Mutating cells and invasion by pathogens triggers inflammatory responses in the body. Inflammation consists of a series of events involving cytokines (immune messages), other immune factors, and circulating white blood cells. Uncontrolled levels of inflammation damages healthy tissues and organs.
Excessive inflammation of the eyes may result in sight-threatening condition.
Uveitis describes a group of eye inflammatory diseases. Symptoms can develop gradually over a few days, or occur suddenly. Symptoms may include: photophobia (sensitivity to light), cloudy or blurred vision, increased floaters, difficulty in vision focus, headaches, “red eye” with pain ranging from a mild ache to intense pain, and loss of peripheral vision (ability to see objects at the side of one’s field of vision). Severe uveitis may lead to permanent damage to vision.
Many cases of eye tissue inflammation are “idiopathic”, i.e., without a known trigger. Some clinicians suggest that uveitis is caused by: a) autoimmune responses in which the body’s immune system mistakenly targets and attacks its own eye tissues, b) infections or cancer, c) trauma to the eye, or d) exposure to toxins. Uveitis is more likely to occur in individuals that have other immune and inflammatory conditions.
Ebola and Uveitis
Two months after an American physician was treated for Ebola, and despite the fact that the virus was no longer detectable in his blood, there were high levels of Ebola virus in his eye. His eye infection was accompanied by an intense inflammatory reaction, uveitis. After much effort, the physician was successfully treated and thankfully did not lose his sight.
In a study of 85 Ebola Virus Disease survivors in Sierra Leone, 40% reported that they had some sort of “eye problem”. (It is not known whether they also had uveitits.)
Retinitis pigmentosa is a genetic disorder in which the light-sensitive retina, the “screen” at the back of the eye that captures images, becomes damaged . Its photoreceptors, rods and cones, begin to die off resulting in a loss of vision. This condition may end in blindness.
There are conflicting opinions as to whether inflammation plays a major role in this disease.
One study that support the contention that immune responses are involved in retinitis pigmentosa measured the levels of TNF-alpha. TNF-alpha is a cytokine, that among other functions, helps regulate immunological responses. Depending on when and how much of the cytokine is produced , TNF-alpha may be pro-inflammatory (initiate inflammation), or anti-inflammatory (inhibit inflammation). In animals with uveitis-like conditions, the levels of TNF-alpha in the eye are increased between 5-10 fold over control animals.
Also, in retinitis pigmentosa, immune white blood cells are attracted to the retina, perhaps to clean up debris from dying cells. Some investigators suggest that when these immune cells are overly stimulated, they initiate an autoimmune response, destroying other light-sensing centers in the retina.
Immune Homeostasis, Immune Balance
Immune inflammation is essential to defend the body against cancerous cells and invading microorganisms. However, the appropriate levels of “protective” cytokines are needed to balance the “destructive” cytokines produced in the eye so that it can maintain immune homeostasis, immune balance. Unchecked inflammation results in tissue damage and an inability of the body to mount stable and proper immune responses in the face of various challenges.
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