No abstract available.
Keratomileusis, Laser In Situ*

PURPOSE: To evaluated the effect of suction ring on eyeball contour and its influence on the corneal flap made in LASIK(laser in situ keratomileusis). METHODS: We measured corneal thickness and axial length of 47 eyes, before and during application of the suction ring, in those which had undergone LASIK. The diameter and thickness of corneal flap made with Automated Corneal Shaper(R) were also measured in operation room. RESULTS: When applying suction ring while making a corneal flap, corneal thickness and axial length were decreased significantly(p<0.05), and the diameter of the flap was decreased as preoperative corneal curvature decreased(p<0.05). CONCLUSIONS: Careful attention is needed not to give an eyeball unnecessary pressure which may result in intraocular damage or flap complications such as free cap especially when their corneal curvature is too flat.
Keratomileusis, Laser In Situ* ; Suction

PURPOSE: This study was performed to evaluate the correlation between the change of the manifest refraction and change of the Orbscan-derived total refractive and axial power after laser in situ keratomileusis (LASIK). METHODS: A total of 34 consecutive eyes of 19 patients who were followed up for at least6 months after LASIK were included in study. The manifest refraction and Orbscan topography analysis of the 2, 3, 4, and 5 mm diameter zones of total refractive power and axial power maps were measured preoperatively and at least 6 month postoperatively. RESULTS: There were statistically significant correlations between all Orbscan-derived corneal power changes and changes of manifest refraction. Especially the total refractive power map in the central 4.0 mm zone gave the best statistically significant correlation with manifest refractive change (r2=0.790, p<0.01). CONCLUSIONS: These results indicate that the change of the manifest refraction in LASIK is best correlated with the change of the total refractive power map in the central 4.0 mm zone.
Humans ; Keratomileusis, Laser In Situ*

No Abstract Available.
Keratitis* ; Keratomileusis, Laser In Situ*

No Abstract Available.
Keratomileusis, Laser In Situ*

Objectives To compare the flap thickness created by two different microkeratomes and its effect on visual outcomes. Methods This prospective study involved 32 eyes of 16 patients who underwent laser in situ keratomileusis (LASIK). Flap creation was randomly assigned to either the Schwind (110 ?m) or Zyoptix XP (120 ?m) microkeratome. Flap thickness was measured using the subtraction technique. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), low-contrast sensitivity, and aberrometry measurements were compared preoperatively and at 6 months postoperatively. Results The mean flap thickness was 97 ± 13 ?m (range, 81 to 116 ?m) and 146 ± 27 ?m (range, 71 to 181 ?m) using the Schwind and XP respectively. The mean deviation from the labeled predicted thickness was –13 ± 13 ?m and 26 ± 27 ?m respectively, and this difference was statistically significant (p = 0.002). Three eyes had flap displacement, 1 had loose epithelium, and 1 had flap striae in the Schwind group. There were no complications in the XP group. At 6 months, 71% of eyes had UCVA of 20/20 or better in both groups. All eyes attained BCVA of 20/30 or better with spherical equivalent within ±1D of targeted emmetropia in both groups. Low-contrast sensitivity scores were higher in the Schwind group in most frequencies; however, the differences were not statistically significant. The mean change in the total higher-order aberration (HOA), trefoil, coma, quadrafoil was comparable between the groups. The mean change in spherical aberration was smaller (p = 0.03) in the Schwind (0.12 ± 0.35) than in the XP group (0.96 ± 1.3). Conclusion Flap thickness was more predictable with the Schwind than the XP. Schwind flaps were thinner, which may have resulted in more flap complications. Vision and refractive results were similar for both groups. There was no statistically significant difference in HOA; however, spherical aberration was significantly lower in the Schwind.
Keratomileusis ; Laser In Situ

Objective: We compared the efficacy, safety, refractive and visual outcomes, and aberrometry results of wavefront-guided aspheric treatment (WTA) versus wavefront-guided treatment (WT). Methods: This prospective, contralateral, comparative study included 60 eyes of 30 patients who underwent myopic LASIK. One eye of each patient was randomized to either WTA or WT. Patients were followed up for 3 months postoperatively. Two-tailed paired t-test was used to determine statistical significance. Results: At 3 months, 93% of eyes in the WTA group and 83% in the WT group had high-contrast uncorrected distance visual acuity (UDVA) of 20/20, while 87% in both groups achieved low-contrast UDVA of 20/40 or better. Sixty-four percent in the WTA gained 1 or more lines of low-contrast corrected distance visual acuity (CDVA) compared to 50% in the WT group. The mean sphere was 0.17D in the WTA and 0.14D in the WT (p = 0.63). The mean spherical equivalent was –0.04D for WTA and –0.03D for WT (p = 0.88). All eyes in both groups were within ±1.00D of the target emmetropia. The mean change in total higher-order aberration (HOA) was 0.07 μm in the WTA compared to 0.15 μm in the WT group (p = 0.04). The mean change in spherical aberration was –0.01 μm in the WTA and 0.18 μm in the WT group (p < 0.001). The mean change in Q value was significantly lower in the WTA (0.31) than in the WT group (0.63) (p < 0.001). Conclusion Wavefront aspheric LASIK (WTA) is a safe and effective treatment for myopic astigmatism. Refractive and visual outcomes were similar for both groups. WTA had less induction of higher-order aberration, lower spherical aberration, and better preservation of corneal asphericity (Q value). This translated to more lines of low-contrast vision gained compared to WT. Keywords: LASIK, Wavefront-guided, Aspheric, Spherical aberration, higher-order aberration, Corneal curvature
Keratomileusis, Laser In Situ

