A device for determining a chemical composition of a living eye including a light emitting unit configured to emit a light beam, a light guidance unit including at least one first focusing lens having an entry surface and an exit surface to be brought in optical contact with the eye and to illuminate at least part of the eye with the light beam emitted by the light emitting unit and to receive and guide at least a fraction of a light beam leaving the eye towards the light detecting unit. The light guidance unit is arranged to illuminate the part of the eye with the light beam having an oblique angle of incidence with respect to a visual axis of the eye, and includes a second focusing lens having an entry surface and an exit surface. Further, the exit surface of the first focusing lens has a curvature conformal to a wave front of the light beam leaving the exit surface and impinging on the part of the eye.