BACKGROUNDIt is unclear whether a laser epithelial keratomileusis (LASEK) has any significant advantage over a photorefractive keratectomy (PRK) for correcting myopia. We undertook this meta-analysis of randomized controlled trials to examine possible differences in efficacy, accuracy, safety and side-effects between two methods, LASEK and PRK, for correcting myopia.

METHODSA systematic literature retrieval was conducted in the PubMed, EMBASE, Chinese Bio-medicine Database, and Cochrane Controlled Trials Register to identify potentially relevant randomized controlled trials. The statistical analysis was performed using a RevMan 4.2 software. The results included efficacy outcomes (proportion of eyes with uncorrected visual acuity (UCVA) > or = 20/20 at 1 month and 12 months post-treatment), accuracy outcomes (proportion of eyes within +/-0.50 diopters (D) of target refraction at 1 month and 12 months post-treatment), safety outcomes (loss of > or = 2 lines of best spectacle-corrected visual acuity (BSCVA) at > or = 6 months post-treatment), mean pain scores on day 1 post-treatment, and mean corneal haze scores at 6 and 12 months post-treatment.

RESULTSSeven articles describing a total of 604 eyes with myopia from 0 to -9.0 D were identified in this meta-analysis. The combined results showed that the efficacy and accuracy outcomes between the two groups at 1 month and 12 months post-treatment were comparable. No patient lost > or = 2 lines of BSCVA at > or = 6 months post-treatment in four relevant trials. Compared with PRK, LASEK did not relieve discomfort on day 1 post-treatment or reduce corneal haze intensity at 6 and 12 months post-treatment.

CONCLUSIONSAccording to the available data, LASEK does not appear to have any advantage over PRK for correcting myopia from 0 to -9.0 D. This meta-analysis focuses mainly on the comparison of the early, mid-term and mid-long term results of the two methods. Additional studies to compare the long-term (> one year) results should be considered.

In the laser ablation refractive surgeries, the corneal ablation model and its realization by laser are difficult to design. They greatly affect the results of those surgeries. This paper firstly presents a mathematical model for corneal ablation to correct the refractive error of spherical myopia, and then gives a technique of planning laser focus positions on cornea to realize the ablation model. Based on the principle of the correction for spherical myopia using small beam laser, our excimer laser corneal surgery system has been able to perform such refractive surgery. Now the corneal surgery system has been applied to clinical practice. Thirty-nine eyes with spherical myopia underwent LASIK using this kind of system. Their refractive states have been greatly improved. Preoperatively, the mean sphere was -5.57+/-2.95 D and the mean uncorrected visual acuity 0.12+/-0.07. One day after surgery, the mean sphere was -0.03+/-0.57 D and the mean uncorrected visual acuity 0.90+/-0.29. One month after surgery, the mean sphere was -0.68+/-0.98 D, and the mean uncorrected visual acuity 1.0+/-0.26.
Humans ; Lasers, Excimer ; Models, Biological ; Myopia ; surgery ; Photorefractive Keratectomy ; methods ; Treatment Outcome ; 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

The excimer laser diopter correction has proven to be efficient and safe. This paper presents the principle of excimer laser refractive surgery. Based on analyzing the mathematics model of the human eye cornea, the authors have proposed a new model which can be used to proceed the myopia, hyperopia, astigmatism diopter correction. Also studied were the excimer laser's ablation mechanism and the flying-spot scanning technology. The research results have been directly applied to Ophthalmic excimer laser system. The correction of diopter is well improved.
Algorithms ; Cornea ; anatomy & histology ; Humans ; Keratomileusis, Laser In Situ ; methods ; Lasers, Excimer ; Models, Theoretical ; Photorefractive Keratectomy ; methods ; Refractive Surgical Procedures

