The Differential Diagnosis of an Optic Nerve Disorder

When you suspect an optic nerve disorder, your differential diagnosis should include retinal, glaucomatous and congenital conditions.

By Denise Goodwin, O.D.

Release Date: April 2010
Expiration Date: April 30, 2013

Goal Statement:

Optic nerve disorders usually have characteristic features; however, other conditions often present similarly. Then, the challenge becomes determining if the disease is of the optic nerve, retina, both or neither. The author reviews several common diseases of the optic nerves, as well as conditions with “lookalike” signs.

Faculty/Editorial Board:

Denise Goodwin, O.D.

Credit Statement:

This course is COPE approved for 2 hours of CE credit. COPE ID 27962-PS. Please check with your state licensing board to see if this approval counts towards your CE requirement for relicensure.

Joint-Sponsorship Statement:

This continuing education course is joint-sponsored by the Pennsylvania College of Optometry.

Disclosure Statement:

Dr. Goodwin has no relationships to disclose.

Eye care professionals must frequently evaluate anomalous optic nerves. Many optic neuropathies are treatable, so we need to understand the features, associated findings, pathology and ancillary testing that will allow us to promptly and correctly diagnose and manage the condition.

Diseases of the optic nerve usually result in characteristic features, including reduced visual acuity and color vision, a relative afferent pupillary defect (RAPD), visual field defects and changes in the optic disc appearance (e.g., swelling, pallor or cupping).

But, it can be a challenge to determine if it is a disease of the optic nerve or retina—or if it is due to another condition altogether.

Optic Atrophy Warns of Nerve Damage

One key warning sign: optic atrophy. This represents irreversible damage to the optic nerve. Atrophy is diagnosed based on the color and structure of the optic nerve, nerve fiber layer and retinal blood vessels. It may be diffuse or sectoral (figure 1A). In many cases of optic atrophy, most notably in ischemic optic neuropathy, the retinal arteries become narrowed or attenuated at the edge of the optic disc (figure 1B). In some cases, however, the retinal vessels remain of normal caliber.

1A, B. Sectoral optic atrophy (left), and diffuse optic atrophy.

Optic Nerve Pathology …

... vs. Retinal Disease

Disorders affecting the optic nerve must be differentiated from other ocular pathologies, which are typically visible on biomicroscopy and fundus examination. Some conditions, however, such as subtle macular edema, epiretinal membrane and cone dystrophy, may not be obvious on routine examination (figure 2). The ability to recognize characteristic signs and symptoms can help differentiate retinal and optic nerve disorders. (See “Features of Macular Dysfunction vs. Optic Neuropathy,” below.) Also, when examining the patient with retinal disease, ensure that the amount of vision loss is consistent with the retinal condition as there may be an underlying neuropathy.

Features of Macular Dysfunction vs. Optic Neuropathy

Features Macular Dysfunction Optic Neuropathy
Visual acuity
Markedly reduced
Vision characteristics
Poor vision in bright light
Poor vision in dim light
Central cloud
Afferent pupillary defect
Absent with subtle retinal disease
Sense of brightness
Very reduced

Color vision
Slightly reduced
Very reduced
Refractive error
May have hyperopic shift
Associated signs Signs of retinal or macular disease
with fundus biomicroscopy, OCT,
fluorescein angiography, or focal
EOM problems
Optic disc abnormalities

... vs. Glaucomatous Optic Neuropathy

The most common optic neuropathy is glaucomatous optic neuropathy. Because other chronic optic neuropathies, including those resulting from ischemia, inflammation and compression, may result in cupping despite normal intraocular pressure, it is important to differentiate glaucoma from other optic neuropathies. Keep in mind that patients can have both glaucoma and another optic neuropathy concurrently.

Loss of visual acuity, color vision and visual field usually occur early in non-glaucomatous optic neuropathies. Acuity loss only occurs late in the glaucomatous process when there is absence of at least a portion of the neuroretinal rim. An RAPD can occur if the glaucoma is unilateral or asymmetric.

Visual field defects secondary to glaucoma generally occur only with significant cupping, and visual field loss should correspond with the area of focal neuroretinal rim loss. In glaucoma, visual field defects are usually arcuate or paracentral in nature, respect the horizontal meridian, and occur between 5º and 30º from fixation. Early visual field loss often presents as a nasal step.

Cupping is more profound in glaucoma than in other optic neuropathies and often has focal loss of the neuroretinal rim. The neuroretinal rim may be absent in glaucoma, but if present, the color of the remaining rim should have a normal pink hue. The rim is rarely absent in non-glaucomatous optic neuropathies, and the remaining neuroretinal rim is usually pale in color.

