Patients with cystic fibrosis (CF) have a greater risk of developing abnormalities in their retinal veins, which can impair visual acuity, a case report suggests.
But researchers claim the higher risk is not due to one single factor, but to several contributing risk factors for vascular events.
Ocular symptoms are common in cystic fibrosis patients, usually as a result of vitamin A deficiency. They usually appear as an irritation in the eye, night-blindness, or optic nerve abnormalities. Recent studies, however, have described two cases of CF patients who developed occlusions in their retinal veins.
In these studies, one patient had high fibrinogen levels and the other had increased homocysteine, leading researchers to speculate that those were the primary causes for the occlusions.
But a third case, presented by researchers at the Mayo Clinic in Rochester, Minnesota, has challenged this hypothesis, suggesting retinal vein occlusions in these patients are multifactorial and not due to a single risk factor.
The patient, a 35-year-old man, had been experiencing persistent blurry vision in his left eye for the past six weeks, before he came to the clinic.
He had been diagnosed with CF and had developed chronic pancreatic insufficiency, which led to diabetes mellitus, chronic sinusitis, hypertension, iron deficiency anemia, and obstructive sleep apnea. He was taking medication, including pancreatic enzymes and antibiotics, for all these conditions.
An eye evaluation did not reveal any changes of concern in visual acuity or intraocular pressure. However, the patient had signs of bleeding in the retina — a layer of tissue at the back of the eye that processes light. The associated retinal thickening was consistent with a blockage in the small vessels of the retina, researchers said.
Additional testing revealed a mild accumulation of fluid in the left retina, which could explain the blurry vision. Also, with resource to a fluorescein angiogram, researchers confirmed impaired blood flow in the small veins of the retina.
Blood tests to understand the causes of the occlusion in retinal vessels were unremarkable, with the exception of fibrinogen, which was 28% higher than normal. Researchers attribute this to the excess inflammation seen in cystic fibrosis patients, or as a response to the patient’s chronic sinusitis.
But while fibrinogen — which is involved in coagulation — increases the risk for abnormalities in retinal vessels, researchers say that all three patients with retinal occlusions “had systemic vascular risk factors likely leading to the retinal venous occlusions in each patient, despite aggressive medical management.”
Since his visual acuity was 20/20 in both eyes, and the fluid did not affect an important light-sensitive region of the eye, the team decided against treating the patient, and to monitor his condition instead.
After six months, his visual acuity remained unchanged in both eyes, and accumulation of fluids resolved by itself.
“Patients with cystic fibrosis are at an increased risk of developing retinal vein occlusions likely due to a variety of systemic thrombogenic factors [that support formation of blood clots] rather than a single risk factor,” the researchers wrote.
“It is important for ophthalmologists to recognize CF as a possible risk factor for the development of retinal vascular abnormalities,” investigators concluded.