OBJECTIVE: To compare the different intraocular lens (IOL) calculation formulas available on the American Society of Cataract and Refractive Surgery (ASCRS) IOL power calculator website among Asian eyes with previous corneal refractive surgery. METHODS: A retrospective cohort study of 84 eyes in 68 Asian patients who had phacoemulsification with previous LASIK or photorefractive keratectomy (PRK) was done. Using the post-phacoemulsification manifest refraction spherical equivalent (MRSE) as target refraction, IOL prediction error (PE) for each formula was calculated as the implanted minus the predicted IOL power. Refractive PE was determined by calculating that 1 diopter (D) of IOL PE produces 0.7 D of refractive error at the spectacle plane. RESULTS: Comparing the Shammas, Haigis-L, Barrett True-K No History, ASCRS Average IOL Power No History, Barrett True-K, and ASCRS Average IOL Power with Change in Manifest Refraction (ΔMR), the mean IOL PEs ranged from -0.23 to -0.62 D, with the Barrett True-K having the lowest PE. The median refractive PEs for all formulas were similar at 0.35 D, except for the Haigis-L at 0.53 D. The ASCRS average with ΔMR had a statistically higher percentage of eyes within 0.5 D of target refraction versus other formulas (p<0.05). The Haigis-L IOL PE and refractive PE were significantly higher than the Barrett True-K (p<0.001), and the ASCRS average with ΔMR (p<0.001) respectively. The ASCRS average with ΔMR produced a significantly smaller variance of IOL PE (p<0.05). CONCLUSION: Accounting for PEs and variance, the ASCRS average IOL power with ΔMR is recommended, followed by the ASCRS average IOL power No History if without historical data.
Keratomileusis, Laser In Situ

PURPOSE: We evaluated the possibility of making a consistent corneal flap by reusing the microkeratome blade. METHODS: We performed LASIK surgery on 40 eyes of 26 patients by reusing the microkeratome blades which made the corneal flap thickness between 120 micrometer and 160 micrometer in the previous LASIK surgery. We selected 40 eyes of 25 patients with the same range of preoperative central corneal thickness, spherical equivalent, keratometry values, and astigmatism as a control group from the patients who had LASIK surgery with new microkeratome blades. We compared the mean and the deviation of the corneal flap thickness between the two groups. RESULTS: The mean central thickness of the corneal flap was 134.3 +/- 18.0 micrometer (range 89.6~161.7 micrometer) in the group using reused blades, and 134.4 +/- 24.6 micrometer (range 62.3~177.0 micrometer) in the control group. The mean deviation of the corneal flap thickness was 14.7 +/- 10.0 micrometer in the group using reused blades and 18.4 +/- 16.0 micrometer in the control group, and there was no significant difference between the two groups (p=0.218). CONCLUSIONS: The amount of deviation of corneal flap thickness was not decreased by reusing the microkeratome blade.
Astigmatism ; Humans ; Keratomileusis, Laser In Situ*

We analysed the relationship between preoperative factors and changes of corneal thickness after LASIK.Between January 1997 and October 1998, 124 eyes underwent LASIK procedure using VISX STAR at Kangnam's St. Mary's hospital.In group 1, 39 eyes had corneal thickness 50 micrometer or more after preoperative corneal thickenss was substracted with postoperative thickness.As control group, 33 eyes had the difference of corneal thickness 0 -5 0 micrometer or less.The each difference was calculated at 1 wk, 1 month, 6 months, 1 year postoperatively.We evaluated the preoperative factors, such as corneal thickness, spherical equivalent, corneal keratometer.The attempted correction for refractive errors was determined by cycloplegic refraction.In group 1, the difference in corneal thickness was 77 +/-2.5 micrometer at 1 week.58 +/-1.4 micrometer at 2 months, 57 +/-1.2 micrometer at 6 months and 58 +/-1.4 micrometer at 1year postoperatively. These results statistically greater than those of control group.And the more spherical equivalent, the thinner corneal thickness, the more difference in corneal thickness was, which was statistically signifi-cant comparing with group 2 (P<0.05).But, preoperative keratometry and the difference in corneal thickness was not significant between two groups (P=0.64).
Keratomileusis, Laser In Situ* ; Refractive Errors