Agreement among optometrists and ophthalmologists in estimating limbal anterior chamber depth using the van Herick method

Purpose To evaluate the inter‐observer agreement for measuring limbal anterior chamber depth ( LACD ) using the van Herick test in community optometrists, glaucoma specialist optometrists and ophthalmologists. Methods The study was divided into two phases. In the first phase, a random sample of 100 UK community optometrists were given an opportunity to select and grade eight digital slit‐lamp images of anterior chamber angles using the original van Herick 4 point grading scale. The images were included in a clinical decision making study using computerised virtual case vignettes. In the second phase, hospital‐based glaucoma specialist optometrists and glaucoma sub‐specialist ophthalmologists graded the LACD of the right eye using a 7‐point % grading scale in 57 consecutively presenting patients with suspect glaucoma. Inter‐observer agreement was assessed using linearly weighted kappa ( κ w ). Results Inter‐observer agreement for community optometrists was moderate, with a mean κ w for grading photographic images of 0.50 (95% confidence interval ( CI ) 0.43–0.57). Overall, ninety‐two percent of observations were within one grade of the actual grade, although grading of narrow angles was associated with a 13% false negative error rate (based on a ≤ grade 2 threshold). For Phase 2 of the study, pairwise comparisons between optometrists and ophthalmologists showed that agreement was moderate to substantial (mean κ w  = 0.54–0.65) with a false negative rate of 1.9% (based on a ≤ 25% threshold). Grading accuracy of specialist optometrists and ophthalmologists were equivalent. Conclusions In summary, the present study found that community optometrists showed moderate inter‐observer agreement for grading LACD . Glaucoma specialist optometrists showed moderate to substantial agreement with weighted kappa values that were equivalent to sub‐specialist ophthalmologists. The augmented 7‐point % grading scale is intuitive and potentially offers greater accuracy for grading narrow angles than the traditional 4‐point scale for grading LACD .