Detection of Primary Angle Closure Using Anterior Segment Optical Coherence Tomography in Asian Eyes
Received 28 October 2005; accepted 31 May 2006. published online 27 October 2006.
Objective
To evaluate noncontact anterior segment optical coherence technology (AS-OCT) as a qualitative method of imaging the anterior chamber angle and to determine its ability to detect primary angle closure when compared with gonioscopy in Asian subjects.
Design
Prospective observational case series.
Participants
Two hundred three subjects were recruited from glaucoma clinics in Singapore with diagnoses of primary angle closure, primary open-angle glaucoma, ocular hypertension, or cataract. Both eyes (if eligible) of each patient were included in the study. Exclusion criteria were pseudophakia or previous glaucoma surgery.
Methods
Images of the nasal, temporal, and inferior angles were obtained with AS-OCT in dark and then light conditions. Gonioscopic angle width was graded using the Spaeth classification for each quadrant in low lighting conditions.
Main Outcome Measures
Angle closure was defined by AS-OCT as contact between the peripheral iris and angle wall anterior to the scleral spur and by gonioscopy as a Spaeth grade of 0° (posterior trabecular meshwork not visible). Comparison of the 2 methods in detecting angle closure was done by eye and by individual. Sensitivities and specificities of AS-OCT were calculated using gonioscopy as the reference standard.
Results
Complete data were available for 342 eyes of 200 patients. Of the patients, 70.9% had a clinical diagnosis of treated or untreated primary angle closure. Angle closure in ≥1 quadrants was detected by AS-OCT in 142 (71%) patients (228 [66.7%] eyes) and by gonioscopy in 99 (49.5%) patients (152 [44.4%] eyes). The inferior angle was closed more frequently than the nasal or temporal quadrants using both AS-OCT and gonioscopy. When performed under dark conditions, AS-OCT identified 98% of those subjects found to have angle closure on gonioscopy (95% confidence interval [CI], 92.2–99.6) and led to the characterization of 44.6% of those found to have open angles on gonioscopy to have angle closure as well. With gonioscopy as the reference standard, specificity of AS-OCT in the dark was 55.4% (95% CI, 45.2–65.2) for detecting individuals with angle closure.
Conclusion
Anterior segment OCT is a rapid noncontact method of imaging angle structures. It is highly sensitive in detecting angle closure when compared with gonioscopy. More persons are found to have closed angles with AS-OCT than with gonioscopy.
Correspondence and reprint requests to Dr Winifred Nolan, Department of Epidemiology and International Eye Health, Institute of Ophthalmology, Bath Street, London EC1V 9EL, United Kingdom.
Manuscript no. 2005-1034.
Financial support: National University of Singapore (grant nos.: R-191000007101, R-191000007112).
Technical support and loan of anterior segment optical coherence tomography machine from Carl Zeiss Meditec, Dublin, California.
ABSTRACT