Nerve fiber layer

Optic nerve head and nerve fiber layer changes occur before visual field changes can be detected. 

Figure 14.1 Schematic diagram of the blood-retinal barrier (BRB). The retinal cell layers seen histologically consist of retinal pigment epithelium (RPE) photoreceptor outer segments (POS) outer limiting membrane (OLM) outer nuclear layer (ONL) outer plexiform layer (OPL) inner nuclear layer (INL) inner plexiform layer (IPL) ganglion cell layer (GCL) nerve fiber layer (NFL) inner limiting membrane (ILM).

Nerve fiber layer Ganglion cell layer Inner plexiform layer... 

There has been a report of retinal changes in 60 users of crack (164). Microtalc retinopathy and retinal nerve fiber layer rake or slit defects were detected by threshold visual field testing and fundus photography. 

Rofsky JE, Townsend JC, Ilsen PF, Bright DC. Retinal nerve fiber layer defects and microtalc retinopathy secondary to free-basing crack cocaine. J Am Optom Assoc 1995 66(11) 712—20. 

Structural Assessment of the Optic Nerve Head and Retinal Nerve Fiber Layer... 

R = Rim tissue and nerve fiber layer V = Vessels (e.g., bearing, bayoneting, disc hemorrhages)... 

Assessment of the optic nerve head and retinal nerve fiber layer should occur for all glaucoma patient and glaucoma suspects. 

Indirect ophthalmoscopic assessment of the optic nerve head and retinal nerve fiber layer at the slit lamp should, whenever possible, be augmented by other techniques such as direct ophthalmoscopy, retinal photography, and/or scanning laser ophthalmoscopy. 

An assessment of the optic nerve and retinal nerve fiber layer should include an assessment of the following disc size, shape, symmetry, color, angle, vessels, and extrapapillary features such as the presence of a zone beta. 

Retinal photography is an important adjunctive tool in the assessment of the optic nerve and retinal nerve fiber layer. 

Disc (Drance) hemorrhages and retinal nerve fiber layer defects that are visible with retinal photography can be overlooked during clinical and/or laser ophthalmoscopy. 

Do not expect visual field findings to correspond to the structural assessment of the optic nerve or retinal nerve fiber layer in early glaucoma. 

Microtalc dusting of the retina may represent minute crystalline deposits of crack cocaine s adulterants lodged in the retinal microcirculation, the inner retinal layers, or both. It has been hypothesized that the retinal nerve fiber layer changes seen in these patients may occm from ischemia induced by focal drug-induced vasospasm of the short posterior ciliary arteries. 

Histopathologic studies have found bilateral optic atrophy with primary involvement of the papillomacular bundle, loss of the retinal ganglion cells, and gliosis of the nerve fiber layer. The presence of peripheral visual field defects in some patients is evidence that there is also involvement of the peripheral portion of the visual pathway. 

Certain vision loss (up to NLP) with retinal complications (infarction, periarteritis/phlebitis, branch artery occlusions, nerve fiber layer hemorrhage, macular edema). 

Note OADRs = ocular adverse drug reactions CV = color vision VF = visual field VL = vision loss NFL = nerve fiber layer lOP = intraocular pressure NSAIDs = nonsteroidal anti-inflammatory drugs TBUT = tear break-up time CL = contact lens IH = intracranial hypertension RD = retinal detachment NAION = nonarteritic ischemic optic neuropathy. 

Consider optical coherence tomography to pick up early toxicity (swelling of the nerve fiber layer) and chronic toxicity (nerve fiber layer thinning). 

The ganglion cell layer (GCL) contains the cell bodies of retinal ganglion cells, with their axons running across the retinal surface (nerve fiber layer) toward the optic nerve head, and on through the optic nerve to the lateral geniculate nucleus in the mid-brain. The inner retinal blood supply (outside the foveal avascular zone), the nerve fiber layer, and a thin membrane (the inner limiting membrane) form the most superficial retinal structures. 

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