Comparison of total keratometry with corneal power measured by optical low-coherence reflectometry and placido-dual Scheimpflug system.

PURPOSE

To compare the total keratometry (TK) and astigmatism measurements in eyes with cataract using automated keratometry of sweptsource optical coherence tomography (ss-OCT), optical low-coherence reflectometry (OLCR), simulated keratometry (SimK), and total corneal power (TCP) of combined placidodual Scheimpflug imaging system.

SETTING

The study was conducted at LV Prasad Eye Institute, Hyderabad, India.

DESIGN

Retrospective evaluation of electronic medical records of patients who were evaluated for cataract surgery.

METHODS

Twenty-eight eyes of 28 patients were included in the study. All patients evaluated for cataract surgery underwent corneal power measurements using three devices: ssOCT, OLCR, and combined placidodual Scheimpflug imaging were included in the study. Vector analysis was performed to evaluate corneal astigmatism and Bland-Altman analysis was conducted to evaluate the limits of agreement of similar parameters among devices.

RESULTS

The mean TK was statistically significantly different from the keratometry obtained from optical biometers and values measured by the Scheimpflug imaging system. The magnitude of mean difference was greater between TK and TCP (0.75 ± 0.25) compared to other variables. The mean difference in astigmatism between TK, ss-OCT-K (0.09 ± 0.12,  = 0.48), OCLR-K (0.10 ± 0.48,  = 0.91), and TCP (0.09 ± 0.47,  = 0.31) was not statistically significant but was statistically significant between TK and SimK values (0.23D ± 0.49D). The axis of orientation (<20°) of astigmatism was comparable (100%, 28 eyes) between two keratometry variables measured by ss-OCT.

CONCLUSION

There appears to be a greater correlation of automated keratometry, and TK values obtained from ss-OCT compared to other variables studied. The measurements from TK, Simk, and TCP cannot be used interchangeably.