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M. Tang, Y. Li, M. Avila, D. Huang; Corneal Power Change After LASIK Accessed by High–Speed Optical Coherence Tomography . Invest. Ophthalmol. Vis. Sci. 2006;47(13):583.
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© ARVO (1962-2015); The Authors (2016-present)
To measure total corneal power using a high–speed corneal and anterior segment optical coherence tomography (CAS–OCT).
Twenty–seven eyes from 14 patients undergoing myopic LASIK operation from 10/22/2003 to 04/22/2004 at Cleveland Clinic were included in this study. OCT and placido–ring corneal topography (Zeiss Atlas) measurements were taken at the same visit preoperatively and 3 month postoperatively. Manifest refraction spherical equivalent (MRSE) was also recorded. OCT scans were performed using a CAS–OCT prototype operating at 1.3 micron wavelength and 2000 A–scans/sec. The scan pattern consists of 8 evenly–distributed radial scans (8mm in length) centered at corneal vertex. Posterior corneal elevation maps were obtained by combining Atlas anterior surface with the OCT corneal thickness map. The anterior and posterior surface power was then calculated by finding the best–fit sphere over the central 4mm–diameter circular region. The total corneal power was obtained by adding the anterior and posterior powers. The Atlas simulated keratometry (Sim–K) values along the 2 meridians were averaged for comparison.
The reproducibility (pooled SD) of posterior corneal power measurement was .04D. The difference between LASIK–induced corneal power change and MRSE change was significantly smaller (p < .001) for total corneal power (–.56 ± .51D) compared to Sim–K (–.90 ± .62D) .
Total corneal power computed by combining OCT and placido–ring topography data is in better agreement with refractive changes than SimK, which take only the anterior surface into account. Total and posterior corneal power measurement with OCT may be helpful for intraocular lens power calculation for post–LASIK eyes.
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