Validation of keratometric measurements obtained with a new integrated aberrometry-topography system

Abstract

Purpose: A clinical evaluation of the L80 videokeratographer (Visionix Luneau, Chartres, France) was performed to assess its validity and repeatability compared with a traditional Bausch and Lomb (B & L) keratometer. Methods: 87 right eyes of 87 subjects, (mean age 23.72 ± 3.62 years old, 70 women and 17 men), participated in this study. Corneal curvature was measured using the L80 instrument by one practitioner and the manual B & L keratometer by a different practitioner. Intratest and intertest repeatability were assessed. Results: Corneal curvature was found to be statistically different between the two instruments (p < 0.001), with the L80 providing a slightly steeper bias of 0.05 mm and 0.07 mm for the horizontal and vertical meridians, respectively than the B & L keratometer. 78.2% and 86.2% of the L80 results were within ±0.1 mm (±0.06 D) and 95.4% and 97.7% within ±0.2 mm (±0.11 D) of the readings obtained with the B & L keratometer along the horizontal and the vertical meridians, respectively. The agreement between the L80 and B & L keratometers axes was 31.0% within ±5°, 54.0% within ±10°, 60.9% within ±15°, 71.3% within ±20° and 87.4% within ±40°. Intratest repeatability was the same for both instruments. Intertest repeatability was better for the L80 videokeratographer compared to the B & L keratometer and showed no significant difference between the two sessions. Conclusion: The L80 videokeratographer is a reliable objective instrument comparable to other autokeratometers which, in addition, combines many other useful clinical features. It provides steeper radii of curvature measurements than the B & L keratometer. An offset incorporated into the instrument could mitigate the difference between the two instruments and make them interchangeable.

Keywords

• Keratometry
• L80 autokeratometer
• Limits of agreement