Laser in situ keratomileusis for hyperopia with the LADARVision 4000 with centration on the coaxially sighted corneal light reflex

PURPOSE: To analyze the visual acuity, contrast sensitivity, and target deviations in patients who had laser in situ keratomileusis (LASIK) for primary hyperopia with the ablation centered on the coaxially sighted corneal light reflex. SETTING: University-based refractive surgery practice. METHODS: Retrospective review comprised 37 consecutive patients (61 eyes) who had LASIK for hyperopia with the LADARVision 4000 excimer laser (Alcon Laboratories). Preoperative and 3-month postoperative visual acuity and contrast sensitivity, as well as the target deviation, were assessed for each eye. The change in best spectacle-corrected visual acuity (BSCVA), best spectacle-corrected contrast sensitivity (BSCCS), and target deviation from the intended correction were analyzed. RESULTS: Postoperatively, the uncorrected visual acuity (UCVA) was 20/20 or better in 44.4% of eyes. The mean deviation from target was +0.25 diopter (D) +/- 0.82 (SD), with 65.6% of eyes within +/-0.50 D of target. None eye lost 2 or more lines of BSCVA. A loss of 3 or more patches of BSCCS were seen in 6.6% of the eyes and a loss of 4 or more patches, in 1.6%. CONCLUSION: Hyperopic LASIK with LADARVision 4000 with the ablation zone centered on the coaxially sighted corneal light reflex did not adversely affect BSCVA and BSCCS.     

Pupil center shift relative to the coaxially sighted corneal light reflex under natural and pharmacologically dilated conditions

PURPOSE: To evaluate the location and shift of the pupil center relative to the coaxially sighted corneal reflex on horizontal and vertical planes under natural and pharmacologically dilated conditions. METHODS: Ninety-four (64 myopic and 30 hyperopic) eyes of 47 patients underwent pupillometry with the NIDEK OPD-Scan under photopic and mesopic conditions before and after instillation of cyclopentolate 1%. Horizontal, vertical, and vectorial shift of the pupil center were calculated between each condition. RESULTS: The pupil center was located temporally to the coaxially sighted corneal reflex a mean distance of 0.336 +/- 0.181, 0.345 +/- 0.195, and 0.339 +/- 0.170 mm under photopic, mesopic, and pharmacologically dilated conditions, respectively. The pupil center shifted primarily inferotemporally (44%), followed by inferonasally (22%), superotemporally (19%), and superonasally (15%) from photopic to pharmacologic dilation. Mean magnitude of pupil shift was 0.084 +/- 0.069 mm (range: 0.010 to 0.385 mm) from mesopic to photopic, 0.149 +/- 0.080 mm (range: 0.013 to 0.384 mm) from photopic to pharmacologic dilation, and 0.102 +/- 0.104 mm (range: 0 to 0.530 mm) from mesopic to pharmacologic dilation. Mean distance between the pupil center and the coaxially sighted corneal reflex was greater in hyperopes than in myopes (P < .05), but no significant difference was observed in pupil center shifts between myopes and hyperopes under all three conditions (P > .05). CONCLUSIONS: The pupil center is located temporally and shifts in every direction, primarily inferotemporally, relative to the coaxially sighted corneal reflex with natural and pharmacologic dilation. The horizontal distance between the pupil center and the coaxially sighted corneal reflex was significantly higher in hyperopes than in myopes.     

Pupil decentration and iris tilting detected by Orbscan: anatomic variations among healthy subjects and influence on outcomes of laser refractive surgeries

PURPOSE: To investigate the anatomic variations of entrance pupil decentration and tilting angle of the iris in healthy subjects and the influence of these factors on the outcome of laser in situ keratomileusis (LASIK). SETTING: Minamiaoyama Eye Clinic, Tokyo, Japan. METHODS: The degree of pupil decentration and tilting angle of the iris in 2280 eyes of 1144 myopic patients without abnormal findings by ophthalmologic examination were assessed using Orbscan. Of these, 901 eyes of 467 patients had LASIK. Multiple analysis of variance (ANOVA) was used to determine risk factors for reduction of postoperative best spectacle-corrected visual acuity (BSCVA) considering patient age, refractive power, tilting angle of the iris, pupil decentration, and corneal power. RESULTS: The mean pupil decentration in all eyes was 0.19 mm +/- 0.11 (SD) (range 0 to 0.9 mm); tilting angle of the iris was 4.06 +/- 1.41 degrees (range 0.19 to 12.69 degrees). By multiple ANOVA, refractive power, pupil decentration, and tilting angle of the iris were significant for the reduction of BSCVA. CONCLUSIONS: Some eyes with pupil decentration or tilting angle of the iris could not be detected under typical ophthalmologic examination but only with topographic examination. Attention should be paid to eyes with large pupil decentration and tilting angle of the iris because these may be risk factors for reduction of postoperative BSCVA during corneal refractive surgeries.     

