September 2009

 

OPHTHALMOLOGY NEWS

 

The sickle cell factor


by Matt Young EyeWorld Contributing Editor

   

Authors of a study in the January 2009 issue of Medicine & Science in Sports & Exercise concluded that, “SCT [sickle cell trait] status could be another genetic risk factor for severe ocular complications, particularly when severe exercise is performed in extreme climatic conditions.”

The conclusion came at the heels of this case report in which central retinal vein occlusion (CRVO) occurred during protracted, intense exercise that led to neovascular glaucoma and blindness in a sportsman with SCT. “Because SCT carriers are often marked by coagulation activity imbalance, blood rheological disorders and abnormalities in vascular adhesion processes both at rest and in response to exercise, we propose that blood and vascular dysfunctions might have contributed to the occurrence of this adverse event,” according to study co-author Philippe Connes, Ph.D., Department of Physiology, University of the French West Indies, Pointe-à-Pitre, Guadeloupe.

A taxing race

After an intense cycling race of 138 km in mountainous, humid terrain, a 26-year-old Afro-Caribbean man was admitted to an ophthalmology department in Guadeloupe.

He was thirsty and had a sudden loss of vision in the left eye to 6/20. Intraocular pressure was normal, but he also suffered from CRVO with massive retinal hemorrhage.

Patient history revealed he had experienced a loss of vision two months earlier, though vision spontaneously recovered then. He also was an SCT carrier. Cardiovascular analysis found four thrombi in the left atrium.

While the department of ophthalmology prescribed troxerutin (Veinamitol, Wockhardt, Mumbai, India) and acetylsalicylic acid (Kardegic, Sanofi-aventis, Paris), cardiologists administered antivitamin K to treat the left atrial thrombi. Having ignored his doctors’ instructions not to exercise, the patient returned a month later with headache, nausea, vomiting, and eye pain and blindness in the left eye. He had been weight lifting when the new medical conditions surfaced. “Biomicroscopic exam demonstrated important iris rubeosis and neovascular glaucoma with corneal edema,” Dr. Connes reported. “Despite anticoagulation medication, a new transesophageal echocardiogram performed [three days] later revealed two remaining thrombi in the left atrium suggesting that blood coagulation disturbances were still persistent.”

Although the patient was again thoroughly treated and his intraocular pressure is now stabilized, the left eye still has total retinal detachment and visual acuity limited to weak luminous perception. “DNA analysis revealed that the patient did not carry any of these genetic risk factors for retinal vascular occlusion and thrombotic event,” Dr. Connes reported.

SCT: benign or not?

If Dr. Connes’ conclusions are accurate, this case suggests SCT is not so benign after all, at least when it comes to ophthalmic complications. “Several studies have reported ocular complications in SCT, but these complications have usually been described as the consequence of traumatic hyphema,” Dr. Connes reported. “Ophthalmologists therefore consider SCT as a benign condition compared with sickle cell anemia (SS) or hemoglobin SC disease. However, this issue is still debated because several reports suggest that SCT could be viewed as a potentially dangerous disorder, particularly in response to prolonged and intense exercise.”

Case reports involving exercise-related sudden death among persons with SCT have even surfaced. Clearly, this cyclist’s case falls under the umbrella of intense exercise. It also jibes with another recent report suggesting that impaired blood rheology is a risk factor for CRVO, Dr. Connes noted. “Exercise is known to further impair blood rheology in SCT carriers due to the increased sickling of erythrocytes, particularly in hot environments,” Dr. Connes reported. “Moreover, the patient reported that, despite its efforts to drink water, he felt particularly thirsty during and after the race. [Other researchers have] hypothesized that dehydration might contribute to the development of sickling and that SCT carriers might be naturally more predisposed to dehydration due to their inability to concentrate their urine when deprived of water. This defect might make SCT carriers less able to conserve water than noncarriers and could have played a role in the occurrence of CRVO.”

However, the researchers were unable to make conclusions about coagulation activity. “The exact reasons for this severe ocular incident are not clearly understood, and the most surprising event was the rapid deterioration of CRVO to neovascular glaucoma,” Dr. Connes reported. “Usually, the occurrence of CRVO (whether induced by exercise or not) in young men is well managed, leading to recovery with minimal visual after effects. However, this was not the case in the present study, and the poor outcome for our patient could be related to its SCT carrier status.”

Dr. Connes suggested that physicians should pay more attention to carriers of SCT whether they are training or not. John D. Sheppard, M.D., professor of ophthalmology, microbiology, and immunology, Eastern Virginia Medical School, Norfolk, Va., agreed that people with SCT could have ocular problems. “I have seen a couple of patients who had the sickle cell trait who have suffered an ocular vascular event,” Dr. Sheppard said. “One involved a branch retinal vein occlusion.” The key to management of SCT carriers during exercise is hydration, Dr. Sheppard said. “That prevents clumping of the cells and coagulopathies, compromised microvascular blood flow, and strokes,” he said.

Editors’ note: Dr. Connes has no financial interests related to this study. Dr. Sheppard has no financial interests related to his comments.

Contact information
Connes: pconnes@yahoo.fr
Sheppard: 757-622-2200, docshep@hotmail.com

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