H47.291-293 Partial Optic Atrophy

Optic atrophy is not a specific disease, but a clinical sign of one of several disease processes.  The condition may be either primary or secondary and is the endpoint of any disease process that causes axon degeneration in the retinogeniculate neural pathway.  

Optic atrophy is commonly associated with the following conditions:

• Glaucomatous optic neuropathy
• Hereditary optic neuropathies
• Intracranial trauma
• Compressive lesions in the brain (e.g., tumor or aneurysm)
• Metabolic optic neuropathies (e.g., toxic or nutritional neuropathy, juvenile diabetes)
• Post inflammatory atrophy (e.g., optic neuritis or Devic disease)
• Circulatory optic neuropathies (e.g., central artery occlusion, cranial arteritis, carotid artery occlusion)

The optic nerve is a bundle of nerve fibers that carry images from your retina to your brain.  Each fiber carries a part of the visual information to the brain.  If these nerve fibers become damaged, the sight may become blurred because the brain isn’t receiving all of this vision information.  Optic atrophy means the loss of nerve fibers in the optic nerve. 

Structural Damage to the Eye

Visual Pathway Retina Optic nerve Optic tract Lateral geniculate nucleus Optic radiations Visual cortex

Functional Damage to the Eye

Some of the symptoms that may be associated with partial optic atrophy include:

• Blurred vision
• Abnormal peripheral vision
• Abnormal color vision
• Decreased brightness in one eye relative to the other

The main goal of the diagnostic evaluation in a patient with partial optic atrophy is to accomplish the following: 

• Make the correct diagnosis of primary vs. secondary optic atrophy (pathologic vs. nonpathologic)
• Determine the underlying cause of the optic atrophy
• Treat the underlying cause if possible

Patient History

Patients will usually present with the following symptoms:

• Painless loss of vision in one or both eyes

Pupillary Examination

• A relative afferent pupillary defect (RAPD) may be present in the affected eye

Ophthalmoscopy

• Temporal pallor of the optic disc in the right eye
• Thinning/narrowing of the small blood vessels on the optic disc surface in the right eye

• Can show attenuation of the retinal nerve fiber layer
• Excavation of the optic disc

OCT Scan of the Retinal Nerve Fiber Layer   Right Eye Cup-to-disc ratio = .60/.70 Diffuse fallout of the retinal nerve fiber layer Retrograde axonal degeneration of the retinogeniculate neural pathway Left Eye Cup-to-disc ratio = .60/.70 Wedge-shaped defect in the superior arcuate bundle of the retinal nerve fiber layer — unknown etiology

Visual Field Examination

		Right Eye Arrangement errors are present Meridional crossing errors indicate a deutan color vision defect secondary to optic atrophy
Left Eye No arrangement errors Minor transposition errors at the top of the hue circle are not clinically significant Normal color vision

Systemic Evaluation

Eye doctors should consider a systemic evaluation in cases of unexplained optic atrophy.  A typical investigative protocol would include the following tests:

• MRI of the brain and orbit with contrast
• Carotid Doppler ultrasound study
• Cardiovascular examination
• Sarcoid examination
• Blood glucose level
• Vitamin B-12 levels
• Antinuclear antibody levels
• Homocysteine levels
• Antiphospholipid antibodies
• Venereal Disease Research Laboratory (VDRL)

Enzyme-linked immunosorbent assay (ELISA)

• Toxoplasmosis
• Rubella
• Cytomegalovirus
• Herpes simplex virus

Primary care eye doctors should communicate as specifically as possible regarding their suspicion of systemic involvement in a patient presenting with partial optic atrophy.  This can and should be as detailed as recommending specific laboratory analysis and/or imaging based on the suspected systemic disease.

Optic atrophy is classified as pathologic, ophthalmoscopic, or etiologic.

