PURPOSE: To compare the efficacy, predictability, stability and safety of excimer laser photorefracive keratectomy(PRK) for mypia and photoastigmatic refractive keratectomy(PARK) for compound myopic astigmatism. METHODS: Two-hundred-three eyes(118 eyes <-7D spherical equivalent, 85 eyes> or =-7D spherical equivalent) received excimer laser correction for compound myopic astigmatism and 152 eyes(116 eyes <-7D, 36 eyes > or =-7D) for simple myopia. A VISX 20/20B VisionKeyTM excimer laser was used to perform either PARK or PRK. Visual acuity with and without correction, refraction, IOP, corneal haze, and topography were evaluated at 1, 3, 6, and 12 months postoperatively. All patients were followed up for more than 12 months. RESULTS: Postoperative refraction were generally stable after 3 months without significant early overcorrection. At 12 months, 110(94.8%) eyes that underwent PRK and 104(88.1%) eyes that underwent PARK achieved UCVA of 20/30 or better in the group who had lower than -7D correction. For eyes treated with -7D or more, these figures were 31(86.1%) eyes after PRK and 57(67.1%) eyes after PARK. The incidence of within 1D of plano refraction at 1 year follow-up were 97.4% after PRK and 93.2% after PARK in group who had lower than -7D correction. For eyes treated with -7D or more, there figures were 80.6% after PRK and 70.6% after PARK. CONCLUSIONS: Myopia with or without astigmatism was successfully treated in most of the eyes using PRK or PARK with VISX 20/20B VisionKeyTM excimer laser. The predictability and stability of the postoperative refraction during the first 12 months seem to be quite reliable. Futher improvement of excimer laser system and software should increase the clinical outcomes and safety of refractive procedures.
Astigmatism* ; Follow-Up Studies ; Humans ; Incidence ; Lasers, Excimer* ; Myopia* ; Photorefractive Keratectomy ; Visual Acuity

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 effect of the amount of cylindrical correction on the accuracy of geometric corneal center-adjusted ablation centration selected by the surgeon in advanced surface ablation-photorefractive keratectomy (ASA-PRK). METHODS: Ninety-five myopic eyes of 62 patients who underwent ASA-PRK were divided into three groups based on the amount of myopic cylindrical correction: Group 1 <-0.50 D, 22 eyes; Group 2 > or =-0.50 D and <-1.00 D, 45 eyes; Group 3 > or =-1.00 D, 28 eyes. The distances and distribution of the ablation centers from the entrance pupil center were analyzed by corneal topography at one month after ASA-PRK. Risk factors for decentration (>0.3 mm) were determined from patient-related factors such as gender, age, laterality, central corneal thickness, and order of procedure and surgery-related factors such as amount of spherical correction, ablation depth, vertical scale bar percentage, and learning effect of surgeon. RESULTS: Mean decentration was 0.26 +/- 0.15 mm (0.04 to 0.83 mm). There was no statistically significant difference in the amount of decentration among the three groups (p = 0.879). Superior-nasal displacement (53.7%) of the ablation center most frequently occurred after ASA-PRK. The amount of decentration among the three groups was not dependent on either patient-related or surgery-related factors. CONCLUSIONS: ASA-PRK using the surgeon-selected ablation center with adjustment toward the geometric corneal center was found to be highly accurate in ablation centration and did not influence the amount of ablation decentration regardless of the amount of myopic cylindrical correction.
Corneal Topography ; Displacement (Psychology) ; Eye ; Humans ; Learning ; Pupil ; Risk Factors

