NOV 30, 2009
This study's authors prospectively measured IOP, corneal biomechanical markers and Ocular Response Analyzer (ORA) waveform parameters preoperatively and six months postoperatively in 14 patients (28 eyes) that underwent myopic microkeratome-assisted LASIK and 15 patients (30 eyes) that underwent myopic LASEK. These results were also compared with a retrospectively identified cohort of 30 patients with low myopia and presbyopia who had undergone unilateral LASIK (30 eyes) and their fellow unoperated eyes.
The authors found that LASIK with standard microkeratome flap thickness combined with deeper stromal ablation has a greater biomechanical effect on the cornea as measured with ORA waveform parameters than LASEK without a stromal flap, which produced the smallest change in the ORA applanation signal. The results also indicate lowered corneal hysteresis and corneal resistance factor values after myopic refractive surgery compared with normal eyes, reflecting altered applanation signal morphology and viscoelastic response parameters.
The study's results provide evidence supporting the use of thinner flaps or the elimination of flap creation in order to maximize the residual stromal bed and minimize biomechanical variability, particularly in eyes with lower central corneal thickness.
Dr. Randleman is a consultant to and receives lecture fees from Allergan, Inc.