Many of us have a virus known as cytomegalovirus (CMV) in our bodies. Usually, the body’s immune system or natural immunity prevents the virus from causing any complications. Nevertheless, if for some reason, our body’s mechanisms for defense in case of infections are severely weakened, the cytomegalovirus can be responsible for causing serious diseases. This is often noticed in patients with AIDS.
In such patients, the typical way for CMV to cause any kind of damage is by attacking the retina, which is the light-sensitive part of the eye. This virus causes inflammation and bleeding and eventually damages the retina and may result in blindness. This is known as CMV retinitis.
The bright side is that if the respective patient receives the appropriate combination of therapies, the probability of getting Cytomegalovirus retinitis is scaled down. However, for treating CMV retinitis, medical therapy is available. Several ways of delivering medicines to treat Cytomegalovirus (CMV) retinitis are summarized below:
- Daily injections used as an IV infusion
- A small implant in the back of the eye that delivers a medicine via a timed-release mechanism
- Oral medicine is taken several times daily
- Monthly injections used into the white area of the eye
The nature of the product is directly associated with the route of administration. Injections into the white part of the eye are not as knotty as most of us might think. After a local anesthetic has been used (a couple of eye drops), the patient normally feels little, if any, pain or irritation. The procedure is easy and fast and enables the patient to catch their periodic/regular activities with a bit of inconvenience. It helps avoid several whole-body adverse reactions that are frequently caused when products used for treating CMV retinitis are given orally (by mouth) or by direct injection into the blood.
All of the various medicines and their methods of delivery mentioned above have both advantages and disadvantages. The respective patient will need to discuss available treatment options with his/her health specialist.
What is Cytomegalovirus (CMV) Retinitis?
Cytomegalovirus (CMV) retinitis is the most common opportunistic infection of the eye, usually occurring in acquired immunodeficiency syndrome (AIDS)-positive patients with CD4 counts <50 cells/µl. This viral eye infection can be serious and even cause blindness.
CMV falls under the member of the herpesvirus family. It is responsible for infecting the retina, the light-sensitive layer of tissue in the back of the human eye. Retina helps convert light that hits the eye into electrical signals so that our brain can interpret the image. Humans can’t have perfect vision without a healthy retina.
CMV (Cytomegalovirus) is a common virus. Approx half of adult individuals get it by the time they turn 40. The virus usually doesn’t cause complications in healthy individuals. But if your immune system is weakened due to HIV, the virus can progress, invade and infect the eye. At the same time, the virus itself can suppress our immune system.
The virus is responsible for infecting and damaging cells in the retina, which causes scars to form. It also may prevent blood from supplying the eyes with oxygen. Individuals can catch this virus from anyone who has it through body fluids, including blood, saliva, semen, and tears.
Cytomegalovirus retinitis can be responsible for causing retinal detachment. This is when our retina peels away from the blood vessels that feed it. Without treatment, this disease can cost us our eyesight. Starting on antiviral medication promptly after the diagnosis can help save vision.
Clinical Features of CMV Retinitis
Individuals with Cytomegalovirus retinitis present with unilateral or bilateral visual loss or floaters, without any pain. It is typically minimal or no vitritis and a clear view of the retina. CMV retinitis has three clinical forms, which are as follows:
- Fulminant: There are dense, white, well-demarcated parts of retinal necrosis with retinal hemorrhages, often seen as a “Pizza Pie” appearance. It tends to occur along the vascular arcades and over weeks gradually extends along the vessels in a ‘Bushfire-like’ pattern. It may also affect the optic nerve head.
- Indolent: Mild, granular opacification of the retina with some retinal hemorrhages, which occurs in the retinal periphery and progresses gradually.
- Frosted branch angiitis: It is the least common form, in which perivascular exudation is the most obvious feature.
Symptoms of CMV Retinitis
Initially, we may not notice any signs. Manifestations start in one eye. Progressively, the virus can also affect the other eye. Cytomegalovirus retinitis is most often diagnosed between ages 20 and 50. The disease may cause:
- Flashing lights
- Light sensitivity
- Blurry vision/eyesight
- Blind spots in the middle of the vision
- Specks, dots, or lines known as floaters in vision
- Shadows along the sides of the view (peripheral vision)
There are some other eye diseases that can cause similar signs/symptoms. In case of any vision complications, get in touch with your eye specialist right away.
A specialist will give drops to widen the pupils and then assess the retina. Eye specialists may also remove a small sample of fluid from the eye in order to test for the virus. It’s recommended that individuals with HIV get vision checkups every 90 days.
How Cytomegalovirus (CMV) is Spread?
Cytomegalovirus (CMV) infection can spread in several ways. It can be passed from individual to individuals, usually through close contact with urine, breast milk, saliva, or other body fluid, or through sexual intercourse with someone with CMV infection.
An individual can have a primary infection (CMV infection for the first time), or a return of a previous Cytomegalovirus infection (reactivation), or may have another infection with a different strain of the virus.
Cytomegalovirus can also be transmitted from one person to another during organ transplants and blood transfusions.
Babies can also catch the infection during delivery and from breast milk, but these babies have few, if any, signs or symptoms or complications from the infection.
Congenital CMV: Those who become infected with CMV or Cytomegalovirus while pregnant may pass the virus to their unborn baby (congenital CMV).
If an unborn child is infected with the virus, some of these childs may develop severe health complications such as developmental delay, hearing loss or learning issues. The CMV infection during pregnancy may also lead to stillbirth or infant death. Congenital Cytomegalovirus is the most common infective cause of congenital hearing loss.
