Perimetry Comparisons for Octopus G Top and Dynamic Programmes versus Humphrey 24-2 SITA Fast and SITA Standard Programmes

Aims: Previous comparisons of Octopus and Humphrey threshold programmes have shown differences, particularly for depth of defects. Recent developments have altered the Octopus background illumination. Thus, we sought to determine the subsequent extent of differences in results from commonly used central static programmes using Octopus and Humphrey perimeters.

Study Design: Diagnostic accuracy study.

Place and Duration of Study: Department of Ophthalmology, Warrington and Halton Hospitals NHS Foundation Trust, between June 2009 and July 2012.

Methodology: We utilised Octopus G-TOP or G-dynamic programmes and Humphrey 24-2 SITA fast or standard programmes. Poor reliability was taken as errors >25%. Comparison was made for global indices (mean sensitivity, mean deviation, pattern standard deviation/loss variance), test duration from each perimeter using unpaired t tests, and Bland Altman plots for correlation of individual differences between perimeters. Clinical agreement for presence/absence of visual field loss was determined by independent assessment of results by two authors (kappa test).

Results: Eighty patients (159 eyes) were recruited. 38 eyes were excluded due to poor reliability. 34 patients (55 eyes) underwent fast static visual field assessment: 17 males and 17 females with a mean age of 63 years (SD 14). 38 patients (64 eyes) underwent standard static visual field assessment: 18 males and 20 females with a mean age of 65 years (SD 13). For both full and fast perimetry, both perimeters showed good agreement for inter observer comparison (K=0.5-0.6). SITA standard perimetry showed a higher mean sensitivity value (+2.5dB±1.0) and SITA fast perimetry showed a higher mean sensitivity value (+3.4dB±1.1) than Octopus values. Bland-Altman analysis showed increasing variability with increasing severity of defect indicating a lack of correlation for moderate to severe visual field results.

Conclusions: Visual field results were comparable for mild defects. Octopus perimetry continues to show greater defect size where there is more extensive visual field loss relating to the different strategies used by both perimeters.