How is LHON diagnosed?

If you are suspected to have LHON, a blood test can tell if you have one of the three most common mutations.

However, as LHON is a rare condition, most doctors may not have heard of it. Even experienced ophthalmologists may have never seen a patient with LHON. The limited amount of knowledge could lead doctors to suspect and treat other causes of vision loss.

Typically, your doctor will perform a series of tests to confirm LHON diagnosis or to exclude any other conditions.

These tests may include:

  • an examination of the optic disc (where blood vessels and the optic nerve enter/exit the eye)
  • an electroretinogram (ERG) to measure the electrical responses in the retina
  • a visual field test to characterise the area of vision loss (scotoma)
  • an MRI or CT scan to rule out any optic nerve flare ups or other causes of optic neuritis

Sometimes a central nervous system infection could be suspected, and your doctor may need to carry out a lumbar puncture. If optic neuritis is suspected, your doctor may prescribe a course of steroids that may be injected or taken by mouth.

If a blood test confirms that you have one of the LHON mutations, you a can ask for a referral to see a consultant knowledgeable about LHON, usually a neuro-ophthalmologist.

There are three specialist centres in the UK. You can contact them directly to make a referral for a clinical opinion or request genetic and biochemical investigations. These centres can be found in: Newcastle, London and Oxford.

On the NHS website, there is more information about Rare Mitochondrial Disease Service for Adults and Children. The information on the site is for patients and health care professionals.