We compared postoperative visual outcome and corneal refractive power depending on preoperative corneal topographic pattern and the predictibility of corneal topographic measurement compared with keratometric measurement after PRK. The subjects were 91 eyes divided into two goups composed of 44 eyes, symmetric bow tie type(SB) and 47 eyes, asymmetric bow tie type (aSB). The visual acuity, central power, and topographic pattern were measured before operation, postoperative 1 week, 1, 2 and 6 month in two groups, but no statistical difference(p>0.05). The averages of uncorrected visual acuity at 6 month were improved to 0.80(SB) and 0.85(aSB) from 0.09(SB) and 0.11(aSB) before operation. Topographic central refractive powers of +42.98D (SB), +43.32D(aSB) before operation were changed to +37.68D(SB), 37.56D(aSB) at 6month. The pattern of the region affected by the excimer laser was classified by key hole type 38%(SB) , 34%(aSB) , uniform roud type 41%(SB), 43%(aSB), semicircular type 21%(SB), 23%(aSB). The proportion of the difference less than one diopter between PRK setting and the change of the corneal refractive power at 6month was 36% and 76% in keratometric and topographic measurement. Above results show that the asymmetricity of bow tie type did not influence the visual outcome. The topographic measurement was better than keratometric measurement in evaluating the corneal refractory change after PRK.
Lasers, Excimer* ; Visual Acuity

Corneal haze and myopic regression are not uncommon complications following photorefractive keratectomy(PRK). To avoid these problems, multipass multizone technique has been introduced. However, it is quite difficult to coincide the center of the each ablation zone during the procedure and needs to take longer operation time. Single-pass multizone software was replaced by Summit technology(USA). The current study evaluates the clinical results of single-pass multizone PRK for high myopia. We performed PRK using single-pass multizone technique on 48 eyes of 44 patients for the treatment of high myopia. Preoperative spherical equivalent refractions ranged from -8.00 diopters((D) to -16.00 D (mean+/-SD, -11.01 +/- 1.84 D). Mean postoperative refraction was +1.12 +/- 1.20 D at one month, -0.42 +/- 1.24 D at six months, and -0.92 +/- 1.09 D at one year. The percentage of patients achieving correction within +/-2.0 D was 79.2% at one month, 85.4% at six months, and 88.2% at one year postoperatively. There was no serious complications after surgery. This study provides evidence that single-pass multizone PRK is a safe, simple and fairly predictable method for high myopic correction. But further studies are needed to confirm the longer-term stability.
Humans ; Lasers, Excimer* ; Myopia*

Corneal haze and myopic regression are not uncommon complications following photorefractive keratectomy(PRK). To avoid these problems, multipass multizone technique has been introduced. However, it is quite difficult to coincide the center of the each ablation zone during the procedure and needs to take longer operation time. Single-pass multizone software was replaced by Summit technology(USA). The current study evaluates the clinical results of single-pass multizone PRK for high myopia. We performed PRK using single-pass multizone technique on 48 eyes of 44 patients for the treatment of high myopia. Preoperative spherical equivalent refractions ranged from -8.00 diopters((D) to -16.00 D (mean+/-SD, -11.01 +/- 1.84 D). Mean postoperative refraction was +1.12 +/- 1.20 D at one month, -0.42 +/- 1.24 D at six months, and -0.92 +/- 1.09 D at one year. The percentage of patients achieving correction within +/-2.0 D was 79.2% at one month, 85.4% at six months, and 88.2% at one year postoperatively. There was no serious complications after surgery. This study provides evidence that single-pass multizone PRK is a safe, simple and fairly predictable method for high myopic correction. But further studies are needed to confirm the longer-term stability.
Humans ; Lasers, Excimer* ; Myopia*

We evaluated the safety and efficacy of photo-astigmatic refractive keratectomy(PARK) with Schwind excimer laser for one year. We performed PARK procedures on 28 eyes with compound myopic astigmatism. Twenty eight eyes were divided into two groups according to their astigmatism: low(up to -1.5D, 15 eyes), high(over -1.5, 13 eyes). Mean preoperative astigmatism was 1.17+/-0.28 in low astigmatism group and 2.67+/-0.90 in high astigmatism group. Mean one year postoperative astigmatism was 0.40+/-0.39 in low astigmatism group and 0.48+/-0.56 in high astigmatism group. Correction rate of astigmatism was 62.3% in low astigmatism group and 79.4% in high astigmatism group. Complications were loss of best corrected visual acuity 2 line or more(2 eyes), temporary increased intraocular pressure(4 eyes), over 0.25mm eccentric ablation(2 eyes). We concluded that the Schwind excimer laser PARK appeared to be a safe and relatively accurate proceudre to correct myopic astigmatism, especially predictability of astigmatism correction was very satisfactory.
Astigmatism ; Lasers, Excimer ; Visual Acuity

