MEDICAL MATTERS: The eye may well be the window to the soul, but it can also tell a lot about what is going on inside the body itself. Diabetes, sarcoidosis and infections such as toxoplasmosis and multiple sclerosis are just some of the diseases which can be diagnosed by carefully examining the human eye. Left untreated, some of these conditions can in time damage the eye.
If you think of the eye as a hollow, fluid-filled, three-layered ball, then the outer layer is the tough-coated sclera, the innermost is the retina which is thin and gathers light to it and the middle layer is called the uvea.
This middle layer, the uvea, is made up of the iris and the ciliary body towards the front of the eyeball and the choroid which is situated further back. When any part of the uvea becomes inflamed the result is a condition called uveitis.
Eye specialists make a distinction between anterior and posterior uveitis. Posterior uveitis affects the choroid and may also arise in or affect the retina and other structures at the back of the eye. It is not a disease in itself, but is a handy label for any inflammatory process which affects the inside and back of the eye.
Because of the complexity of uveitis and its treatment, some opthalmologists now train specifically in the condition. And within the specialist treatment of uveitis, there are those who sub-specialise in either anterior or posterior uveitis.
The Eye and Ear Hospital in Dublin has two opthalmologists with fellowship sub-specialist training in uveitis. Dara Kilmartin is a newly appointed consultant opthalmologist at the hospital and he has recently set up a dedicated posterior uveitis clinic at the hospital.
"While many patients with uveitis can be treated locally in the regional eye units, when they require systemic immunosuppression or the condition becomes uncontrolled they need referral to a medical retinal specialist or a uveitis specialist," he says.
Noting that there is a low public awareness of the condition, Kilmartin says that uveitis is an important cause of visual impairment in the working-age population. "It accounts for up to 10 per cent of registerable blindness and may equal diabetes as a cause of visual impairment in the 20- to 45-year-old group."
At the time he set up the clinic, he estimated that up to 20 patients were travelling to Britain for sight-saving treatment. These patients can now be managed here.
Although the symptoms of posterior uveitis are varied, many patients with the condition can develop sight-threatening inflammation. Typical symptoms include a gradual loss of vision in one eye. It usually remains painless but can become red and inflamed.
When severe inflammation is present, and the cause is a non-infective one, it may be necessary to use strong immunosuppressive drugs to save the person's sight. Treatment involves taking steroids and other anti-inflammatory drugs orally.
The aim of treatment is to suppress the inflammation until the inflammatory process burns itself out. This means using large doses of drugs which have the potential to affect the whole body, increasing the likelihood of unwanted side-effects.
Relatively high doses of steroids may have to be taken for six weeks or longer and there is a risk of other drugs depressing the immune system. Some immunosuppressants can cause kidney problems and raise blood pressure. Prolonged use of others may increase the risk of cancer of the blood (lymphoma).
However, when faced with the alternative of going blind, most patients opt for treatment.
Sandra, a 26-year-old single woman who works in finance, is typical of a patient who has been treated in the Eye and Ear's new clinic. In January this year, she noticed blurring of vision in both eyes and went to the emergency department of the hospital.
Examination showed some inflammation at the back of the eyes, suggesting posterior uveitis. But an X-ray of her chest showed signs of sarcoidosis, an autoimmune disease.
Sandra's vision continued to deteriorate to the point where there was a black area where ever she looked. At this point she was admitted to hospital under the care of Kilmartin and started on intravenous steroids.
However, as a diabetic of long-standing, the doctors had to monitor her very closely because steroids interfere with the control of blood sugar. As she improved, her treatment was switched to a potent immunosuppressant called Mycophenolate Mofetil and she was given laser treatment.
Six months later her vision is back to normal and she has been able to reduce the dose of the powerful anti-inflammatory drug. She attends for monthly blood tests to ensure that its two major side effects - bone marrow suppression or liver inflammation - have not occurred.
"I have not had any problems with the drug and I am back to myself," she says, grateful to have avoided permanent damage to her eyes and sight.
For further information on uveitis see www.uveitis.net
Dr Muiris Houston can be contacted at mhouston@irish-times.ie. He regrets he cannot reply to individual medical queries