What Is the Evaluation of Optic Atrophy?
A 47-year-old patient with impaired vision and optic atrophy bilaterally was seen for routine eye examination. What etiologies should be considered? What is the likelihood of discovering a treatable etiology for the atrophy?
Optic disc pallor and atrophy are terms used synonymously, but there is a wide range of “normal” color of the disc. If true atrophy (damage) exists, it should be accompanied by visual loss (acuity and/or peripheral vision), decreased color perception (if acuity is compromised), and a relative afferent pupillary defect if the atrophy is unilateral. I will assume that your patient has no other cause of visual loss and that true optic atrophy exists. Primary optic nerve damage is our first consideration, but you should keep in mind that retinal damage (eg, old vascular event, retinitis pigmentosa) can also result in optic atrophy.
A complete ophthalmic examination including a comprehensive history will lead to an underlying diagnosis in the vast majority of optic atrophy cases. The most common etiologies of optic neuropathy, non-arteritic anterior ischemic optic neuropathy (NAION) and optic neuritis, are also the most common causes of optic atrophy. Your patient is 47 years old, a “gray zone” for differential diagnosis by age, and thus either previous ischemia or inflammation is possible. If there was sudden, painless visual loss, I would lean toward a vascular etiology; if it was subacute painful visual loss, then perhaps inflammation had occurred whereas gradual visual loss may indicate a compressive or nutritional etiology. One caveat, however, is that sudden discovery of chronic monocular visual loss may confound the history. Optic atrophy develops several months after damage and thus the patient who presents with acute or subacute visual loss (days to several weeks) and optic atrophy must have a more chronic process. If there has been no change in vision since the loss, then I would favor previous ischemia or trauma whereas progressive visual loss may indicate continued damage from compression or nutritional deficits. Old records documenting prior disc swelling would indicate probable prior NAION.
Past medical illnesses, such as multiple sclerosis, severe vascular disease, sarcoidosis, or malignancy, may suggest the cause of the optic atrophy. History of focal paresthesias or weakness may indicate demyelinating disease and shortness of breath and/or skin rash may occur with sarcoidosis. Gradual bilateral visual loss in other family members suggests possible dominant optic atrophy whereas a maternal family history suggests Leber’s hereditary optic neuropathy. Finally, toxic exposures (methanol), contact with animals (cats, ticks), medications (ethambutol), and vitamin deficiencies (history of alcoholism) may direct diagnostic evaluation.
You should look carefully for clues in the ophthalmologic exam that may aid in determining the underlying etiology of optic atrophy. Anterior segment exam may reveal evidence of previous trauma such as iris tears. Additionally, the presence of active or previous inflammation such as keratic precipitates or vitreous cell may point toward an infectious or inflammatory cause of optic atrophy such as sarcoid, syphilis, cat-scratch disease, or Lyme disease. Formal visual field testing may detect specific patterns of visual loss helpful in the differential diagnosis. Central scotomas occur more commonly in nutritional, hereditary, or toxic optic neuropathies. Hemianopic field deficits suggest chiasmal or retrochiasmal damage.
Although diffuse optic atrophy is nonspecific, examination may reveal subtle clues about causes of the optic atrophy. An altitudinally atrophic disc is most often seen in NAION (Figure 29-1). Remember to confirm that the contralateral disc is small and congested (the disc-at-risk) when entertaining the diagnosis of NAION. Horizontal band (or “bow-tie”) atrophy may be present with optic chiasmal or retrochiasmal pregeniculate lesions (Figure 29-2). Optociliary collateral vessels may become apparent when retinal venous outflow is compromised by an optic nerve sheath meningioma (Figure 29-3). Of course, one must examine the nerve with slit lamp biomicroscopy to obtain a good three-dimensional view and to rule out subtle cupping that might occur in glaucoma.
Figure 29-1. Note the superior altitudinal optic atrophy in a patient with previous NAION.
Figure 29-2. Note the band atrophy present in the left disc and temporal atrophy in the right disc of a patient with a right optic tract glioma.
Figure 29-3. Optociliary collateral vessels in a patient with an optic nerve sheath meningioma.
Laboratory testing such as angiotension-converting enzyme, FTA-ABS, Lyme titer, and cat-scratch titer (Bartonella henselae), Leber’s hereditary optic neuropathy, or dominant optic atrophy (OPA1) may prove useful but only when history or examination (as described above) has suggested the possibility of one of these diseases. I do not recommend “shot-gun” testing for isolated optic atrophy without cause from history or exam. Lab tests for infectious causes of optic atrophy can produce false-positive results and are not useful without clinical correlation.
Recently, we reported imaging results of a series of patients referred with unexplained, isolated, unilateral optic atrophy. Twenty percent of these patients had compressive lesions demonstrated by magnetic resonance imaging (MRI) with fat suppression and gadolinium administration. Thus, if our patient has no clues in the history or examination and has seen his or her family physician for physical examination, I would obtain MRI with gadolinium and fat suppression. If an MRI has been previously obtained, then I would review the films.
Unfortunately, I do not always discover a definite cause of the atrophy. If our patient’s evaluation conducted as described above is negative, then I would recommend repeating the evaluation with automated perimetry in 3 months to be sure there is no progressive loss of vision. If the exam is stable, I would see the patient on several occasions over the next 2 years to prove stability. If vision worsened during follow-up, I would consider progressive entities such as compression, nutritional deficiency, and dominant optic atrophy and investigate further.
* Examination including a comprehensive history will lead to an underlying diagnosis in approximately 92% of cases of optic atrophy.
* Optic atrophy develops several months after damage and thus the patient who presents with acute or subacute visual loss (days to several weeks) and optic atrophy must have a more chronic process.
* The most common etiologies of optic neuropathy, NAION and optic neuritis, are also the most common causes of optic atrophy.
* In a neuroimaging study of 91 patients referred with unexplained, isolated, unilateral optic atrophy, 20% of patients had compressive lesions demonstrated by MRI with fat suppression and gadolinium administration.
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