PATHOLOGIC OPTIC ATROPHY

Anterograde Degeneration

• Deterioration of the retina begins and proceeds toward the lateral geniculate body
• Axon thickness determines the rate of degeneration
• Swelling and degeneration of the axon terminal in the lateral geniculate body is observed as early as 24 hours

Retrograde Degeneration (optic nerve compression by intracranial tumor)

• Deterioration begins from the proximal portion of the axon and proceeds toward the optic disc
• The natural history of this degeneration is independent of the distance of the injury from the ganglion cell body
• Damage to the retrobulbar portion of the optic nerve causes pathologic and visible degeneration of the ganglion cell body simultaneously

Trans-Synaptic Degeneration

• A neuron on one side of a synapse degenerates as a consequence of the loss of a neuron on the other side
• Patients with occipital lobe damage in this type of degeneration have incurred it either in utero or during early infancy

OPHTHALMOSCOPIC OPTIC ATROPHY

Primary Optic Atrophy

• Optic nerve fibers degenerate in an orderly manner and are replaced by columns of glial cells without alteration in the architecture of the optic nerve head
• Disc is chalky white and sharply demarcated
• Retinal vessels are normal
• Lamina cribrosa is well defined

Secondary Optic Atrophy  Optic nerve fibers exhibit marked degeneration with excessive proliferation of glial tissue Indistinct margins are created due to architecture being lost Disc is grey or dirty grey, margins are poorly defined, and the lamina cribrosa is obscured due to proliferating fibroglial tissue Drusen or hyaline bodies may be observed Peripapillary sheathing of arteries and tortuous veins may be observed Visual field defects may be seen as well

Consecutive Optic Atrophy

• Disc is waxy pale with a normal disc margin
• Marked attenuation of arteries
• Normal physiologic cup

Glaucomatous Optic Atrophy

• Marked cupping of disc
• Vertical enlargement of cup
• Visibility of the laminar pores
• Backward bowing of the lamina cribrosa
• Bayoneting and nasal shifting of retinal vessels
• Splinter hemorrhage at the disc margin may be observed

Glaucomatous Optic Atrophy  Advanced glaucomatous atrophy Diffuse enlargement of the optic cup Wipe out of all or a portion of the neuroretinal rim Nasalization of the vascular tree The overall disc pallor seen in advanced glaucoma is due to a more excavated cup rather than pallor of the neuroretinal rim

Temporal Optic Disc Pallor

• May be observed in traumatic or nutritional optic neuropathy
• Commonly seen in patients with multiple sclerosis, particularly in those with a history of optic neuritis
• Disc is pale with a clear, demarcated margin and normal vessels
• Physiologic pallor temporally is more distinctly pale

Temporal Optic Disc Pallor — Right Eye Patient is a 39-year-old black female with multiple sclerosis Image of disc taken 18 months after initial episode of optic neuritis

ETIOLOGIC OPTIC ATROPHY

Hereditary

• Congenital or infantile optic atrophy (recessive or dominant form)
• Behr hereditary optic atrophy
• Leber optic atrophy

Consecutive Atrophy

• Ascending type of atrophy that usually follows diseases of the choroid or retina

Circulatory Atrophy

• Ischemic optic neuropathy observed when the perfusion pressure of the ciliary body falls below the intraocular pressure
• Observed in central retinal artery occlusion, carotid artery occlusion, and cranial arteritis

Metabolic Atrophy

• Observed in disorders such as nutritional amblyopia, toxic amblyopia, thyroid ophthalmopathy, tobacco, juvenile diabetes, methyl alcohol, and other drugs

Demyelination Atrophy

• Observed in diseases such as multiple sclerosis and Devic disease

Pressure or Traction Atrophy

• Observed in diseases such as glaucoma and papilledema

Post-inflammatory Atrophy

• Observed in diseases such as optic neuritis, perineuritis secondary to inflammation of the meninges, and sinus and orbital cellulites

Traumatic Optic Neuropathy

• Optic nerve avulsion and transection, optic nerve sheath hematoma, and optic nerve impingement from a penetrating foreign body or bony fragment all reflect traumatic forms of optic nerve dysfunction that can lead to optic atrophy
• Traumatic optic neuropathy occurs in 4% of patients with head trauma
• Automobile and bicycle accidents are the most common cause (60% of optic nerve injuries)

There are several conditions that are similar in nature to optic atrophy.

