The retinal nerve fiber layer (RNFL) or nerve fiber layer, stratum opticum, is formed by the expansion of the fibers of the
optic nerve
In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i ...
; it is thickest near the
optic disc
The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc, it corresponds to a small blind spot in each eye.
The ganglion cell axons form the ...
, gradually diminishing toward the
ora serrata
The ora serrata is the serrated junction between the choroid and the ciliary body. This junction marks the transition from the simple, non-photosensitive area of the ciliary body to the complex, multi-layered, photosensitive region of the retina ...
.
As the nerve fibers pass through the
lamina cribrosa sclerae they lose their
medullary sheath
Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be ...
s and are continued onward through the
choroid
The choroid, also known as the choroidea or choroid coat, is a part of the uvea, the vascular layer of the eye, and contains connective tissues, and lies between the retina and the sclera. The human choroid is thickest at the far extreme rear ...
and
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
as simple axis-cylinders.
When they reach the internal surface of the retina they radiate from their point of entrance over this surface grouped in bundles, and in many places arranged in
plexuses.
Most of the fibers are centripetal, and are the direct continuations of the axis-cylinder processes of the cells of the
ganglionic layer, but a few of them are
centrifugal and ramify in the
inner plexiform and
inner nuclear layer
The inner nuclear layer or layer of inner granules, of the retina, is made up of a number of closely packed cells, of which there are three varieties, viz.: bipolar cells, horizontal cells, and amacrine cells.
Bipolar cells
The bipolar cells, by ...
s, where they end in enlarged extremities.
Patients with
retinitis pigmentosa
Retinitis pigmentosa (RP) is a genetic disorder of the eyes that causes loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision (side and upper or lower visual field). As peripheral vision worsens, people may ...
have abnormal thinning of the RNFL which correlates with the severity of the disease.
However the thickness of the RNFL also decreases with age and not visual acuity. The sparing of this layer is important in the treatment of the disease as it is the basis for connecting retinal prostheses to the optic nerve, or implanting stem cells that could regenerate the lost photoreceptors.
RNFL is a sensitive structure which may vary based on ethnicity. Some process can excites its natural apoptosis. Harmful situation can make some damage on RNFL such as high intraocular pressure, high fluctuation on phase of intraocular pressure, inflammation, vascular disease and any kind of hypoxia. Gede Pardianto (2009) reported 6 cases of RNFL thickness change after the procedures of
phacoemulsification
Phacoemulsification is a modern cataract surgery method in which the eye's internal lens is emulsified with an ultrasonic handpiece and aspirated from the eye. Aspirated fluids are replaced with irrigation of balanced salt solution to maintain ...
. Sudden intraocular fluctuation in any kind of intraocular surgeries maybe harmful to RNFL in accordance with mechanical stress on sudden compression and also ischemic effect of micro emboly as the result of the sudden decompression that may generate micro bubble that can clog micro vessels.
[Pardianto G, Moeloek N, Reveny J, Wage S, Satari I, Sembiring R et al. Retinal thickness change after phacoemulsification. ''Clin Ophthalmol.'' 2013(7):2207-2214 ] Glaucoma is the lead cause of irreversible blindness in contemporary times. Furthermore, greater research in the RNFL and even optic nerve head (ONH) abnormalities, can pave the way for early detection and diagnosis of glaucoma
References
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Human eye anatomy