Inclusion Criteria:  Subjects must be over 18 and under 60 years of age Completed a comprehensive eye exam in the last two years Contact lens wearers must have stopped wearing for a minimum of two days if wearing soft contact lenses and one week if wearing RGP lenses. The subject must have an adequate understanding of the English language to be able to comprehend the oral and written instructions.  Exclusion Criteria:  Determination during enrolment:  Pregnancy or breast-feeding whilst the examination Application of any eye drops within the last 48 hours before the examination Application of medication within the last 30 days which influences the body water regulation system (e.g. antidepressants, diuretics, corticosteroids, histamine-receptor antagonist, immune-modulators) Change of ocular therapy within the last 30 days before the examination Permanent application of eye drops or ocular medication On-going ocular treatment Any kind of ocular pathology or history of refractive surgery Any kind of systemic disease which affect collagen and the body water regulation system (Marfan syndrome, osteogenesis imperfect, pseudoxanthoma elasticum, Ehlers-Danlos, diabetes, rosacea, acne, cardiovascular disease, thyroid disease)  Early termination of the study:  Drop-out: active termination (decision made by the test person) Decision made by the examiner (inadequate compliance, change in the medical condition, as a result, the exclusion criterion is fulfilled) Decision made by the lead investigator/ sponsors  It is possible to withdraw the participation in the study at any time. The participant is not liable to give any reasons for withdrawing. If the study is withdrawn because of the decision of the investigator, the reasons must be given in the screening form.