PURPOSE: To investigate the shifting trends of pathogenic organisms, antibiotic resistance, and clinical characteristics of patients with Gram-positive bacterial keratitis and to elucidate the prognostic factors. METHODS: We performed a retrospective chart review of 152 isolates in 146 eyes with Gram-positive bacterial keratitis between January 1998 and December 2012. The study was divided into 5 periods for analysis of the bacteriological profiles and in vitro antibiotic resistance. The epidemiological and clinical characteristics were compared according to bacterial isolates. Logistic regression analysis was performed to determine the risk factors. RESULTS: Gram-positive bacterial keratitis tended to decrease and significant change in the distribution of isolates was not observed. Commonly isolated organisms were S. epidermidis (48.7%), S. aureus (25.0%), and S. pneumoniae (7.2%) in order of frequency. The resistance to fluoroquinolone tended to increase (p = 0.104) and resistance to gentamicin was significantly decreased (p = 0.01). S. epidermidis had the shortest corneal epithelium healing time (p = 0.035) and the most favorable visual outcome after treatment (p = 0.035) compared with the other species. Risk factors for poor visual outcomes included a best corrected visual acuity less than 0.1 at initial evaluation and an epithelial healing time greater than 10 days. CONCLUSIONS: Gram-positive bacterial keratitis tended to decrease and S. epidermidis was the most common isolate. The clinical prognosis was most favorable in S. epidermidis. The BCVA less than 0.1 at initial evaluation was an important risk factor for poor visual outcome and surgical treatment in Gram-positive bacterial keratitis.
Drug Resistance, Microbial ; Epithelium, Corneal ; Gentamicins ; Humans ; Keratitis* ; Logistic Models ; Pneumonia ; Prognosis ; Retrospective Studies ; Risk Factors ; Staphylococcus aureus ; Staphylococcus epidermidis ; Visual Acuity

PURPOSE: To investigate the clinical results, recurrence rates, and recurrence-related risk factors of temporary amniotic membrane patch (TAMP) after excision of primary pterygium. METHODS: Recurrence grade was evaluated for 73 eyes with a mean follow-up of 15.5 months (range 9 to 56 months). Surgical results were classified into surgical success (G0/G1), conjunctival recurrence (G2), and corneal recurrence (G3). Recurrence rates were analyzed based on gender, age, Tan's preoperative grading system, horizontal and vertical length of the preoperative pterygium, the corneal involvement size of the preoperative pterygium, planned or unplanned removal of amniotic membrane, and epithelial healing time. Using Kaplan-Meier survival analysis, the cumulative proportion of integrated G0/G1 was evaluated. RESULTS: In the postoperative grading, 58 (79.5%) and 9 (12.3%) eyes were graded as clinically recurrence-free G0 and G1, respectively; 4 (5.5%) and 2 (2.7%) eyes were graded as clinically recurrence-occurred G2 and G3, respectively. The cumulative proportion of integrated recurrence-free G0/G1 at 24 months after surgery was 0.83 +/- 0.08. T3 of Tan's preoperative grading system was identified as the only risk factor for recurrence above G1 through multivariate logistic regression analysis (p = 0.02). CONCLUSIONS: The recurrence rate of the present TAMP study showed better results in comparison with 9.1 to 56.1% of recurrence rates in other studies. The TAMP has advantages of surgical procedure with ease, low complications, and low recurrence rates. Therefore, after surgical excision of primary pterygium, the authors concluded the TAMP is highly recommended for good clinical outcomes and low recurrence rates.
Amnion ; Eye ; Follow-Up Studies ; Logistic Models ; Pterygium ; Recurrence ; Risk Factors

