Optical coherence tomography in measurement of the optical power of the cornea after laser correction of myopia

Aim
To compare total corneal power (TCP) values obtained from optical coherence tomography with conventional keratometry in intraocular lens (IOL) power calculation methods in corneas after laser correction of myopia.

Material and methods
The retrospective analysis included 64 eyes of patients after laser vision correction (LVC) of myopia. The results of optical coherence tomography of the anterior segment of the eye (Avanti RTVue XR) – central corneal thickness (CCT) and TCP – parameters from the optical biometry of IOLMaster 500 and the corneal tomography of Sirius were analyzed. Based on the obtained measurements, the IOL power was calculated using Haigis-L, Barrett True K No History and OCT formulas as well as the average from the ASCRS IOL Calculator for Eyes with Prior Myopic LASIK/PRK.

Results
The average spherical equivalent value before LVC was –3.99 ±2.13 D. The average decrease in mean keratometry after keratorefractive surgery measured with IOLMaster 500 and Sirius was 3.34 ±1.89 D and 3.14 ±1.83 D, respectively. Mean difference between TCP after LVC and keratometry measured by two conventional keratometers was 1.344 ±0.5 D for IOLMaster 500 and 1.267 ±0.82 D for Sirius. We did not observe a statistically significant difference in the IOL power using different calculation formulas for post-myopic eyes, but we found the highest agreement between the OCT formula and ASCRS average.

Conclusions
Optical coherence tomography of the anterior segment of the eye (Avanti RTVue XR) allows measurement of the TCP in patients after LVC, which makes the calculation of the IOL power in these patients more accurate.