Posterior uveitis: symptoms, causes, tests and treatment in the UK

The uvea is the middle layer of the eye. Moorfields describes it as made up of the iris, the ciliary body and the choroid, a layer of blood vessels that supports the retina. Uveitis is the name for inflammation in this layer, and it is named according to the part of the eye that is involved: anterior at the front, intermediate in the middle and posterior at the back.

In posterior uveitis the inflammation affects the choroid and the retina. RNIB lists three patterns: inflammation of the choroid (choroiditis), of the retina (retinitis) and of the retinal blood vessels (vasculitis). Several of these can be present together. The retina is the light-sensing tissue that sends visual signals to the brain, so inflammation here can interfere with sight even when the eye looks calm from the outside.

Moorfields describes posterior uveitis as a more serious form of ocular inflammation than anterior uveitis and notes that it can be more damaging to the eye. RNIB adds that there are many types of posterior uveitis, some affecting only the eye and some occurring as part of a condition that affects other parts of the body. Panuveitis, in which all parts of the uvea are inflamed together, is a related pattern that is managed along similar lines.

It helps to keep the numbers in proportion. The NHS describes uveitis as a rare condition, and Moorfields puts the UK figure at roughly 2 to 5 in every 10,000 people each year. Most cases of uveitis, of all types, recover well when they are treated, and the outlook is considerably better when treatment starts early.

Anterior uveitis typically produces a red, painful, light-sensitive eye. Posterior uveitis is different. RNIB says it is less likely to cause a painful red eye or sensitivity to light, and Moorfields says it is usually painless and slower to develop. The symptoms RNIB lists as common are blurred or reduced vision, floaters, flashes of light, distortion of vision and reduced colour vision. They can develop gradually or suddenly and may affect one or both eyes.

Because pain is often missing, people sometimes wait. RNIB points out that some people with uveitis notice no symptoms at all, so it can go undetected for weeks or months, which is a good reason not to put new floaters or a change in vision down to tiredness.

• Blurred or reduced vision, or vision that seems misty.

• New floaters: dots, shapes or wispy lines that drift across your vision.

• Flashes of light, or distorted vision where straight lines look bent.

• Colours that seem washed out compared with before.

• Eye pain, a very red eye or light sensitivity, which are less typical of posterior uveitis but still need attention.

The NHS advises asking for an urgent GP appointment or getting help from NHS 111 if you have eye pain, sensitivity to light, changes in your vision such as flashing or blurring, or very red eyes. It says to go to A&E or call 999 if you cannot see, meaning you have lost vision.

Moorfields says that if you have any uveitis symptoms you should contact your GP promptly, and that an optometrist may be able to detect uveitis and recommend referral to a specialist. It adds that urgent attention from an ophthalmologist is recommended if signs of uveitis come with sudden or pronounced blurred vision.

Floaters and flashes can also be a sign of a retinal tear or detachment, which is a separate emergency. If you notice a sudden shower of floaters, a dark curtain or shadow across your vision, or a sudden loss of sight, get same-day help rather than waiting for a routine appointment.

For many people no cause is found. The NHS says that in most cases the cause of uveitis is unknown, and Moorfields reports that about 40% of patients have no cause identified after clinical investigation. When a cause is found it usually falls into one of a few groups.

• Autoimmune and inflammatory conditions. Moorfields lists HLA-B27 positivity as the most common association, along with rheumatoid arthritis, ankylosing spondylitis, psoriasis, inflammatory bowel disease, Behcet disease and sarcoidosis.

• Infections. Moorfields names toxoplasmosis, herpes simplex, herpes zoster (shingles), tuberculosis, Lyme disease and syphilis among infectious causes. The NHS also names the herpes simplex virus, the herpes zoster virus and toxoplasmosis.

• Reduced immunity. Moorfields notes that people with conditions such as leukaemia, lymphoma or HIV/AIDS can be vulnerable to opportunistic infections in the eye, for example cytomegalovirus retinitis.

• Injury or eye surgery, which are described as less common causes.

• Rarely, a growth in the eye, which the NHS describes as rare.

A GP or optometrist who suspects uveitis will usually arrange referral to an eye specialist. The NHS says that with uveitis you will usually be seen by an ophthalmologist within 24 hours so that treatment can start quickly. Posterior disease may be picked up on a routine eye test, in which case the referral is arranged through the same route.

The ophthalmologist examines the inside of the eye after the pupil has been widened with drops, looking at the retina, choroid and vitreous. RNIB states that examination by an ophthalmologist is needed for an accurate diagnosis. Because posterior uveitis can be linked to infection or to conditions elsewhere in the body, the team may also look for an underlying cause, and the specific investigations depend on the findings in your eye.

Follow-up is part of the picture. The NHS says that after treatment starts you will be seen again to see how it is working, to check for side effects and to look for complications such as vision loss.

RNIB explains that, apart from certain uveitis caused by infection, treatment usually focuses on reducing inflammation and controlling the immune system. The choice depends on the cause, how severe the inflammation is, whether one or both eyes are affected and what other health conditions you have.

Uveitis needs prompt treatment to reduce the risk of further eye problems. RNIB lists raised eye pressure, macular oedema (swelling at the centre of the retina), cataract, floaters, new blood vessel growth and retinal detachment as possible complications. Moorfields adds that cataracts and glaucoma can follow if uveitis is not treated.

RNIB makes a point that is worth remembering when medicines have side effects: the treatments may need monitoring, but controlling the inflammation properly gives a much better outcome for sight than under-treating it. Most people respond, although posterior uveitis tends to be longer-term than an episode of iritis, and some people need treatment over months or years.

Moorfields says most cases recover well with treatment and that early diagnosis improves the result. The practical message is to attend follow-up even when your vision feels stable, and to take prescribed eye drops and tablets exactly as advised. RNIB specifically warns for steroid drops that stopping early can let the inflammation return.

A diagnosis can be unsettling, particularly when it involves your sight. RNIB acknowledges that it is natural to be upset and to worry about managing a change in vision, and it offers a sight loss advice service and information on low vision assessments. If your vision has been reduced, you can ask your ophthalmologist, optometrist or GP about low vision aids and a low vision assessment, and local social services may offer information on staying safe at home and mobility training.

Patient organisations can help too. RNIB mentions the Uveitis Information Group, and the Birdshot Uveitis Society for people with birdshot retinochoroiditis, a specific type of posterior uveitis.

In terms of care routes, uveitis is managed by hospital eye services in the NHS, with shared follow-up through community optometry in some areas. Some people also choose to see an ophthalmologist privately for assessment or monitoring. Either way, the treatment plan is made by the specialist.