The inter-observer reproducibility of Shafer's sign

Abstract

Pigment cells in the anterior vitreous (Shafer's sign) are known to be associated with retinal breaks. We sought to identify the reproducibility of Shafer's sign between different grades of ophthalmic staff. In all 47 patients were examined by a consultant vitreo-retinal surgeon, a senior house officer (SHO) and optician for Shafer's sign. Cohen's kappa for consultant vs SHO assessment of Shafer's sign was 0.55 while for consultant vs optician assessment, kappa was 0.28. Retinal tears were present in 63.8% of our series. Consultant assessment of Shafer's sign with fundoscopy findings, we found specificity to be 93.5% while sensitivity was 93.8%. Kappa for consultant assessment of Shafer's sign vs break presence was 0.86. Consultant and SHO assessment of Shafer's sign is of moderate agreement while optician assessment is fair. These results suggest a relationship between training and the assessment of Shafer's sign. We feel this study suggests caution in undue reliance on Shafer's sign particularly for inexperienced members of staff. © 2009 Macmillan Publishers Limited All rights reserved.