OCT Angiography in the Glaucoma Diagnosis

Overview

Glaucoma is a chronic degenerative disease of the optic nerve. It is the second cause of blindness worldwide and a frequent cause of irreversible blindness. In 2020, epidemic health authorities have predicted about 80 million glaucoma patients. Glaucoma can be treated by topical treatment (eye drops), laser or surgery. A premature diagnosis of glaucoma is very important to prevent irreversible blindness. Pachymetry, Optical Coherence Tomography (OCT) and visual fields exams are fundamental for the development of the glaucoma diagnosis. The severity of glaucoma is defined with Hodapp-Parrish-Andersen visual field criteria. According to these criteria, glaucoma can be classified as early (with average visual field deviation, MD, of 0 to -6 dB), moderate (MD of -6 to -12 dB) and severe (MD worse than -12 dB). The progression of glaucoma is being identified by the visual fields tests, and also by the progression of alterations in the optic nerve head. The visual fields tests are long and difficult (30 minutes). It is therefore important to create additional tests and anticipate the diagnosis, in order to avoid the irreversibility of glaucoma.

The OCT Angiography (OCTA) is a non-invasive technology, marketed since 2014, that uses OCT with infrared light, with no radiation nor side effects, to evaluate within seconds the vascularization of the fundus, retina and optic nerve head, which may be useful for the glaucoma diagnosis. A recent meta-analysis has shown a decrease of the vascular density (DV) in glaucoma, so that OCTA may be useful in the advanced diagnosis of glaucoma. However, the VD values obtained were different depending on the device. In addition, no studies with the OCT Triton (Topcon®) device were considered in the analysis. The authors suggested the development of dedicated software, which would allow the evaluation of VD with different devices for a more independent and valid assessment. On the other hand, recent studies show that the diagnostic capacity of OCTA may be superior to that of OCT, and that OCTA may be more useful in determining the severity of glaucoma than OCT. It is therefore necessary to evaluate the additional diagnostic tests whether they are non-invasive and whether it allow us to give a faster diagnosis. This study is aimed at comparing the diagnostic utility of OCTA with standard complementary glaucoma examinations (OCT and CV).