Optical Coherence Tomography: Creating a Roadmap of the Eye

Our eyesight is truly precious, it allows us to function and enjoy our lives in ways that we often take for granted. Many sight-threatening eye conditions damage our eyes so slowly that there are often no symptoms until they are very advanced. The key to the preventing permanent vision loss from these sight-threatening conditions is early detection, along with careful monitoring, and prompt action when required. At Mortimer Hirst, we are dedicated to providing the most up-to-date, cutting-edge methods to deliver the best in eye care, to every single one of our patients. 


An optical coherence tomographer, or OCT for short, is a device that allows the accurate measurement of the parts of the eye vital to normal vision. An OCT does this without even touching the eye; light rays and advanced computer analysis are used to generate highly detailed images of the important parts of the eye. This device enables your optometrist to have greater insight into your eye health, and therefore your eyesight. Importantly, it can help to detect even the subtlest areas that may be of concern before permanent vision loss occurs from several conditions including: age-related macular degeneration, glaucoma, myopia and keratoconus. Below is a brief overview of these conditions and how the OCT is essential to detecting and managing these conditions. The optometrists at Mortimer Hirst are also dedicated to patient education, visit our website mortimerhirst.co.nz to learn more about these conditions and you can now even book in to see one of our specialist optometrists through our website!


Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a condition where the central vision becomes increasingly blurry and distorted, eventually being lost completely. Glasses and contact lenses cannot correct AMD vision loss due to it is permanent. However, the OCT can establish a precise map of the macula (the affected area), and detect early changes often before symptoms are experienced. Then with appropriate management, which is informed by the OCT results, vision loss can be prevented or minimised. The OCT can also assist your optometrist in deciding the urgency of referrals to an ophthalmologist (AMD specialist) if required.



Glaucoma is a condition where the pressure that keeps the eyeball round gets too high and causes the peripheral vision to progressively reduce and eventually can result in complete vision loss. It is often symptomless until the later stages. Glaucoma occurs due to damage at the level of the optic nerve, the cable that connects the eye to the brain. Once the nerve fibres are lost, they cannot be recovered. In order to prevent nerve fibre damage, early detection is paramount, as vision loss can be prevented with current treatments. The OCT essentially measures the thickness of the optic nerve, thus can assist your optometrist in detecting even the earliest stages of glaucoma. Additionally, an OCT is essential in monitoring the success of glaucoma treatment. 


Myopia (Short-Sightedness) 

Myopia, or short-sightedness, is often incorrectly viewed as an inconvenience rather than a sight-threatening condition. Myopia is related to abnormal growth of the eyeball, which leads to blurred vision in the distance. As the eyeball lengthens, the glasses or contact lens prescription increases. A longer (more short-sighted) eyeball is associated with an increased risk of potentially sight-threatening conditions, such as retinal detachments. Myopia often arises in childhood and progresses into early adult life. The optometrists at Mortimer Hirst employ various methods for slowing the rate of eye growth, therefore preventing the risk of sight-threatening complications. The OCT plays an important role in this, as it allows your optometrist to accurately measure the length of your eyeball, and therefore provides a more accurate means of monitoring how effective the treatment to slow myopia is. 


Keratoconus is a progressive condition where the cornea (the clear window at the front of the eye) becomes increasingly thin and distorted, compromising vision. New Zealand has a particularly high rate of keratoconus. In many of these cases, glasses are inadequate in correcting vision, and specifically designed contact lenses are often required. As every eye that has keratoconus is different this often results in a highly complex lens design. The contact lens specialists at Mortimer Hirst utilise the precise measurements from the OCT to assist in the fitting of these contact lenses. In addition, the progression of keratoconus can be monitored, and referrals for further interventions can be arranged where required. 


From childhood to later life, the OCT can assist your optometrist in measuring and monitoring the eye conditions discussed above. The highly detailed information that the OCT provides ensures that your eyes are cared for in the best possible way. 


Words: Oliver Munro