Assessment of the anterior chamber angle is of major importance in diagnosing angle closure. The “gold standard” to diagnose angle closure is gonioscopy. However, the diagnostic value of gonioscopy is limited. It is a subjective assessment, which requires experience for correct interpretation, and substantial interobserver variability has been shown.
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Recently, swept-source optical coherence tomography (SS-OCT; CASIA SS-1000; Tomey Corporation, Nagoya, Japan) has become available. This novel noncontact Fourier-domain OCT is equipped with a swept laser source at a wavelength of 1310 nm to image the anterior segment of the eye,
2–4 which is capable of precisely delineating fine-angle structures of the anterior chamber angle.
2,5 Compared with other anterior segment OCT devices (such as AS-OCT, Visante; Carl Zeiss Meditec, Inc., Dublin, CA, USA), the SS-OCT technology promises a superior assessment of the anterior chamber angle (i.e., more accurate visualization of the scleral spur and angle recess), because of the higher resolution of the images (≤10-μm axially and ≤30-μm laterally), higher scanning speed (2,000 A-scans/s vs. 30,000 A-scans/s) and fewer motion artifacts.
4,5 Another strength of the SS-OCT is that it is capable of acquiring 128 images in a single measurement, allowing anterior chamber angle measurements in any direction, while the AS-OCT can only acquire a single image in a single direction. An advantage SS-OCT has over gonioscopy is its ability to perform an exam under controlled light conditions, without alteration of the anterior chamber angle by inadvertent contact to the eye. However, indentation gonioscopy cannot be replaced by SS-OCT.
The scleral spur is used as a reference point for the relative position of the trabecular meshwork, from which anterior chamber angle parameters can be calculated to assess the anterior chamber angle. Thus, accurate scleral spur marking is crucial for correct analysis of an OCT-image.
In the ideal world, a nonexpert (someone with limited knowledge of ophthalmology) should be able to obtain reliable analyses and get reliable estimates of anterior chamber angle parameters with the SS-OCT. Since we have no evidence on the quality of the analyses of nonexperts, we were interested to compare outcomes of experts with nonexperts. The purpose of the present study was therefore to assess the variability of anterior chamber angle values with SS-OCT together with interobserver agreement, for expert and nonexpert observers.