Study wants to compare central corneal thickness (CCT) obtained through 3 different no-contact instruments and to compare them with contact ultrasound pachymetry, actually the gold standard technique.

Corneal pachymetry is the measurement of corneal thickness, usually expressed in microns (μ).

Pachymetry is systematically used for the monitoring of corneal oedema, for the management and assessment of the progression risk of the ocular hypertension, for the diagnosis, the management and follow-up of keratoconus, as well as it is important in the pre and postoperative management of corneal surgical procedures. CCT is a factor well known to influence tonometry. Its assessment is fundamental in glaucoma practice to allow a correct intraocular pressure (IOP) evaluation.

The purpose of this study is to compare CCT measurements using four different instruments: Scheimpflug camera tomography, spectral-domain optical coherence tomography (SD-OCT), anterior chamber SD-OCT and ultrasound pachymetry.

Inclusion Criteria:

• subjects that gave a valid consensus to be included in this experimentation,
• aged between 18 and 75 years,
• Best-Corrected Visual Acuity (BCVA) of 20/100 or better,
• refraction included between -6 and +6 dioptres,
• astigmatism included between -2 and +2 dioptres.

Exclusion Criteria:

• History of refractive surgery or any keratoplasty procedure,
• corneal opacities or diseases that make not suitable applanation tonometry or pachymetry.
• Use of contact lenses.
• History of corneal dystrophies or degenerative diseases, (like keratoconus and pellucid marginal degeneration).
• History of glaucoma or ocular hypertension.

Healthy volunteers recruited among subject that underwent a routine ophthalmologic evaluation or among both students and workers at our clinic