|Year : 2015 | Volume
| Issue : 1 | Page : 1-2
Retinal nerve fiber layer defects
DORCS, MRCOphth, FRCOphth, FICS, FACS Professor of Ophthalmology BIJO Editor-In-Cheif, Faculty of Medicine, Al-Neelain University, Khartoum, Sudan
|Date of Web Publication||10-Nov-2015|
DORCS, MRCOphth, FRCOphth, FICS, FACS Professor of Ophthalmology BIJO Editor-In-Cheif, Faculty of Medicine, Al-Neelain University, Khartoum
|How to cite this article:|
Saleem M. Retinal nerve fiber layer defects. Albasar Int J Ophthalmol 2015;3:1-2
(This review does not purport to be comprehensive but was written to raise awareness of issues on Retinal Nerve Fiber Layer Defects.)
For years, ophthalmologists have recognized that ophthalmoscopic features of normal retinal nerve fiber layer (RNFL) could be observed by "white" and "red-free" direct ophthalmoscopy. Moreover, can be documented by a high-resolution red-free fundus photography. Normal RNFL shows the fine parallel striated appearance of the arcuate bundle, especially along the vascular temporal arcades. Therefore, careful scrutiny of the RNFL should be an integral part the routine evaluation of the fundus.
Diseases of the anterior visual pathway beside some systemic can produce defects in the RNFL: Optic nerve diseases, glaucoma, ocular hypertension, papilledema, toxic amblyopia, and congenital hemianopia, cotton wool spots, and obstructive sleep apnea syndrome. Localized RNFL defects were found to be associated with cotton wool spots.
Thinning of the RNFL is associated with brain atrophy in multiple sclerosis., Grazioli results support potential usefulness of optical coherence tomography (OCT) for MS patient monitoring.
Macular RNFL imaging could protect the optic nerve from axonal loss of optic neuritis.
In Leber's hereditary optic neuropathy the temporal fibers (papillomacular bundle) are the first and most severely affected; the nasal fibers seem to be partially spared in the late stage of the disease.
Central retinal artery occlusion may lead to the optic disc and RNFL damage. Patterns of these RNFL defects may be localized  or generalized attrition of RNFL. Small slit or sector-shaped defects also can be occurs.
RNFL and visual field defects are uncommon (5%) in eyes with buried optic nerve Drusen (OND). Although most of the eyes with OND always have normal average RNFL thickness, very few may have clinically nonsignificant focal RNFL defects.
Age-related RNFL defect is not uniform in all the quadrants, with a maximum loss in the superior quadrant, and seems to reach a maximum after the age of 50 years. Furthermore, it seems that inferior quadrant RNFL is more resistant to loss.
The average superior and inferior RNFL thickness is usually inversely related to age. For creating a normative database of SOCT RNFL values have to be age adjusted.
The majority (86%) of the patients with retinitis pigmentosa develop well recorded RNFL damage. Some demonstrate thickening of the peripapillary RNFL (42%) in one or more quadrants whereas others (36%) show thinning of the peripapillary RNFL in one or more quadrants. Few (8%) may develop both thinning and thickening of the peripapillary RNFL thickness.
Early diagnosis of glaucoma is critical to prevent permanent structural damage and irreversible vision loss. Preperimetric glaucoma. can be early diagnosed by OCT assessment of the RNFL, optic nerve head, and macular thickness, as a good combined parameters improve the diagnostic accuracy for early glaucoma. Nerve fiber atrophy usually precedes the onset of glaucomatous field loss.
RNFL thickness decreases with the axial length and negative spherical equivalent of the eye. Highly myopic eyes have significantly lower RNFL thickness than other type of refractive error.
Many factors can affect the variability of RNFL thickness measurements because of changes in signal strength:
Soft contact lenses wearing at the time of examination, ocular media opacity (cataract, cornal, or vitreous opacity), and cataract extraction and intraocular lens implantation.,
Reliable RNFL thickness measurement is done with:
- 1. OCT
- Time domain OCT (e.g.: Stratus; Carl Zeiss Meditec)
- 2. Spectral domain OCT (SD-OCT, e.g., Cirrus HD-OCT; Carl Zeiss Meditec)
- 3. Heidelberg retinal tomography
- 4. Scanning laser polarimetry
- Confocal scanning laser ophthalmoscopy.
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