Uveitis is inflammation and irritation of the uvea or middle layer of the eye. Types of uveitis include anterior uveitis or iritis; intermediate uveitis or pars planitis; posterior uveitis or chorioretinitis, and pan-uveitis. Moreover, uveitis can be classified depending on duration to acute, recurrent, and chronic uveitis.

The occurrence of uveitis may be attributed to unknown causes in most cases, however, common known causes include autoimmune disorders such as ankylosing spondylitis and sarcoidosis, infections such as herpes simplex virus and syphilis, and several eye problems such as eye injury or eye surgery.

Several risk factors that can lead to developing uveitis include having specific genes, belonging to specific age group or ethnicity, and smoking.

The pathophysiological process of uveitis involves breaking down of blood-eye barrier that normally prevents the cells and large protein entering the eye. Symptoms of uveitis may develop rapidly and can include loss of peripheral vision, eye redness, blurry vision, and hypersensitivity to bright light.

To diagnose uveitis, an ophthalmologist examines the inside of the eye and perform a thorough examination. Tests that used to assess the eye may involve eye chart or visual acuity test, ophthalmoscopy, and slit lamp exam.

Treatment options differ according to the type of uveitis present. To treat anterior uveitis, a physician may recommend the using of dark glasses along with eye drops to reduce pain and inflammation. Moreover, intermediate, posterior, and pan-uveitis can be treated with corticosteroids, immunosuppressive agents, or antibiotics and antivirals if uveitis is caused by an infection.

Uveitis has the ability to cause several complications if not managed properly, these complications include glaucoma, cataracts, retinal detachment, and permanent vision loss. However, most episodes of anterior uveitis improve within few days to weeks with proper treatment, but, The chance increases for intermediate uveitis and posterior uveitis to recur or to last for a longer time.

The available epidemiological data regarding uveitis is limited; however, the disease is rare in the UK for example, and can only affect two to five per 10,000 every year.

Uveitis is inflammation and irritation of the uvea. The uvea represents the middle layer of the eye, which contains much blood vessels that supply the eye.  

Uveitis can cause permanent vision loss due to the destruction of vital eye tissue. However, this disease is not limited to the uvea; it can also damage the lens, optic nerve, retina, and vitreous, leading to reduced vision or blindness.

There are several different types of uveitis, including:

• Anterior uveitis: This type is also known as iritis, which is the inflammation of the iris, and it is considered as the most common form of uveitis.  This type can suddenly appear and symptoms can last up to 8 weeks.
• Intermediate uveitis or pars planitis: This type can appear in cycles that vary in severity. This type is commonly seen in young adults and mostly results in floaters and blurred vision.
• Posterior Uveitis or chorioretinitis: This is the least common type of uveitis that results in inflammation of the choroid, retina and other structures at the back of the eye with symptoms that develop gradually and may last for many years.
• Pan-Uveitis: The term “Pan-Uveitis” is used to describe inflammation of all three major parts of the eye.

Moreover, uveitis can be classified according to the duration of infection. For example:

• Acute uveitis: This type develops quickly, but improvement within three months has been reported in most cases.
• Recurrent uveitis: This type develops in form of several episodes of inflammation separated by periods of improvements for several months.
• Chronic uveitis: This type can result in inflammation that lasts longer and returns within three months of discontinuing therapy.  

The exact etiology of uveitis remains unknown in many cases. However, common known causes include:

• Autoimmune disorders: These diseases occur when healthy body tissue is attacked by the immune system by mistake. Examples include ankylosing spondylitis, psoriasis, rheumatoid arthritis, Reiter's syndrome, and sarcoidosis.
• Infections: Many infections can cause uveitis such as shingles virus, herpes simplex virus, syphilis, Lyme disease, AIDS, histoplasmosis, tuberculosis, in addition to parasites such as toxoplasmosis.
• Eye problems: These problems involve eye infection, eye surgery, injuries or bruises to the eye, ulcer on the eye’s surface, or a scratch to the cornea.
• Certain types of cancers: These cancers may involve lymphoma, although this is a very rare cause of uveitis.
• Exposure to toxins: The exposure to certain kinds of toxins can lead to uveitis.

Risk factors associated with uveitis include:

• Genes: The likelihood of developing uveitis increases in case of people with changes in certain genes. Some researchers believe that a gene known as HLA-B27 can be linked to an increased risk of getting anterior uveitis.
• Age: Systemic diseases play a major role in causing uveitis among children younger than 16 years.Diseases such as sarcoidosis and herpes infection are the common causes of uveitis among people over 60 years.
• Race: Sarcoidosis associated uveitis, for example, is more prevalent in black people than in white people.
• Environmental factors: Incidence of eye inflammatory diseases is significantly affected by environment and lifestyle factors. Toxoplasmosis, for example, is prevalent among people who have contact with domestic animals and it is one of the most common causes of posterior uveitis in the world.
• Smoking: Smokers of cigarettes, cigars or pipes are at an increased risk of developing uveitis.

