Oral Propranolol for Prevention of Threshold Retinopathy of Prematurity

Inclusion criteria: * Preterm infant born before 28 week's gestation * Birth weight below 1250 g * At least 5 weeks of age (at randomisation) * PMA 310/7 - 36 6/7 weeks * Ophthalmoscopic evidence of incipient ROP (stage 1 or 2, with or without plus disease in any zone) * Written informed consent by parents or legal guardian, according to national requirements Exclusion Criteria: * ROP stage ≥ 3, AP-ROP or suspected AP-ROP, or any other ROP requiring an intervention (study endpoint already reached). * Conditions that indicate open label propranolol such as: thyrotoxicosis, arterial hypertension or certain heart diseases (such as tetralogy of Fallot, paroxysmal supraventricular tachycardia, or long QT syndrome) etc. * Major congenital malformations or known chromosomal anomalies * Colobomas and other eye malformations * PHACE syndrome (posterior fossa anomalies, large infantile hemangiomas of the face, neck, and/or scalp, arterial lesions, cardiac abnormalities/coarctation of the aorta, eye anomalies) (risk of cerebrovascular complications) * Very large hemangioma (risk of hyperkalemia), as judged by the attending physician * Medication of the infant with rifampicin or phenobarbitone (enhanced metabolic clearance) * Chronic kidney impairment (serum creatinine \> 1.3 mg/dl \[115 μmol/L\]) * Severe liver dysfunction (ALT (GPT) \> 900 U/L) * Known hypersensitivity to propranolol or any of the excipients (see 6.3.1.) * Prinzmetal's angina, Raynaud's phenomenon (severe peripheral arterial circulatory disturbance), or pheochromocytoma (contraindications for propranolol in adults, not occurring in newborn infants) * Any circumstances that make the investigator believe that participation in the study leads to exceptional medical or organizational problems for the patient * Conditions that prohibit propranolol therapy such as: Atrio-ventricular block grade 2 or 3 hypertrophic cardiomyopathy, sinoatrial block, uncontrolled heart failure or cardiogenic shock, bronchial asthma * Medication of the infant or the mother if breastfeeding with clonidine, reserpine, angiotensin-converting enzyme inhibitors, angiotensin-receptor antagonists (contraindicated in preterm infants) or antiarrhythmic drugs including amiodarone, propafenone, lidocaine, digoxin/digitoxin, quinidine, verapamil, diltiazem, bepridil (pharmacodynamic interaction)