Corneal asphericity changes after implantation of intracorneal ring segment (kerarings) in the treatment of Keratoconus

Purpose: To evaluate changes in visual outcome, refractive error and  corneal asphericity after implantation of intracorneal ring segments (ICRS) (keraring) for the treatment of keratoconus
Setting: Memorial institute for ophthalmic research, Egypt
Methods: This study was conducted on 23 eyes of 17 patients with keratoconus. ICRS was implanted intrastromally in the cornea as a treatment for  keratoconus.  One or two rings with  thicknesses ranging from 150 µm to 300 µm and arc lengths ranging from 160^o to 210^o were implanted. Uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA)and refractive error (sphere, cylinder)changes were assessed. Keratometric values (k1,K2,Kmax)and corneal asphericity values anterior and posterior respectively(Q ant and Q post )  were obtained  from  Pentacam .
Results: There was clinically significant improvement regarding UCVA from 0.1±0.04 to 0.31±0.17 and improvement in BCVA was from 0.37±0.15 to 0.46±0.1. The spherical and cylindrical errors significantly decreased postoperatively (p < 0.001).  K2 showed a highly significant decrease (p =0.001) while K1 showed a significant reduction (p=0.022) and Kmax showed non-significant changes postoperatively with p=0.469.Q anterior shows significant decrease from -1.29±0.55 to -0.78±0.77 (p < 0.001) while Q posterior shows non-significant change (p =0.692).
Conclusion: ICRS implantation for the treatment of keratoconus changes the anterior corneal asphericity by approximating the Q value to the ideal Q value (-0.46) and improves the UCVA and BCVA of patients in addition to decreasing the refractive sphere and cylinder values.