The purpose of this study is to evaluate the relationship between intraocular pressure and central corneal thickness using various instruments in ocular hypertension, normal-tension glaucoma, primary open angle glaucoma, keratoconus and normal eyes.

The purpose of this study is to evaluate the relationship between intraocular pressure and ultrasound pachymetry measured central corneal thickness using Goldman tonometry and PASCAL instruments.

Patient groups examined include:

ocular hypertensives normal-tension glaucoma primary open angle glaucoma keratoconus control normal eyes

Inclusion Criteria:

Adults over the age of 18 years Clinical diagnosis of glaucoma, open angle; ocular hypertension; glaucoma (low-tension); keratoconus and other healthy volunteers.

Exclusion Criteria:

Children under the age of 18 years Adults with learning disabilities Adults who are unconscious or severely ill Adults who have known terminal illness Adults in emergency situations Adults with dementia Prisoners Young offenders Those who could be considered to have a dependant relationship with the investigator (i.e. those in care homes or medical students) Other vulnerable groups

Clinical diagnosis of glaucoma, open angle; ocular hypertension; glaucoma (low-tension); keratoconus and other healthy volunteers.