Refractive and aberrometric outcomes of intracorneal ring segments for keratoconus: mechanical versus femtosecond-assisted procedures

Ophthalmology. 2009 Sep;116(9):1675-87. doi: 10.1016/j.ophtha.2009.05.016. Epub 2009 Jul 29.


Objective: To compare visual, refractive, and corneal aberrometric outcomes in keratoconic eyes implanted with intracorneal ring segments (ICRS) implantation using either a mechanical or a femtosecond laser-assisted procedure.

Design: Retrospective, consecutive case series.

Participants: A total of 146 consecutive eyes of 106 patients with the diagnosis of keratoconus (68 unilateral and 39 bilateral) were included. Two groups were created according to the surgical technique used for corneal tunnelization: Mechanical group (mechanical tunnelization, 63 eyes) and Femtosecond group (femtosecond laser-assisted tunnelization, 83 eyes). Intracorneal ring segments implantation was indicated because of the existence of reduced best spectacle-corrected visual acuity (BSCVA) or contact lens intolerance.

Methods: Intracorneal ring segments implantations were performed by 6 surgeons following the same protocol except for the incision location. A total of 55 eyes were implanted with Intacs (Addition Technology, Inc, Fremont, CA) and 8 eyes were implanted with KeraRings (Mediphacos, Belo Horizonte, Brazil) in the Mechanical group, and 25 eyes were implanted with Intacs and 58 eyes were implanted with KeraRings in the Femtosecond group. Mean follow-up was 10.66+/-8.20 months, ranging from 1 month to 24 months.

Main outcome measures: Uncorrected visual acuity (UCVA), BSCVA, refraction, keratometry, and root mean square (RMS) for different kinds of corneal aberrations.

Results: By reporting only for statistically significant changes, UCVA improved in both groups at 6 months (P< or =0.02) and BSCVA improved in the Femtosecond group (P<0.01). The refraction improved in both groups at 6 months (P< or =0.02). The cornea on average was flatter in both groups at 6 months (P<0.01). Root mean square astigmatism was reduced in the Femtosecond group (P = 0.03), but there was an increase in some higher-order aberrations (P = 0.03). Significant differences were found between the 2 groups for eyes implanted with Intacs for primary spherical aberration, coma, and other higher-order aberrations, favoring the Femtosecond group (P< or =0.01). A significant negative correlation was found between the preoperative corneal aberrations and the postoperative BSCVA in the Mechanical group (r>0.63, P< or =0.04).

Conclusions: Intracorneal ring segments implantation using both mechanical and femtosecond laser-assisted procedures provide similar visual and refractive outcomes. A more limited aberrometric correction is observed for eyes with mechanical implantation.

Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Publication types

  • Comparative Study
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Corneal Stroma / physiopathology
  • Corneal Stroma / surgery*
  • Corneal Topography
  • Female
  • Humans
  • Keratoconus / physiopathology
  • Keratoconus / surgery*
  • Laser Therapy
  • Lasers, Solid-State
  • Male
  • Middle Aged
  • Prostheses and Implants
  • Prosthesis Implantation / methods*
  • Refraction, Ocular / physiology*
  • Retrospective Studies
  • Surgically-Created Structures*
  • Visual Acuity / physiology*
  • Young Adult