Frequency doubling technology staging system 2.

PURPOSE

To develop and evaluate a new staging system that can specifically be used for the classification of visual field defects with Humphrey Matrix Frequency Doubling 30-2 threshold test.

MATERIALS AND METHODS

The new frequency doubling technology staging system version (FDT SS 2) was created on the basis of a total of 200 tests obtained from 34 normal subjects, 67 patients with ocular hypertension (OHT), and 99 with primary open-angle chronic glaucoma (POAG). This system was used to classify defect severity in another group of 54 patients having POAG tested with the Humphrey Matrix 30-2 threshold test. A modified 5-stage classification method of Aulhorn and Karmeyer was taken as the gold standard. The reliability of FDT SS2 in categorizing according to type of defect (generalized, mixed, and localized) was also compared with a clinical classification on the basis of the analysis of probability maps. A control sample of 48 normal subjects was also analyzed.

RESULTS

With regards to the glaucomatous patients, 38 of 54 (70.4%) resulted with the same severity classification. All FDT SS2 grades (100%) were within 1 level of the clinical grade. The ability of FDT SS2 to correctly define the type of defect was also quite good (Spearman test: 0.719, P<0.001). In the control group, the FDT SS2 classified 45 of 48 cases as stage 0, giving a specificity of 93.7%.

CONCLUSIONS

The new FDT SS2 is able to both stage the severity of functional damage studied with the Humphrey Matrix 30-2 threshold test, and to correctly distinguish between generalized, localized, and mixed defects.