AUTHOR AND EDITOR INFORMATION

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• Medication
• Follow-up
• Miscellaneous
• Multimedia
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INTRODUCTION

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• Follow-up
• Miscellaneous
• Multimedia
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Background

The optic nerve extends from the back of the eye, traverses through the orbit and the optic canal, to the optic chiasm. The intraocular optic nerve is about 1 mm in length, the intraorbital segment is 25 mm in length, the intracanalicular segment is about 9 mm in length, and the intracranial component is about 16 mm in length. The optic nerve is most vulnerable to compression where it is adjacent to or surrounded by bone and is relatively immobile.

The hallmark of compressive optic neuropathy is a slowly progressive visual loss accompanied by a relative afferent pupillary defect and typically a central scotoma. Delay in diagnosis of compressive optic neuropathy is not uncommon because patients may not note early symptoms, or the visual loss may be misinterpreted as optic neuritis. Consider compressive optic neuropathy in the differential diagnosis of all corticosteroid responsive optic neuropathies. A workup of incidentally discovered optic atrophy should be completed to exclude a compressive lesion. Management of compressive optic neuropathy is difficult. Many of the conditions causing the compression are resistant to current treatment. Even well-performed surgery can worsen vision.

Pathophysiology

Optic nerve compression may result in ischemia or disruption of axonal transport.

Frequency

United States

This condition is relatively rare. Incidence in a large health maintenance organization was found to be about 4 cases per 100,000 per year. Most of these cases were due to thyroid ophthalmopathy.

Mortality/Morbidity

• Lesions that cause compression of the optic nerve are quite rare, but, when they occur, blindness is not uncommon.
• A small number of lesions that cause optic nerve compression are primary malignancies or metastases, which may result in death.
• Optic nerve tumors may occasionally extend intracranially and be life threatening.
• Optic nerve gliomas in adults are rare but very aggressive, lethal lesions. Optic nerve gliomas are much more common in children, have a much better prognosis, and are frequently associated with neurofibromatosis.
• Optic nerve sheath meningiomas presenting in childhood are rare but are considered more aggressive lesions. Optic nerve sheath meningioma presents more commonly in adulthood and generally has a slowly progressive course.

Sex

Thyroid ophthalmopathy and meningiomas are more common in women than in men and may cause compressive optic neuropathy.

Age

• This condition may occur at any age.
• It rarely is seen in children, with the exception of optic nerve glioma.
• It is most commonly encountered in patients aged 30-50 years.

CLINICAL

Section 3 of 11  

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• Follow-up
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History

• Patients with compressive optic neuropathy typically present with slowly progressive visual loss.
• Visual complaints may be somewhat vague and nonspecific. The chronicity of the lesion may be indeterminate since patients may incidentally discover their visual loss when one eye becomes blind.
• Rarely, patients with compressive optic neuropathy will have sudden visual loss (eg, pituitary apoplexy, bleeding optic nerve glioma).
• Compressive optic neuropathy may be found during routine eye examination or refraction.
• It may be discovered following cataract surgery when the expected improvement in visual acuity does not occur.
• Observant patients may complain of ipsilateral dyschromatopsia (ie, objects seem less bright and colors are subdued in the affected eye compared with the uninvolved side).
• Patients sometimes present with complaints of visual field loss.
• It is not uncommon in cases of compressive optic neuropathy for a friend or relative to note the appearance of proptosis (ie, affected eye appears larger or more protuberant).

Physical

Compressive optic neuropathy may affect visual acuity, brightness perception, color vision and desaturation of hue, visual fields, pupils, relative position of the eyes, resistance to retropulsion of the globe, extraocular motility, and the fundus.

