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Post-LASIK ectasia may be related to amount of tissue removed
Greater corneal biomechanical destabilization, increased corneal steepening and a worse prognosis were associated with a high amount of tissue removed during LASIK, according to a study.
The retrospective case series included 96 eyes of 96 consecutive patients who developed corneal ectasia after LASIK from 1996 to 2010 at two institutions. The main outcomes measures were post-LASIK ectasia corrected distance visual acuity, corrected distance visual acuity loss, spherical equivalent and corneal bulge. To determine their role in ectasia severity, the outcomes were correlated with residual stromal bed, ablation depth, ablation ratio, corneal depth and corneal ratio.
Ablation ratio was found to have the strongest correlation with post-LASIK ectasia corrected distance visual acuity (P < .001), while the corneal ratio had the strongest correlation with the post-LASIK ectasia spherical equivalent and corneal bulge (P < .001).
Ablation ratio was determined to be the main predictive factor for post-LASIK ectasia corrected distance visual acuity loss (P = .049).
“By comparing the eyes that did not lose vision with the eyes with an increased vision loss, we found that the ablation ratio was the only variable related to post-LASIK ectasia [corrected distance visual acuity] loss. … Risk does not necessarily mean that the exposure causes the outcome; however, we observed that the more tissue removed from the central cornea in a given eye, the worse the prognosis of the post-LASIK ectasia,” the study authors said.