Leber Hereditary Optic Neuropathy Lhon

Overview

LHON is a rare inherited condition that damages the optic nerve — the bundle of nerve fibres that carries signals from your eye to your brain. It usually causes vision to blur or fade in the centre of one eye, often followed weeks or months later by the other eye. The change is painless, and it mainly affects the central part of vision, which is the part you use for reading, recognising faces and seeing detail. Side (peripheral) vision is usually kept.

No, it is rare. It is thought to affect roughly 1 in 30,000 to 1 in 50,000 people worldwide, so most general practice teams will see very few cases in their careers.

It most commonly affects young men, who are around four to five times more likely than women to lose vision if they carry the gene change. Women can be affected too, sometimes at an older age. Children under 10 are rarely affected. Because the condition runs in families through the mother's line, brothers, sisters, cousins and uncles on the mother's side may also carry it.

Symptoms

Common symptoms

• Painless blurring or cloudiness in the centre of vision in one eye — often described as a smudge, fog or smear that cannot be blinked away
• Colours looking washed out or dull, especially reds and greens
• A blank or grey patch in the middle of what you are looking at (doctors call this a central scotoma)
• The second eye usually becoming affected within weeks to a few months of the first
• Vision tends to get worse over a few weeks and then stabilise
• Side vision, and the ability to get around a room, usually stay intact

Symptoms in children

• LHON is uncommon before age 10, but when it happens children may simply seem to stop seeing things clearly rather than say their vision has changed
• Holding books or screens very close, or sitting close to the television
• Struggling at school with reading or copying from the board
• Bumping into things or seeming clumsy on one side
• Squinting, rubbing the eyes, or complaining that colours look odd
• Any child with a sudden change in vision should be seen by an eye professional quickly

Symptoms in older adults

• LHON can start later in life, and this is more often seen in women
• The pattern may be less typical, so it can be mistaken at first for other optic nerve or eye problems
• Vision loss may be slower or less complete than in younger people
• Because other eye conditions are also more common with age, a full eye assessment matters

Causes

Main causes

• A change (variant) in the mitochondrial DNA — mitochondria are tiny energy factories inside your cells, and they have their own small set of genes
• These gene changes are passed from a mother to all of her children, because we inherit our mitochondria from our mother. A father cannot pass LHON to his children
• The cells of the optic nerve need a lot of energy, so they are especially sensitive when mitochondria do not work as well as they should
• LHON is not caused by anything the person did, ate, or failed to do

Risk factors

• Being male — men who carry the gene change are much more likely to lose vision than women
• Carrying one of the known LHON gene changes (this can be found with a blood test)
• Smoking, which is the strongest known trigger and also harms the optic nerve directly
• Heavy or regular alcohol use
• Contact with certain toxins and some medicines that can affect the optic nerve — always tell any doctor or pharmacist about your family history before starting new medicines
• Some people report that vision loss began around a time of illness, stress or poor nutrition, though this link is not fully proven

When to see a doctor

See a doctor urgently if:

• Any sudden or rapid change in your vision — contact your optician, GP or an urgent eye service the same day
• You have a known LHON gene change in the family and notice any new visual symptom
• A close relative on your mother's side has been diagnosed with LHON and you develop visual changes

Book a routine appointment if:

• You have a family history of LHON and would like advice about genetic testing
• You are a carrier and want to talk about reducing triggers, or about planning a family
• Your vision is stable but you are finding reading, work or daily tasks harder and want to know about low vision aids
• You feel low, anxious or isolated because of your sight

Diagnosis

A specialist eye doctor (ophthalmologist or neuro-ophthalmologist) usually makes the diagnosis. They will ask about your vision, your family history and your general health, examine the back of your eyes, and arrange a blood test to look for the mitochondrial gene changes linked to LHON. Because the condition runs in families, the doctor will often suggest that relatives be offered testing and genetic counselling too.

Tests that may be done

• A full eye examination, including looking at the optic nerve at the back of the eye
• Vision (acuity) tests and a test of how well you see colours
• Visual field test — mapping out which parts of your vision are affected
• OCT scan — a quick, painless photo-like scan that measures the layers of the retina and optic nerve
• Blood test for the mitochondrial DNA changes that cause LHON
• Sometimes other tests, such as electrical tests of the eye or a scan of the brain, to rule out other conditions
• Genetic counselling, to explain what the results mean for you and your family

What to expect at your appointment

You will usually have a few appointments rather than one. The eye tests are quick and painless. The genetic blood test result can take several weeks to come back. Waiting can feel hard, so it helps to write down your questions and take someone with you to appointments. Your team should explain each step and talk you through what the results mean for you and for relatives who may want testing.

Treatment

There is no cure for LHON at present, and no treatment can reliably bring back vision that has been lost. Care focuses on protecting the optic nerve as much as possible, supporting you practically with low vision aids and rehabilitation, and keeping you informed about research. Because LHON is rare, you should be looked after by a specialist centre with experience of the condition where possible.