• Visual acuity
• • Visual acuity usually is reduced in the affected eye.
  • Refraction or at least pinhole acuity should be performed.
  • Compressive lesions causing axial proptosis may result in a hyperopic shift.
• Brightness perception usually is reduced in the affected eye.
• Color vision often is reduced in the affected eye. The Ishihara test plate is one of the most common methods of testing color vision in the office setting.
• Desaturation of hue: When a bright color, especially red, is viewed by each eye separately, the patient usually will describe the color to be less vivid or washed-out in the affected eye.
• Pupils
• • Examination of the pupils usually will reveal an ipsilateral relative afferent pupillary defect (Marcus Gunn pupil). This test is performed in a dimly lit room with the patient fixing his gaze on a distant object.
  • A bright focused light (eg, pen light, Finnoff transilluminator, indirect ophthalmoscope) is then shifted from one eye to the other about every 3 seconds.
  • The affected eye may appear to dilate, not constrict, or show increased pupillary escape when compared to the unaffected eye.
• Proptosis
• • It is best noted by viewing the globes from above the patient's forehead.
  • Formal measurement of the position of the anterior surface of the cornea in relation to the lateral wall of the orbit can be recorded with a Hertel exophthalmometer. This is a useful test in all cases of suspected optic nerve dysfunction. 
  • If more than 2 mm of proptosis exists, a space-occupying lesion of the orbit may be suspected, especially in the setting of decreased orbital retropulsion. 
  • Mild proptosis often is not noticed by patients and their physicians.
• Extraocular motility
• • The movement of the eye often is not affected by conditions causing compression of the optic nerve.
  • Disturbance of ocular motility or ptosis along with other signs of compressive optic neuropathy may suggest an infiltrative process, an inflammatory condition, or that the location of the lesion is at the apex of the orbit.
• Relative resistance to retropulsion of the globe
• • Pressing on the globes through the closed lids may reveal that more force is required to gently push one of the eyes into the orbit.
  • This suggests the presence of a space-occupying lesion in the orbit.
• Visual field examination
• • Because of the arrangement of nerve fibers as they course through the optic nerves and the chiasm, the site of compression produces specific visual field abnormalities.
  • The most common defects found with compression of the optic nerve anterior to the chiasm include enlarged blind spot, relative central scotoma, and constriction.
  • When compression of the optic chiasm occurs, a bitemporal hemianopia usually is found, although unilateral field loss or homonymous hemianopia may occur if the lesion is prefixed or postfixed.
  • Nearly all types of visual field abnormalities have been reported with compression of the optic nerve.
• Dilated fundus examination
• • A careful examination of the optic disc is important. Often, the optic disc may appear normal or pale.
  • With chronic compression of the optic nerve, optic atrophy results.
  • The triad of optic disc swelling followed by optic atrophy, optociliary shunt veins (optochoroidal collaterals), and progressive visual loss commonly is reported in compressive lesions of the orbital and intracanalicular optic nerve.
  • Optochoroidal collaterals are not pathognomonic of optic nerve sheath meningioma and can be seen with central retinal vein occlusion, chronic papilledema, and various compressive optic nerve lesions.
  • A finding of unilateral optic disc swelling may be the first sign of compressive optic neuropathy.
  • Even in the absence of visual and neurologic symptoms and an otherwise unremarkable complete ophthalmic examination, unilateral optic disc swelling should be investigated promptly with CT scan or MRI.
  • If no intracranial explanation is found, careful evaluation should be made to rule out an intraorbital or intracanalicular mass.
  • The presence of a swollen optic disc should raise the index of suspicion for a primary nerve sheath meningioma. However, a great variety of tumors have been reported with this finding.
  • Similarly, swollen discs have been reported more commonly in the presence of tumors within the orbit.
  • Less frequently, there have been reports of disc swelling with intracanalicular and intracranial tumors compressing the optic nerve.
  • Tumors causing proptosis may result in choroidal folds.

Causes

Causes of compressive optic neuropathy include the following:

• Primary malignancies or metastases
• Optic nerve tumors
• • Optic nerve gliomas
  • Optic nerve meningiomas
• Thyroid ophthalmopathy
• Cavernous hemangiomas
• Sarcoidosis
• Trauma
• Solid orbital tumors
• • Meningiomas
  • Hemangiomas
  • Schwannoma
• Cystic tumors
• Dermoid cysts
• Cholesterol granuloma
• Mucoceles
• Conjunctival orbital cysts
• Inflammatory and infiltrative processes

DIFFERENTIALS

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Other Problems to be Considered

