Glaucoma is a progressive optic neuropathy characterized by optic nerve damage and typical visual field defects due to retinal ganglion loss caused by a number of deseases affecting the eye. Although clinical examination and photography of the optic disc and retinal nerve fiber layer (RNFL) have been considered as sensitive tests for detecting glaucomatous damage and its progression, they are highly dependent on observer skills, inducing high interobserver and intraobserver variation that affects the utility of these diagnostic modalities. Objective and reliable methods of detecting optic nerve head and RNFL pathologies, and their progression as well, would help the clinician in the diagnosis and monitoring of glaucomatous damage. Researches during the past two decades have resulted in the development of several imaging technologies designed to detect glaucomatous damage at early stages of disease. This review outlines optical coherence tomography (OCT), which is a noncontact noninvasive imaging technology that can create high-resolution, real-time, cross-sectional tomographic images of retina and optic nerve head using light with a wavelength of ~800 nm. Cross-sectional images of the optic disc and retina are obtained using the optical backscattering of near-infrared light in a manner analogous to B-scan ultrasonography. OCT can differentiate the anatomic layers of retina, measure the thickness of RNFL and produce the optic nerve head parameters. Thus, OCT has became a widely used imaging modality that enables clinicians to obtain objective measurements of RNFL thickness and optic nerve head parameters in glaucoma.