The paper included the case study of a 29-year-old man, who told an emergency eye clinic that he noticed "an obstruction in the central vision of his left eye, which he had noticed on waking that morning."
The diagnosis was unclear at first, and clinicians asked the man to return for a follow-up visit three days later, according to the case study.
A different clinician asked the patient specific questions about his sexual activity. The patient responded that he had "vigorous sexual intercourse" the night before he started experiencing symptoms.
The doctor concluded that the man performed the "Valsalva maneuver," meaning that he tensed his abdominal muscles and held his breath during sex.
This caused a blood vessel in his eye to pop because of the increased pressure to his chest.