Prospective, open-labeled, randomized, controlled, multicenter study at two clinical investigative sites in Tucson, Arizona. The subjects will undergo intraocular pressure measurement with the CATS tonometer prism and the Goldmann applanation tonometer prism (GAT).

Of the 200 eyes, at least 10 highly astigmatic eyes (>3 D of corneal astigmatism) each in the low, medium and high IOP ranges shall have the same clinical testing and analysis of results, with the analysis kept separate from that of the main group.

Inclusion Criteria:

• Written informed consent (and assent when applicable)obtained from subject or subject's legal representative and ability for subject to comply with the requirements of the study.
• Male and female patients, at least 18 years of age

Exclusion Criteria:

• Subject has undergone ocular surgery within the last 3 months
• Uncontrolled systemic disease that in the opinion of the Investigator would put the subject's heath at risk
• Pregnant or nursing women
• Subjects with only one functional eye
• Those with one eye having poor or eccentric fixation
• Eyes displaying an oval contact image
• Those with corneal scarring or who have had corneal surgery including corneal laser surgery
• Microphthalmos
• Buphthalmos
• Contact lens wearers
• Severe Dry eyes
• Lid squeezers - blepharospasm
• Nystagmus
• Keratoconus
• Any other corneal or conjunctival pathology or infection.
• Central corneal thickness greater than 0.600 mm or less than 0.500 mm (2 standard deviations about the human mean)