Uveitis can be regarded as a response that the eye produces when it is affected by a wide spectrum of intraocular inflammatory diseases of infectious, traumatic, genetic or autoimmune nature.

The specific types of causes that can lead to uveitis mostly determine the pathophysiological pathway that the disease may take, however, there is a breach in the blood-eye barrier in all types.

In similar fashion to the blood-brain barrier, the blood-eye barrier normally prevents the cells and large protein entering the eye. However when inflammation occurs, the barrier breaks down, and white blood cells enter the eye.

The outcome of the process will lead to the presence of inflammatory cells and sustained production of cytotoxic cytokines, in addition to other ocular immune regulatory proteins.

One or both eyes can be affected by uveitis, and symptoms may develop rapidly and can include:

• Reduction in the ability to see objects at the side of field of vision which sometimes known as loss of peripheral vision,
• The sudden seeing of specks or moving clouds in the vision that sometimes called floaters,
• Eye redness with or without pain,
• Hypersensitivity to bright light,
• Small or distorted pupil,
• A different colored iris,
• Blurry vision,
• Watery eye.

Usually, the ophthalmologist examines the inside of the eye and perform a thorough examination to diagnose uveitis, in addition to asking questions regarding the past and present health history.

The eye exams that an ophthalmologist may use include:

• Eye chart or visual acuity test: This test investigates the reduction that occurred in patient’s vision.
• Ophthalmoscopy or funduscopic Exam: When an ophthalmologist performs this exam, he/she uses an instrument called an ophthalmoscope that enables careful inspection of the back, inside part of the eye in a noninvasive way. 
• Ocular pressure test: In order to measure the pressure inside the eye, an ophthalmologist may use instruments such tonometer or tonopen.
• Slit lamp exam: A slit lamp exam provides a better inspection for most of the front and back parts of the eye in a noninvasive way, in addition, some lamps come with a tonometer to measure eye pressure.

The type of uveitis determines best treatment option:

• Anterior uveitis or iritis is mostly mild and can be treated by: 
• Wearing dark glasses.
• Relieving pain by using eye drops that dilate the pupil.
• Reducing inflammation by prescribing eye drops containing steroids, such as prednisone.
• Intermediate, posterior, and pan-uveitis can be treated with : 
• Giving corticosteroids orally or by injection around the eye.
• Surgically implanting time-release capsules inside the eye, which contain corticosteroid medication.
• Giving other immunosuppressive agents such as cyclosporine, methotrexate, mycophenolate, and azathioprine.
• Antibiotics or antivirals may be prescribed if uveitis is caused by an infection along with other medications.
• Vitrectomy may be necessary to manage the condition in some cases. The surgery is performed to remove some of the vitreous in the eye.

If not well treated, uveitis may lead to complications such as:

• Glaucoma, which involves a harmful build-up of fluid within the eyeball.
• Cataracts, which is clouding of the lens that situated behind the iris.
• Optic nerve damage.
• Retinal detachment.
• Permanent vision loss.
• Fluid in the retina.
• Irregular pupil.
• Macula edema, which is swelling of the central retina, resulting in blurriness.
• Posterior synechia, which causes the iris to stick to the lens of the eye because of inflammation in the area.

In case a person develops a body-wide or systemic infection or disease, treating the condition may be considered as a prevention method to prevent uveitis.

Most episodes of anterior uveitis improve within few days to weeks with proper treatment, however, the problem often returns. Posterior uveitis may last from months to years and it can result in permanent vision damage, even with therapy. However, the factors are unclear when determining which cases will improve without intervention.

The chance increases for intermediate uveitis and posterior uveitis to recur or to last for a longer time, but uveitis associated with an infection generally improve and does not recur when the infection is treated.

The available epidemiological data regarding uveitis is limited. However, the following is part of the available data:

• According to publications of National Health Service (NHS), in the United Kingdom, uveitis is rare and can be found in two to five per 10,000 every year. Moreover, uveitis is more common in people aged 20 to 59, but children are vulnerable to develop uveitis as well.
• A Study published in JAMA Ophthalmology journal that released by American Medical Association has found that the overall uveitis incidence rate was 24.9 cases per 100 000 person every year in a Hawaiian population. Moreover, white individuals had a higher prevalence rate than nonwhite individuals.
• A Study published in  Indian Journal of Ophthalmology has investigated the epidemiology of uveitis for 9378 patient in Indian hospitals, in addition to reviewing the global variation and pattern changes in the epidemiology of uveitis.The study has concluded : 
• It is more common for uveitis to affect young adults.
• The majority of uveitis surveys that come from developed countries report equal gender distribution.
• Uveitis that associated with infection is accounted for relatively a minority of cases in most surveys from the developed world.
• Uveitis that associated with infection occurs in greater frequency in the developing world, accounting for 11.9% to 50% of cases.
• Toxoplasmosis was the most common cause of infectious uveitis followed by herpetic anterior uveitis.