Mooren's ulcer: a rare autoimmune ulcer of the cornea

No UK source dedicated to Mooren's ulcer was found when this guide was prepared. The two sources used here are from the United States: EyeWiki, an educational resource of the American Academy of Ophthalmology, and the Ocular Immunology and Uveitis Foundation. Treat them as specialist reference material rather than UK guidance, and expect a UK ophthalmologist to adapt management to the individual and to local practice.

The cornea is the clear front window of the eye. In Mooren's ulcer, the Ocular Immunology and Uveitis Foundation explains, there is a destructive lesion of the peripheral cornea, with minimal involvement of the sclera (the white of the eye), which progresses sideways around the cornea and then centrally and posteriorly. It can involve the full thickness of the cornea and lead to perforation.

EyeWiki describes how corneal changes begin within a few millimetres of the limbus (the edge of the cornea) as grey swellings that furrow and then spread around the cornea and towards the centre over months. The ulcers are often described as crescent-shaped with an overhanging central edge. The name comes from the German ophthalmologist who described it.

Pain is the dominant symptom. The foundation says Mooren's ulcer causes moderate to severe pain that is often out of proportion to how inflamed the eye looks, with a red eye. EyeWiki says the disease generally begins with intense inflammation at the limbus and swelling of the surface tissues of the eye.

EyeWiki also describes different patterns of disease. One form is unilateral and usually affects older people, with severe pain. Another is bilateral and tends to affect younger people and can be aggressive, and a third form, bilateral and indolent, occurs in middle-aged people with little inflammation. The sources note that how these groups are defined is debated, so they should be seen as descriptions rather than strict categories.

The NHS says to ask for an urgent GP appointment or call NHS 111 for eye pain, sensitivity to light, changes in vision or very red eyes, and to go to A&E or call 999 if you cannot see. These are general eye-emergency instructions from the NHS page on uveitis, not specific to Mooren's ulcer, but a painful red eye is exactly the situation they cover. A rare diagnosis such as this is made by an ophthalmologist after examination.

Both sources agree that Mooren's ulcer is a diagnosis of exclusion. EyeWiki says it requires the absence of any ocular infection or systemic rheumatological disease known to cause peripheral corneal ulceration. The sources do not set out a fixed list of tests, so what is arranged depends on the examining ophthalmologist.

Risk factors reported by the sources include previous corneal trauma or surgery, a certain tissue-type pattern (HLA-DR17 and DQ2), hepatitis C virus exposure and hookworm infestation. EyeWiki notes that the disease is more common in the southern hemisphere, including southern and central Africa and India.

The foundation says it typically responds to aggressive steroid or immunosuppressive treatment. EyeWiki says initial treatment consists of topical corticosteroids, with topical cyclosporine suggested too. If steroids do not control the inflammation, surgery on the conjunctiva next to the ulcer may be performed, and other surgical options include lamellar keratoplasty and patch grafts. Systemic immunosuppressants such as cyclophosphamide, azathioprine or methotrexate can be attempted if conjunctival surgery does not help, and biologic medicines have been used in refractory cases.

Other local measures mentioned include bandage contact lenses, tissue adhesive, artificial tears and amniotic membrane grafting, and in advanced cases a full-thickness corneal transplant. EyeWiki points out that corneal transplants can fail because of recurrence or rejection, and that there are no randomised trials comparing treatments, so decisions are individual.

EyeWiki lists complications including glaucoma, cataract, inflammation inside the eye and corneal perforation, with perforation rates varying between studies. Recurrence after surgery is also described. The foundation describes the lesion as destructive and able to lead to perforation, so prompt specialist assessment of a painful red eye matters.

Because the condition is rare and the evidence base is small, many people are looked after in specialist corneal or uveitis clinics. Keeping track of your medicines, some of which suppress the immune system and may need monitoring, and having a plan for what to do if pain suddenly worsens are important parts of living with it.

In the UK an urgent eye problem is usually assessed through an eye casualty or hospital ophthalmology service, with referral onwards to corneal or uveitis specialists. Private ophthalmology can offer quicker access to specialist examination, imaging and corneal surgery. Immunosuppressant treatment requires monitoring, and agreeing with your NHS GP who will do the blood tests avoids gaps in safety checks.