Biomechanical and morphological corneal response to placement of intrastromal corneal ring segments for keratoconus.
OBJECTIVE
To evaluate the biomechanical and morphological changes in keratoconic corneas after Intacs intrastromal corneal ring segment (ICRS) implantation.


METHODS
Department of Ophthalmology, National Reference Center for Keratoconus, Bordeaux University, Bordeaux, France.


METHODS
Keratoconic eyes were retrospectively analyzed after ICRS implantation; preoperative and 6-month postoperative evaluation were done using the Ocular Response Analyzer (ORA) and the Orbscan II topographer. Biomechanical parameters included corneal hysteresis (CH), the corneal resistance factor (CRF), and other parameters extracted from the signal curves. Morphological parameters included simulated keratometry and the cone location magnitude index from the axial map (aCLMI) and tangential map (tCLMI). Parameters were extracted using software designed to read and process topographic maps.


RESULTS
There were no significant differences between preoperatively and postoperatively in mean CH (7.7 mm Hg +/- 1.4 [SD] versus 7.4 +/- 1.4 mm Hg) or mean CRF (6.6 +/- 1.8 mm Hg versus 6.1 +/- 1.4 mm Hg). Only 2 ORA signal parameters were significantly different. Topographic parameters with significant decreases were minimum central keratometry (K) (mean change -5.8 +/- 2.9 diopters [D]) (P<.001), minimum central K (mean change -5.8 +/- 2.3 D) (P<.001), mean aCLMI (9.6 +/- 2.7 preoperatively versus 7.7 +/- 2.5 postoperatively) (P<.009), and mean tCLMI (18.9 +/- 2.8 versus 12.9 +/- 4.4) (P<.002). The only significant correlation between biomechanical and topographic parameters was postoperative ORA infrared signal peak 1 and postoperative aCLMI.


CONCLUSIONS
Intrastromal corneal ring implantation significantly decreased corneal curvature, with preoperative values predicting magnitude of change. However, it did not alter the viscoelastic biomechanical parameters of CH and CRF.
Department of Ophthalmology, Reference National Centers for Keratoconus, Bordeaux University, France.
Caroline
C
Dauwe
David
D
Touboul
Cynthia J
CJ
Roberts
Ashraf M
AM
Mahmoud
Julien
J
Kérautret
Pierre
P
Fournier
François
F
Malecaze
Joseph
J
Colin
D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D003319:Corneal Stroma / Q000503:physiopathology* / Q000601:surgery*; D019781:Corneal Topography; D004547:Elastic Tissue / Q000503:physiopathology; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019904:Polymethyl Methacrylate; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
D019904:Polymethyl Methacrylate