The Clinical Skills of Optometrists in Assessing the Anterior Chamber Angle

Introduction The number of cases of glaucoma is predicted to increase considerably over the next few decades. The current reference standard method used to distinguish between primary open angle and primary angle closure glaucoma is gonioscopy, but there is a lack of evidence on anterior chamber angle (ACA) assessment methods outside Asia. Optometrists who show competence at gonioscopy are well placed to play an important future role in glaucoma care provision in the UK. Aims:  To investigate the impact of the NICE guideline on glaucoma on the clinical practice of optometrists.  To investigate the ability of optometrists and other healthcare professionals (HCPs) at gonioscopy.  To assess the intra-observer repeatability and agreement between gonioscopy, van Herick method and anterior segment Optical Coherence Tomography (AS-OCT). Methods Optometrists were invited to complete an online questionnaire investigating clinical practice before and after the introduction of the NICE guideline. Gonioscopy findings for optometrists and other HCPs were compared to those of a consultant ophthalmologist. Sensitivity and specificity were calculated, weighted kappa (κw) was used to assess inter-observer repeatability. Gonioscopy, van Herick method and AS-OCT were performed on two occasions. Sensitivity and specificity of van Herick method and AS-OCT were calculated, using gonioscopy as the reference standard. Kappa (κ) was used to measure the intraobserver repeatability. Results A significant increase in the use of applanation tonometry (p < 0.01) but no significant change in gonioscopy usage (p=0.47) was found after the introduction of the NICE guideline. Sensitivity and specificity values for HCPs’ gonioscopy findings compared to a consultant ophthalmologist were good: 92% and 92% respectively. The repeatability of gonioscopy was fair κ=0.29, while that of the van Herick method (κ=0.54) and AS-OCT (κ=0.47) were better. The van Herick method showed good sensitivity (visit 1: 82%, visit 2: 75%) and very good specificity (visit 1: 88%, visit 2: 95%). The sensitivity of AS-OCT was fair (visit 1: 46%, visit 2: 25%), specificity was high (visit 1: 87%. visit 2: 89%). Discussion In this thesis new evidence is presented comparing ACA assessment tests. There has been no change in gonioscopy practice since the guideline on glaucoma was issued. Optometrists along with other HCPs, are able to perform gonioscopy accurately and competently. The van Herick method and AS-OCT have better repeatability than gonioscopy. The van Herick method showed good agreement with gonioscopy but AS-OCT agreement with gonioscopy was less. The van Herick method would therefore appear to be a more useful test than AS-OCT for optometrists assessing patients at risk of glaucoma.