Nine point corneal thickness measurements and keratometry readings in normal corneas using ultrasound pachymetry

Central, paracentral, and peripheral corneal thickness measurements using ultrasound pachymetry and keratometry readings were performed in 303 normal corneas. The mean central corneal thickness was 515 +/- 34 microns (standard deviation) ranging from 410 to 625 microns. Mean paracentral thickness measurements ranged from 522 +/- 40 microns inferiorly to 574 +/- 41 microns superiorly; mean peripheral thickness measurements ranged from 633 +/- 50 microns inferiorly to 673 +/- 49 microns superiorly. Central corneal thickness measurements were not found to be correlated with age, however, paracentral and peripheral thickness measurements tended to become thinner with age. There was also a trend that central corneal thickness decreased as the average keratometry reading increased. These trends, however, were not statistically significant. The mean difference between right and left central corneal thicknesses was 25 microns, ranging from zero to 136 microns. No significant differences in corneal thickness or keratometry readings were found between males and females or right and left eyes. No differences in these measurements were found with regard to time of day, month of the year, or systemic medication use. We conclude that there is a wide range of corneal thickness centrally, paracentrally, and peripherally in normal corneas.