Agreement of keratometric readings measured using rotating Scheimpflug imaging, auto-refractokeratometer, and biograph in eyes with keratoconus.

AIM

To determine agreement in keratometric readings obtained using rotating Scheimpflug imaging with Pentacam, biograph with Lenstar LS900, and Topcon KR-8100P auto-keratorefractometer in eyes with different stages of keratoconus.

METHODS

A total of 89 eyes of 58 patients with keratoconus were examined in this study, retrospectively. The eyes were divided into two groups: mild group (group 1: 42 eyes) (Amsler-Krumeich stage 1) and moderate-to-severe group (group 2: 47 eyes) (Amsler-Krumeich stage 2, 3, 4). The keratometric readings measured using the Pentacam Scheimpflug system, Lenstar LS900, and Topcon KR-8100P auto-keratorefractometer were compared between the groups. The effects of the measurements of anterior chamber depth, Q value, axial length, central corneal thickness (CCT), and maximum value of keratometry (Kmax) on the differences of devices for keratometric readings were investigated.

RESULTS

The mean values of the keratometric readings obtained using the Lenstar were steeper than with the Pentacam and Topcon, especially in group 2. In group 1, the mean K2 values measured using the Lenstar were significantly steeper than with the Topcon (p < 0.05); however, the devices were accordant for the other keratometric readings. In group 2, there was an agreement between the Pentacam and Topcon for the mean K1 and Km values; however, there were significant differences between the devices for the other values. The Q value and CCT had a negative correlation, and Kmax had a positive correlation with the differences of Lenstar-Pentacam and Lenstar-Topcon (p < 0.01).

CONCLUSION

According to our results, Pentacam-Topcon and Pentacam-Lenstar can be used interchangeably for keratometry in mild stages of keratoconus. The keratometric readings of Lenstar were found steeper than the other devices with increasing grades of keratoconus. None of these devices can be used interchangeably in moderate-to-severe stages of keratoconus.