Optic nerve atrophy is a condition in which the nerve fibres that carry images from the eye to the brain gradually die and do not recover. It is a neuro-ophthalmic problem at the border of ophthalmology and neurology, so it requires careful diagnosis to find the true cause and preserve the remaining vision.
What optic nerve atrophy is
The optic nerve is a “cable” made of about a million thin fibres that carries signals from the retina to the brain. When these fibres are damaged and die off, the nerve becomes pale and thinner, and visual signals pass through poorly or not at all. Unlike many other eye diseases, fibres that have already died cannot be restored — which is why the atrophy is called irreversible. However, timely treatment of the cause can often stop further loss and preserve what still works. Atrophy is not a disease in itself, but the consequence of another process that has damaged the nerve.
Causes
- Glaucoma — long-standing raised intraocular pressure slowly destroys the nerve fibres.
- A previous episode of optic neuritis (inflammation), including in the context of multiple sclerosis.
- Ischaemia — impaired blood supply to the nerve (anterior ischaemic optic neuropathy), often in people with hypertension, diabetes or atherosclerosis.
- Compression — pressure on the nerve from a tumour, aneurysm or other mass inside the skull or the orbit.
- Hereditary conditions — for example, Leber hereditary optic neuropathy or Kjer atrophy.
- Toxic and nutritional causes — methanol poisoning, certain medicines, tobacco, alcohol abuse, vitamin B12 deficiency.
- Head and orbital injuries, as well as the after-effects of past infections.
Symptoms
- Persistent loss of visual acuity that cannot be corrected with glasses.
- Narrowing or gaps in the field of vision (“blind spots”, a sense of “tunnel vision”).
- Impaired colour perception — colours look dull, especially red.
- Worse vision in twilight and reduced contrast sensitivity.
- Sometimes pain on eye movement (if the cause is inflammation).
- On examination the doctor sees the characteristic pallor of the optic disc.
Why this is a neuro-ophthalmic condition
The optic nerve is effectively part of the brain extended out to the eye. That is why its damage can signal not only an eye problem but also a neurological one: multiple sclerosis, a brain tumour, a vascular disorder or a hereditary disease. Working out exactly where the visual pathway has “broken” and what it means for the whole body is the job of a neuro-ophthalmologist — a doctor who works at the border of ophthalmology and neurology. It is this specialist who decides whether additional brain imaging and consultations with related specialists are needed.
Diagnosis
- Testing visual acuity and colour perception.
- Perimetry — mapping the visual fields to detect gaps.
- Fundus examination (ophthalmoscopy) — assessing the pallor and margins of the optic disc.
- OCT (optical coherence tomography) — precise measurement of the nerve fibre layer thickness.
- MRI of the brain and orbits — searching for tumours, inflammation, or demyelination foci.
- Visual evoked potentials — assessing how fast the signal travels along the nerve.
- Blood tests when needed — to rule out infections, deficiencies, inflammatory and hereditary causes.
Treatment
Treatment of atrophy is primarily aimed at the cause: lowering intraocular pressure in glaucoma, anti-inflammatory therapy in neuritis, managing vascular factors in ischaemia, and removing or monitoring a tumour in compression. The goal is to stop further loss of fibres and preserve the vision that remains. In addition, agents supporting the nerve’s blood supply and metabolism may be used, and for hereditary forms — special drugs and low-vision rehabilitation. The key to success is early referral: the sooner the cause is found and removed, the more fibres can be saved. Delay leads to irreversible loss of vision.
When to seek urgent care
Seek help immediately if your vision suddenly worsens over hours or days, if a “curtain” or a gap appears in part of your field of vision, if there is pain on eye movement, double vision or a sharp change in colour perception. Sudden loss of vision is an emergency that may be caused by ischaemia, inflammation of the nerve or a mass in the brain. Every hour can affect how much vision can be saved.
German Eye Clinic, phone 0 800 507 670, the “Neuro-ophthalmologist consultation” service page.
