Though not used very often, anterior segment optical coherence tomography (ASOCT) is a highly-effective, non-invasive test that takes images of the anterior segment of your eye. To help you understand the procedure a little better, we’ve put together this guide on what ASOCT scans are, and  how it may be helpful. 

What is the anterior segment in the eye?

The anterior segment is the front third of the eye. The structures in this segment control the amount of light that enters the eye, allows the light to pass through to the lens, and helps to focus light rays on the retina in order to form images. The main parts of the eye within the anterior segment include:

  • Pupil (the black, circular opening that allows light to enter the eye)
  • Iris (the circular muscle that gives us our eye colour and controls pupil size)
  • Cornea (the transparent front part of the eye that covers the pupil and iris)
  • Sclera (the white of the eye)
  • Ciliary body (the muscle that controls the shape of the lens)
  • Lens (a crystalline structure that changes shape and focuses light rays on the retina)
  • Anterior chamber (the space filled with a fluid called aqueous humour)

You can find a more visual guide to the different parts of the eye here.

Since it encompasses so many parts of the eye, some ophthalmologists specialise in the treatment and management of anterior segment diseases — the most common being cataracts.

What is the purpose of anterior segment optical coherence tomography?

Optical coherence tomography (OCT) was initially developed to view the retina (the light-sensitive layer in the back of the eye) in more detail. Anterior segment optical coherence tomography (ASOCT) is a variation of OCT that is used to produce high-resolution 3D images of the anterior segment. It can therefore be used to help detect and monitor a number of anterior segment diseases and conditions, including:1 

  • Conjunctival diseases such as pterygium and pinguecula
  • Anterior segment tumours
  • Corneal diseases and infections
  • Dry eye syndrome
  • Trauma or injuries to the anterior segment
  • Sharp eye pain caused by closed angle glaucoma

Find out more about the detection and management of eye diseases with anterior segment optical coherence tomography in our OCT resource.


1. Han SB, Liu YC, Noriega KM, Mehta JS. Applications of Anterior Segment Optical Coherence Tomography in Cornea and Ocular Surface Diseases. J Ophthalmol. 2016;2016:4971572. [Online]. Available at: [Accessed 13 November 2019].