Detection of biomechanical changes after corneal cross-linking using Ocular Response Analyzer software.
OBJECTIVE
To investigate biomechanical changes after corneal cross-linking (CXL) with riboflavin/ultraviolet-A (UVA) in keratoconus using the recently developed Ocular Response Analyzer (ORA, Reichert Technologies) software.


METHODS
Through use of the new ORA software (version 2.04), 37 new parameters derived from the best measurement signal with the highest wavescore of 4 measurements from 50 eyes of 46 patients with keratoconus were obtained before and 1 year after CXL. The parameters of 96 eyes from 96 age-matched, healthy individuals with a spherical equivalent refraction <3.00 diopters served as controls.


RESULTS
Corneal hysteresis (CH) and corneal resistance factor (CRF) before CXL were 7.38±1.42 mmHg and 6.16±1.42 mmHg, respectively, compared to 7.37±1.26 mmHg (P=.971) and 6.16±1.50 mmHg after CXL (P=.997), respectively. Based on these 37 new parameters, the area under peak 2 (p2area) showed a statistically significant increase from 1262.3±623.1 before CXL to 1704.3±732.3 1 year after CXL (35%; P=.001). The related value for the p2area of the healthy control group was 3374.9±1099.9. A significant negative correlation was observed between the p2area and the difference in CH-CRF values (r=-0.29, P=.001).


CONCLUSIONS
The area under peak 2 appears to be a more sensitive parameter to detect biomechanical changes after CXL than CH or CRF alone. After CXL, keratoconic corneas display altered biomechanical properties, which remain different to those observed in healthy corneas.
Department of Ophthalmology, Carl Gustav Carus University Hospital, Dresden, Germany. eberhard.spoerl@uniklinikum-dresden.de
Eberhard
E
Spoerl
Naim
N
Terai
Freia
F
Scholz
Frederik
F
Raiskup
Lutz E
LE
Pillunat
D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D003094:Collagen / Q000627:therapeutic use*; D003315:Cornea / Q000187:drug effects / Q000503:physiopathology* / Q000528:radiation effects; D003432:Cross-Linking Reagents / Q000627:therapeutic use*; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy; D008875:Middle Aged; D012029:Refraction, Ocular; D012189:Retrospective Studies; D012984:Software; D016896:Treatment Outcome; D014464:Ultrasonic Therapy / Q000379:methods*; D055815:Young Adult
D003432:Cross-Linking Reagents; D003094:Collagen