Study to Assess the Influence of Three Different α-antagonists and Placebo on the Extent of Weekly Phenylephrine-induced Mydriasis at Three Different Concentrations of Phenylephrine in Healthy Male Volunteers

Inclusion Criteria: * Healthy male * Age ≥ 21 and ≤ 55 years * Body Mass Index (BMI) ≥ 18.5 and ≤ 29.9 kg/m2 * Signed and dated written informed consent in accordance with Good Clinical Practice (GCP) and local legislation Exclusion Criteria: * Any finding of the medical examination (including blood pressure, pulse rate and Electrocardiogram (ECG)) deviating from normal and of clinical relevance * Gastrointestinal, hepatic, renal, respiratory, cardiovascular, metabolic, immunological or hormonal disorders * Diseases of the central nervous system (such as epilepsy) or psychiatric disorders or neurological disorders * History of orthostatic hypotension, fainting spells or blackouts * Chronic or relevant acute infections * History of allergy/hypersensitivity (including drug allergy) which is deemed relevant to the trial as judged by the investigator * Intake of drugs with a long half-life (\> 24:00 hours) within at least one month or less than ten half-lives of the respective drug before enrolment in the study or during the study * Use of any drugs which might influence the results of the trial up to seven days prior to enrolment in the study or during the study * Participation in another trial with an investigational drug (≤ two months prior to administration or during the trial) * Smoker (\> 10 cigarettes or \> 3 cigars or \> 3 pipes/day) * Inability to refrain from smoking on in-house trial days * Alcohol abuse (\> 60 g/day) * Drug abuse * Blood donation (≥ 100 mL within four weeks prior to administration or during the trial) * Any laboratory value outside the clinically accepted reference range * Excessive physical activities within the last week before the trial or during the trial The following exclusion criteria are of special interest for this study: * Hypersensitivity to any alpha agonist, or to phenylephrine * Supine blood pressure at screening of systolic \< 110 mmHg and diastolic \< 60 mmHg * Ophthalmological criteria: * Corrected visual acuity \< 0.5 * Refractive Error with a spherical equivalent \> +6 or smaller - 6 D * Elevated intraocular pressure (higher than 22 mmHg) * Relevant anisocoria or pupil deformation * History of eye surgery apart from laser trabeculoplasty less than three months previously or extraocular surgery such as strabismus surgery * Topical ocular medication influencing IOP (intraocular pressure) or pupil size within 3 months prior to study-start