Congenital Anomalies

• Optic nerve hypoplasia. In this case, the optic nerve head appears abnormally small due to a low number of axons. The disc may appear gray or pale and is surrounded by a light-colored peripapillary halo (figure 3). At the normal junction between the sclera and lamina cribrosa, there is another change in pigmentation, a “double ring sign,” associated with the hypoplasia.

• Megalopapilla. Megalopapilla, an abnormally large optic disc, usually occurs bilaterally and is associated with a large cup-to-disc ratio (figure 4). These discs have a surface area greater than 2.5mm2. The round or horizontally elongated cup, as well as the lack of rim notching, helps distinguish megalopapilla from normal tension glaucoma. The neuroretinal rim may be pale due to axons being spread over a larger surface area.

• Morning glory disc anomaly. Morning glory disc anomaly is evidenced by a congenital funnelshaped excavation of the posterior pole (figure 5). The disc appears enlarged and may be recessed or elevated centrally. A white tuft of glial tissue covers the central portion of the cup. Blood vessels appear to be increased in number and emanate from the edge of the disc. After arising from the disc, the vessels turn sharply at the edge of the cup and have an abnormally straight pattern in the peripapillary region.

• Peripapillary staphyloma. In this condition, the area around the disc is deeply excavated, with atrophic changes in the retinal pigment epithelium (figure 6). It is generally unilateral, and the disc may be normal or appear pale. As opposed to those in morning glory disc anomaly, the blood vessels have a normal pattern. These eyes are normally emmetropic or slightly myopic, but they can also be highly myopic.1

• Colobomatous optic discs. Colobomas result from an incomplete closure of the embryonic fissure. They can be either unilateral or bilateral and are often familial. A coloboma of the optic disc appears as a white, bowlshaped excavation of the inferior optic nerve head. The optic disc is typically enlarged. The inferior neuroretinal rim is thin or absent, and the superior neuroretinal rim is relatively normal. The coloboma may involve the choroid and retina (figure 7). Iris and ciliary colobomas may also be present.

• Optic pit. An optic pit appears as a round or oval, gray or white depression in the optic disc (figure 8). They are most commonly found temporally, but can be found in any area of the disc.

• Tilted disc. Typically, the optic nerve exits the sclera at a 90º angle. A tilted optic nerve occurs when the nerve exits the eye at an oblique angle. Tilted disc is usually a bilateral condition in which the superiortemporal disc is raised, simulating disc swelling, while the inferiornasal disc is flat or depressed (figure 9). This results in an oval-shaped disc with the long axis at an oblique angle. The blood vessels also enter the globe at an oblique angle. There is thinning of the RPE and choroid in the inferior nasal quadrant.

6, 7, 8, 9. Peripapillary staphyloma (left). The patient’s refraction in that eye: -1.25 -1.75 x 014. Next, a coloboma that involves the retina, choroid and optic nerve. Figure 8 shows an inferior temporal optic pit. Figure 9 (far right) shows a tilted optic disc.

• Myelinated nerve fiber layer.
Myelinated nerve fibers manifest as white, feathery patches that follow the NFL bundles and have a striated appearance (figure 10). The peripheral edges appear fanned out. The myelination can simulate disc edema due to elevation of the optic nerve and obscuration of the disc margins and retinal vasculature.

Normally, myelination does not extend past the lamina cribrosa; however, in 0.6% to 1.0% of the population, myelinated NFL occurs.2,3 Myelination is bilateral in just 8% of cases and is continuous with the optic nerve head in only 33% of eyes.3

Optic Nerve Head Drusen

Nerve elevation due to disc drusen is usually apparent in childhood as a “full” optic nerve that simulates papilledema (figure 11A). As the person ages and this pseudopapilledema changes, the optic nerve takes on a scalloped appearance at the nasal disc margin (figure 11B). Finally, subtle excrescences appear on the surface of the disc (figure 11C). The drusen enlarge, calcify and become more visible. In later adulthood, the disc elevation decreases, the nerve becomes pale and NFL defects appear.

Buried drusen elevate the disc and blur the disc margins. This effect is differentiated from true papilledema by the lack of hyperemia, dilated capillaries and vessel obscuration. With pseudopapilledema due to disc drusen, the physiologic cup is absent, and the center of the disc is most elevated (figure 12A). Patients often have anomalous vascular patterns, including arterial or venous trifurcation, that create the appearance of increased number of vessels on the disc, abnormal or premature branching, tortuosity, vascular loops, and cilioretinal vessels.

