In order to prevent the development of central island after excimer laser photorefractive keratectomy(PRK), 547 eyes which had undergone PRK were studied to evaluate the incidence, width and height of central island retrospectively. Based on this result, PRK was performed on 63 eyes under conventional protocol(software version 3.20, VISX Twenty/twenty Inc, Santa Clara, CA) and then additional laser ablation with a correction amount of 2.5D and adiameter of 3mm was performed whether the incidence has been decreased and additional complications have occurred. As a result of conventional protocol, central island had occurred in 121 eyes out of 547(22.1%) and the width was 2.94+/-0.22mm and the height was 2.64+/-0.89D. In case of 63 eyes which underwent additional laser ablation, central island occurred in 4 eyes (6.34%) and overcorrection occurred only in 3 eyes(4.76%) at one month after PRK. From the standpoint of the above results, we reached the conclusion that the additional ablation for 2.5D by a 3mm in diameter after PRK under conventional protocol is effective. By using this method, we could reduce the incidence of central island without the aid of the upgraded version that contains the anti-central island program.
Incidence ; Laser Therapy ; Lasers, Excimer* ; Myopia* ; Photorefractive Keratectomy* ; Retrospective Studies

Surgical modalities to correct hyperopia include photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), Ho:YAG laser thermal keratoplasty (LTK), conductive keratoplasty (CK), phakic IOL, and refractive lens exchange. Excimer laser-based techniques, which include LASIK, LASEK, and PRK, are currently the most popular forms of surgery to correct not only myopia and astigmatism but also hyperopia. These techniques have been reported to be safe and effective for both primary surgeries and enhancements. However, various complications related to the flap and loss of best corrected visual acuity associated with a smaller optic zone, decentration, and irregular ablation caused by longer treatment time in high hyperopia over +5 diopter can have adverse effects on visual outcomes. The development of non-excimer laser-based techniques offers viable alternatives for laser vision correction techniques. More recent non-excimer-based thermal refractive techniques include LTK and CK. Earlier forms of thermal techniques showed a lack of predictability and stability, resulting in no further development of them. Recently, CK, a laserless, radiofrequency-based technique, has been approved by the FDA for the correction of low to moderate hyperopia even though the refractive instability has not been solved yet. In high hyperopia, lens approach like phakic IOL or refractive lens exchange instead of corneal surgery is preferred. ICL (Implantable contact lens) and Artisan is the most popular lens model that has well proven clinical results concerning its safety and effectiveness. Accommodative IOL or multifocal IOL could be the solution for pseudophakic presbyopia in refractive lens exchange in the future.
Astigmatism ; Corneal Transplantation ; Hyperopia* ; Keratectomy, Subepithelial, Laser-Assisted ; Keratomileusis, Laser In Situ ; Lasers, Excimer ; Myopia ; Photorefractive Keratectomy ; Presbyopia ; Visual Acuity

PURPOSE: We compared laser assisted in situ keratomileusis (LASIK) mode and photorefractive keratectomy (PRK) mode ablation methods in laser subepithelial keratomileusis (LASEK) surgery using the MEL-80 excimer laser. METHODS: All patients were followed up for a minimum of 1 year. The PRK mode group consisted of 46 eyes of 23 patients and the LASIK mode group consisted of 97 eyes of 56 patients. The central corneal thickness (CCT), ablation thickness, manifest refractive error and uncorrected visual acuity were compared preoperatively, 1 month and 1 year postoperatively. Spherical equivalent (SE) of cycloplegic refraction at postoperative 1 month and the uncorrected visual acuity (UCVA) ratios of 1.0 or better at postoperative 1 year were compared between the two groups to evaluate clinical efficacy. RESULTS: The SE of refractive error, CCT and target corneal ablation thickness of the two groups were not significantly different preoperatively. The PRK mode group obtained an actual ablation mean thickness of 82.8% of the target and the LASIK mode group obtained an actual ablation mean thickness of 94.1% of the target at postoperative 1 month. In each group, a statistically significant difference was observed between the actual corneal ablation thickness and target corneal ablation thickness. In the PRK mode group, the mean SE of postoperative 1 month cycloplegic refraction was +0.24 +/- 0.47 D and in the LASIK mode group, +0.87 +/- 0.54 D, indicating a statistically significant difference between the two groups. One year postoperatively, the UCVA ratios of 1.0 or better were 83% in the PRK mode group and 96% in the LASIK mode group, showing a statistically significant difference between the two groups. However, SE of manifest refractive error and CCT in the two groups were not statistically different at postoperative 1 year. CONCLUSIONS: The LASIK mode ablation method showed better results than the PRK mode ablation method in postoperative UCVA prognosis after LASEK surgery using the MEL-80 excimer laser.
Humans ; Keratectomy, Subepithelial, Laser-Assisted* ; Keratomileusis, Laser In Situ* ; Lasers, Excimer* ; Photorefractive Keratectomy ; Prognosis ; Refractive Errors ; Visual Acuity

