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Purpose: To evaluate the postoperative visual outcomes, that is, corneal higher?order aberrations (HOAs) and visual quality, of patients with an angle kappa greater than 0.30 mm who underwent angle kappa adjustment during small?incision lenticule extraction (SMILE) 2 years after surgery compared to eyes with an angle kappa less than 0.30 mm. Methods: This was a retrospective study and included 12 patients from October 2019 to December 2019 who underwent the SMILE procedure for correction of myopia and myopic astigmatism and had one eye with a large kappa angle and another eye with a small kappa angle. Twenty?four months after surgery, an optical quality analysis system (OQAS II; Visiometrics, Terrassa, Spain) was used to measure the modulation transfer function cutoff frequency (MTFcutoff), Strehl2D ratio, and objective scatter index (OSI). HOAs were measured with a Tracey iTrace Visual Function Analyzer (Tracey version 6.1.0; Tracey Technologies, Houston, TX, USA). Assessment of subjective visual quality was achieved using the quality of vision (QOV) questionnaire. Results: At 24 months postoperatively, the mean spherical equivalent (SE) refraction was ? 0.32 ± 0.40 and ? 0.31 ± 0.35 in the S?kappa group (kappa <0.3 mm) and the L?kappa group (kappa ?0.3 mm), respectively (P > 0.05). The mean OSI was 0.73 ± 0.32 and 0.81 ± 0.47, respectively (P > 0.05). There was no significant difference in MTFcutoff and Strehl2D ratio between the two groups (P > 0.05). Total HOA, coma, spherical, trefoil, and secondary astigmatism were not significantly different (P > 0.05) between the two groups. Conclusion: Adjustment of angle kappa during SMILE helps reduce the decentration, results in less HOAs, and promotes visual quality. It provides a reliable method to optimize the treatment concentration in SMILE.
ABSTRACT
@#AIM: To study the postoperative optical zone decentration and visual quality by taking visual axis corneal reflect point(VACRP)and corneal vertex(CV)as the ablation center, exploring the femtosecond laser small incision lenticule extraction(SMILE).<p>METHODS: Prospective randomized controlled trial. Totally 70 myopic patients(140 eyes)who underwent SMILE surgery in our hospital from May to June 2020 were randomly divided into two groups, 68 eyes of 34 cases took the VACRP as the ablation center(VACRP group), and 72 eyes of 36 cases took the CV as the ablation center(CV group). The visual acuity, refractive diopter, offset from corneal ablation center, and high-order corneal aberrations were observed before and 3mo after surgery. <p>RESULTS: Three months after operation, there was no difference in uncorrected visual acuity, best corrected visual acuity and refractive diopter between the two groups(<i>P</i>>0.05). The ablation center deviation in CV group(0.20±0.13mm)was less than that in VACRP group(0.27±0.14mm, <i>P</i><0.01). The total corneal high-order aberration(totHOA), spherical aberration(totZ40), vertical coma(totZ3-1)and horizontal coma(totZ31)in CV group were lower than VACRP group(<i>P</i><0.05). Three months after operation, the totHOA, total high-order aberration change(ΔtotHOA), totZ40, totZ3-1 in VACRP group were correlated with ablation center deviation(<i>r</i>=0.470, 0.486, 0.254, -0.366, <i>P</i><0.001, =0.001, 0.037, 0.002), totZ31 in CV group was correlated with the ablation center deviation(<i>r</i>=-0.352, <i>P</i>=0.002).<p>CONCLUSION: SMILE surgery can obtain satisfactory uncorrected visual acuity and the same level of refractive diopter with the VACRP and the CV as the ablation center, but taking the CV as the ablation center can reduce the postoperative decentration and high-order corneal aberrations and obtain better visual quality.
ABSTRACT
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 or =-0.50 D and 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.
Subject(s)
Humans , Corneal Topography , Displacement, Psychological , Eye , Learning , Pupil , Risk FactorsABSTRACT
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.
Subject(s)
Humans , Corneal Topography , Photorefractive Keratectomy , Pupil , Retrospective StudiesABSTRACT
PURPOSE: To identify factors influencing the ablation center and to evaluate the size of the ablation zone after PRK and LASIK using Technolas 217 C. METHODS: This study examined the results of refractive surgery using Technolas 217 C Excimer laser with eye tracking system in 69 eyes, of which 31 underwent PRK and 38 LASIK. The ablation zone and degree of decentration were determined through corneal topography. We divided the eyes into two groups according to the degree of decentration: less than 0.5 mm as the first group, and from 0.5 to 1.0 mm as the second. The ablation zone diameter in topography was compared with the programmed preoperative optical zone. RESULTS: The only factor influencing the ablation center in the PRK group was preoperative spherical equivalent(p=0.016), and no factor influenced the ablation zone in the LASIK group. In both groups, the long axis of the ablation zone was longer than that of the programmed optical zone(p=0.003), while the short axis was shorter (p=0.001). CONCLUSIONS: After refractive surgery using Technolas 217 C Excimer laser with eye tracking system, there was no clinically significant decentration. With greater preoperative spherical equivalent, more decentered ablation was noted in the PRK group. The topographical long axis of the ablation zone was longer than that of the programmed ablation zone, while the short axis of the ablation zone was shorter. During refractive surgery, we should be aware of the possibility that the short axis of the postoperative ablation zone may be shorter than that of the programmed preoperative optical zone.