Continuous Light Increment Perimetry Compared to full Threshold Strategy in Glaucoma

Abstract

Purpose

Continuous light increment perimetry (CLIP) is an improved testing strategy for automated static perimetry designed to save test time and enhance patient compliance. CLIP uses a modified ramp stimulus where stimulus intensity is continuously increased according to patient reaction time, starting from a subthreshold intensity until recognition. The test is constantly modified according to patient performance. As CLIP showed good results in normal subjects in previous studies, the authors now compared CLIP to the standard 4/2-full threshold (4/2) strategy in glaucoma patients.

Methods

Fifty-two patients with glaucomatous visual field defects (mean sensitivities 2.9 to 18.4 dB), all with perimetric experience, were tested with CLIP (three times) and 4/2 in a randomized fashion. Tests were performed at 55 test locations within the central 30° visual field (24-2 area) using the Twinfield perimeter.

Results

Average mean sensitivity was significantly higher for CLIP than for 4/2 (t test, p<0.0001). Absolute scotomas and extension of scotomas were comparable for both strategies, whereas CLIP found less deep relative scotomas in some cases. Mean test time was significantly shorter for CLIP (5.6 min) compared to 4/2 (8.9 min) (Wilcoxon signed rank test, p<0.0001). Patient acceptance was better for CLIP than for 4/2.

Conclusions

CLIP showed comparable results to 4/2 with excellent patient acceptance. Mean sensitivities are 1.8 dB higher than for 4/2; similar results were found previously in normal subjects. CLIP was able to save a mean 38% of test time compared to full threshold strategy with good reproducibility.