Sickle Cell Disease (SCD) is a genetic blood disorder that affects the shape and function of red blood cells, which are responsible for carrying oxygen throughout the body. Healthy red blood cells are flexible and disk-shaped. In SCD, a mutated hemoglobin causes them to become rigid, sticky, and crescent-shaped, resembling a sickle. This change in cell structure leads to numerous health complications, one of the most visible being the yellowing of the eyes. This symptom is a direct consequence of the disease’s impact on the body.
The Link Between Sickle Cell Disease and Jaundice
Sickle cell disease definitively causes the eyes to turn yellow; this symptom is known medically as jaundice. Jaundice causes a yellowish discoloration of the skin and, most noticeably, the whites of the eyes (the sclera). This yellow tint is caused by the accumulation of a yellowish pigment in the bloodstream called bilirubin. Bilirubin is a natural byproduct of the body’s process for recycling old or damaged red blood cells. In people with SCD, the continuous and rapid destruction of sickled cells leads to a chronic overproduction of this pigment. This constant influx of bilirubin overwhelms the liver’s capacity to process and excrete it efficiently. While jaundice is a common sign of SCD, its appearance can fluctuate, ranging from persistent, low-level yellowing to more intense discoloration during a painful crisis or when complications like liver issues or gallstones arise.
How Sickling Causes Bilirubin Buildup
The mechanism behind the bilirubin buildup begins with the premature destruction of the abnormal red blood cells, a process called hemolysis. Unlike healthy red blood cells, which circulate for approximately 120 days, sickled cells have a drastically reduced lifespan, often surviving for only 10 to 20 days before breaking apart. This rapid turnover significantly increases the amount of material the body must process. When a sickled red blood cell ruptures, it releases its contents, primarily hemoglobin, into the bloodstream. Specialized cells then capture this free hemoglobin and convert it into unconjugated bilirubin. The liver normally takes this unconjugated bilirubin, processes it into a conjugated form, and excretes it via bile. In SCD, the sheer volume of bilirubin exceeds the liver’s ability to keep pace with the conversion and excretion process, leading to hyperbilirubinemia. This excess bilirubin then deposits in various tissues, causing the characteristic yellowing observed in the eyes and skin.
Other Eye Complications of Sickle Cell Disease
Beyond the cosmetic symptom of jaundice, the abnormal red blood cells of SCD can cause vision complications by affecting the blood vessels within the eye. The most significant of these is Sickle Cell Retinopathy (SCR), which results from the sickled cells blocking the tiny blood vessels that supply the retina. This blockage, known as vaso-occlusion, deprives areas of the retina of oxygen and nutrients, leading to tissue damage and ischemia.
SCR can manifest in two main forms: non-proliferative and proliferative. The non-proliferative form involves localized vessel damage and minor hemorrhages, which often cause no noticeable vision symptoms. The more concerning stage is Proliferative Sickle Cell Retinopathy (PSR), where the oxygen-starved retina attempts to compensate by growing new, fragile blood vessels. These abnormal vessels often form distinctive networks described as “sea fans” on the outer edges of the retina. Because they are weak, these new vessels can easily rupture, leading to a vitreous hemorrhage—bleeding into the jelly-like substance that fills the eye. The subsequent scarring can cause the retina to be pulled away from the back of the eye, resulting in a retinal detachment and permanent vision loss.
Monitoring Eye Health in Sickle Cell Patients
Given the risk of serious complications like Proliferative Sickle Cell Retinopathy, proactive monitoring of eye health is an important component of SCD management. Since the early stages of retinopathy are often asymptomatic, regular, comprehensive eye exams are required even if a patient reports no vision problems. The American Academy of Ophthalmology recommends that SCD patients undergo a dilated funduscopic examination every one to two years, starting around age ten. These examinations are typically performed by an ophthalmologist or retina specialist who can inspect the peripheral retina for signs of vessel damage or “sea fan” growth. Early detection allows for timely intervention. For patients who develop PSR, treatments such as laser photocoagulation can be used to destroy the abnormal, fragile vessels and reduce the risk of bleeding and detachment.