Incubation Period: Incubation period, or time between becoming infected and developing symptoms is 3 to 12 weeks.
Infectious period: Infectious period is time during which an infected individual can infect others. The virus often exists for months in saliva or urine following infection in children and adults.
Infants and immunosuppressed adult individuals can shed the CMV virus for months to years following infection or reactivation of infection.
Diagnosis of CMV Retinitis
The diagnosis of CMV Retinitis is typically made clinically through dilated fundoscopy. Most common differential diagnoses include necrotising herpetic retinitis caused by varicella zoster virus or herpes simplex virus, as well as toxoplasmosis gondii and syphilis. If the clinical diagnosis is not certain, then syphilis serology and an aqueous or vitreous sample forwarded for PCR for CMV, VZV, HSV and Toxoplasma gondii is helpful. If the status of human immunodeficiency virus is not known, then perform HIV serology, CD4 count and viral load. Cytomegalovirus retinitis is an acquired immunodeficiency syndrome (AIDS)-defining disease in HIV positive individuals.
Prevention of CMV Retinitis
A decisive way to avoid Cytomegalovirus retinitis is to keep your human immunodeficiency virus under control. That means use your highly active antiretroviral therapy (HAART) medicines on a regular basis. HAART helps lower the existence of HIV in the body. That makes the immune system stronger so it can effectively fight off invaders like Cytomegalovirus.
Individual’s blood may be tested for their CD4 count. CD4 is a sort of immune cell. A low immune cell or CD4 level may be an indication of weakened immunity.
Treatment and Prognosis of CMV Retinitis
Approximately, up to 95% of individuals with Cytomegalovirus retinitis do well with the help of treatment. Antiviral medicinal products include ganciclovir (Cymevene, Vitrasert, Cytovene, Zirgan), valganciclovir (Valcyte), foscarnet (Foscavir), and cidofovir (Vistide) are effective. These medications can be taken in a few ways:
- In form of a pill
- In form of an injection into a vein
- In form of an injection into the eye
- Through an implant in the eye that gradually releases the medication over time
Cytomegalovirus can grow resistant to medicines the longer we take them. So the purpose is to clear up the retinitis as rapidly as possible. If CMV damages the retina, we might need laser surgery in order to fix the weakened parts.
As Cytomegalovirus is an opportunistic infection, if the HIV isn’t well managed (have a CD4 count below 50), we’re extremely likely to catch CMV retinitis again.
Those with CMV retinitis must be managed by a multidisciplinary team including a physician or infectious disease specialist and an ophthalmologist. Anti-CMV therapy (systemic and/or intravitreal) is given by the ophthalmologist, whilst the infectious disease specialist or physician should start antiretroviral treatment (ART) and help with monitoring and treatment of any adverse reactions of the medicine.
Systemic anti-CMV Treatment: Oral Valcyte-valganciclovir (induction dose 900 mg twice in day for 14 to 21 days, followed by the maintenance dose of 900 mg daily) is the choice of CMV treatment because of its ease of administration. The disadvantage of this treatment is that monitoring for renal toxicity and bone marrow suppression is required routinely in order to detect side effects. The drug is also expensive and does not exist in all centers.
Intravenous ganciclovir (induction dose 5 mg per kg every 12 hours for 14 to 21 days, followed by maintenance dose of 5 mg/kg daily) can be considered as an alternative, but this needs inpatient treatment for intravenous therapy. Those who have sight-threatening Cytomegalovirus retinitis (infection within 1 disc diameter of the fovea or optic disc) should also take weekly intravitreal ganciclovir injections for the initial 2 weeks.
Intravitreal anti-CMV Treatment: Weekly injections of intravitreal ganciclovir (2.5 mg in 0.1 mL) into the affected eye/s is the therapy of choice in several resource-limited units. The drug is not expensive and can be given as an outpatient treatment. The disadvantages of this therapy are that it does not help in protecting the fellow eye or treating systemic CMV infection. This treatment requires trained and highly experienced clinicians. It carries the low, but potentially sight-threatening risks such as endophthalmitis.
Antiretroviral Treatment (ART): Ideally, antiretroviral treatment should be started 2 weeks after starting CMV treatment in order to scale down the risk/probability of immune recovery uveitis, but it may be more apt to start both at the same time in resource-limited settings.
Foscarnet (Foscavir) is typically considered as a 2’nd-line therapy for treating CMV retinitis, specifically for CMV retinitis that is resistant to medications ganciclovir or valganciclovir, or for those who cannot be treated with medicine ganciclovir because of dose-limiting leukopenia or neutropenia. Induction therapy usually consists of 180 mg per kg total daily and 90 mg/kg daily for maintenance, ranging from some weeks to months, administered intravenously. It has been noticed that in those with CMV retinitis and HIV/AIDS, foscarnet offers a survival benefit over therapy with IV ganciclovir. However, a potential risk of this therapy is related to nephrotoxicity and electrolyte abnormalities.
Cidofovir (Vistide) is another antiviral medication given intravenously that has promising activity against CMV. A randomized control trial compared the treatment of cidofovir to oral/intravitreal ganciclovir treatment and found that both groups had identical efficacy in treating Cytomegalovirus retinitis. The use of cidofovir is also limited by its side effects, such as ocular inflammation, nephrotoxicity, ocular hypotony, and neutropenia. Due to this, probenecid is used prior to and after the infusion of cidofovir, as well as IV fluids, to scale down renal toxicity.
NOTE: The piece of content on this site is for informational purposes only, and should not be taken as professional medical advice.