Doctors at Erlangen Eye Clinic in Germany gave the drug BC 007 -- originally designed to fight heart failure -- to treat the patient's glaucoma, the DailyMail reported.
Glaucoma is a condition where the optic nerve, which connects the eye to the brain, becomes damaged by a fluid build-up in the front part of the eye. The patients also have high levels of auto-antibodies, which reduce blood flow in the eye.
The drug, developed by German firm Berlin Cures, neutralises auto-antibodies, which attack the body and are common in coronavirus survivors plagued with persistent symptoms.
The patient, suffering from glaucoma and long-Covid symptoms, was given BC 007 through a single dose infusion, the report said.
His sense of taste and difficulty concentrating "disappeared", his auto-antibody levels dropped and the blood flow to his eyes "improved significantly". "Even within a few hours, an improvement became apparent," Dr Bettina Hohberger, who treated the patient, was quoted as saying.
The experts said they will now use the drug in wider trials to determine its effectiveness, the report said.
Blood flow problems are thought to be at the root of the long-Covid conundrum, with researchers at the Max Planck Center for Physics and Medicine in Germany, last week, identifying changes to the shape of blood cells in people who have the condition.
They claimed the virus changes the size and stiffness of red and white blood cells, which make it harder to get oxygen and nutrients around the body. They believe the disruption to oxygen flow is the root of the common symptoms which plague long Covid patients a" breathing issues, tiredness and headaches, the report said.