Self-care at home

• Do not smoke, and avoid second-hand smoke — this is the single most important thing you can do
• Keep alcohol to a minimum, or avoid it, especially around the time of any visual change
• Eat a balanced diet and stay generally well hydrated
• Tell every doctor, optician and pharmacist about your diagnosis before accepting any new medicine, so they can check it is safe for the optic nerve
• Use good lighting, magnifiers and larger text settings on phones and computers
• Ask about a low vision assessment — simple aids often make a big difference to reading and daily tasks
• Keep up regular eye checks and general health checks

Medical treatments

Treatment is led by a specialist eye or neuro-ophthalmology team. Some specialist centres offer a medication aimed at supporting the energy production inside cells; how much it helps is still being studied, and availability differs between countries, so ask your specialist whether it is an option for you. Experimental approaches, including gene-based treatments, are being tested in research studies, and your team can tell you if any are suitable. Alongside this, the mainstays are low vision aids and equipment, vision rehabilitation, help with work, study and driving, and emotional support. No treatment should ever be started without your specialist's advice.

When is surgery considered?

Surgery cannot repair or replace the optic nerve, so it is not used to treat LHON itself. In some situations, surgery may be considered for other eye problems that happen at the same time, such as cataracts. Your eye specialist would discuss this with you if it applied to your situation.

Living with this condition

Most people with LHON keep their side vision and can walk around, cook and care for themselves. The harder parts are often reading, recognising faces, seeing in low light, judging steps, and coping with glare. Practical changes help a lot: brighter lamps, high-contrast labels, talking watches and scales, text-to-speech and screen magnification on phones and computers, and keeping things in the same place at home. Many people find that asking for a low vision assessment and a workplace or study assessment opens the door to useful equipment and adjustments.

Lifestyle tips

• Stop smoking if you smoke, and ask for help to do so — this matters more than anything else
• Keep alcohol low, and avoid binge drinking
• Stay physically active within your comfort and safety, and ask about safe ways to exercise if your sight has changed
• Use a white cane or symbol cane if it helps you feel confident and lets others know you have low vision
• Keep a simple note of your diagnosis and medicines in your phone or wallet, in case you need to tell a new doctor quickly
• Build a routine that gives your eyes regular rest if you find screen work tiring

Diet and exercise

There is no special diet that treats LHON, but eating a varied, balanced diet and staying a healthy weight support your general health and energy levels. Some people with mitochondrial conditions are advised to avoid long periods without food, so regular meals can help. Exercise is encouraged for general wellbeing; choose activities you can do safely with your level of vision, and ask your doctor or a physiotherapist for advice if you are unsure. Avoid extreme or exhausting exercise if your specialist has advised against it.

Mental health and emotional wellbeing

Losing part of your sight suddenly is a real loss, and it is completely normal to feel shocked, frightened, angry or very low. Many people also feel anxious about the second eye or about the future. These feelings usually soften with time and support, but they deserve attention rather than being pushed aside. Talking to a counsellor, a clinical psychologist, or other people with LHON can help a great deal. If at any point you feel you cannot cope, or you have thoughts of harming yourself, please reach out straight away — contact your local crisis line, your doctor, or your local emergency number. You do not have to manage this alone.

Prevention

You cannot prevent inheriting a mitochondrial gene change, and nothing a parent does or does not do causes it. What you can do is lower the chance that the gene change leads to vision loss. Not smoking, keeping alcohol low, and checking with a doctor or pharmacist before taking any medicine that could affect the optic nerve are the most useful steps. Anyone in a family with LHON should be able to get advice on this.

Screening programmes

Genetic testing and genetic counselling are available for relatives of someone with LHON, particularly on the mother's side of the family. This can tell people whether they carry the gene change, which helps them make informed choices about triggers, monitoring and family planning. Ask your GP or eye specialist for a referral to a genetics service.

Complications

If left untreated

• Permanent loss of central vision in one or both eyes, which is the usual outcome once the optic nerve has been damaged
• Difficulty reading, recognising faces, driving and doing detailed work
• Problems with colour vision, which can affect work and everyday choices
• Higher risk of falls or trips, especially in poor light or on stairs
• Impact on work, study, income and independence
• Low mood, anxiety or isolation, which are common and treatable
• In a small number of families, other neurological problems can occur alongside the eye changes — your specialist can explain whether this applies to your family

Long-term outlook

The honest picture is that vision loss from LHON is usually permanent, and there is no cure yet. But the outlook is not bleak. Most people keep useful side vision and learn to do everyday tasks in new ways, and many go on to work, study and live full lives. Some people do regain a degree of central vision over months or years, particularly with certain gene changes. Research into treatments is moving forward, and support services for sight loss have improved enormously. With the right help, most people adapt well.

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