Ocular myasthenia is a form of myasthenia in which the extraocular muscles, the muscles that control the eyes and eyelids, are easily fatigued and weakened.

Symptoms

If you have ocular myasthenia you are likely to have experienced double vision (diplopia) and/or drooping eyelids (ptosis). Your eyes will not move together in balanced alignment, causing you to see 'double' images. One or both of your eyelids may also droop to cover all or part of the eye pupil, thus obstructing vision.

Eye weakness will often change from day-to-day and during the day. Problems with eyes are often worse at the end of the day or after the eyes have been used for a prolonged period of time. You may find that your eye problems are temporarily improved if you rest your eyes by closing then for several minutes when your symptoms are troubling you.

If you have ocular myasthenia, you will NOT have difficulty swallowing, speaking or breathing, nor will you experience any weakness of your arms and legs.

What makes ocular muscles so vulnerable?

The most important difference between the eye and eyelid muscles compared to those in the rest of the body, is that they respond differently to immune attack.

They are structurally different to the muscles in the body and limbs and have fewer acetylcholine receptors (AChRs). This is where the defect occurs in autoimmune myasthenia. To add to this, eye muscles contract much more rapidly than other muscles, so may be more likely to fatigue anyway, regardless of myasthenia.

Diagnosis

Diagnosis is made by the neurologist examining your clinical features and the result of the antibody blood test. The blood test is to detect the anti-acetylcholine receptor (AChR) antibodies, which are positive in around 50% of people with ocular myasthenia.

If the test comes back negative, you may receive a very sensitive electrical test (electromyography test (EMG)) on your facial muscles.

Many people with ocular myasthenia first consult their optician about their eye problem. Optometrists are frequently the first medical professionals to suspect myasthenia and will refer you to a neurologist for further tests.

Treatments

Pyridostigmine (Mestinon®)

Some people control their myasthenia with pyridostigmine alone, which temporarily improves nerve-muscle transmission to help muscle strength. The medication boosts the message from the nerve to the muscle resulting in easier muscle contraction and movement. It has to be taken periodically throughout the day for it to take full effect.

More information about pyridostigmine can be found on its designated information sheet.

Prednisolone

This is a steroid that is often prescribed for myasthenia (typically on alternate days). Steroids reduced the production of antibodies by "damping down" the bodies immune system. Prednisolone is often started on a relatively high dose and gradually reduced until the optimum dosage is achieved. Symptoms usually start to improve 2-4 weeks after treatment is started. Maximum benefit is usually seen after 6-12 months of treatment.

More information can be found on its designated information sheet.

Azathioprine (Imuran®)

Azathioprine helps to reduce or suppress your body's own immune defense system. It acts slowly and can take up to a year to take full effect. Azathioprine can be used by itself or in conjunction with other medications. Regular blood tests are required.

More information can be found on its designated information sheet.

Methotrexate

Methotrexate helps to reduce or suppress your body's own immune defense system. It can take up to 8-12 weeks to take full effect. Methotrexate can be used by itself or in conjunction with other medications. Regular blood tests are required.

More information can be found on its designated information sheet.

Mycophenolate

Mycophenolate helps to reduce or suppress your body's own immune defense system. It can take up to 3-6 months to take full effect. Mycophenolate can be used by itself or in conjunction with other medications. Regular blood tests are required.

More information can be found on its designated information sheet.

Ciclosporin

Ciclosporin helps to reduce or suppress your body's own immune defense system. It can take up to 2-3 months to take full effect. Ciclosporin can be used by itself or in conjunction with other medications. Regular blood tests are required.

More information can be found on its designated information sheet.

Lundie Loops

You may also be offered a device called the Lundie Loop, which is a circle of stainless steel wire. They are designed so you can look through the middle of the loop. The upper part of the loop, which bears lightly on the eyelid, is fitted with a short piece of silicone rubber tubing.

Traditional bar ptosis props

These can be fitted to most glasses. The length and size of them will be determined by the optometrist. Rubber tubing can also be used to cushion the bar.

Eye prisms

A prism is a wedge-shaped piece of glass or plastic that bends the light that shines through it. Fresnel prisms can be attached to your glasses and are an effective way of treating double vision. Fresnel prisms are thin, see through sheets of plastic. One side sticks to the lens of your glasses and the other side has special grooves in it that changes the way light enters your eye.

You may need to wear prisms for several months. The strength can be adjusted to suit your eyes. If the Fresnel prisms are successful, you can have glasses made with prisms built in.