Eighteen healthy, male, nonsmoking volunteers were included (age range: 22–32 years, mean: 26.4 ± 2.8 years [SD]). The nature of the study was explained, and all subjects signed a written, informed consent to participate. The study protocol was approved by the Ethics Committee of Vienna University School of Medicine and adhered to the guidelines of Good Clinical Practice and the Declaration of Helsinki. Each subject passed a screening examination, including medical history and physical examination; 12-lead electrocardiogram; complete blood count; activated partial thromboplastin time; thrombin time; fibrinogen; clinical chemistry (sodium, potassium, creatinine, uric acid, glucose, cholesterol, triglycerides, alanine aminotransferase, aspartate transcarbamoylase, γ-glutamyl-transferase, alkaline phosphatase, total bilirubin, total protein), total IgE antibodies; hepatitis A, B, and C and HIV serology; urinalysis; and a urine drug screening. Only subjects with IgE plasma levels of less than 100 kU/L were included. Subjects were excluded if any abnormality was found as part of the pretreatment screening, unless the investigators considered the abnormality to be clinically irrelevant. Further exclusion criteria were a history of migraine or other types of headaches. Moreover, an ophthalmic examination, including slit lamp biomicroscopy and indirect funduscopy, was performed. Inclusion criteria were normal ophthalmic findings, ametropia of less than 3 D, and anisometropia of less than 1 D.