Clinical and experimental validation of a slit lamp modification to measure toric lens position
Achyut N Mukherjee1, Chunwah So, Vinod Kumar
1Cardiff Eye Unit and Princess of Wales Hospital, 19 Glan Rhymni, Wales, Cardiff CF24 2TW, UK. hatch.mukherjee@gmail.com
Aim:
A simple novel slit lamp beam angular scale modification is described to allow more accurate measurement of toric contact and intraocular lens position.
Methods:
The modified slit lamp measuring technique was validated in both an experimental and a clinical setting, with two independent observers. The device was tested against a known reference source, and intraobserver variability in a clinical setting measuring toric intraocular lens (IOL) position was ascertained.
Results:
In the experimental setting 80 paired observations were analysed. Mean variance was 0.19° (95% CI 0.01-0.37), with a typical measurement error of 0.49°. Intraobserver variation had variance of -0.03° (95% CI -0.2 to 0.15) with a typical error of 0.47°. Clinical assessment of toric IOL position was made in 21 eyes. For this group, intraobserver variation had variance of -0.1° (95% CI -0.281 to 0.62) with a typical error of 1.36°. Intraclass correlation coefficient for all measures was 1.0.
Conclusion:
This simple technique has sufficient precision to be valuable in the clinical setting where photographic techniques may not be available or practical.