Imaging the Optic Nerve Head, Peripapillary, and Macula Regions in Glaucoma

Glaucoma is the second leading cause of blindness worldwide. ^{1, 2} There is no current cure for this irreversible disease; therefore, it is best managed with early diagnosis and timely medical treatment. Glaucoma presents as an optic neuropathy, accompanied by characteristic vision loss and structural damage. Early methods of clinical glaucoma assessment included optic nerve head (ONH) examination, intraocular pressure (IOP) measurement, and visual field testing. However, these methods are limited because they are subjective and rely heavily on clinical interpretation. Additionally, it has been shown that 25% to 35% of the retinal ganglion cells (RGCs) are damaged before the appearance of visual field abnormalities. ^{3, 4} Recent advances in imaging technologies have greatly improved glaucoma management because they are capable of obtaining quantitative and reproducible measurements of the ONH, peripapillary and macula regions. However, in early stages of glaucoma, the functional abnormalities are often not detected even when changes in circumpapillary retinal nerve fiber layer (RNFL) are present. A “tipping point” was reported before in which there is structural changes without functional changes and after which there is a strong association between the two. ⁵ Studies have shown imaging technologies offer a similar or improved glaucoma diagnostic ability to that of clinical evaluation of optic disc photographs. ^6-11 Current clinical glaucoma management combines both structural and functional evaluation to establish glaucoma diagnosis and detect progression.