June 19th is World Sickle Cell Day. Sickle cell disease (SCD) is a genetic blood disorder that affects millions of children and adults across the globe. Those with this disease can spend their days fighting exhaustion, often missing school and sports for hospital visits. Adults, too, must schedule their lives around the monthly transfusions that keep them under medical care for an entire day.
SCD is a common genetic disease affecting the blood: a mutation in the HBB gene creates abnormal hemoglobin, which usually resembles a crescent or sickle shape. The mutated configuration of these cells causes red blood cells to be rigid, sticky, and misshapen. Due to this shape, they can block blood vessels, lead to intense pain, hypertension, and swelling. Additionally, the cells are not fully capable of transporting oxygen or travelling through the bloodstream, causing those with sickle cell disease to feel fatigued most of the time.
Sickle cell disease is typically diagnosed in childhood. Children inherit the recessive trait if both their parents are carriers of the mutated gene. Individuals who have the recessive gene sometimes have some sickle cell hemoglobin in their bloodstream, but not enough to cause problems or symptoms. They will never develop sickle cell disease, but there is a chance that they could pass it on to their children: this is known as the sickle cell trait.
Sickle cells break apart easily and die much earlier than typical red blood cells. These cells would normally last for about 120 days, but in a patient with SCD, they only last for 10 to 20 days. This results in a lack of oxygen and a shortage of red blood cells, making the patient tired and anemic. Due to the lack of oxygen and red blood cells, sickle cell disease can stunt the growth of babies and kids, or delay puberty in teens. This disease can also damage major organs, creates a higher risk of infection, and vision complications.
For more information on sickle cell disease, read our blog World Sickle Cell Day: The Disease and Your Vision
Those suffering from SCD can have a variety of complications in their eyes due to the increased thickness, a lack of oxygen, and excessive acid in the blood. Jaundice is a common side effect, causing the whites of the eyes to look yellowish. Patients with sickle cell disease can be more prone to developing cataracts at a younger age. While cataracts usually form in those over the age of 60, those with sickle cell disease can develop this disorder as early as in their 30s. Sickle cell patients can also be at risk of developing iris atrophy, retinal thinning, and corkscrew conjunctival blood vessels.
The biggest ocular risk for those with sickle cell disease is vascular occlusion, or a blockage of a blood vessel. These blockages can happen anywhere in the body, including the conjunctiva (white part of the eye and extending onto the inside surfaces of the lid), the iris, and the retina. Retinal vascular occlusion can cause fluid to build up in the retina, causing swelling. If the swelling is in a central vein, we call it central retinal vein occlusion, or CRVO; if the swelling occurs in a smaller vein, it is known as branch retinal vein occlusion, or BRVO.
This ophthalmologic complication is the most prevalent in sickle cell disease, occurring when the sickle-shaped cells stop flowing through the vessels and instead become stuck on each other, blocking the flow of blood through narrow vessels. A blockage like this tear the vessel wall, causing blood to leak into the retina. The outcome of retinopathy can range from a discolouration of the retina without any effect on the eyesight to significant retinal damage or detachment, which could lead to vision loss.
Proliferative sickle cell retinopathy is a more advanced form of this eye disease. When retinopathy begins to break down the blood vessels in the retina, the body attempts to create new ones. These new blood vessels are abnormal, or weaker than the originals, causing them to break down and leak fluid into the retina. This causes clouded vision, scar tissue, and, in some cases, retinal detachment or damage to the optic nerve.
As with any eye condition, early detection is the key to maintaining healthy eyesight. Regular exams look deeply into the health of your blood vessels, retinas, optic nerve, and vision. Any retinal vascular changes can be assessed and treated before they become a permanent problem.
To learn more about living with sickle cell or to get involved in improving the lives of those with this disease, visit the Sickle Cell Disease Association of Canada. If you have questions about how sickle cell affects your vision and ocular health, talk to a doctor at your local Visique.