Sir,

I read with interest the above communication by Bhogal et al,1 published recently in the Eye journal.

The authors presented images of B scan ultrasound, correctly demonstrating choroidal effusion as the primary trigger in precipitating angle closure glaucoma in their patient. The anterior segment OCT images however failed to show the anatomical mechanism of angle closure, which, in many cases, is caused by the anterior rotation of ciliary body and most probably associated with annular ciliary body detachment. These findings would have been best illustrated by high frequency ultrasound (HFU). The value of HFU in cases of pseudophakic pupillary block and other post-operative ciliary body abnormalities was demonstrated by us in previous publications.2, 3

Anterior segment OCT is an ‘optical scan’ and therefore obeys the simple optical principle of inability to penetrate through opaque media. This is the domain of ultrasound. It is tempting to use anterior segment OCT in many clinical situations, as it is noninvasive and easy to use. Anterior segment OCT produces excellent images of the cornea, anterior iris tissue, trans-pupillary lens and angle configuration. It is however inferior to HFU in imaging of the posterior iris surface, ciliary body, posterior chamber, zonules, pars plana and periphery of choroid. An excellent prospective observational case series, comparing anterior segment OCT and HFU in the imaging of anterior segment masses, tend to confirm the above assertion and was published by Pavlin et al4 in 2009.

It is reasonable to recommend to readers that whenever imaging of the ciliary body is desirable, then HFU should remain the technique of choice.