Usefulness of frequency doubling technology perimetry 24-2 in glaucoma with parafoveal scotoma

The standard automated perimetry (SAP) 24-2 test cannot adequately test the paracentral region because test points are located sparsely in macular area where is crowded with retinal ganglion cells (RGCs), even though paracentral scotoma is clinically related to a risk of losing visual function. More sensitive visual field (VF) tests are needed to assess paracentral VF defects precisely. We investigated the structure-function relationship on the SAP 10-2 test and the frequency doubling technology (FDT) 24-2 test as well as the SAP 24-2 test in glaucoma with parafoveal scotoma (PFS). Glaucoma patients with PFS (134 patients) were included in this cross-sectional study. Sub-analysis was performed with isolated PFS (51 patients). Global and sectoral mean sensitivities (MS) were evaluated using SAP 24-2, 10-2, and FDT 24-2 program. MS was analyzed as dB or unlogged 1/lambert (SAP) or 1/Michelson contrast (FDT). Ganglion cell-inner plexiform layer (GCIPL) thickness was measured using spectral domain optical coherence tomography. Topographic relationships between the structure and the function were analyzed. In the total PFS group, good structure-function correlations were found in all zones with SAP 24-2, 10-2, and FDT 24-2 test. For glaucoma with isolated PFS, average GCIPL thickness was significantly correlated with central cluster MS (dB) using the SAP 10-2 test (r = 0.279, P = .047) and the FDT 24-2 test (r = 0.289, P = .039), but not the SAP 24-2 test (r = 0.264, P = .061). Topographically, the FDT 24-2 test showed significant correlations in all sectors between sectoral MS and corresponding GCIPL thickness. With regard to the SAP 10-2 test, there was significant topographical structure-function correlations for the superotemporal, inferotemporal, and inferonasal sectors. For SAP 24-2, only inferonasal GCIPL thickness was correlated with the corresponding VF sensitivity. Topographical structure-function on the macula was better with the SAP 10-2 test (superotemporal sector) and the FDT 24-2 test (superotemporal sector) than with the SAP 24-2 test in glaucoma with isolated PFS. In conclusion, FDT 24-2 and SAP 10-2 tests performed more favorably than the SAP 24-2 test in the structure-function relationship of glaucoma patients with isolated paracentral scotoma. FDT 24-2 tests can be another good option for detecting and monitoring RGC loss on the macular area while not missing VF defects outside the central 10°.