Optical coherence tomography (OCT) can also aid in differentiating optic disc drusen from optic disc edema. Patients with disc edema have a smooth internal disc contour compared to the lumpy appearance found with optic disc drusen.4 In addition, optic disc edema demonstrates a V-shaped hyporeflective space between the sensory retina and the RPE that is minimal or absent with optic disc drusen (figure 12B).4,5 OCT is also useful to follow NFL changes over time.5

IIH and Papilledema

Patient symptoms help to differentiate papilledema and idiopathic intracranial hypertension (IIH) from other optic neuropathies. Between 90% and 98% of patients with IIH present with headache.6-8 Other manifestations include nausea and vomiting (40%), pulsatile tinnitus (16% to 60%), dizziness, and photophobia.6-8 Visual symptoms of IIH include transient visual obscurations (32% to 80%) and horizontal diplopia (30% to 32%).6-8

It is rare for patients with IIH to have loss of central vision, color vision dysfunction, RAPD or visual field defects (other than an enlarged blind spot). Normal visual acuity helps distinguish papilledema from other causes of disc edema in which visual acuity is often affected early. Other features may help to differentiate papilledema from other causes of optic disc edema (See “Differential Diagnosis of Optic Disc Edema,” below).

Differential Diagnosis of Optic Disc Edema

Laterality Visual Acuity Visual Field
Headache, pulsatile
tinnitus, TVO
Bilateral VA is spared Enlarged blind
spot or
Retinal vein
cotton-wool spots

Abruptly reduced

Optic neuritis
Pain with eye
movement; other
neurologic symptoms
Abruptly reduced
depression or
focal loss
Small, crowded disc
in fellow eye or
signs of GCA
Abruptly reduced
Altitudinal VF
shunt vessels
Gradually lost
Other cranial
Bilateral Abruptly reduced Generalized

The appearance of the optic nerve and retina can help determine the presence of papilledema. Papilledema is usually bilateral and symmetric (figure 13). The optic nerve head appears hyperemic. Paton’s lines (circumferential retinal folds surrounding the disc) are often present. Linear or curvilinear folds in the choroid may also develop. This is often accompanied by progression of hyperopia.

Flame-shaped hemorrhages, cotton-wool spots, and tortuous retinal vessels on or surrounding the disc may be observed. Flameshaped hemorrhages indicate acute or subacute edema. A thin, radial hemorrhage on or around the disc margin can indicate distended capillaries of the optic nerve—an early sign of papilledema.

Lack of spontaneous venous pulsation (SVP) can indicate increased intracranial pressure (ICP). SVP is absent in cases of papilledema. It is thought that SVP is present only if the ICP is less than 200mm of water; however, only 80% of normal patients will have SVP, so the absence of the pulse does not necessarily mean papilledema is present.

Typical Demyelinating Optic Neuritis

Like papilledema, characteristics associated with typical demyelinating optic neuritis help to differentiate this condition from other causes of optic nerve disease. Symptoms of optic neuritis include acute vision loss, usually in one eye. Vision often worsens over hours to days before stabilizing and improving after several weeks. In addition to vision loss, 87% to 92% of patients experience pain behind the eye that worsens with eye movement.9,10 (This symptom helps to differentiate this from other causes of optic neuropathy associated with painless vision loss, such as NAION.)

Only one-third of optic neuritis patients demonstrate visible swelling of the optic nerve head, which may be mild or severe and does not correlate with loss of visual acuity or visual field.10 It is rare to find peripapillary hemorrhages, exudates or cotton-wool spots.

Over four to six weeks, the optic nerve develops pallor—even as visual function improves. The pallor is typically temporal, but it can be sectoral in other areas of the disc or diffuse.


Giant cell arteritis (GCA), also known as temporal arteritis, is the most common cause of arteritic anterior ischemic optic neuropathy (AAION) but accounts for only 6% of ischemic optic neuropathy cases.11 Other causes of AAION include polyarteritis nodosa; Wegener’s granulomatosis; connective tissue diseases, such as systemic lupus erythematosus; Churg-Strauss syndrome; and rheumatoid arthritis. The mean age at AAION diagnosis is 75 to 76 years, and it is rare under age 50.12-14 Women and white patients are affected more frequently.12,15

Patients with AAION typically have systemic symptoms, such as headache, pain while chewing, pain and tenderness of the temporal artery or scalp, malaise, anorexia, weight loss, fever, and joint and muscle pain. However, 20% do not have any systemic symptoms despite vision loss.16

Disc edema is more likely to be pallid with AAION than with non-arteritic anterior ischemic optic neuropathy (NAION) (figure 14). Flame hemorrhages and cotton-wool spots are associated with AAION, and the optic disc of the fellow eye is usually of normal diameter with an average-sized cup. The visual field is severely reduced, but in early cases, the most common visual field defect is an altitudinal defect.

