Intraobserver and interobserver reliability of the R/D score for evaluation of iris configuration by ultrasound biomicroscopy, in patients with pigment dispersion syndrome.

UNLABELLED

The work has been presented at The Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting, Fort Lauterdale, Florida, May 1999.

PURPOSE

To evaluate inter- and intraobserver variability of the R/D score in assessing the iris configuration in Pigment Dispersion Syndrome patients.

METHODS

Fifty-seven high-resolution ultrasound biomicroscopy images were obtained by a single ophthalmologist. All images were examined twice by each of three ophthalmologists, the second assessment being at least 2 weeks after the first. Each observer was masked to their colleagues' and their previous measurements. R/D scores were calculated at each examination. Agreement between and amongst observers was assessed using Bland-Altman plots. In addition, the R/D scores were categorised and reassessed using the Kappa statistic.

RESULTS

Intraobserver variability was small, the average differences between first and second scores of each observer being less than 0.01 units. Agreement within observers was 89% or higher, with Kappa values of 0.8 or higher, indicating almost perfect agreement. Interobserver variability was, however, greater. Although there was substantial agreement between two of the observers (87% agreement, first assessment; 80%, second assessment with respective kappa statistics of 0.78 and 0.66), they only moderately agreed with the other observer (kappa statistics between 0.55 and 0.68).

CONCLUSIONS

This study suggests that when using R/D scores to demonstrate changes in iris configuration, assessments should preferably be made by the same observer.