Abstract: A device for the in vivo determination of an optical property of the aqueous humor in the anterior chamber of the eye includes a light source to irradiate light along a primary-side light path into the anterior chamber of an eye. A detector is provided, in order to detect light issuing from the anterior chamber along a secondary-side light path. A signal processing unit is provided to determine the optical properties on the basis of the measured signal of the detector. A routine in vivo examination of the aqueous humor of the eye, with minor inconvenience to the patient, can be achieved due to the fact that the device can be easily positioned in front of the eye. The central rays of the primary-side light path and of the secondary-side light path form, with the normals to surface of the cornea bordering the anterior chamber, an angle (.alpha., .beta.) such that the detector detects light reflected from the front interface of the eye lens.