Optic Atrophy, Causes, Symptoms, Diagnosis, Treatment

Optic atrophy

Optic atrophy refers to the death of the retinal ganglion cell axons that comprise the optic nerve with the resulting picture of a pale optic nerve on funduscopy. Optic atrophy is an end stage that arises from myriad causes of optic nerve damage anywhere along the path from the retina to the lateral geniculate. Since the optic nerve transmits retinal information to the brain, optic atrophy is associated with vision loss. Optic atrophy is somewhat of a misnomer as atrophy implies disuse and optic nerve damage is better termed optic neuropathy.

Causes Optic Atrophy

The optic nerve is composed of nerve fibers that transmit impulses to the brain. In the case of optic atrophy, something is interfering with the optic nerve’s ability to transmit these impulses. The interference can be caused by numerous factors, including:

Primary optic nerve disease

  • Chronic glaucoma.
  • Retrobulbar optic neuritis – eg, due to multiple sclerosis.
  • Traumatic optic neuropathy.
  • Lesions compressing the optic nerve (eg, tumour, aneurysms, Paget’s disease of bone).

Primary retinal disease

  • Central retinal artery occlusion or central retinal vein occlusion.

Secondary optic nerve disease

  • Ischaemic optic neuropathy, which may be:
    • Arteritic ischaemic optic neuropathy – usually giant cell arteritis.
    • Non-arteritic anterior ischaemic optic neuropathy.
  • Chronic papilloedema.
  • Chronic optic neuritis.

Less common causes

  • Hereditary optic neuropathies (eg, Leber’s optic neuropathy).
  • Retinal degeneration (eg, retinitis pigmentosa).
  • Retinal storage diseases (eg, Tay-Sachs disease).
  • Radiation neuropathy.
  • Syphilis.
  • A rare autosomal dominant condition, optic atrophy 1 (also known as juvenile optic atrophy, or Kjer-type optic atrophy) is characterised by insidious onset of visual impairment in early childhood.[2]
  • Glaucoma.
  • Stroke of the optic nerve, known as anterior ischemic optic neuropathy.
  • A tumor that is pressing on the optic nerve.
  • Optic neuritis, an inflammation (swelling) of the optic nerve caused by multiple sclerosis.
  • A hereditary condition in which the person experiences loss of vision first in one eye, and then in the other (known as Leber’s hereditary optic neuropathy).
  • Improper formation of the optic nerve, which is a congenital problem (the person is born with it).

Toxic optic neuropathies

  • Methanol toxicity remains a significant problem in some parts of the world.
  • Possible drug causes of toxic optic neuropathy are disulfiram, halogenated hydroquinolones (amoebicides), ethambutol, isoniazid, chloramphenicol, vincristine and ciclosporin. Cimetidine has (rarely) been associated with optic neuropathy which reversed on stopping the drug.
  • People who abuse alcohol and tobacco and who are also malnourished are at greater risk, probably through deficiency of B-complex vitamins.
  • Metabolic disorders such as severe renal impairment may cause toxic optic neuropathy through build-up of toxins.

Symptoms of Optic Atrophy

The symptoms of optic atrophy relate to a change in vision, specifically

  • Blurred vision
  • Abnormal side vision
  • Abnormal color vision
  • Decreased brightness in one eye relative to the other
  • Difficulties with peripheral (side) vision.
  • Difficulties with color vision.
  • A reduction in sharpness of vision.
  • In a young patient, previous history of eye pain, paraesthesiae, ataxia or weakness suggest demyelination
  • In an older patient, previous history of transient visual loss, diplopia, temporal pain, jaw claudication, fatigue, weight loss and myalgia suggests arteritic ischaemic optic neuropathy due to giant cell arteritis.
  • In children, history of flu-like illness or vaccination could suggest para-infectious or post-vaccinial optic neuritis.
  • Diplopia and facial pain suggest multiple cranial neuropathies due to inflammatory or neoplastic lesions behind the eye.
  • Medication history should be noted – in particular, drugs which can be toxic to the optic nerve (eg, ethambutol, amiodarone, alcohol, methotrexate, ciclosporin).
  • History of diabetes, hypercholesterolaemia and hypertension is common in patients with non-arteritic anterior optic neuropathy.
  • Patients with known malignancy may have infiltrative or para-neoplastic optic neuropathy.
  • Detailed family history may suggest hereditary autosomal and mitochondrial optic neuropathies.[2]