PURPOSE: To compare the effect on visual performance of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with mesopic contrast sensitivity using CSV-1000S in excimer laser refractive surgery using the broad beam type and manual microkeratome. METHODS: Postoperative visual performance for 40 eyes undergoing PRK and 40 eyes undergoing LASIK was compared with mesopic contrast sensitivity at 1, 3, and 6 months postoperatively using the CSV 1000 (VectorVision, Ohio, USA). Eyes were divided into two groups: less than 6.0 D and over 6.25 D. Mesopic contrast sensitivity was performed with the patient's uncorrected-visual acuity of 20/20 or better under photopic condition. RESULTS: Under mesopic conditions a significant decrease in contrast sensitivity for the postoperative PRK and LASIK group was obtained at all spatial frequencies compared to the preoperative baseline (p<0.05). At 6 months postoperatively, LASIK decreased mesopic contrast sensitivity significantly more than PRK in myopia below -6.0 D, especially at the middle and high spatial frequencies of 6, 12, and 18 cpd (p<0.05). However, there were not statistically significant differences in mesopic contrast sensitivity between PRK and LASIK in myopia above -6.25 D (p>0.05). CONCLUSIONS: In the broad beam excimer laser, in cases of myopia with below 6.0 D, PRK seemed to have a more significant effect on mesopic contrast sensitivity than LASIK using manual microkeratome at postoperative 6 months.
Contrast Sensitivity* ; Keratomileusis, Laser In Situ ; Lasers, Excimer ; Myopia ; Ohio ; Photorefractive Keratectomy ; Refractive Surgical Procedures

To assess the predictability and accuracy of photorefractive keratectomy (PRK) in myopia, we reviewed the charts of 182 patients who underwent PRK and were followed up for more than 12 months. The mean visual acuity was improved from 0.11 to 0.80 at 12 months postoperatively, and the mean refraction change shows from -7.94D to -0.89D. 47% of the treated eye achieved final visual acuity of 1.0, and 97% achieved 0.5 or better. In the case of postoperative refraction, 96% of cases who were less than -6 D myopia achieved final refraction within +/- 1D, while 66% of cases who were more than -6 D myopia did. These results suggest that PRK is a safe and predictable procedure in treating mild to moderate myopia.
Adult ; Female ; Human ; *Keratectomy, Photorefractive, Excimer Laser ; Male ; Middle Age ; Support, Non-U.S. Gov't

PURPOSE: To evaluate the effect of rotary epithelial scrubber and post-laser corneal chilling on clinical outcomes of excimer laser PRK (VISX 20/20B VisionKeyTM) METHODS: PRK with a rotary epithelial scrubber and post-laser chilled BSS irrigation was performed in 231 eyes of 141 patients (Group I: -4.33+/-0.98 D, July 1997~July 1999). Conventional PRK with mechanical epithelial removal was performed in 282 eyes of 181 patients (Group II: -4.33+/-0.99 D, September 1994~April 1997). A retrospective clinical data of two different PRK procedures was compared. RESULTS: Mean epithelial removal time was significantly short in group I (8.6+/-3.4 sec) than in group II (29.8+/-12.8 sec) (p<0.05). More rapid epithelial healing was achieved in group I (2.6+/-0.7 days) than in group II (2.8+/-0.7 days) (p<0.05). At 12 months, UCVA was 0.7 or better in 99.4% (162/163 eyes) of group I and 92.8% (77/88 eyes) of group II (p<0.05). At 12 months, 98.8% (161/163 eyes) in group I and 95.2% (79/83 eyes) in group II were within +/-1.0 D of emmetropia (p<0.05). After 2 years follow-up, there were no cases showing corneal haze worse than grade 1 in group I. CONCLUSIONS: Excimer laser PRK after precise removal of the epithelium with a rotary scrubber and post-laser corneal chilling provided more rapid epithelialization and visual recovery than conventional PRK. There was statistically significant improvement in clinical outcomes and occurrence of corneal haze in group I comparing with group II. We think that this excimer laser PRK technique be more ideal for the correction of mild to moderate myopia to avoid the serious flap complication of LASIK.
Emmetropia ; Epithelium ; Follow-Up Studies ; Humans ; Keratomileusis, Laser In Situ ; Lasers, Excimer* ; Myopia ; Photorefractive Keratectomy* ; Retrospective Studies

