Outcomes of corneal crosslinking for central and paracentral keratoconus.

Background: The aim of the study was to compare the therapy of corneal collagen crosslinking (CXL) for central and paracentral keratoconus. Methods: 64 eyes of 43 central keratoconus patients whose highest power of the cornea located in the central 3mm zone and 24 eyes of 16 paracentral keratoconus patients whose highest power located out of the central 3mm zone received standard corneal CXL were included. Maximum keratometry (Kmax) and astigmatism according to topography, uncorrected distant visual acuity (UDVA), corrected distant visual acuity (CDVA) were studied preoperatively and 2 years postoperatively. Results: Central group: Preoperative UDVA and CDVA were 0.9 +/- 0.4 and 0.5 +/- 0.4 logMAR, respectively. At 2 years, UDVA and CDVA significantly improved to 0.8 +/- 0.4 and 0.4 +/- 0.3 logMAR(P< 0.01). Preoperative Kmax and astigmatism were 61.5 +/- 4.7 diopter (D) and 4.0 +/- 2.9 D, respectively. At 2 years, Kmax and astigmatism significantly decreased to 57.0 +/- 10.4 and 3.0 +/- 2.2 D (P< 0.01). Paracentral group: preoperative UDVA and CDVA were 0.8 +/- 0.7 and 0.2 +/- 0.4 logMAR, respectively. At 2 years, UDVA significantly improved to 0.4 +/- 0.4 logMAR(P< 0.01), whereas CDVA remained 0.2 +/- 0.3 logMAR(P> 0.05). Preoperative Kmax and astigmatism were 50.3 +/- 5.3 and 2.4 +/- 1.7 D, respectively. At 2 years, Kmax significantly decreased to 48.8 +/- 4.6 (P< 0.01), whereas astigmatism remained 2.2 +/- 1.8 D (P> 0.05). Conclusion: This study indicated that CXL was more effective for central keratoconus than paracentral keratoconus.