Persistence of the Cone on the Posterior Corneal Surface Affecting Corneal Aberration Changes After Intracorneal Ring Segment Implantation in Patients With Keratoconus.

PURPOSE

To analyze the changes in anterior and posterior corneal surfaces and aberrations in patients who underwent intracorneal ring segment (ICRS) implantation for the treatment of keratoconus.

METHODS

Eighty-nine eyes of 59 patients with keratoconus who underwent ICRS implantation were analyzed. All eyes were evaluated using a tomography system combining a Placido disc and Scheimpflug photography before and at least 6 months after surgery. Total, anterior, and posterior corneal aberrations, anterior and posterior sagittal and tangential anterior and posterior curve analysis, keratometry (K), minimum corneal thickness, and anterior chamber depth were analyzed before and after surgery.

RESULTS

Flattening with a decrease in the cone shape on the anterior corneal surface and steepening in the paracentral area with persistence of cone appearance on the posterior corneal surface were noted in all cases after ICRS implantation. The total corneal higher-order aberrations (HOAs) significantly decreased from 1.09 ± 0.43 to 0.71 ± 0.32 μm, and anterior corneal HOAs significantly decreased from 0.98 ± 0.46 to 0.81 ± 0.37 μm, whereas the posterior corneal HOAs increased from 0.53 ± 0.29 to 0.66 ± 0.25 μm after ICRS implantation (P < 0.05). There was a significant decrease in anterior maximum keratometry, but there was a significant increase in posterior maximum keratometry after ICRS implantation (P < 0.05).

CONCLUSIONS

The cone shape persists on the posterior corneal surface despite its correction on the anterior corneal surface, leading to a decrease in anterior corneal aberrations and an increase in posterior corneal aberrations after ICRS implantation in eyes with keratoconus.