Bogdănici Camelia MD, PhD
U.M.Ph. “Grigore T. Popa”, Iasi
County Emergency Clinical Hospital “St. Spiridon” Iasi
Optic Coherence Tomography and glaucoma
Author: Camelia-Margareta Bogdănici
Glaucoma is the leading cause of irreversible blindness worldwide and is the most common cause of permanent vision loss in persons older than 40 years of age, after age-related macular degeneration. Early diagnosis and treatment of glaucoma has been shown to reduce the rate of disease progression, and improve patients’ quality of life. Imaging technologies such as optic coherence tomography (OCT) are playing an increasing role in glaucoma diagnosis, monitoring of disease progress, and quantification of structural damage. OCT is a non-invasive, non-contact imaging modality that provides high-resolution cross-sectional imaging of ocular tissues (retina, optic nerve, and anterior segment).
Recent reports have shown that spectral domain optical OCT (SD-OCT) can measure peripapillary retinal nerve fiber layer (RNFL) thickness and can be useful in detecting glaucoma in the pre-perimetric stage. The advent of SD-OCT has renewed interest in the potential uses of macular imaging in glaucoma due to its ability to segment and measure individual retinal layers better.
Swept-source OCT (SS-OCT) can evaluate RNFL and macular thickness, but can also more clearly image deeper ocular structures such as the choroid and lamina cribrosa (LC) in patients. Swept-source OCT is able to scan at higher speeds and can acquire high- quality wide-angle scans that contain a large area of the posterior pole, including both the optic disc and macula. Swept-source OCT affords high repeatability in terms of anterior chamber angle width measurements, such as angle opening distance, trabecular iris space area, and trabecular iris angle and is able to capture extremely high resolution images of the AC.
Detection of disease progression remains challenging in glaucoma due to the variable and slowly progressive nature of the disease, measurement variability of SAP and of imaging devices, and the lack of a commonly acceptable reference standard. Some eyes show structural changes in the ONH or RNFL before any indication of glaucomatous damage can be detected with SAP. Some reports shows that using SD-OCT RNFL parameters was useful for detecting glaucoma progression.
In TD-OCT (time-domain OCT) structural progression was associated with functional progression in preperimetric, glaucoma suspect, and glaucomatous eyes and eyes with significant SAP progression have higher rates of RNFL thickness loss compared with nonprogressing eyes.
In conclusions, OCT has established itself as the dominant imaging modality in diagnosis, progresssion and also OCT is widely used as an adjunct in routine glaucoma patient management., providing high-resolution visualization of ocular microstructures and objective quantification of tissue thickness and change.