The uvea lies between the whites of the eye or the sclera and the retina. The uvea is supplied richly by blood vessels and is deeply pigmented. The choroid layer (choroid plexus, ciliary body and iris together) is also termed as uveal tract.
The term uveitis refers to inflammation at any point of the uveal tract with or without inflammation of neighbouring structures like the retina at the back of the eye or the vitreous humor or the liquid that fills the inner part of the eye ball.
There are several types of classifications of uveitis. The commonest classification is by the anatomical location of the inflammation. This includes :
- Anterior uveitis – This type of uveitis affects the iris and is also called iritis. It may also be referred to as iridocyclitis because it may affect the iris as well as the ciliary body.
- Intermediate uveitis – This type affects the vitreous humor and the back part of the ciliary body.
- Posterior uveitis – This type affects the choroid or back part of the uvea. It is also called choroiditis if only choroid is affected or chorioretinitis if there is involvement of the retina as well.
- Panuveitis – This type refers to inflammation throughout the uvea.
The causes of uveitis are several. Some of these include :
- Due to an autoimmune disease and other diseases of the immune system. Some of the diseases associated with uveitis include Ankylosing spondylitis, Sacroiliitis, Reiter’s syndrome, Inflammatory bowel diseases like Crohn’s disease and Ulcerative colitis, Psoriasis, Sarcoidosis, Behçet’s disease and Juvenile idiopathic arthritis.
- Due to an infection of the eye. Some of the infections that may lead to uveitis include toxoplasmosis, cytomegalovirus infection, Herpes simplex virus infection, herpes zoster virus, tuberculosis, syphilis, AIDS (leading in increased risk of human syncitial virus, cytomegalovirus, Cryptococcus and candida infection) etc.
- Due to infiltration of the eye by a cancer
- After an eye injury
- After a surgery, inadvertent trauma, or medication used for an eye disease occurring as a side effect.
- As an inherited condition occurring as a manifestation of a metabolic disease that runs in families
- Ischemia caused by narrowing of blood vessels supplying the uvea
The beginning of uveitis may usually be sudden and is described as acute. It is acute if it takes less than three months to develop and is described as chronic if it takes more than three months to develop. There may be recurrent episodes of the condition.
- Symptoms of anterior uveitis – one sided painful red eye, blurred vision, small pupil, change in color of iris, sensitivity to light, shadows that move across the field of vision also called floaters, headaches etc.
- Symptoms of intermediate uveitis – floaters and blurred vision usually in one eye. Symptoms of pain, redness and photophobia are not usually present in cases of intermediate uveitis.
- Symptoms of posterior uveitis – floaters and blurred vision, loss of peripheral vision or ability to see objects at the side of the field of vision, flashing lights etc.
Diagnosis is made on the basis of clinical examination, detailed history of the disease as well as laboratory and imaging tests. A detailed history of eye injury, infections and familial diseases are obtained. The eye is examined using a slit lamp after dilating the iris. Many persons with immunosuppression or a depressed immune system are prone to uveitis. Thus immunosuppression needs to be ruled out in patients with uveitis.
- Loss of vision. This may occur due to cystoids macular edema,
- Cataract – due to the disease or due to steroids
- Glaucoma – due to the uveitis or due to steroids
- Retinal detachment and damage to the retina, optic nerve, or iris
- Macular deficiency of blood supply and optic neuropathy
- General principles of management – Delay in appropriate management of uveitis may lead to permanent loss of vision. All patients with anterior disease and most with intermediate or posterior disease require treatment. Those with a disease affecting the whole body need a wholesome approach rather than treatment of the uveitis alone.
- Steroid therapy – In most cases of uveitis the underlying pathology is inflammation within the eye. Steroids are drugs that reduce inflammation.Prednisolone 1% eye drops are the first-line treatment for the management of uveitis. Steroid ointment may also be prescribed for treatment overnight. These should be prescribed by a specialist, as they can cause cornea ulcers and damage, glaucoma and steroid cataract.
In more severe cases or posterior disease oral pills of steroids may be given. These are also started at high doses and tapered down until the condition resolves. In case of very severe disease, steroids are given as injections around the eyeball. This is needed in cases of cystoid macular oedema.
- Dilatation of the pupils – Dilating drops are prescribed along with steroids. These help to relieve the spasmodic pain of the iris in anterior uveitis. These also break any attachments that are caused between structures underlying the inflamed iris. These attachments are called synecchiae. Drugs used include atropine 1% and cyclopentolate 1% drops. Cyclopentolate is usually preferred, as it is much shorter acting than atropine. These agents lead to increased sensitivity to light, blurring of vision and objects may appear larger.
- Immunosuppressants are useful when uveitis is caused by immune diseases. Drugs like Azathioprine, Ciclosporin, tacrolimus are used.
- Surgical therapy includes removal of vitreous humor in cases of severe disease. Other reasons for surgery include removal of a secondary cataract or in glaucoma due to uveitis.