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While gonioscopy is the standard for detecting individuals with angle closure, its inevitable need for minimal illumination to visualize the angle, the uncertainty on the change in angle configuration when a goniolens is in direct contact on the cornea, and the dependence on individual skill and experience for interpretation of the angle configuration, serve to limit its role in providing precise angle assessment. Nolan et al. (147) performed an excellent study showing the potential of the anterior segment optical coherence tomography (ASOCT) in identifying angle closure. With gonioscopy as the reference standard, ASOCT demonstrated a high sensitivity (98%) for detection of angle closure. Of subjects, 44.6% were found to have open angles on gonioscopy were also identified as angle closure by the ASOCT performed in the dark. This result suggests ASOCT may detect angle closure missed by gonioscopy, which could be related to the fact that gonioscopy can be hardly performed in the absence of illumination.
In this study, angle closure was defined as having visible contact between the peripheral iris and any part of the angle wall anterior to the scleral spur.
ASOCT may detect angle closure missed by gonioscopyHowever, it should be noted that the scleral spur may not be always visible in the OCT images. Defining narrow angles and measuring the angle width could be problematic in eyes with poor visibility of scleral spur. While the ASOCT is holding promise for detection of angle closure / narrow angle, further studies are required to determine its reliability.