SCD, sickle cell trait may increase risk of diabetic eye disease: Study
Patients with diabetes and SCD or SCT more likely to have eye procedures
Sickle cell disease (SCD) and sickle cell trait (SCT) can increase the risk of eye diseases associated with diabetes mellitus, according to a recent study.
Findings indicated patients who had diabetes along with SCT or SCD were more likely to have procedures to treat eye disease and poorer overall vision than those who had diabetes alone.
“Individuals with [diabetes and sickle cell] represent a vulnerable population with a high burden of potential for health care morbidity,” researchers wrote.
The study, “Sickle Cell Trait or Sickle Cell Disease Associated with Increased Diabetic Retinopathy Risk,” was published in Ophthalmology Science.
Inherited gene mutation causes SCD
Individuals with SCD have mutations in the two copies of the beta-globin gene inherited from both parents, leading to the production of a defective form of hemoglobin, the protein that carries oxygen through the body. The faulty protein causes red blood cells, which are normally oval-shaped, to acquire a crescent-like shape. The misshaped cells tend to die prematurely and get trapped inside blood vessels, obstructing blood flow and leading to symptoms that may include pain crises.
When someone inherits one faulty copy of the beta-globin gene rather than two, they are said to have SCT. People with SCT generally do not show symptoms of SCD, but may still pass the disease-causing mutation on to their biological children.
SCD or SCT can cause eye damage, as can diabetes, which can ultimately lead to vision loss.
In people with diabetes, high blood sugar can damage blood vessels in the retina — a region at the back of the eye that contains light-sensitive cells that play a key role in vision — leading to a type of eye disease called diabetic retinopathy. Potential complications of diabetic retinopathy include proliferative diabetic retinopathy, an advanced form of the disease, and diabetic macular edema, which is caused by fluid buildup and swelling in the central part of the retina.
The relationship between SCD or SCT and diabetes is unclear, however, with some studies suggesting that their combined effect can worsen eye disease and others showing that it may lower that risk.
To investigate the relationship between sickle cell and diabetes, the research team used the IRIS Registry, the largest clinical registry of eye disease in the world.
The researchers identified 3,742 individuals in the registry who had been diagnosed with diabetes and SCD or SCT. They then randomly selected an equal number of individuals with diabetes, but without SCD or SCT, to be used as a control group.
Patients in the SCD or SCT group tended to be younger than those in the control group (mean of 53.5 vs. 63.4 years). The sickle cell group was also predominately composed of female and Black or African American individuals, while the control group had a more even sex and race distribution.
Diabetic eye disease more common in patients with SCD, SCT
Proliferative diabetic retinopathy was significantly more common in the group of patients with SCD or SCT than in the control group (37.1% vs. 8.4%). Likewise, rates of diabetic macular edema were significantly higher in the SCD or SCT group (31.9% vs 11.1%). Greater proportions of people with SCD or SCT also had undergone procedures to treat diabetic retinopathy and its complications.
Additional analyses indicated that patients in the SCD or SCT group were 7.37 times more likely to develop proliferative diabetic retinopathy, and 4.22 times more likely to develop diabetic macular edema than those in the control group.
The researchers also compared how well people in both groups could see details at a distance using a visual acuity score. A 20/20 score indicates normal eyesight, while lower scores represent worse eyesight. In both the left and right eyes, the group of patients with SCD or SCT had significantly lower visual acuity than those without SCD or SCT.
“The present findings contribute to our understanding of the relationship between [sickle cell and diabetes], demonstrating the additional burden of disease and intervention that [diabetes] patients may experience with a diagnosis of SCD or SCT carrier status,” the researchers wrote.
“Further research efforts may build on the findings of this retrospective study to expand our understanding of the relationship between [sickle cell and diabetes],” they wrote.
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