PURPOSE: To investigate the preoperative characteristics and postoperative change of the higher-order wavefront aberrations (HOAs) in myopic photorefractive keratectomy (PRK). METHODS: Standard PRK was performed in 39 eyes (spherical equivalent -4.71+/-1.56D) using the VISX(R) STAR S4(TM) excimer laser system. Wavefront analysis was performed preoperatively and 6 months postoperatively using the VISX(R) WaveScan(TM) aberrometer. Statistical analysis was performed to assess the preoperative characteristics of the HOAs and the PRK-induced aberrations. RESULTS: The preoperative root mean square (RMS) value of the total HOAs was 0.291 micrometer: coma 0.159 micrometer, trefoil 0.157 micrometer, spherical aberration 0.093 micrometer. Among the 3 HOAs, only the spherical aberration showed moderate magnitude negative correlation with the spherical equivalent (p=0.012) and sphere (p=0.005). The magnitude of all of the HOAs, except trefoil, were significantly increased at postoperative 6 months: total HOAs 183% (0.533 micrometer, p<0.001), spherical aberration 341% (0.317 micrometer, p<0.001), coma 185% (0.294 micrometer, p<0.001), trefoil 104% (0.163 micrometer, p=0.681). In the postoperative correlation analysis, only the PRK-induced spherical aberration showed the increase of magnitude with increasing preoperative spherical equivalent (p=0.036) and sphere (p=0.019). CONCLUSIONS: The HOAs, especially spherical aberration and coma, were increased after PRK. Among the 3 HOAs, the spherical aberration showed the greatest increase of magnitude and percent change; it also showed a positive correlation with increasing preoperative spherical equivalent and sphere. Further software improvements in the wavefront-guided surface ablations need to have a diminution of PRK-induced spherical aberration.
Coma ; Lasers, Excimer ; Lotus ; Photorefractive Keratectomy

PURPOSE: To evaluate the accuracy of the surgeon-selected ablation center in active eye-tracker-assisted ASA-PRK and to identify factors influencing the ablation center. METHODS: This retrospective study included 109 eyes of 62 patients who underwent active eye-tracker-assisted ASA-PRK (VISX STARTM S4 with ActiveTrakTM System). The location the surgeon-selected ablation center and its distance from the center of the entrance pupil were analyzed by corneal topography (EyeSys Corneal Analysis SystemTM with pupil finding software). The factors influencing centration were investigated. RESULTS: The mean decentration was 0.24+/-0.13 mm (range 0.04 to 0.83 mm). One-hundred and five eyes (96%) were within 0.5 mm of the pupillary center. Supero-nasal displacement of the ablation center occurred most frequently in 44 eyes (40%) after ASA-PRK. The decentration amount was not dependant on factors related to the patient, the surgeon, or the surgery. There was no significant correlation between the amount of decentration and the vertical scale bar of the ActiveTrakTM icon on the screen representing the distance from the pupil center determined by the tracking system, to the surgeon-selected ablation center. CONCLUSIONS: This method of tracking the ablation center, which was selected by the surgeon according to each patient's specific pupil decentration with the active eye tracking system, was highly accurate and effective in avoiding severe decentration in ASA-PRK.
Corneal Topography ; Humans ; Photorefractive Keratectomy ; Pupil ; Retrospective Studies

PURPOSE: To evaluate the effect of rotary epithelial scrubber, cold BSS(R) irrigation, and bandage contact lens on the clinical outcome of excimer laser PRK. METHODS: This updated PRK was performed in 90 eyes (Group I: -4.54 +/- 0.91 D). Conventional PRK with mechanical epithelial removal using Beaver(R) blade and patch dressing was performed in 181 eyes (Group II: -4.30 +/- 0.97 D). Clinical outcome was compared between group I and group II retrospectively. RESULTS: Mean epithelial removal time was significantly shorter in group I (6.6 +/- 0.9 sec) than in group II (33.2 +/- 11.2 sec) (p<0.05). Mean epithelial healing time showed more rapid epithelial healing in group I (2.0 +/- 0.3 days) than in group II (3.0 +/- 1.0 days) (p<0.05). At 1 week and 24 months, UCVA of 0.7 or better was achieved in 91.1%, 97.8% in group I and in 71.8%, 88.2% in group II (p<0.05). At 6 and 24 months, spherical equivalent within 0.5 D of emmetropia was in 91.1%, 91.3% in group I and in 80.7%, 56.9% in group II (p<0.05). After 1 year follow-up, no eye in group I showed either corneal haze worse than grade 1 or loss of 2 or more lines of BSCVA. CONCLUSIONS: Updated PRK provided more rapid epithelialization than conventional PRK. And there was significant improvement in clinical outcome and safety in group I compared with group II. We suggested that updated PRK should be used for the correction of mild to moderate myopia.
Bandages* ; Emmetropia ; Follow-Up Studies ; Lasers, Excimer ; Myopia ; Retrospective Studies

