Conversion of Age–Specific Normative Differential Luminance Sensitivity Obtained With the Tuebingen Computer Campimeter and the Octopus 101 Perimeter

Abstract

Abstract: : Purpose: To convert age specific normative hills of vision from the Tuebingen Computer Campimeter (TCC) to the Octopus 101. Methods: Static automated perimetry within the central 30° was conducted with TCC and Octopus 101 in a randomised order on 83 eyes of 83 ophthalmologically healthy subjects (approximately12 per decade) aged between 10 and 79 years. For each test, we used an identical grid of 68 circularly arranged points with centripetal test point condensation, representing the approximately rotation symmetric 30°–hill of vision. On TCC the examination was run with a 4–2–1–1 staircase strategy (4 reversals), on Octopus 101 with a 4–2–2–(1) staircaise strategy (3 reversals). Thresholds of differential luminance sensitivity (DLS) were estimated by the maximum–likelihood method. In both devices, background luminance was kept constant at 10 cd/m². For the TCC, as well as for the Octopus 101, a smooth mathematical model called hill of vision was fitted to the normative data. For conversion, DLS differences per subject and per location were analyzed. Results: The model fit was satisfactory (R² = 0.78 for the TCC and R² = 0.74 for the Octopus). The model was defined by the variables age, eccentricity, cyclic transforms of angle and their interactions and random factor "subject". Mean threshold difference between Octopus and TCC was 1.1 dB. The DLS differences depended on eccentricity. The minimal difference occurred at an eccentricity of 15° (0.6 dB). DLS differences increased towards the centre (2.1 dB) and towards the periphery (2.1dB at 30°). The converting formula was estimated to the 2nd degree polynomial in eccentricity: DLS_Octopus = DLS_TCC + 2.1 dB – 0.195 dB/deg * ecc + 0.00645 dB/deg² * ecc². The effects of age and angle were negligible. Standard deviations of both, reference values and differences, were 1.7 dB. Conclusions: When switching from the TCC to the Octopus instrument, a simple converting formula allows further use of normative DLS data and defect measures.

Keywords: perimetry • visual fields