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 effects of the amount of myopic correction on long-term changes in higher-order wavefront aberrations (HOAs) in advanced surface ablation-photorefractive keratectomy (ASA-PRK). METHODS: The 193 eyes of 101 patients who underwent ASA-PRK were divided into two groups according to the amount of myopic correction by the median value (Group 1 < or = -4.37D, 97 eyes, mean -3.26 +/- 0.77D; Group 2 > -4.37D, 96 eyes, mean -5.77 +/- 1.00D). Wavefront aberrometry was performed to measure total HOA, coma, trefoil, and spherical aberration preoperatively and at 1, 3, 6, 12, and 24 months after ASA-PRK. Statistical analysis was performed to compare changes in all HOAs between the two groups. RESULTS: Each magnitude of total HOA, coma, and spherical aberration except trefoil significantly increased at 1, 3, 6, 12, and 24 months postoperatively in each group (p<0.05), and the increases were statistically significantly higher in group 2 compared to those of group 1 (p<0.05). The amount of changes in all HOAs except trefoil revealed that statistically significantly higher increases in group 2 compared to those of group 1 were determined only in the short-term period (up to 1 month, p<0.05), but not in the medium-term (1 to 6 months) or long-term periods (6 to 24 months). CONCLUSIONS: Postoperative total HOA, coma, and spherical aberration significantly increased in both groups, and these increases in surgery-induced HOAs were significantly higher in group 2 (> -4.37D). Increases in ASA-PRK-induced HOAs primarily originated from short-term changes in the postoperative one-month period and did not return to the preoperative level during the postoperative two-year period.
Aberrometry ; Aniline Compounds ; Coma ; Eye ; Humans ; Lotus

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

PURPOSE: To evaluate the safety, clinical outcome, and change in higher-order wavefront aberrations (HOAs) of Advanced Surface Ablation-Photorefractive Keratectomy (ASA-PRK) for the correction of mild to moderate myopia in cases with a thin cornea. METHODS: ASA-PRK was performed, using a rotary epithelial scrubber, post-laser chilled BSS(R) irrigation, and bandage contact lens, in 127 eyes of 70 patients who had a preoperative spherical equivalent within -7.0 D and who were followed-up for more than six months. The patients were divided into two groups, according to their central corneal thickness (CCT), by ultrasonic pachymetry (Group: CCT< or =520 micrometer, 32 eyes, mean 506.6+/-8.6 micrometer; Group: CCT>520 micrometer, 95 eyes, mean 552.3+/-24.8 micrometer). The clinical outcomes of Group I and II were compared. RESULTS: At six months, 100% of Group I (32/32 eyes) and 93.7% of Group II (89/95 eyes) had an UCVA of 1.0 or better (p>0.05). At six months, a spherical equivalent within 0.5 D of emmetropia was observed in 100% (32/32) of the eyes in Group I and in 94.7% (90/95) of the eyes in Group II (p>0.05). At the 12-month follow-up, all eyes showed good stability of the refractive errors, and none showed corneal haze of grade 1 or more, loss of two or more lines of BSCVA, or serious iatrogenic keratectasia. The magnitude of total HOAs, spherical ablation, and coma were significantly higher six and 12 months after surgery in both groups (p<0.05). The postoperative changes in the HOAs at six and 12 months were similar in both groups (p>0.05). CONCLUSIONS: ASA-PRK performed on patients with mild to moderate myopia and a thin cornea (> or =490 micrometer) showed a high level of efficacy, predictability, stability, and safety. There was no statistically significant difference in surgically induced HOAs between Groups I and II. The authors suggest that ASA-PRK be used for the correction of mild to moderate myopia, especially in cases with a thin cornea. Further study will be needed to determine the safety of this procedure for thinner corneas in surface keratorefractive surgery.
Bandages ; Coma ; Cornea* ; Emmetropia ; Follow-Up Studies ; Humans ; Myopia* ; Refractive Errors ; Ultrasonics

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 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 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: In this study we investigated pathogenic organisms, antibiotic susceptibility, and clinical characteristics of patients with Gram-negative bacterial keratitis and elucidated risk factors for poor visual outcomes. METHODS: The authors performed a retrospective chart review of 161 eyes (169 isolates) with Gram-negative bacterial keratitis between January 1998 and December 2012 at Yeungnam University Hospital. The study was divided into 5 periods for analysis of the bacteriological profiles and in vitro antibiotic sensitivity. The epidemiological and clinical characteristics were compared according to 3 groups (Pseudomonas species, Enterobacter species, and Serratia marcescens). Additionally, logistic regression analysis was performed to determine the risk factors. RESULTS: The prevalence of Gram-negative organisms increased from 34.7 to 73.2% between the 1st and 5th periods (p < 0.001). Pseudomonas spp. was the most commonly isolated organism (55 eyes, 32.5%) over the total period, followed by Enterobacter spp. (41 eyes, 24.3%) and Serratia marcescens (33 eyes, 19.5%). The effective antibiotics against Gram-negative bacterial pathogens isolated from culture were cefepime (94.5%), levofloxacin (93.4%), ciprofloxacin (93.0%), and amikacin (92.3%). The incidence was higher in the elderly over 60 years of age and in early adulthood patients in their 20s and 30s. The frequent predisposing factors were contact lens wearing and corneal trauma. S. marcescens had the shortest corneal epithelium healing time (p = 0.012) and the most favorable visual outcome after treatment (p = 0.004) compared with the other species. Risk factors for poor visual outcomes included a best corrected visual acuity less than 0.1 at initial evaluation (p < 0.001) and central corneal lesion (p = 0.027). CONCLUSIONS: Gram-negative bacterial keratitis tended to increase and Pseudomonas spp. was the most common isolate. The clinical prognosis was most favorable in S. marcescens. Early diagnosis of Gram-negative bacterial keratitis and appropriate antibiotic selection including cefepime, quinolone, or amikacin are recommended.
Aged ; Amikacin ; Anti-Bacterial Agents ; Causality ; Ciprofloxacin ; Early Diagnosis ; Enterobacter ; Epithelium, Corneal ; Humans ; Incidence ; Keratitis* ; Levofloxacin ; Logistic Models ; Prevalence ; Prognosis ; Pseudomonas ; Retrospective Studies ; Risk Factors ; Serratia ; Serratia marcescens ; Visual Acuity

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