Central Field Index Versus Visual Field Index for Central Visual Function in Stable Glaucoma.

OBJECTIVE

To compare the variability of central field index (CFI) versus visual field index (VFI) in stable glaucoma with central fixation involvement.

MATERIALS AND METHODS

For this retrospective study, we identified multiple visual fields (VFs) of patients with repeatable central fixation involvement on Humphrey VFs (24-2 and 10-2 program) which were stable (clinically and on VFs) over a very short period of 2 to 3 months. The VFI and CFI were calculated as described in earlier reports. We graded the fields as early [mean deviation (MD)>-6 dB], moderate (-6.1 to -12 dB), and severe glaucoma (<-12 dB) based on MD on 24-2 program. The variability of CFI and VFI between visits and across different severity of glaucoma was compared. Relation of the divergence to field indices and clinical parameters were assessed.

RESULTS

The intervisit difference for VFI was greater than CFI ranging from -4% to 9% versus -1% to 8% in early (P=0.9), -13% to 18% versus -6% to 17% (P=0.056) in moderate, and -21% to 19% versus -9% to 9% (P<0.001) in severe glaucoma. The CFI within each group had narrower range than VFI with maximum range in severe glaucoma (33% to 95%). The divergence of CFI from VFI started at MD 24-2 beyond (worse) -10 dB. This difference between CFI and VFI was associated significantly with number of points with P<1% on 24-2 (R=80.3%).

CONCLUSIONS

CFI is less variable than VFI in stable eyes with fixation involvement especially in severe glaucoma indicating need for incorporating CFI calculation for monitoring advanced disease in eyes with central defects.