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UL Tran, O Kagan, H-M Yang, DJ Shen, MX Wang; Preoperative Predictive Factors Influencing the Clinical Outcome of LASIK After Penetrating Keratoplasty. . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4151.
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Purpose:To analyze the predictive values of preoperative parameters influencing the clinical outcome of post-penetrating keratoplasty (PKP) LASIK. Methods:A retrospective study was conducted on 31 consecutive eyes of 26 patients who had undergone LASIK after PKP by one surgeon (MXW) with VISX Star excimer laser and Moria LSK One microkeratome at a single laser center. The patients were separated into two groups by the median values of each preoperative parameter: patient age (52 years), graft age (8.5 years), preop central pachymetry (571um), preop keratometry ( 4 D deviation from 44D), and the presence or absence of high risk characteristics for PKP. These preoperative factors were then analyzed for their predictive values for LASIK (% of patients with improvement in UCVA, % of patients with residual spherical equivalent (SE) within 1D of emmetropia, and % of patients with decrease in BCVA). Results:1) Patient age: The average age of all patients was 52 years (range 23-86 years). The postop results for the younger (52 yo, n=12) groups are as follows: % of patients with improved UCVA is 93% vs. 100%; % of patients with residual SE within 1 D of emmetropia is 42% vs 50%; % of patients with loss of BCVA is 26% vs. 58% (p<0.01); 2) Graft age: The average graft age was 8.5 years (range 2 to 22 years). 60% of the grafts younger than 8.5 years were within 1D of emmetropia vs. 1% in older group (p<0.01). The % of patients with loss of BCVA and improved UCVA was approximately equal between the two groups. 3) Preop central pachymetry: The average central pachymetry was 571um (range 480um to 659um). The % of patients that had improved UCVA for the group with thin preop corneas (571um) was 95% vs. 100%; 50% in each group were within 1D of emmetropia, and 35% vs. 42% had lost BCVA. 4)Preop keratometry: The postop outcomes for the group with K values deviating 4D from 44D are as follows: 80% vs. 100% had an increase in UCVA, 40% vs. 42 % were within 1D of emmetrpia, and 60% vs. 31% lost BCVA (p<0.01). 5) High PKP risk: Three patients had a history of graft rejection preoperatively. 33% of this group was within 1D of emmetropia (vs. 46% in the remaining patients without high risks) (p<0.01)), 67% lost BCVA (vs. 36%) (p<0.01). Conclusion:The efficacy and safety of post-PKP LASIK is improved when performed on younger patients, younger grafts (but at least 2 years old), moderate preop Ks, and corneas that have no high risk characteristics for PKP.
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