To evaluate the efficacy and safety of Excimer Laser Photorefractive Keratectomy (PRK) on the correction of high myopia, we performed planned double-pass PRK procedure at the same session on 62 eyes of 55 patients with myopia ranging from -6.30D to -15.25D (mean, -9.94D). In the first pass, a myopic correction of -6.00D with a 4.5 millimeter ablation zone was performed, and immediately after, a second correction of remaining myopia with a 5.0 millimeter ablation zone was performed. Attempted correction ranged from -6.30D to -9.50D (mean, -8.70D). The eyes were divided into two groups which were -10.50D or less (group A), and higher than -10.50D (group B). All the eyes received topical corticosteroid therapy postoperatively. One year after double-pass PRK, uncorrected visual acuity in group A and B improved to 20/40 or better in 84.0%, and 73.3% of the eyes and to 20/30 or better in 75.0% and 33.3% of the eyes respectively. The mean refractive errors at 12 months after PRK were -0.3 +/- 1.6D in group A, and -1.5 +/- 2.1D in group B. The percent of achieved correction within +/- 1.0D were 70.8% in group A, and 46.7% in group B 12 months after surgery. The epithelium healed by three days and there were no corneal erosions. Corneal haze (Grade 2 or more) was seen in 9.0% in group A and 36.4% in group B at 12 months after PRK. A planned double-pass PRK is a promising approach to correct high myopia (up to -10.50D), but long-term follow up will be required.
Adult ; Cornea/*surgery ; Female ; Humans ; Lasers, Excimer ; Male ; Middle Aged ; Myopia/*surgery ; Photorefractive Keratectomy/*methods ; Postoperative Complications ; Refraction, Ocular ; Visual Acuity ; Wound Healing

To evaluate the relationship between ablation zone demm in PRK and 88.7% were decentered less than 0.75 mm in LASIK. The most meridional displacement was toward the superonasal quadrant; 46% in PRK and 51% in LASIK. There was less decentration in males, in the 2nd-operated eye, in older age, PRK, in larger ablation diameter, and in shallower ablation depth, but these differences were not statistically significant.
Adult ; Corneal Transplantation/methods* ; Factor Analysis, Statistical ; Female ; Human ; Keratectomy, Photorefractive, Excimer Laser* ; Laser Surgery* ; Male ; Middle Age ; Myopia/surgery* ; Pupil*

Photo refractive keratectomy (PRK) and laser Situ Keratomileusis (LASIK) have been used for over a decade and become popular in China. Principles and characteristics of eye trackers made by several famous foreign manufacturers are introduced in this paper and their developing direction in the future is pointed out too.
Cornea ; surgery ; Eye Movements ; Humans ; Keratomileusis, Laser In Situ ; instrumentation ; Lasers, Excimer ; Myopia ; surgery ; Photography ; instrumentation ; methods ; Photorefractive Keratectomy ; instrumentation ; Refractive Surgical Procedures ; Video Recording

No abstract available.
Adult ; Corneal Opacity/etiology/pathology/*surgery ; Female ; Humans ; Male ; Monitoring, Intraoperative/*methods ; Photorefractive Keratectomy/*adverse effects ; Postoperative Complications/etiology/pathology/*surgery ; Young Adult

PURPOSE: The corneal change induced by refractive procedures influence both the postoperative refractive status and the ocular spherical aberration (SA). We evaluated changes in corneal SA after three types of surface ablation: phototherapeutic keratectomy (PTK), myopic photorefractive keratectomy (PRK), and myopic wavefront-guided laser epithelial keratomileusis (LASEK). METHODS: Twenty-six eyes (25 patients) were subjected to PTK 26 eyes (14 patients) to PRK, and 34 eyes (17 patients) to wavefront-guided LASEK. Corneal SA was measured with the iTrace in all patients both preoperatively and 6 months postoperatively. RESULTS: Six months after surgery, mean corneal SA was -0.173 +/- 0.171 micrometer in the PTK group, 0.672 +/- 0.200 micrometer in the PRK group, and 0.143 +/- 0.136 micrometer in the wavefront-guided LASEK group. The mean difference between the preoperative and postoperative corneal SA (DeltaSA) was -0.475 micrometer in the PTK group, 0.402 micrometer in the PRK group, and -0.143 micrometer in the wavefront-guided LASEK group. CONCLUSIONS: Surgically induced changes in corneal SA vary with procedure. The prediction of the pattern of SA change induced by various surface ablation procedures may be helpful for developing future surgical procedures.
Adult ; Aged ; Corneal Dystrophies, Hereditary/*surgery ; Corneal Wavefront Aberration/*surgery ; Female ; Follow-Up Studies ; Humans ; Keratomileusis, Laser In Situ/*methods ; Male ; Middle Aged ; Myopia/*surgery ; Photorefractive Keratectomy/*methods ; Prospective Studies ; Treatment Outcome