What is Sickle Cell Retinopathy?
Sickle cell retinopathy is a major ocular complication of sickle cell disease (SCD), which causes permanent loss of vision. Sickle cell retinopathy is present in some patients with sickle cell disease.
Sickle cell disease or sickle cell anemia is a group of inherited red blood cell disorders. All major organs can be affected by sickle cell disease. The liver, heart, kidneys, gallbladder, bones, joints, and eyes can suffer damage from the abnormal function of the sickle cells and their inability to flow through the small blood vessels correctly.
Genotypes – Sickle cell disease comprises several different forms of genetically mutated hemoglobin. Sickle cell disease happens because of an inherited genetic mutation called an autosomal recessive pattern. Autosomal means two copies of the mutated gene are needed for the disease to become apparent in an individual.
It’s possible to carry one copy of the gene, known as sickle cell trait. These genetic mutations affect hemoglobin, one of the main molecules of the red blood cells responsible for transporting oxygen to all the parts of our body.
Sickle cell disease and the eye
Sickle cell disease not only affects any part of the body, but it also affects any part of the eye. Notably, sickle cell anemia can cause damage because of defective oxygen transport of the red blood cells. In conditions of low oxygenation, it causes mutated hemoglobin to polymerize, ultimately altering the shape of the red blood cell to the characteristic sickle shape.
Sickle cell disease affects tissues that are particularly vulnerable because they have a high oxygen demand, such as the retina, the nerve tissue in the back lining of the eye, is a very high oxygen-demanding tissue.
Sickle cell disease can manifest vision loss most commonly by its effects on the retina. Retinal changes can show up as a lack of blood flow, called retinal ischemia. If that condition becomes widespread and severe enough, abnormal new blood vessels can form, and that’s called neovascularization.
These new blood vessels are dangerous because they can burst and bleed, threatening vision and eyesight. The burst blood vessels can turn into scar tissue and pull on the retina, and that causes separation of the retinal layers called retinal detachment, which is a sight-threatening urgency and requires surgery to repair.
Screening for sickle cell disease
Because this is a genetically determined disease, doctors can screen for sickle cell disease and sickle cell trait. Since the early 2000s, children are screened at birth. Newborn screening has been instituted in all 50 states and U.S territories for the sickle cell gene.
Even though hospitals screen these children, many patients with late-onset disease are still unaware that they have sickle cell disease or sickle cell trait.
Characteristics that define patients with sickle cell retinopathy
When examining patients with sickle cell disease to determine their risk of sickle cell retinopathy, the retina specialist will look at; the severity of sickle cell disease, how much it affects the body, how frequently the person gets symptoms of the disease.
An essential indicator is if there is pain when oxygen doesn’t get to the tissues. These episodes may come and go and can cause enough severe pain to be hospitalized, called sickle cell pain crises.
Depending on the genotype of the patient, much of the overall bodily disease can be determined. People who have the homozygous trait gene (two copies of the same abnormal hemoglobin gene) tend to be more affected systemically.
In this case, they may have more vaso-occlusive pain crises, more risk of lung problems, called acute chest syndrome, bone problems, vascular necrosis, where the bone becomes infarcted (tissue death due to inadequate blood supply). They may also have strokes or kidney problems as well.
Interestingly enough, in sickle cell retinopathy, where there are abnormal retinal blood vessels, the severity of the abnormal blood vessels is much lower in patients with homozygous, two copies of the same hemoglobin mutation. The risk of severe eye disease is as low as 15 to 20 percent in those patients with homozygous hemoglobin mutations.
Individuals with a heterozygous mutation (two different mutations) often have minor systemic problems or pain crises hospitalizations. However, their eye disease can be much more likely to progress into the severe stages of retinopathy. The patients with the heterozygous mutations often are the ones that can present suddenly to the retina specialist.
A patient may have a hemorrhage in the eye or a detached retina without having systemic problems or pain crises. Patients with heterozygous mutations may feel well when they’re active and may not even realize they have the hemoglobin mutation. Depending on the gene, it can be very different how sickle cell retinopathy presents.
Homozygous patients with a history of crisis are plugged into the system well just by the severity of their systemic disease. But those that present with sickle cell trait often aren’t aware of that, even if there’s a family history and may not have ever seen a retina specialist.
It is recommended that patients be screened for sickle cell retinopathy by a retina specialist starting at age ten and every one to two years afterward, depending on how severe the disease is.
Symptoms of sickle cell retinopathy
Patients with sickle cell disease that have affected the retina may not have any symptoms depending on the occlusion severity. When symptoms present, patients describe:
- Blind spots
- Sudden onset of floaters or blurred vision
- Flashes of light
- Loss of side vision or curtains
Patients may see flashes, floaters, or dark shadows, which may indicate vitreoretinal traction or detachment.
Nonproliferative and proliferative retinopathy
Sickle cell retinopathy is one end-organ manifestation of the disease. Similar to diabetic eye disease, both nonproliferative and proliferative forms occur. Proliferative disease is associated with more significant visual dysfunction.
Proliferative sickle cell retinopathy causes visual loss primarily with vitreous hemorrhage and retinal detachment. Fortunately, the incidence of proliferative disease is low. The hallmark of the disease is neovascularization (natural formation of new blood vessels).
See your Phoenix retina specialists now!
Sickle cell retinopathy can go undetected for years without an eye exam. Schedule an appointment with Arizona Retinal Specialists today. Early detection could save your vision. Call 623 – 474 – 3937 (EYES).