A subarachnoid hemorrhage occurs in about 10 out of 100,000 people each year. This bleeding leads to irritation and constriction of blood vessels in the brain (vasospasm) in two out of three people affected within four to 21 days and thus to reduced blood flow. This can lead to a stroke and serious damage. In order to be able to diagnose and treat a constriction of the blood vessels at an early stage, there are various examination methods which, however, have various disadvantages such as radiation exposure of the patient, low sensitivity or high effort. Therefore, the prediction and timely therapy of vascular constrictions is currently only successful in a few cases before the reduced blood flow has already led to irreversible damage.

The aim of this study is to investigate whether the so-called retinal vascular analysis can be used in addition to previous standard examinations for the early detection of diseases of the cerebral blood circulation. This method has few side effects and has been successfully used for 50 years to examine the blood circulation in the eye.

Inclusion Criteria:

• Female or male patient, age ≥ 18 years
• Inpatient stay in the clinic
• Written informed consent for participation in the study prior to beginning of treatment
• Written consent for further evaluation of the images and for the scientific publication of the study results
• Non-traumatic subarachnoid haemorrhage confirmed by computer tomography or magnetic resonance tomography or cerebrospinal fluid puncture (collection of nerve water from the lower part of the lumbar spine

Exclusion Criteria:

• Female or male patient < 18 years
• Pregnancy, Lactation
• Lack of written consent to participate in the study and to further evaluate the image material collected
• Known allergy to MS eye drops (active substance: phenylephrine/tropicamide
• Narrow chamber angle, narrow angle glaucoma, Terson syndrome (if it makes retinal vascular imaging impossible
• Persons in a dependency or employment relationship with the investigator
• Persons who are accommodated in a facility by judicial or administrative order
• Receipt and intake of a study drug within the last 30 days
• Supine position in bed