Purpose: To evaluate the efficacy and safety of placement of Intacs in subjects with keratoconus.
Design: Retrospective, nonrandomized comparative trial.
Intervention: Intrastromal corneal ring segment implantation.
Participants: Seventy-four eyes of 50 subjects (41 male and 9 female) were evaluated. The mean age of subjects in the study was 35 years, ranging from 20 to 73 years. Twenty-six subjects underwent single-eye treatment, and 24 subjects had both eyes treated.
Methods: A modified Intacs procedure was performed on subjects with keratoconus. Pachymetry was measured at the incision site, and the incision was made at 66% of the corneal thickness. A thicker ring segment was typically placed inferiorly, and a thinner segment was placed superiorly on the basis of a refractive nomogram.
Main outcome measures: Differences between preoperative and postoperative uncorrected visual acuity, best spectacle-corrected acuity, and spherical equivalent. Changes in irregular astigmatism were evaluated with the inferior-superior value from comeotopographic maps, and differences in refractive cylinder groups were studied.
Results: Preoperative mean best-corrected logarithm of the minimum angle of resolution (LogMAR) visual acuity was 0.41 (20/50 - 1) (standard deviation [SD], +/-0.48), which improved to a postoperative mean of 0.24 (20/32 - 2) (SD, +/-0.31) (two lines of improvement). Preoperative mean uncorrected LogMAR visual acuity was 1.05 (20/200 - 2 1) (SD, +/-0.48), which improved to a mean of 0.61 (20/80-) (SD, +/-0.52) (four lines of improvement) at postoperative follow-up. Preoperative mean best-corrected LogMAR acuity in the corneal scarring group was 0.96 (20/200 + 2) (SD, +/-0.72), which improved to a mean of 0.54 (SD, +/-0.43) (20/63 - 2) (five lines of improvement). Uncorrected mean LogMAR acuity in the eyes with corneal scarring was 1.42 (20/400 - 4) (SD, +/-0.27), which improved to a mean of 1.03 (20/200 - 1) (SD, +/-73) (three lines of improvement). The mean spherical equivalent before surgery was -3.89 diopters (D) (SD, +/-5.16), which was reduced to a mean of -1.46 D (+/-4.11) at the postoperative follow-up.
Conclusions: Asymmetric Intacs implantation can improve both uncorrected and best spectacle-corrected visual acuity and can reduce irregular astigmatism in corneas with and without corneal scarring.