الفهرس 
Anatomy of retinal nerve fiber layerOnly 14 pages are availabe for public view
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Abstract
Retinal nerve fiber layer is the innermost layer of the
retina, it is formed of the axons of ganglion cells. Attrition of
nerve fibers in the anterior visual pathways is reflected directly
in the nerve fiber layer of the retina. These retrograde
degenerative changes are subtle but they can be seen with an
ophthalmoscope and can be photographed with a fundus
camera.
In routine clinical practice identifying pathologic
alterations in the RNFL ophthalmoscopically necessitates
optimal viewing conditions, familiarity with the appearance of
the normal RNFL, and a high index of suspicion.
So, the importance of the new objective quantitative
technologies for RNFL assessment which are the optical
coherence tomography, the confocal scanning laser
ophthalmoscopy, the scanning laser polarimetry and the retinal
thickness analyzer had been proved.
Retinal nerve fiber layer (RNFL) can be evaluated both
structurally and functionally. This is helpful for early diagnosis
and following up of the optic nerve diseases .
For structural evaluation, RNFL can be evaluated by
clinical examination of the optic disc, stereoscopic optic nerve
photography, red-free monochromatic RNFL photograph as
well as computer-based devices such as: optical coherence
tomography, Confocal scanning laser ophthalmoscopy, and
scanning laser polarimetry, that provide quantitative
assessments of structural damage.
For functional evaluation, RNFL can be evaluated by
perimetry as well as electrophysiology; there are now many
different methods for performing visual field testing including
standard automated perimetry (SAP) as well as selective
techniques including short wavelength automated perimetry
(SWAP), frequency doubling technology (FDT) perimetry,
high pass resolution perimetry (HRP) and motion perimetry.
Glaucoma is a multi-factorial optic neuropathy
characterized by Irreversible progressive loss of the retinal
ganglion cells (RGCs) and thinning of the retinal nerve fiber
layer (RNFL), leading to visual field loss and eventually, total
loss of vision. 40% to 50% of the RNFL could be lost before
visual field defects are detected by conventional perimetry.
Thus, RNFL assessment had emerged as an important
parameter for pre-perimetric diagnosis of glaucoma.
Diabetic retinopathy (DR) is the fifth most common
cause of blindness worldwide. In addition to typical
retinopathies, neuro-visual impairments had been reported.
Focal retinal nerve fiber layer loss in diabetic patients with
preclinical DR was detected. In vitro studies had demonstrated
that diabetes affects both retinal neurons and glial cells.
Panretinal photocoagulation causes a sequential decrease in the
peripapillary retinal nerve fiber layer (RNFL) thickness.
Optic neuropathies are conditions that involve
degeneration of the optic nerve, and can be hereditary or
acquired. These neuropathies result in characteristic changes to
the optic nerve head and the surrounding retinal nerve fiber
layer as a result of direct and indirect damage to the retinal
ganglion cells and their axons.
Assessment of optic disc edema can be done by follow
up the resolution of axonal swelling and thinning of the RNFL,
which are essential aspects of optic atrophy.
RNFL assessment appeared to be an important clue in
the diagnosis of other disorders like neurodegenerative
disorders including multiple sclerosis, Alzheimer’s and
parkinson’s disease which show affection of the nerve fiber
layer causing visual function affection.
The majority of hereditary retinal dystrophies originate
within the outer retinal layers. A secondary degeneration of t
middle and inner retinal layers could be caused by a transsynaptic
degeneration or by toxic products associated with the
death of outer retinal structures. Middle and inner retinal
layers in hereditary retinal dystrophies had gained more
interest because some of the new potential therapeutic
concepts such as transplantation of photoreceptors or pigment
epithelium cells and visual prosthesis require functional
second and third order retinal neurons .
It was reported that clinically evident retinal nerve fiber
layer thinning could be detected on fundus photography in
various diseases of the outer retina.
Some diseases had been thought to change RNFL, but
studies had proved the opposite and that aided in the true
understanding of these pathologies as in amblyopia in which
RNFL assessment was insignificant.
Evaluation the effect of LASIK on RNFL thickness
measurements obtained with SLP, OCT, and HRT.
Increased numbers of clinically visible optic nerve head
drusen correlated with NFL thinning shown by OCT
measurements and both visual field defects and NFL loss seen
by red-free photography.
Significant thinning of the RNFL occurs in HIV-positive
patients without a history of CMV retinitis and with a history
of low CD4 cell counts in comparison to the same group of
patients with CD4 cell count increased above 100 and HIVnegative
control subjects.
RNFL thinning in Obstructive sleep apnea syndrome was
correlated with the severity of this condition, as the disease
becomes more severe, RNFL thinning is proportionally.