Can the current oculokinetic perimetry chart be improved?

Methods: Several studies have been performed to determine the effectiveness of oculokinetic perimetry (OKP) as a glaucoma screening test. In a previous study, we noted that OKP sensitivity and specificity was lower in mildly defective fields compared with moderately or severely, defective fields. In this study, we looked at visual fields with 'glaucomatous' defects. The visual field was divided into zones and points. The frequency of glaucomatous defects and visual sensitivity levels in these areas was recorded. The sensitivity and specificity of OKP to detect these defects were analysed.

Results: Ninety-six glaucomatous fields from 57 subjects were assessed. An OKP chart testing the 8 to 16 degrees of eccentricity, and an extended nasal region, would cover all the defective fields present in this study. The 12-16 degree eccentricity zone has the best sensitivity (75%) and specificity (65%). Points within the nasal, inferior temporal and 8-12 degree eccentricity might be less sensitive, but 11 (11.5%) fields had defects only in these areas. Zonal and point sensitivities and specificities were very similar suggesting that fewer points could be used in each zone with similar results. Many of the eyes with false-negative OKP results had Humphrey Field Analyser visual sensitivity levels in the 10-18 dB range (i.e. associated with a mild or moderate defect). Decreasing the target stimulus might increase the detection rate of these milder defects; however, it might also increase overall false-positive rates. Our proposed experimental chart consists of two to four test points in each quadrant within the 12-16 degree of eccentricity, five within the 8-12 degree zone and two in the nasal region, and a central 1 or 1.5 mm black target.

Conclusions: Analysis of results with modifications of the testing device may permit the OKP chart to achieve its full potential.