HIV/AIDS--Related Vision Loss
Any discussion of HIV/AIDS--related illness reminds us of the astonishing volley of attacks our bodies continually fend off. Healthy bodies usually prevail in these daily skirmishes with invaders. But an immune system compromised by human immunodeficiency virus (HIV) may be unable to defend itself.
We call the resulting infections opportunistic because they exploit the body's weakened state. The development of such infections is what marks the transition from HIV-positive status to a diagnosis of active acquired immunodeficiency syndrome (AIDS), sometimes called “full blown” AIDS.
Pathogens of every description can ransack the body of a person with HIV. Each organ is vulnerable to a particular set of infections. The lung, for instance, may be assailed by tuberculosis, mycobacteriosis, candidiasis, or other infections. Likewise, the eye is subject to a wide range of infections that may damage its structure or function, causing low vision or blindness.
Types of Infections
Cytomegalovirus (CMV) retinitis is inflammation of the retina caused by infection with a virus from the herpes family--La Cosa Nostra of infectious diseases (see the sections below on herpes zoster and herpes simplex). Most people have been exposed to CMV, and a healthy body is able to fight it off, no sweat. But when the immune system is compromised by HIV infection, chemotherapy, an autoimmune disorder such as rheumatoid arthritis, or some other challenge, it's no match.
About 15% to 40% of patients with advanced HIV disease in the United States develop CMV retinitis. Since the initiation of effective antiretroviral therapy, however, the rate has fallen by about 75%. Symptoms are subtle and may consist only of floaters and a sensation of seeing flashing lights. Immediate treatment is necessary to preserve vision.
Patients who have CMV retinitis are at risk for immune recovery uveitis when they begin antiretroviral therapy. As the first two words of its name suggest, this syndrome is a kind of immune system backlash. A complex antibody reaction can occur during recovery that causes the middle layer of the eye to swell, a condition called uveitis. Patients who have a low T cell count when they begin therapy or who have a relatively large area of the retina affected by CMV are at greater risk of developing immune recovery uveitis.
Toxoplasmosis is caused by a parasite transmitted to humans by eating contaminated, improperly cooked food. Transmission can also occur after direct contact with cat feces. HIV/AIDS patients with toxoplasmosis may develop inflammation of the choroid and retina that causes vision loss. Eye manifestations of toxoplasmosis include the following:
- Blurred vision
- Blind spots
- Sensitivity to light
Most of us think of tuberculosis as a lung disease, but it's caused by a bacillus (Mycobacterium tuberculosis) that can affect the bones and joints, skin, gastrointestinal system, genitourinary system, and other body organs and systems. In the eye, it can cause uveitis, an inflammatory condition associated with retinal detachment, glaucoma, cataracts, and other causes of low vision. Early diagnosis may prevent vision loss.
The person with ocular tuberculosis can have a range of symptoms:
- Blurry vision
- Red-green color blindness
- Blind spots in the center of the visual field
- Eye pain and light sensitivity
- Excessive tear production
Ocular tuberculosis is treated with an onslaught of powerful antibiotics. These medicines are sometimes given as a preventive measure to those with compromised immune systems.
Other common pathogens
Many other pathogens (viruses, bacteria, fungi, and other organisms that can cause infection) normally associated with sites elsewhere in the body can also take hold in the eye:
- Herpes zoster. Herpes zoster is the virus that causes chickenpox. In older adults and in those with immune system compromise, the virus is sometimes reactivated as the painful neurological disease known as “shingles.” In the eye, shingles can irritate the cornea, causing an infection. It may also cause inflammation of the optic nerve, retina, iris, and other structures. In addition, having a herpes zoster infection of the eye increases the risk of developing glaucoma.
- Herpes simplex. Herpes simplex is the virus that causes cold sores (type 1) and genital herpes (type 2). In the eye, the virus can stimulate inflammation of the cornea, eyelids, and conjunctiva. If the infection settles into the middle layers of the cornea, it can cause scarring that impairs vision. Symptoms include eye pain and redness, sensitivity to light, increased tear production, and a gritty sensation in the eye.
- Syphilis. Syphilis is a sexually transmitted infection (STI) cause by a parasite. The course of the disease is generally divided into three stages, and the ocular manifestations of syphilis usually occur during the second stage. The infected person may have a sore throat, fever, swollen lymph glands, or a rash, along with eye redness, blurred vision, and sensitivity to light. Inside the eye, the infection causes inflammation of the iris and other structures of the middle eye.
Ocular toxic or allergic drug reactions
Allergic reactions to medications taken to treat HIV/AIDS, particularly sulfa antibiotics, can cause a severe allergic reaction throughout the body. Such a reaction may lead to corneal scarring and consequent vision loss.
Some kinds of infections that can take up residence in the eye, such as the sinister-sounding Cryptococcus neoformans, tend not to take hold until the patient is already ill with other opportunistic infections. Thus the development of these late-stage eye infections may be a grave sign that the patient's immune system is failing.
Risk factors and treatment
The goal of therapy for HIV-positive patients is to keep the virus from replicating--that is, making copies of itself--in the body. Drugs that accomplish this are called antiretroviral agents. They reduce the viral load, or the amount of virus in the bloodstream, allowing the immune system to recover and T cell counts to increase.
The single most potent factor in reducing the risk of HIV/AIDS--related vision loss has been the introduction of highly active antiretroviral therapy (HAART) for the treatment of HIV/AIDS. HAART is a combination of antiretroviral agents that has markedly reduced the rate of visual complications, especially CMV, among HIV-positive patients, prompting some scientists to speculate that viral load and clinical stage correlate with the likelihood of vision loss.
Opportunistic infections in people with HIV/AIDS must be diagnosed and treated on an individual basis. They may have a common site--the eye--but each infection is as different as the specific pathogen that caused it.
Vision rehabilitation services are available for people with HIV/AIDS--related low vision. Such programs help people adapt to visual impairment and make decisions about their care, and they teach friends and loved ones in caregiver roles how to help effectively. Teaching hospitals, community centers, senior centers, and government agencies often offer such services.