Diagnosis of Optic Atrophy

Suggestive Findings

Optic atrophy type 1 (OPA1 or Kjer type optic atrophy) should be suspected in individuals with the following clinical, electrophysiologic, and family history findings:

Clinical findings

  • Childhood onset
  • Bilateral vision loss that is usually symmetric
  • Visual field defect that is typically centrocecal, central, or paracentral
  • Peripheral field that is usually normal, although inversion of red and blue isopters may occur.
    Note: The isopters are lines joining points of equal sensitivity on a visual field chart. The red isopter represents the largest/brightest stimulus; the blue isopter represents the smallest/dimmest stimulus. Persons with OPA1 have scotomas (areas of impaired visual acuity) in the central visual fields and sparing of the peripheral visual fields.
  • Color vision defect, often described as acquired blue-yellow loss (tritanopia)
Opthalmoscopic examination that demonstrates
  • Optic nerve pallor (the cardinal sign) that is most often bilateral and symmetric, but may be temporal (50% of individuals) and global (50%)
  • Profound papillary excavation (21% of eyes with OPA1)
  • Neuroretinal rim pallor in most cases, sometimes associated with a temporal pigmentary gray crescent.

Electrophysiology

  • Visual evoked potentials (VEPs) are typically absent or delayed, indicating a conduction defect in the optic nerve.
  • Pattern electroretinogram (PERG) shows an abnormal N95:P50 ratio, with reduction in the amplitude of the N95 waveform. Since the N95 component of the PERG is thought to be specific for the retinal ganglion cell, this finding supports a ganglion cell origin for the optic atrophy.
    Note: The PERG originates from the inner retinal layers, enabling an assessment of ganglion cell function, and is increasingly used in the assessment of anterior visual pathway dysfunction. The normal PERG consists of a prominent positive peak at 50 ms (P50), and a slow, broad trough with a minimum at 95 ms (N95). The positive P50 component is invariably affected in retinal and macular dysfunction, whereas the negative N95 component is principally affected in optic nerve disease. Furthermore, the ratio between N95 and P50 has been shown to be an effective measure of retinal ganglion cell function.

Establishing the Diagnosis

The diagnosis of optic atrophy type 1 (OPA1) is established in a proband with the above clinical findings and/or a heterozygous pathogenic variant in OPA1 by molecular genetic testing .

Molecular testing approaches can include single-gene testing, use of a multigene panel, and genomic testing.

Single-gene testing

  • Targeted analysis for the pathogenic variant can be performed first in individuals of Danish ancestry.
  • In individuals who are not of Danish ancestry or if targeted analysis does not identify a pathogenic variant, sequence analysis of OPA1 is performed, followed by gene-targeted deletion/duplication analysis if no pathogenic variant is found.
  • If no pathogenic variant is identified, molecular genetic testing of OPA3 for autosomal dominant optic atrophy type 3 (OPA3) and for the common mitochondrial DNA (mtDNA) single-nucleotide pathogenic variants responsible for Leber hereditary optic neuropathy (LHON) should be considered.

A multigene panel that includes OPA1 and other genes of interest may also be considered. Note:

  • (1) The genes included in the panel and the diagnostic sensitivity of the testing used for each gene vary by laboratory and are likely to change over time.
  • (2) Some multigene panels may include genes not associated with the condition discussed in this GeneReview; thus, clinicians need to determine which multigene panel is most likely to identify the genetic cause of the condition at the most reasonable cost while limiting identification of variants of uncertain significance and pathogenic variants in genes that do not explain the underlying phenotype.
  • (3) In some laboratories, panel options may include a custom laboratory-designed panel and/or custom phenotype-focused exome analysis that includes genes specified by the clinician.
  • (4) Methods used in a panel may include sequence analysis, deletion/duplication analysis, and/or other non-sequencing-based tests.

More comprehensive genomic testing (when available) including exome sequencing, genome sequencing, and mitochondrial sequencing may be considered if serial single-gene testing (and/or use of a multigene panel) fails to confirm a diagnosis in an individual with features of optic atrophy type 1.

Treatment

Coming

References

Optic atrophy