Research progress of measurement of retinal ganglion cell complex using optical coherence tomography in glaucoma

Glaucoma mainly affects the axon and cell body of retinal ganglion cells (RGCs). Optical coherence tomography (OCT) is a kind of imaging machine with noncontact, high scanning speed and high resolution, can be used for quantitative measurement of retinal ganglion cell complex (GCC) thickness or ganglion cell-inner layer (GCIPL) thickness.GCC includes nerve fiber layer, ganglion cell layer and inner cluster layer, GCIPL only includes ganglion cell layer and inner cluster layer time domain OCT (TD-OCT) can only measure the total thickness of the macular region, in fact, some levels are not involved in the progress of glaucoma, which leads to a decrease in specificity and sensitivity.At present, spectral domain OCT (SD-OCT) is used for measuring GCC and GCIPL.It gains faster scanning speed than traditional TD-OCT, and can scan more locations and form 3D images in macular region.Therefore, it is helpful to improve the sensitivity and specificity of detecting the damage of glaucoma by refining the stratification of the macular retina and making the qualitative measurement of the inner layer of retina.Three scanning modes and methods are commonly used, RTVue-100 OCT, Cirrus HD-OCT, 3D OCT, and the three methods have their own advantages.Measurement of the thickness of GCC by OCT may be influenced by factors such as age, sex, axial length, race and signal intensity.In recent years, many studies have indicated that GCC or GCIPL has a good consistency with the visual field, and can be used in early diagnose and regular follow-up of glaucoma.The future research should be devoted to normal database establishment of GCC and GCIPL thickness parameters with different age and different ethnic and clinical trials and follow-up study should be performed to explore the change rules of those paremeters.