In order to evaluate the effect of topical prostaglanduin synthesis inhibitor(Diclod) and therapeutic contact lens(T-lens) on pain control and epithelial wound healing following excimer laser photorefractive keratectomy(PRK) we examined the score of subjective pain & the degree of corneal epithelial defect on 40 consecutive patients with or without above treatment. The patients were subdivided into 4 groups : 10 patients treated with only pressure patch(Group 1), 10 patients with pressure patch & Diclod(Group 2), 10 patients with only T-lens(Group 3), and 10 patients with T-lens & Diclod(Group 4). Diclod(Group 2&4) was effective on pain control during three days after excimer laser PRK, while T-lens treatment was not effective. Subjective pain score between the patient with Diclod(Group 2&4) and those without Diclod(Group 1&3) was significantly different(p< 0.05). In the point of epithelial wound healing after excimer laser PRK, 95% of patients treated with T-lens(Group 3&4) revealed no epithelial defect three days after excimer laser PRK, while only 65% of the patients treated with pressure patch revealed that. The difference was statistially significant(p< 0.05). Diclod, however, did not influence the epithelial wound healing in both pressure group and T-lens group. In this study we could find that the combination of Diclod & T-lens was a recommendable method to decrease the pain & to increase the epithelial wound healing after excimer laser PRK.
Humans ; Lasers, Excimer* ; Wound Healing

No Abstract Available.
Lasers, Excimer* ; Myopia* ; Photorefractive Keratectomy*

No abstract available.
Angioplasty ; Angioscopy ; Lasers, Excimer ; Stents

Objective: To compare the predictability of flap thickness, visual and refractive outcomes, and higher order aberrations in eyes that underwent myopic LASIK using either a Technolas femtosecond laser or a Zyoptix XP mechanical microkeratome for flap creation. Methods: The study involved a total of 44 eyes of 22 patients who underwent LASIK. Flap creation was randomized to using the Technolas femtosecond laser in one eye and Zyoptix XP microkeratome in the contralateral eye. Flap thickness was measured intraoperatively using ultrasonic pachymetry and postoperatively using the Visante ASOCT. Refractive outcome, visual acuity (VA), higher order aberrations, and contrast sensitivity were compared between the two groups. Results: Twenty-two patients had LASIK for myopia or myopic astigmatism. Using ultrasonic pachymetry intraoperatively, the mean flap thickness was 134 (±10) um and 124 (±23) um in the femtosecond (FS) and microkeratome (MK) groups respectively. Comparing the deviation of the actual from the intended flap thickness, the FS group had statistically lower standard deviation compared to the MK group (p=0.04). Using the AS-OCT, the mean flap thickness at 3 months postoperatively was 119 (±10.82) um and 123 (±15.77) um in the FS and MK groups respectively. The difference in standard deviation between the two groups did not reach statistical significance (p=0.19). The mean spherical equivalent at 3 months was -0.45D (±0.42) and -0.13D (±0.16) respectively. Eightynine percent (89%) of eyes had uncorrected VA of 20/20 or better in both groups. All eyes attained best corrected VA of 20/20 or better in both groups. Differences in total higher order aberrations (p=0.09) and contrast sensitivity scores (p=0.47) were not statistically different between the two groups. Conclusion Flap thickness predictability was better using the Technolas femtosecond laser compared to the XP microkeratome blade. Visual and refractive outcomes, higher order aberrations, and contrast sensitivity were comparable between the 2 groups.
Keratomileusis, Laser In Situ ; Lasers, Excimer

PURPOSE: To assess the refractive outcomes in photorefractive keratectomy (PRK) of two eximer lasers: Broad beam and Flying spot laser. METHODS: We compared the refractive outcomes of 74 eyes (group I) treated with a VISX 20/20(excimer laser (VISX Inc. USA) using broad beam laser with those of 96 eyes (group II) treated with a Technolas 217 C-Lasik(TM) (Bausch and Lomb, USA) using flying spot laser. Each patients had been followed up for more than 6 months after surgery. RESULTS: Corneal astigmatism at preoperation were 1.25 +/- 0.62D in group I and 1.03 +/- 0.51D in group II and at postoperative 6 months, decreased to 1.12 +/- 0.53D in group I and 0.60 +/- 0.83D in group II. Manifest refraction were outside +/- 1D of spherical lens or 0.5 D of cylinder lens in 23.6 % in group I and 13.5% in group II. CONCLUSIONS: We suggests that PRK using flying spot laser effectively more reduces corneal astigmatism and provided more satisfactory predictability in refractive results than that of broad beam laser.
Astigmatism ; Diptera* ; Humans ; Lasers, Excimer* ; Photorefractive Keratectomy*

PURPOSE: We evaluated the effect of Mitomycin C (MMC) applied by different methods, on corneal healing after excimer laser phototherapeutic keratectomy (PTK) in rabbits. METHODS: PTK was performed on 34 eyes of 17 New Zealand white rabbits. The control group underwent PTK alone, while the experimental groups underwent PTK with intraoperative application of either annular or discoid filter paper soaked with 0.02% MMC for 2 minutes. At postoperative 4, 12, and 24 weeks, the degree of corneal haziness was determined using a slit lamp biomicroscope, and the proliferation of keratocytes was observed histologically. RESULTS: At 4 weeks, the degree of corneal haziness was significantly lower in both MMC-treated groups than in the PTK-alone group (P<0.001). The two MMC-treated groups also showed decreased corneal haziness at 12 and 24 weeks, although the change was not statistically significant. In addition, the MMC-treated groups showed less proliferation of keratocytes at 4 and 12 weeks. At 24 weeks, the group that received annular application of MMC showed a significant decrease of keratocytes compared with the control group(p=0.026), while the group with discoid application showed no significant difference. CONCLUSIONS: In this study, we found that the annular application of MMC after PTK not only shows similar effect on wound healing but also reduces the side effects of MMC by minimizing the application surface.
Cornea* ; Lasers, Excimer* ; Mitomycin* ; Rabbits ; Wound Healing