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Factors related to the correction of astigmatism by LASIK after penetrating keratoplasty.

PURPOSE
To analyze the preoperative factors related to successful correction of astigmatism by LASIK after penetrating keratoplasty (PKP).


METHODS
This retrospective chart review included 71 patients (75 eyes) undergoing LASIK after PKP. The full refractive cylindrical (thus near-spherical) errors were treated by laser ablation. Postoperative follow-up examinations included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest autorefraction, slit-lamp examination, topography, specular microscopy, and simple questionnaire regarding satisfaction with LASIK at 1 day, 1 week, and 1, 6, and 12 months.


RESULTS
Before surgery, no eye had UDVA of 20/60 or better and 42 (56%) eyes had CDVA of 20/40 or better. At 1 year, 45 (60%) eyes had UDVA of 20/60 or better and 57 (76%) eyes had CDVA of 20/40 or better. The mean astigmatism was 6.80±2.10 diopters (D) preoperatively. The mean reduction of astigmatism was 3.80±2.30 D (53.9±28.7%) at 12 months after LASIK and was relatively stable between 6 and 12 months. Although mean achieved correction showed a tendency toward undercorrection, CDVA and contact lens/spectacle tolerance were significantly increased. The younger the patient, the lesser magnitude of refractive cylinder, and greater endothelial cell density showed better astigmatism reduction in the multiple regression analysis.


CONCLUSIONS
LASIK is a safe and effective procedure with stability for reducing astigmatism following PKP and increasing spectacle or contact lens tolerance. For optimal predictability and visual outcomes after LASIK, we recommend the full identification of astigmatism after PKP and preoperative analysis of the endothelial cell density.