Within six to eight weeks, the optic disc develops atrophy with cupping similar to that seen with glaucoma. Unlike glaucomatous cupping, however, AAION patients have pallor of the remaining neuroretinal rim.

GCA is an ophthalmic emergency. Patients with GCA are at high risk for developing vision loss in the other eye, as well as systemic complications such as stroke or myocardial infarction. For those suspected of GCA, treatment with high dose steroids should be started immediately without waiting for confirmation of the diagnosis with a temporal artery biopsy.


The most common cause of disc edema in people over age 50 years is non-arteritic anterior ischemic optic neuropathy.17,18 The mean age of onset is approximately 61 to 66 years.19-21

Visual acuity loss with NAION is usually not as severe compared with that in AAION. Diffuse or segmental disc edema is present with NAION and may be more severe either superiorly or inferiorly. Swelling can be hyperemic or pale, but pallor is less likely to be seen than in cases of AAION. Altitudinal visual field loss, usually inferior or inferior nasal, is the most common visual field defect, but any other pattern can occur.

Peripapillary hemorrhages and focal retinal arterial attenuation around the disc are common. The contralateral optic nerve head is often undersized with a small or absent cup. Additionally, the contralateral optic nerve has mild disc elevation and blurred margins.

Inflammatory Optic Neuropathy

The most common cause of inflammatory infiltrative optic neuropathy is sarcoidosis. Sarcoidosis is more common in women and blacks. Visual loss is usually severe when sarcoidosis affects the optic nerve.

If sarcoidosis affects the anterior optic nerve, the disc will be either diffusely or sectorally elevated (figure 15). In many cases, the findings may appear identical to those related to demyelinating optic neuritis. Or, sometimes, a white, lumpy, nodular appearance of the optic nerve will suggest a granulomatous process. Other evidence of intraocular inflammation is usually present, including inflammation of the vitreous or anterior chamber.

Infectious Optic Neuropathy

Optic nerve disease can occur with a large number of infectious conditions. Common viral and bacterial causes associated with optic neuritis all result in similar clinical signs and symptoms. Toxoplasmosis can also result in optic neuritis due to direct involvement or when a lesion is contiguous with the optic disc.22,23

Cat-scratch disease is the most common infection associated with neuroretinitis. Up to 5% of cases result in neuroretinitis.24 In this situation, vision loss is painless. Unilaterial disc edema is common, and a stellate pattern of infiltrates surround the macula to form a macular star two to four weeks after the disc edema begins (figure 16).

Parainfectious optic neuritis usually occurs one to three weeks after a viral (though sometimes bacterial) infection. The neuritis is most common in children and often occurs bilaterally. Bilateral optic neuritis can also occur one to three weeks after viral or bacterial vaccination. Spontaneous visual recovery usually occurs over several months.

Compressive Optic Neuropathy

Compressive neuropathy, due to optic nerve sheath meningiomas, causes proptosis, congestion and extraocular muscle motility limitations. Disc swelling typically occurs even if the patient is asymptomatic. Optic disc swelling is generally mild or moderate. Peripapillary hemorrhages are not usually present. Horizontal or vertical chorioretinal striae adjacent to the optic disc may be present when the lesion is pressing on the globe. Optociliary shunt veins and optic atrophy often become apparent (figure 17).

Optic nerve compression due to thyroid eye disease (TED) can present with swelling, hyperemia, pallor or increased cupping of the optic nerve. Normal-appearing optic discs are present in up to half of all eyes.25 Restriction of the extraocular muscles, most commonly the inferior and medial recti, is likely.26

Conjunctival hyperemia over the horizontal rectus muscle insertions, punctate epithelial erosions, superior limbic keratoconjunctivitis, swelling of the eyelids, eyelid retraction, and lid lag are commonly—but not always—seen with TED.25,27

Glioma-Based Optic Neuropathy

A glioma within the orbit causes proptosis (94%) and a swollen (35%) or atrophic (59%) optic disc.28 These patients can develop optociliary shunt vessels. Increased volume of the optic nerve can cause retinal striae and increasing hyperopia.

