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.