 24-2 and 24-2+ was obtained using criteria based on the number of locations and cluster size, and was calculated in the healthy cohort using false detections. Finally, researchers compared partial areas under the detection curve (pUACs) at specificities of at least 95%.

The study’s main outcome measure was matched specificity comparison of the ability to detect glaucomatous macular defects between the 24-2 and 24-2+ grids. The researchers found that cluster detection identified more macular defects within the 24-2+ (mean increase=8% for TD-5% maps; 5% for TD-2% maps) compared with the 24-2 (mean increase=10% for PD-5% maps; 6% for PD-2% maps) at matched specificity. The percentage of eyes with macular defects ranged from 30% to 50%, and test time for 24-2+ was longer (21% increase). At least 1 location with sensitivity lower than 20dB was detected in between 74% and 98% of defects missed by the 24-2.

The researchers explain that their study did not compare the diagnostic precision of the 2 perimetric grids, noting that the 24-2 grid may fail to detect central defects but correctly identify glaucoma cases based on peripheral damage. The research was limited in that it focused only on the detection improvement provided by the central 10 degrees.

“The pAUC analysis partially confirmed this view, showing a consistent improvement with the cluster detection, less so with the overall detection,” the study explains. “It should be noted that the improvement in interpolated pAUC with the 24-2+ grid was modest for both methods,  indicating very similar overall performance.”

Reference

Montesano G, McKendrick AM, Turpin A, et al., Do additional testing locations improve the detection of macular perimetric defects in glaucoma? Ophthalmol. Published online June 17, 2021. doi:10.1016/j.ophtha.2021.06.012.