PURPOSE: To evaluate the safety, stability and effectiveness of the LADARVision active tracking narrow beam excimer laser system using laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for the correction of spherical myopia and astigmatism. METHODS: We reviewed 233 eyes that underwent LASIK (Group A: -6D) and PRK (Group C) from August 2002 to March 2003. We investigated uncorrected visual acuity (UCVA), manifest refraction, spherical equivalent, cyclotorsion, and astigmatic change before undergoing refractive surgery. The evaluation was repeated at 1 week, 1 month, 3 months, and 6 months after surgery. RESULTS: AT one week following surgery, the mean UCVA was 1.39+/-0.30 in Group A, 1.25+/-0.34 in Group B, and 1.06+/-0.25 in Group C. At postoperative 6 months, the mean UCVA was 1.32+/-0.30, 1.09+/-0.16, and 1.32+/-0.24 in Groups A, B, and C, respectively. In all 215 eyes, cyclotorsion was 74.4%: counterclockwise, 48.4% (4.01+/-3.01); and clockwise, 26.0% (-4.42+/-3.18). The astigmatism correction rate was 79.16% in Groups A and B (LASIK groups), and 70.10% in Group C. CONCLUSIONS: The LADARVision 4000 laser yielded excellent results in myopia, with or without astigmatism and showed early refractive stability, good UCVA outcomes, and effective correction of astigmatism at 6 months postoperatively. Further studies are needed to compare custom LASIK and conventional LASIK using LADARVision.
Astigmatism ; Keratomileusis, Laser In Situ* ; Lasers, Excimer ; Myopia ; Photorefractive Keratectomy* ; Refractive Surgical Procedures ; Visual Acuity

Laser in situ kratomileusis(LASIK) is a prefered method to excimer laser photorefractive keratectomy (PRK) because the former cuts only corneal stroma, while the latter cuts corneal epithelium, Bowmans membrane, and stroma, LASIK is a complex procedure composed of corneal flap preparation and photo-ablation. In corneal flap preparation, two types, manual and automatic, of microkeratomes have been used. We experienced problems during and after LASIK procedure using a manual microkeratome in learning curve period(8 months) and criticized the problems to shorten a learning curve of manual microkeratome. One hundred eighty six myopic eyes treated with LASIK using manual microkeratome(MLK, SCMD, USA) from January 1997 to August 1997 by one operator(Joo) were subjects. Problems occurred in 24 eyes(12.9%) and consisted of hole in corneal flap (5 eyes), thin corneal flap(3 eyes), winkling of corneal flap (2 eyes), hinge inside optical zone of laser(3 eyes), haze of interface (3 eyes), and free corneal flap(8 eyes). Majority of complications occurred in the first 3 months and most complicated cases were preventable when the speed of microkeratome enhancement was slow in late series of study. It seems that a manual microkeratome takes longer learning curve than automated microkeratome. Therefore, to decrease the number of problem cases in learning curve of LASIK using manual microkeratome a didatic course, advices from experienced surgeons, and participation in wet lab would be mandatory.
Bowman Membrane ; Corneal Stroma ; Epithelium, Corneal ; Keratomileusis, Laser In Situ* ; Lasers, Excimer ; Learning Curve ; Methods ; Photorefractive Keratectomy

The present study compares three centering methods for excimer laser photorefractive keratectomy (PRK. VISX 20/20) by analyzing the corneal topography. The subjects were grouped according to three different centering methods used in the procedure: an ablation using a light reflex from the patient's cornea pursued by both eyes of the surgeon (Group 1, n = 49); an ablation using a red light reflex from the patient's cornea pursued by the surgeon's left eye only while the right eye remained closed (Group 2, n = 27); an ablation using the patient's center of the pupil pursued by the surgeon's left eye only while the right eye remained closed (Group 3, n = 21). The mean distance from the center of ablation zone to the center of the pupil were; 0.69 +/- 0.45 mm for Group 1, 1.05 +/- 0.48 mm for Group 2 and 0.63 +/- 0.28 mm for Group 3. The degree of deviation in Group 2 was significantly greater than in Group 1 or Group 3. The deviation was greater in the right eyes than the left eyes in Group 2 only. The decentration of the right eye in Group 2 was due to angle Kappa with misalignment of the fixation light and viewing tube containing reticule.
Adult ; Comparative Study ; Female ; Human ; Keratectomy, Photorefractive, Excimer Laser/methods* ; Male

Both mechanical ablation and laser ablation have been introduced for removal of the corneal epithelium in excimer laser photorefractive keratectomy(PRK). We analyzed the differences of the clinical outcome between mechanical ablation and laser ablation on 256 consecutive eyes followed up more than 6 months after PRK from August 1991 to June 1993. During the follow up period. pre- and post- operative visual acuity, refractive errors, corneal clarity, epithelial healing time, post-operative pain, and central island were compared between two groups. Anova and X2 test were used for statistical analysis. The uncorrected visual acuity at 6 months after operation was 0.81 in group A and 0.75 in group B(p<.05). The degree of corneal haziness was more severe in group B than group A at 6 months after operation(p<.05). Mean refractive errors and keratometer readings were not statistically signigicant between two groups. Average epithelial healing times after operation were 3.18 days in group A and 2.73 days in group B(p<.001). The incidence ot central island was lower in group B than in group A(p<.001). Post-operative pain was less severe in group B than in group A. This results suggest that mechanical ablation seems to achieved better visual acuity and less complication than laser ablation for removal of the corneal epithelium in PRK.
Epithelium, Corneal* ; Follow-Up Studies ; Incidence ; Laser Therapy ; Lasers, Excimer* ; Photorefractive Keratectomy* ; Reading ; Refractive Errors ; Visual Acuity