Schwannoma
Pituitary adenoma
Craniopharyngioma
Lymphoma
Aneurysms
Fibrous dysplasia
Orbital hemorrhage
Mucocele
Orbital pseudotumor
Metastatic carcinoma
Carcinomas extending from sinuses

WORKUP

Section 5 of 11  

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• Clinical
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• Medication
• Follow-up
• Miscellaneous
• Multimedia
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Lab Studies

• Blood tests are sometimes helpful in the diagnosis of compressive optic neuropathy.
• • If thyroid ophthalmopathy is suspected, blood tests for thyroid function and anti-thyroid antibodies should be performed.
  • An elevated angiotensin-converting enzyme may be seen in sarcoidosis.
  • An elevated prostate specific antigen (PSA) may be helpful in male patients with suspected bony orbital metastases and optic nerve compression.

Imaging Studies

• CT scans and MRIs are the foundation for determining the cause of optic nerve compression. CT scans better illustrate bony detail, and MRIs better delineate soft tissue lesions. The two imaging studies often offer complementary information. Interpretation of both the axial view and the coronal view and, occasionally, sagittal projections is required. MRI of the orbit should be ordered with gadolinium and fat suppression.
• MRIs and CT scans are essential in evaluating cases of compressive optic neuropathy.
• • In addition to revealing the extent and location of the lesion, the imaging characteristics of the lesion will probably permit an experienced neuroradiologist to differentiate between optic nerve sheath meningiomas and optic nerve gliomas. Optic nerve sheath meningiomas will show "tram tracking" on axial views and a "target sign" on coronal views. Optic nerve glioma may show kinking, especially on sagittal views. On axial views, fusiform enlargement of the nerve is present. On coronal views, gliomas may show diffuse enhancement.
  • A characteristic pattern of enlargement of the extraocular muscles is found in thyroid ophthalmopathy.
• Occasionally, ocular ultrasound is helpful. Orbital ultrasound may be useful in lesions affecting the portion of the optic nerve near the globe, but such cases also should undergo either MRI or CT scan.
• In the modern era of neuroimaging, plain x-ray studies play little role in the evaluation of suspected optic nerve compression. Findings, such as asymmetric enlargement of the optic foramen or hyperostosis of the optic nerve canal, require further workup with CT scan and MRI.

TREATMENT

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Medical Care

• Corticosteroids are useful in compressive optic neuropathy caused by inflammation and thyroid ophthalmopathy.
• Symptoms from other causes of compressive optic neuropathy also may improve with use of corticosteroids.
• Radiation therapy often is appropriate for malignant lesions and may benefit intracanalicular and possibly intraorbital meningiomas.
• A favorable response to treatment with corticosteroids should not be considered as confirmation of a diagnosis until good quality MRIs and CT scans are obtained.
• A practical approach for those cases in which the MRI and/or CT scan strongly indicates a meningioma (both intraorbital and intracanalicular) is to monitor the patient with serial visual acuity measurements and field testing. If visual loss progresses, consider treatment with radiation, and, if growth continues, then also consider surgery.

Surgical Care

• Consider surgical excision or decompression as a treatment option when orbital tumors compress the optic nerve. Well circumscribed apical optic nerve tumors (eg, cavernous hemangioma) may require an orbitocranial approach.
• The definitive procedure for optic neuropathy of Graves disease is orbital decompression. Although advocates of steroids and radiation exist, decompression is the best and most assured way of reversing the compression aspect of this disorder.
• Optic canal decompression for tumors in the intracanalicular area is extremely risky and not uncommonly results in the loss of any remaining vision, unless the tumor has a large exophytic component.
• If the tumor is intimately involved with the optic nerve, as often is the case with nerve sheath meningiomas, surgical removal often results in further loss of vision. This is thought to be due to a compromise of the shared blood supply.

Consultations

Patients with compressive optic neuropathy should be managed in consultation with a neuro-ophthalmologist or an orbital surgeon whenever possible.

Activity

Prescribe polycarbonate safety glasses to patients with compressive optic neuropathy to protect the vision in the unaffected eye.

