Causes and treatments of CMV retinitis
Cytomegalovirus (CMV) retinitis is an eye disease that closely relates to Acquired Immunodeficiency Syndrome (AIDS). CMV is a DNA virus in the family Herpesviridae and it can produce large cells containing nuclear and cytoplasmic inclusions. This virus can be found in everyone but a normal immune system can fight against is and prevent related damage. However, an ineffective immune system can not avoid the development of CMV retinitis, which always invades the retina and affects the light-sensitive receptors, leading to acuity reduction and peripheral vision decrease. Without proper treatment, a detached retina and blindness can be caused within two to six months.
The link between CMV and the immune system
Statistics show that 80% of adults can protect themselves from the danger of CMV, which is a common virus. It is widely known that people with AIDS have an ineffective immune system, so that they can not fight against CMV. In the past, CMV retinitis bothered a quarter of AIDS patients, whereas now this rate has been lowered to 5%, due to the use of potent combination of drugs. CMV can also be found on people with weakened or suppressed immune system at a lower rate. For example, individuals who are undergoing chemotherapy or a bone marrow transplant also have fewer antibodies to CMV.
How CMV retinitis causes ocular damage
By damaging the macula of the retina, CMV retinitis can cause vision loss to different degrees. Currently, there are a huge number of researchers who are searching out the reason for the progression of CMV retinitis, involving mechanisms of cell death. Present results show that CMV starts at the outer layer of the retina, and then invades into deeper layers. Symptoms caused by this ocular problem include blurred vision, eye pain, photophobia, redness and most seriously blindness. At first, only one eye will be affected.
Highly active antiretroviral therapy is indirect treatment
For CMV retinitis treatment, AIDS patients should visit a retina specialist every two to four weeks for primary disease control. During the following days, regular doctor’s visit every three months is enough. The most thorough treatment is the highly active antiretroviral therapy (HAART), which cures CMV retinitis from its root by suppressing the HIV. HAART can improve the immune system within a short period, which in turn controls the development of CMV retinitis. Certain patients may react to HAART abnormally and develop immune recovery uveitis, which is a severe inflammation.
Some drugs can slow down directly CMV retinitis progression
As described above, the HAART treats CMV retinitis by improving the immune system. In this sense, it is an indirect treatment. Yet there are also a couple of drugs that deal with CMV retinitis directly, including ganciclovir, foscarnet and cidofovir. Ganciclovir is available in forms of pill, intravenous infusion and intravitreal implant named Vitrasert. Accompanied by certain side effects that are to a certain degree unavoidable, all of these drugs are capable of slowing down CMV retinitis progression.