Optic Nerve Pit Congenital defect characterized by an excavation of the tissue Optic pits appear as depressions in the optic nerve head Lesions vary in size, shape, depth and location

Myelinated Nerve Fiber Layer

In most patients myelination does not extend past the lamina cribrosa, however, in some patients the nerve fibers are myelinated and manifest as white, feathery patches that follow the nerve fiber layer bundles.  The myelinated nerve fibers have a striated appearance and the peripheral edges appear fanned out.  The myelination can mimic the appearance of optic disc edema due to elevation of the optic nerve and obscuration of the optic disc margins and vasculature. 

Myelinated Nerve Fiber Layer Occurrence is 0.6% to 1% of the population Myelination is bilateral in 8% of patients Myelination is continuous with the optic nerve head in 33% of patients

Optic Disc Drusen

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

Optic Disc Drusen Classic appearance involves bilaterally elevated optic discs with irregular or scalloped margins Small, refractile hyaline deposits visible on the surface of the optic disc and/or in the peripapillary area A small or nonexistent optic cup Unusual vascular branching patterns that stem from a central vessel core Drusen most often manifest on the nasal optic disc margin, but can be found within any part of the nerve head

Optic Nerve Hypoplasia

Optic nerve hypoplasia (ONH) is a medical condition arising from the underdevelopment of the optic nerve(s).  This condition is the most common congenital optic nerve anomaly.  The optic disc appears abnormally small, because not all the optic nerve axons have developed properly.  It is often associated with endocrinopathies (hormone deficiencies), developmental delay, and brain malformations.  The optic nerve, which is responsible for transmitting visual signals from the retina to the brain, has approximately 1.2 million nerve fibers in the average person.  In those diagnosed with ONH, however, there are noticeably fewer nerves.

Scleral Crescent

A myopic crescent is a moon-shaped feature that can develop at the temporal border of disc (it rarely occurs at the nasal border) of myopic eyes.  It is primarily caused by atrophic changes that are genetically determined, with a minor contribution from stretching due to elongation of the eyeball.  In myopia that is no longer progressing, the crescent may be asymptomatic except for its presence on ocular examination.  However, in high-degree myopia, it may extend to the upper and lower borders, or form a complete ring around the optic disc and form a central scotoma.

Tilted Disc

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.  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. 

Axial Myopia

Myopia, commonly known as near-sightedness, is a condition of the eye where the light that comes in does not directly focus on the retina but in front of it, causing the image that one sees when looking at a distant object to be out of focus, but in focus when looking at a close object.  Axial myopia is attributed to an increase in the eye’s axial length. 

Brighter-than-normal Luminosity

Presentations in which one eye has a cataract and the other does not usually will give the optic nerve the appearance of being more pale in color in the eye in which no cataract is present. 

There is no local (retinal) treatment for partial optic atrophy so no referral to a retinal specialist is warranted.  

The key to proper treatment is determining the etiology of the optic atrophy because early diagnosis and treatment of the underlying causes of optic atrophy can help prevent further damage from the disease.

For example, early diagnosis and aggressive treatment can prevent further optic nerve damage in patients with compressive and toxic optic neuropathies.  In addition, intravenous steroids are helpful in some cases of optic neuritis or anterior ischemic optic neuropathy.  

Stem cell treatment can hold a key in the future treatment of neuronal disorders.  Neural progenitor cells delivered to the vitreous can integrate into the ganglion cell layer of the retina, turn on neurofilament genes, and migrate into the host optic nerve.

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