Increased Blood Flow Resistance in Eye Arteries May Explain Ophthalmological Symptoms in Sickle Cell Disease
Patients with sickle-cell anemia have more eye blood flow resistance than those without the disease — a symptom closely linked to hemolysis, or rupture of red blood cells. This can lead to a better understanding of the disease as well as improved classification and care for sickle-cell patients.
The Brazilian study, “Doppler velocimetry of the orbital arteries in patients with sickle-cell anemia: relationship with biomarkers of hemolysis,” appeared in the journal Radiologia Brasileira.
Sickle cell anemia, also known as homozygous sickle-cell disease (HbSS), is characterized by abnormal production of hemoglobin S. This deficiency leads to cellular rigidity of the red blood cells, which reduces blood flow and, ultimately, serious tissue damage.
Deficient blood flow can affect virtually all tissues. The most common and relevant eye symptom among HbSS patients involves the retina, with formation of new vessels leading to hemorrhage and retinal detachment.
It is not yet clear to what extent HbSS damages eye tissues. To find out, researchers from the Universidade Federal de Sergipe in northeastern Brazil evaluated the blood flow of several eye vessels using a noninvasive method called Doppler ultrasound. The study involved 105 subjects, including 73 patients with HbSS and 32 age- and gender-matched healthy participants.
HbSS patients were shown to have increased blood flow velocity in the ophthalmic artery and reduced velocity in the central retina artery, compared to the control group. In addition, the study group also presented increased eye vascular resistance, measured by the resistance index (RI) and pulsatility index (PI) of both arteries. Researchers evaluated if these eye vascular alterations were related to any known biomarkers of the disease.
They found that overall, both increased levels of reticulocytes and low hemoglobin levels were associated with higher eye vascular resistance. Researchers did not found any association with other disease biomarkers, such as lactate dehydrogenase or bilirubin values.
“To our knowledge, there have been no studies explaining why RI and PI correlate only with some biomarkers of hemolysis,” the authors wrote. “This is an interesting starting point for additional investigations.”
According to the study, HbSS is most common in communities consisting largely of people of African descent. Some 2,500 children are born annually with HbSS in Brazil. Just over half of Brazil’s population is considered non-white, and between 1 and 6 percent of these people reportedly have HbSS.