This single-center, prospective, interventional clinical study is conducted to evaluate the repeatability and reproducibility of structural parameters of the optic nerve head, the peripapillary retinal nerve fiber layer, and the macula using the Heidelberg Spectralis OCT (Optical Coherence Tomography) device. Data obtained from healthy volunteers in this study are compared to those from a previous, larger healthy volunteer study that was conducted in the United States and Europe (S-2012-1), and data from glaucoma patients are compared to those from the healthy volunteers.

The study will include approximately 15 normal subjects and approximately 15 subjects who have glaucoma of varying degree. All subjects will undergo Spectralis OCT imaging and other study procedures in one single visit. All examinations performed on the subjects are non-significant risk procedures because the medical devices are cleared for marketing in Europe and in the U.S. Total study duration is anticipated to not exceed 4 weeks.

Inclusion Criteria:

• Subject is not an employee of the eye clinic.
• Age ≥18
• Able and willing to undergo the test procedures, give consent, and to follow instructions.
• For "normal subjects": Healthy eye without prior intraocular surgery (except cataract surgery and Lasik - laser-assisted refractive surgery) and without clinically significant vitreal, retinal or choroidal diseases, diabetic retinopathy, or disease of the optic nerve.
• For "glaucoma subjects": Early to advanced glaucoma according to existing medical charts.
• Refraction between +6 and -6 diopters and astigmatism ≤ 2 diopters.
• When both eyes are eligible, one randomly selected eye will enter the study.

Exclusion Criteria:

• Insufficient quality of Spectralis OCT images (this is not determined until after Spectralis OCT examination, and is an unusual circumstance). Minimum requirements are:

• Retina completely included in image frame,
• Quality Score ≥ 20 in the stored ART mean images