Anterior segment imaging: identifying the landmarks

Optical coherence tomography (OCT) has recently been adapted to enable rapid, non-contact detailed imaging of the anterior segment of the eye. Anterior segment optical coherence tomography (AS-OCT) was originally developed for use in refractive surgery but the ability to provide cross-sectional images of the angle and its key anatomical landmarks makes it potentially useful in glaucoma research and clinical management of primary angle closure. Objective recordings of the anterior chamber angle can then be analysed by qualitative or quantitative means to provide an assessment of whether the angle is open or closed and degree of angle width/opening.

Currently qualitative categorical outcomes (angle open or closed) are used to define the presence or absence of angle-closure on AS-OCT images. Quantitative measurements of angle width are useful for comparing angle configuration before and after interventions including laser iridotomy or cataract surgery and for reporting these outcomes in a quantifiable way. Parameters that are used for measuring angle width on anterior segment images include the angle opening distance (AOD) at a fixed distance anterior to the scleral spur, the angle recess area (ARA) and the trabecular iris space area (TISA).

In this edition of the journal, Console et al1 report the use of new image analysis software for AS-OCT (see page 1612). This …