MEDICATION

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Many cases of compressive optic neuropathy (eg, thyroid ophthalmopathy, orbital pseudotumor, lymphoma, sarcoid) will improve at least transiently with steroid treatment. Intravenous steroids may hasten visual recovery. It may be difficult to withdraw steroid treatment from such patients without deterioration of vision.

See Thyroid Ophthalmopathy for details of medical treatment.

Drug Category: Corticosteroids

Treatment of compressive optic neuropathy.

FOLLOW-UP

Section 8 of 11  

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Complications

• Surgery to remove orbital tumors compressing the optic nerve is frequently associated with injury to the third, fourth, and/or sixth cranial nerves, which may result in paralytic strabismus and ptosis.
• Surgery to remove lesions that are intimately involved with the nerve sheath (eg, meningiomas, schwannomas) often results in further loss of vision or blindness.

Prognosis

• Prognosis depends on the type of lesion causing compression of the optic nerve.
• Some tumors are relatively easy to excise, while others are likely to result in loss of vision.

Patient Education

• Adequately inform the patient that vision may deteriorate despite surgery or radiation.

MISCELLANEOUS

Section 9 of 11  

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Medical/Legal Pitfalls

• Although optic neuritis is much more common than compressive optic neuropathy, avoid confusing the two conditions.
• • Optic neuritis usually presents with acute or subacute visual loss in a patient younger than 50 years and is frequently associated with pain on eye movement. The vision usually improves substantially in optic neuritis with or without steroid treatment.
  • Compressive optic neuropathy presents as gradually progressive visual loss, which may not be painful. Vision may improve with steroid treatment only to deteriorate again when steroids are withdrawn. Compressive optic neuropathy should be considered in the following situations:
  • • A patient who is suspected of having acute optic neuritis continues to lose vision after 2 weeks or fails to recover vision in 2-3 months.
    • Disc swelling increases or optic atrophy is not seen within 6-10 weeks in a patient who is suspected of having anterior ischemic optic neuropathy.
    • A diagnosis of posterior ischemic optic neuropathy is being considered in a patient.
  • An MRI of the optic nerves with gadolinium and fat suppression should be obtained promptly in the situations described above. Patients with incidentally discovered optic atrophy require neuroimaging studies to exclude a possible compressive lesion.

Special Concerns

• Cavernous hemangiomas and meningiomas may enlarge during pregnancy, causing optic nerve compression.

MULTIMEDIA

Section 10 of 11  

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• Follow-up
• Miscellaneous
• Multimedia
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Media file 1:  Axial MRI taken 3 weeks after the onset of distorted vision in the right eye; visual acuity is reduced to counting fingers at 1 ft. Evidence of optic nerve compression is not seen; disease in the sphenoid sinus is reported.
	View Full Size Image
Media type:  MRI

Media file 2:  MRI of same patient as in Media file 1 taken 4 months later. Patient responded well to IV Solu-Medrol, but symptoms returned when steroids were reduced. Large mass compressing the right optic nerve is seen. Biopsy revealed lymphoma.
	View Full Size Image
Media type:  MRI

REFERENCES

Section 11 of 11

• Authors and Editors
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• Miscellaneous
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• References

• Lee AG, Chau FY, Golnik KC, Kardon RH, Wall M. The diagnostic yield of the evaluation for isolated unexplained optic atrophy. Ophthalmology. May 2005;112(5):757-9. [Medline].
• Miller NR, Newman NJ, Biousse V. Walsh and Hoyt's Clinical Neuro-Ophthalmology. 6^th ed. Lippincott, Williams & Wilkins; 2004.
• Schiefer U, Wilhelm H, Hart, W. Neuro-ophthalmic presentations of orbital disease. In: Clinical Neuro-Ophthalmology: A Practical Guide. Wien & New York: Springer; 2007.
• Shields AJ, Shields CL, Scartozzi R. Survey of 1264 patients with orbital tumors and simulating lesions: the 2002 Montgomery Lecture, Part 1. Ophthalmology. 2004;111(5):997-1008. [Medline].
• Spoor, TC. Atlas of Oculoplastic and Orbital Surgery. Informa Healthcare; 2007.

Article Last Updated: Sep 10, 2007