Because the average age for adult gliomas is 52 years, the condition can be misdiagnosed as NAION.29 If vision loss is progressive, the disc swelling lasts longer than six weeks, or a central retinal vein or artery occlusion occurs several months after the onset, patients should undergo neuroimaging.29

Infiltrative Optic Neuropathy

Astrocytic hamartomas can infiltrate the optic disc. The lesion becomes glistening and yellow, with a mulberry appearance composed of calcific concretions (figure 18). The appearance must be differentiated from optic nerve head drusen; drusen are within the substance of the nerve, whereas astrocytic hamartomas overlie the disc.

Melanocytomas are elevated, gray or black intraocular tumors that occur within the substance of the optic nerve (figure 19). The majority are less than two disc diameters. These tumors are benign. Slight growth may occur, but malignant transformation is rare.

Secondary tumors may also infiltrate the optic nerve. These include metastasis, carcinomas, lymphoma and leukemia. In patients with a history of cancer, the cause of an acquired optic neuropathy should be considered cancer until proven otherwise. Neuroimaging should be obtained.

Toxic and Metabolic Optic Neuropathy

The characteristics of optic neuropathy resulting from toxicity or metabolic problems are similar to other optic neuropathies, especially those that are bilateral and simultaneous. Toxic or metabolic optic neuropathy causes mild, bilateral disc swelling. Early stages may have a normal disc appearance. Disc hemorrhages may be present. Optic atrophy, most commonly of the temporal disc, occurs in later stages (figure 20).

Other ocular signs may aid in the diagnosis. For example, nystagmus and ophthalmoplegia can occur with ethylene glycol ingestion. Pigmented, whorl-shaped corneal epithelial deposits occur with amiodarone use, and keratopathy may be present in cases of nutritional deficiency.

Leber’s Hereditary Optic Neuropathy

Vision loss from Leber’s hereditary optic neuropathy (LHON) typically occurs between the ages of 15 and 35, but it can occur in both younger and older individuals.30-32 Males are much more likely to acquire the disease and to be symptomatic.32-35

During the acute phase, the optic nerve head becomes hyperemic with obscuration of the disc margins. Retinal blood vessels become tortuous and dilated. In many cases, a classic triad of circumpapillary telangiectasia, swelling of the NFL around the disc and absence of leakage from the disc on fluorescein angiography is visible. The absence of fluorescein dye leakage distinguishes LHON from true optic nerve edema.

Despite continued vision loss, the telangiectasia and NFL swelling resolve. The optic nerve head does not become pale for some time, but eventually, optic atrophy ensues. The pallor is most pronounced in the temporal area with coexistent damage of the papillomacular NFL. Attenuation of retinal arteries and non-glaucomatous cupping may also be evident.

Autosomal-Dominant Optic Atrophy

Autosomal-dominant optic atrophy is the most common hereditary optic neuropathy.36 It occurs in the first decade of life, with an average onset of four to six years of age. Optic atrophy may be subtle. The pattern of pallor can be either temporal or diffuse.37 A wedgeshaped excavation of the temporal disc is characteristic for autosomal dominant optic atrophy (figure 21). Peripapillary atrophy, absent foveal light reflex, arterial attenuation and non-glaucomatous cupping may also be present.

Traumatic Optic Neuropathy

Traumatic optic neuropathy occurs in 4% of patients after head trauma.38 Motor vehicle and bicycle accidents—the most common causes of injury to the optic nerve—account for up to 60% of optic nerve injuries.39-42 Nearly all patients develop pallor after injury to the optic nerve.40

Examination of ocular structures may reveal other evidence of trauma including orbital rim fractures, hyphema, angle recession or dislocated lens. Resistance to retropulsion of the globe is indicative of retrobulbar hemorrhage. Blood in the vitreous may obscure the retinal view. Commotio retinae or a choroidal rupture may also be responsible for vision loss.

In differentiating the cause of optic neuropathy, first look at the age of the patient. If the patient is younger than 40, look for signs of typical demyelinating optic neuritis. Suspect anterior ischemic optic neuropathy in patients who are older than 40. If signs are not consistent with typical optic neuritis or anterior ischemic optic neuropathy, perform neuroimaging, serologic testing or lumbar puncture to rule out compressive, infiltrative, infectious or inflammatory optic neuritis. Also look for evidence of current or past uveitis that may indicate an inflammatory or infectious cause. Toxic, nutritional and hereditary optic neuropathy should also be considered in the differential diagnosis. Occasionally, only time will tell the cause of the optic neuropathy.

Dr. Goodwin is an Associate Professor at Pacific University College of Optometry. She teaches Functional Neuroanatomy and Neurobiology, Ophthalmic Imaging and Optometric Clinical Procedures. She also advises thirdyear students in primary care clinic. She is Coordinator of the Neuroophthalmic Disease Referral Service at Pacific University.


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