Endophthalmitis
Definition
Endophthalmitis is a term that describes an inflammation of the intraocular spaces that is usually caused by infection. Endophthalmitis can be exogenous or endogenous. The most common type of exogenous endophthalmitis is post-operative, such as after a cataract surgery. Other exogenous causes include ruptured globe or intraocular foreign body.
Endogenous endophthalmitis results from bacteria that originated from another part of the body, which spread to the eye from the source of infection through the blood stream. Non-infectious, or sterile, endophthalmitis can result from inflammation related to retained lens material or a reaction to intraocular drugs such as steroids.
Causes and Associations
Normally, the eye has many barriers to infection. The eyelashes, tear film, cornea, conjunctiva, and sclera all serve to prevent bacteria or other organisms from entering the eye. The blood vessels in the eye also have special, tight junctions between their cells to form a blood-ocular barrier that limits the chance that infection will spread from the blood stream into the eye. The three main causes of Endophthalmitis are:
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Exogenous Endophthalmitis
The most common cause of Exogenous Endophthalmitis is direct inoculation of bacteria, and less often fungus, in the course of surgery. Even though all surgery involves sterile technique, it is impossible to completely preclude the risk of infection. Often, the offending bacteria are thought to be normal flora residing on the eyelids. Postoperative endophthalmitis accounts for about 60% of endophthalmitis cases. Cataract extraction, which is the most common ophthalmologic procedure performed in the United States, carries about 0.1-0.3% risk of infection. The most common causative organisms are staphylococcus epidermidis, staphylococcus aureus, and streptococcus species. Infection can result from any penetrating surgery, including injections of intraocular medicines.Another cause of Exogenous Endophthalmitis is trauma. Anytime the eye is ruptured there is a risk that bacteria can enter the eye and cause infection. This risk is much greater if there is a foreign body in the eye such as wood, stone, dirt, or metal. In these cases, delay in seeking treatment greatly increases the risk of endophthalmitis. Common offending organisms in traumatic cases are bacillus cereus, staphylococcus, streptococcus, pseudomonas, Escherichia coli, and enterococcus.
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Endogenous Endophthalmitis
Endogenous Endophthalmitis is less common, representing about 2-15% of endophthalmitis cases. Any infection of the blood stream can carry microorganisms to the eye. Common sources include endocarditis, wound infections, infected indwelling catheter sites, and intravenous drug use. -
Non-Infectious Endophthalmitis
Non-infectious endophthalmitis is also characterized by severe inflammation in the eye. Sometimes this occurs when lens material is found outside of its protective capsule. This can occur when a mature cataract liquefies and leaks lens material or if some lens is left behind after cataract surgery. In addition, inflammation can occur in response to certain pharmacologic agents or to the preservatives added to their formulation.
Symptoms
Endophthalmitis typically causes fairly sudden decreased vision, pain, and eye redness. Other symptoms include light sensitivity, headache, and periocular inflammation. Sometimes, however, there is little pain or redness. Most cases of postoperative enophthalmitis occur within days of the surgery. Sometimes, more indolent organisms can cause chronic, low-grade inflammation or cause infection months after surgery. In endogenous cases the patient may have a fever or other symptoms related to the infectious source elsewhere in the body.
Examination &Testing
The diagnosis of endophthalmitis is made by clinical examination. Sometimes, the ophthalmologist cannot visualize the back of the eye because the inflammation is so severe in the front of the eye. In these cases, an ultrasound (or B-scan) can be used to image the back of the eye, including the vitreous cavity, retina and choroidal layers of the eye wall.
If endophthalmitis is suspected, it is important to inject strong antibiotics into the eye, specifically into the intravitreal space. This gets the antibiotics right where they will do the most good. Eye drops and oral antibiotics do not result in adequate intraocular concentrations of the antibiotics. Before injecting antibiotics, the doctor will want to take a sample of the eye fluid to send for a culture and Gram stain. These tests can help identify what organism is causing the infection. Infection with different bacteria and fungi can help the doctor know whether an infection will respond well to treatment. Tests can be performed to determine the sensitivity of the organisms to different antibiotics.
In cases of endogenous endophthalmitis without an identified source, the doctor will take a careful history asking about risk factors such as heart problems, diabetes, cancer, any cause of immunosuppresion such as AIDs or bone marrow transplant, presence of indwelling catheters, or intravenous drug use. Tests such as an echocardiogram, blood cultures, and urine cultures may be done to find the source of the infection. Fungal organisms are responsible for many cases of endogenous endophthalmitis.
What the Doctor Sees
When a doctor examines the patient, he or she will use a slit lamp which projects a bright light on and into the eye. Typical features of endophthalmitis include a red eye, corneal edema, and a dense collection of white blood cells that settle at the bottom of the front of the eye called a hypopyon. If it is possible to see through the dense inflammation in the anterior part of the eye, the doctor may also see white blood cells behind the lens in the posterior part of the eye.
Prognosis
The prognosis for visual recovery after endophthalmitis is variable. Patients who present early with less virulent organisms may do very well. Patients infected with very virulent organisms or after traumatic injury to the eye may have difficulty regaining much vision. In either case, the road to recovery is long, probably several weeks to months. The doctor will follow the patient frequently to make sure the infection is improving. It takes a long time for severe inflammation in the eye to clear up. The most important thing to do is to contact an eye doctor as soon as possible if any of the above symptoms occur, because injection of antibiotics should be done as promptly as possible.
Prevention
Aside from avoiding trauma and endogenous infections, there is nothing else that can be done to avoid endophthalmitis. All ocular surgery and injections are done with sterile technique, which usually includes betadine rinsing of the periocular skin, eyelashes, and conjunctiva. Sometimes patients with severe eyelash inflammation are asked to use lid scrubs in the days leading up to the surgery. It is important to follow the physician’s instructions in using antibiotic drops before and after surgery.
Treatment
The treatment of infectious endophthalmitis requires injection of intravitreal antibiotics. In this procedure, the doctor will numb the eye and prepare the eye in sterile fashion. The doctor will then take a very small needle and withdraw fluid from the eye. This fluid will be sent for testing. Then the doctor will usually inject two strong antibiotics (one for gram positive bacteria and one for gram negative bacteria) such as vancomycin and ceftazidime. If a fungus is suspected, the doctor might inject amphotericin. Some doctors may also inject steroid into the eye. Additional treatments include strong, fortified antibiotic drops every hour around the clock, oral or intravenous antibiotics, steroid drops, and a dilating drop for comfort. Often patients are admitted to the hospital; sometimes patients are followed daily as outpatients. In cases of endogenous endophthalmitis the source of the infection should be found and treated.
An important study called the Endophthalmitis Vitrectomy Study was conducted to determine which patients would benefit from vitrectomy surgery to clear out the inflammation inside the eye versus injection of antibiotics alone (without surgery). The study showed that injection of antibiotics alone was preferred in all but the most severe cases. Specifically, injection of antibiotics alone was recommended if visual acuity was hand motions or better. For patients with only light perception visual acuity, vitrectomy surgery could be considered. This study only considered endophthalmitis cases that were post-cataract surgery, not other causes of endophthalmitis.
The ophthalmologist may want to follow the patient daily for two to three days. Thereafter, visits can gradually become more spaced out as it is clear that the infection is subsiding. Many patients find that their vision becomes appreciably better, though not as good as before the infection began.
Endophthalmitis
Author: Allen C. Ho, M.D.
Andrew Lam, MD
