From the Guidelines
Optic disc pallor is primarily caused by glaucomatous optic neuropathy, characterized by vertical elongation of the optic cup, excavation of the cup, thinning of the retinal nerve fiber layer (RNFL), and other structural changes, as evidenced by studies such as the OHTS, which found that optic nerve damage alone without visual field loss occurred in 69 eyes and accounted for 55% of the study endpoints reached 1. The causes of optic disc pallor can be multifactorial, but the key underlying factor is damage to the optic nerve fibers. Some of the main causes include:
- Glaucoma, which damages nerve fibers through increased intraocular pressure
- Ischemic optic neuropathy, where blood supply to the optic nerve is compromised
- Optic neuritis, an inflammation of the optic nerve often associated with multiple sclerosis
- Compressive lesions like tumors or aneurysms that press on the nerve
- Nutritional deficiencies, particularly vitamin B12 or folate
- Toxic exposures to substances like methanol or ethambutol
- Hereditary optic neuropathies such as Leber's hereditary optic neuropathy It is essential to note that optic disc pallor typically develops weeks after the initial insult to the nerve fibers as axonal degeneration occurs, and this pallor represents irreversible damage and often correlates with permanent vision loss in the affected areas, as seen in studies where disc hemorrhage was associated with progression of glaucoma 1. Early detection through comprehensive eye examinations is crucial, as treatment must target the underlying cause to prevent further vision deterioration, though existing damage usually cannot be reversed. The appearance of the optic nerve should be documented, and the preferred technique for ONH evaluation involves magnified stereoscopic visualization, preferably through a dilated pupil 1.
From the Research
Causes of Optic Disc Pallor
- Ischemic optic neuropathy, which can be caused by various factors such as giant-cell arteritis, hypertension, diabetes, and traumatic injuries or surgeries, can lead to optic disc pallor 2, 3, 4
- Hypovolemic events, such as blood loss due to trauma, surgery, or internal bleeding, can also cause ischemic optic neuropathy and subsequent optic disc pallor 2
- Non-arteritic anterior ischemic optic neuropathy (NAION) can cause optic disc pallor, and deeply buried optic disc drusen may be a predisposing factor for NAION 4
- Ocular hypertension and glaucoma can also cause changes in the optic disc, including cupping and pallor, due to abnormalities in the blood supply to the optic disc 5, 6
- Reversal of optic disc cupping and pallor can be observed in some cases of glaucoma patients who have undergone surgical or medical therapy, particularly when ocular pressure is decreased 6