Corneal thickness in an ophthalmologically normal Japanese population

To investigate the distribution of central corneal thickness (CCT) and factors correlating with CCT in a large-scale population of ophthalmologically normal Japanese persons.

Cross-sectional study.

Participants (n = 7313; 2848 men and 4465 women) were selected as an ophthalmologically normal Japanese sample using the following exclusion criteria: abnormal results suggestive of any eye diseases revealed on slit-lamp examination, fundus photography, or visual field test using frequency doubling technology; corrected visual acuity worse than 0.7; and contact lens wear within 1 week. All study participants were identified from The Eye Disease Screening Service in Tajimi city during the period from September, 2000, through October, 2001.

The CCT was measured by SP-2000P specular microscopy (Topcon, Tokyo, Japan). Age, gender, body mass index, systolic blood pressure, laterality, refraction, corneal radius, and intraocular pressure (IOP) data were collected from the records.

The CCT value and its correlating factors.

Average CCT in this ophthalmologically normal Japanese population was 517.5+/-29.8 microm (mean+/-standard deviation; n = 7313) and was greater in men (521.5+/-30.3 microm) than in women (514.4+/-29.0 microm). The CCT positively correlated with IOP and corneal radius and negatively correlated with refraction, although the correlation was weak. Intraocular pressure measured with a Goldmann applanation tonometer positively correlated with CCT, and the correction was not affected by age (corrected IOP = IOP reading -0.012 [CCT (microm) - 520]).

Using optical pachymetry, CCT in normal Japanese persons was defined as 517.5+/-29.8 microm. Men had greater CCT measurements than women. The CCT measurements positively correlated with IOP and corneal radius and negatively correlated with age and refraction in men. Intraocular pressure positively correlated with CCT, regardless of age.