In order to get a good visual outcome following excimer laser photorefractive keratectomy(PRK) the centration of ablation is very important. In this study, the ablation center of excimer laser PRK using VISX 20/20 B(R) with VisionKeyTM(VISX, Inc. Santa Clara, CA) was evaluated by using corneal topography. Corneal topography was performed before operation and one month after operation to 190 eyes of 123 patients. The location and distance of center of ablation from center of the entrance pupil were calculated by using EyeSys Corneal Analysis System(R) with pupil-finding software(EyeSys Laboratories, Inc. Houston, TX). Supero-nasal displacement of ablation center occurred in 84 eyes(44%) after excimer laser PRK. The mean distance was 0.33 +/- 0.21mm(range: 0.02~1.36mm). The distance less than 0.5mm was found in 157 eyes(83%) and that between 0.5mm and 0.75mm was found in 26 eyes(14%). The decentering amount following excimer laser PRK was not depending on laterality(OD vs. OS), sex, age, amount of attempted correction(6D down vs. 6D up), type of software(ver 3.20 vs. 4.01) or type of procedure(PRK vs. PARK). In contrast, the second eye receiving excimer laser PRK showed a better centration of ablation than the first eye. And the centration results improved with surgeon's experience in the most recent 50 eyes(0.28 +/- 0.16mm). However, there was no relation between amount of decentration and visual improvement. In this study, it was found that decentering of ablation center less than 0.75mm did not influence the visual outcome in excimer laser PRK.
Cornea ; Corneal Topography ; Humans ; Lasers, Excimer* ; Photorefractive Keratectomy* ; Pupil

PURPOSE: To investigate causative microorganisms, clinical characteristics, and prognostic factors for inpatients with contact lens related bacterial keratitis. METHODS: Seventy-three eyes of inpatients with contact lens related bacterial keratitis and hospitalized at Yeungnam University Hospital between January 1998 and December 2011 were reviewed retrospectively. Their bacteriological profiles and clinical characteristics were evaluated. RESULTS: Females in their 20s (35/73 eyes, 47.9%) were the most common gender and age group. Thirty eyes (30/45 eyes, 66.7%) used daily-wear soft contact lenses. The most common predisposing factor was sleeping while wearing contact lenses (30 eyes, 41.1%). Positive culture rate was 53.4%. The ratio of gram-positive and -negative bacteria was 8.3%: 91.6%. The most commonly-isolated microorganisms were Pseudomonas spp. (39.6%), followed by Serratia spp. (29.2%). The characteristics of the corneal lesions were: a central lesion in 49 eyes (67.1%), a lesion less than 5 mm2 in size in 54 eyes (74.0%), and hypopyon in 8 eyes (11.0%). The mean log MAR BCVA improved from 0.93 +/- 0.88 on the initial visit to 0.25 +/- 0.48 on the final visit. Twelve eyes (16.4%) had a BCVA of 0.3 or less after remission medical treatment. A BCVA less than 0.1 on the initial visit was a significant risk factor for poor visual outcome (p = 0.005) after remission medical treatment. CONCLUSIONS: BCVA less than 0.1 on the initial visit, epithelial defect sized over 5 mm2, epithelial healing time over 10 days, and central corneal lesion were associated with poor visual outcome after remission medical treatment in contact lens related bacterial keratitis.
Bacteria ; Contact Lenses ; Contact Lenses, Hydrophilic ; Eye ; Female ; Humans ; Inpatients ; Keratitis ; Pseudomonas ; Retrospective Studies ; Risk Factors ; Serratia