Staging of functional damage in glaucoma using frequency doubling technology.

PURPOSE

To evaluate three new approaches for staging severity of glaucomatous visual field defects using frequency doubling technology.

PATIENTS AND METHODS

One hundred and four patients with either ocular hypertension or chronic glaucoma were tested with both standard automated perimetry (SAP, 30-2 Humphrey threshold test) and frequency doubling technology (N-30 threshold test). Standard automated perimetry results were classified into four groups (normal tests, early defects, moderate defects, and severe defects) using the Glaucoma Staging System. Frequency doubling technology tests were also classified in four groups using three different approaches: frequency doubling technology probability map analysis, considering the number and location of disturbed points, frequency doubling technology MD and PSD indices, graphed on a two-axis diagram (FDT Staging System), and an abnormality score, based on both the statistical significance and the spatial location of depressed points. A control group of 20 eyes from 20 normal subjects was also tested and classified in the same way. The Cohen Kappa was used to compare the level of agreement between the three frequency doubling technology methods of classification and the glaucoma staging system.

RESULTS

Measure of agreement was 0.679 using probability map assessment, 0.793 using the frequency doubling technology staging system, and 0.663 using the abnormality score. The specificity rate was 95% for all three methods.

CONCLUSIONS

All the studied approaches were able to correctly stage the glaucomatous functional damage, but the frequency doubling technology staging system was the easiest and quickest method. Moreover, it is the only method that supplies information on the characteristics of the defect, without requiring any other time-consuming procedures.