The retinal nerve fiber layer (RNFL) is formed by retinal ganglion cell axons and represents the innermost layer of the fundus. The nerve fiber layer collects the visual impulses that begin with the rods and cones. These impulses travel through the ganglion cells as they pass from the rods and cones to the nerve fiber layer.
In the retina the axons are spread out as a thin layer and appear as opaque striations (axon bundles). These bundles have an almost straight horizontal course and form an arch around the macula.
The thickness of the RNFL increases toward the optic disc. At the optic disc the axons bend and pass through the scleral canal and form the neuroretinal rim of the optic nerve head. Optic disc cupping represents the area that does not contain nerve fibers.
Because the RNFL thickness decreases in glaucoma, objective methods for measuring these changes are being investigated which may facilitate early diagnosis of glaucoma.
General characteristics of the RNFL are as follows:
collects impulses that start with the rods and cones
carries neural impulses to the optic disc
lack of function causes loss of visual acuity or scotoma
lack of function causes the loss of vision in glaucoma patients