An education-based intervention investigating the accuracy of community-based optometrists evaluating limbal anterior chamber depth

In the UK, referrals for suspected primary angle closure (PAC) by community-based optometrists (CBO) to the hospital eye service show moderate accuracy. This study aimed to assess the interobserver agreement of limbal anterior chamber depth (LACD) between CBOs and ophthalmologists and evaluate the impact of an education intervention.

Using a 7-point LACD grading scale, consultant ophthalmologists graded an LACD image dataset developed from 100 patients attending Moorfields Eye Hospital. Two sets of 84 images were utilised for two LACD online assessments. CBO were recruited and undertook assessments before and after a PAC education package (EP) between August 2023 and January 2024.

Fifty-two optometrists completed the initial LACD assessment with a median of 19.0 (IQR 9.3–24.8) years post-registration experience. Using the 7-point LACD grading scale, mean weighted kappa (Kw) for pre-EP was moderate, 0.42 (95% CI, 0.36–0.48), increasing to 0.47 (0.42–0.53) post-EP. Conversion to the 4-point grading scale, Kw was substantial, pre-EP 0.61, (0.56–0.66) and post-EP Kw 0.64 (0.58–0.69). An LACD threshold (<25%) sensitivity and specificity pre-EP was 86.0% (79.9–91.3%) and 84.6 (82.3–86.9), respectively. Post-EP sensitivity decreased to 78.2% (74.1–85.1%) (p = 0.049) but specificity increased to 90.4 (88.1–92.8) (p < 0.001).

The 4-point LACD grading scale would be more applicable for a case-finding setting. An accessible EP improved agreement and specificity using the joint Royal College of Ophthalmologists/College of Optometrists PAC referral threshold. This EP may reduce false positive PAC referrals and could be rapidly disseminated to CBO. Further research is needed to assess real-world PAC referrals after an education intervention.