Ablation centration in laser in situ keratomileusis for hyperopia: comparison of VISX S3 ActiveTrak and VISX S2

PURPOSE: To compare ablation centration and outcome measurements in laser in situ keratomileusis (LASIK) for hyperopia using the pupil-tracking VISX S3 ActiveTrak or the nontracking VISX S2 excimer laser. METHODS: In a retrospective study, 49 consecutively treated hyperopic eyes (32 patients) that had LASIK by the VISX StarS3 ActiveTrak were compared to 49 control-matched eyes treated with the VISX StarS2 without pupil-tracking. Primary outcome variables including ablation centration, uncorrected visual acuity, best spectacle-corrected visual acuity, manifest refraction, complications, and induced cylinder analyzed by vector analysis were evaluated 3 months postoperatively. RESULTS: Hyperopic sphere ranged between plano and +5.50 D and cylinder between 0 and +2.75 D. Ninety-five of 98 eyes (96.9%) were available for analysis at 3 months. Of these 95, 52 eyes could be used for analysis of ablation centration. Mean decentration of the ablation zone from the entrance pupil was 0.30 +/- 0.20 mm in tracked eyes (n=31) and 0.41 +/- 0.39 mm in nontracked eyes (n=21), P=.17. Two eyes (6.5%) in the tracked group were significantly decentered between 0.5 and 1 mm from the pupil center. In the nontracked group, decentration was between 0.5 and 1 mm in one eye (4.8%) and greater than 1 mm in two eyes (9.5%). CONCLUSIONS: Comparable ablation centration in LASIK for hyperopia was achieved between actively-tracked and nontracked eyes. Decentrations (greater than 1 mm) were not seen with a tracking system in this study. Visual and refractive results were similar between the VISX StarS3 ActiveTrak and VISX StarS2 laser systems.     

Topographic centration of ablation after LASIK for myopia using the CustomVue VISX S4 excimer laser

PURPOSE: To determine the ablation centration, efficacy, predictability, and safety of CustomVue LASIK using the VISX S4 excimer laser for the treatment of myopia and myopic astigmatism. METHODS: A retrospective review of 20 myopic eyes of 12 patients treated with LASIK CustomVue VISX S4 was conducted. Corneal topography was used to determine ablation centration. Primary outcome variables including manifest refraction, best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), and complications were evaluated at 3 months postoperatively. RESULTS: Mean decentration (from ablation zone to entrance pupil) was 0.23 +/- 0.08 mm at 3 months postoperatively. No eyes were decentered > 0.5 mm. Preoperatively, the mean spherical equivalent refraction was -4.81 +/- 11.39 diopters (D) (range: -6.75 to -2.25 D). At 3 months postoperatively, mean spherical equivalent refraction was -0.63 +/- 0.25 D (range: -2.00 to 0.25 D). Nineteen (95%) of 20 eyes had UCVA of 20/40 and 16 (80%) of 20 eyes had UCVA of 20/20 at 3 months postoperatively. Fourteen (70%) eyes were within +/- 0.50 D and 18 (90%) eyes were within +/- 1.00 D of emmetropia. No eye lost > 1 line of BSCVA. CONCLUSIONS: Wavefront-guided LASIK using the CustomVue VISX S4 for myopic eyes results in minimal decentration ablation and effective, predictable, and safe visual outcomes.     

准分子激光角膜切削中心的角膜地形图分析

目的探讨准分子激光角膜切削术（ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｋｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）的切削中心对视功能的影响。方法采用Ｅｙｅｓｙｓ角膜形态分析系统对随访６个月以上的９８例（１５８只眼）ＰＲＫ前、后１０天的角膜地形图进行分析，确定激光切削中心相对入射瞳孔中心的方向、距离；比较单区和多区域激光切削的偏中心差异。结果切削区中心相对入射瞳孔中心：０～０．５ｍｍ者１００只眼（６３．３％），０．５～１．０ｍｍ者５５只眼（３４．８％），＞１．０ｍｍ者３只眼（１．９％），平均０．４５ｍｍ。多区域切削３８只眼及单区域切削１２０只眼，其偏心量分别为０．５５ｍｍ和０．４４ｍｍ。差异有显著性（ｔ检验，Ｐ＜０．０５）。偏中心切削致术后最好矫正视力下降１～２行者４只眼，其偏心量＞０．５ｍｍ。结论严重的偏心切削将影响术后视功能恢复，术中眼球跟踪系统（ｐａｓｓｉｖｅｅｙｅ－ｔｒａｃｋｉｎｇ，ＰＥＴ）的应用有利于切削中心的确定，减少偏心量。     

Comparison of visual effects of FS-LASIK for myopia centered on the coaxially sighted corneal light reflex or the line of sight

AIM: To compare visual quality after femtosecond laser in situ keratomileusis (FS-LASIK), between the coaxially sighted corneal light reflex (CSCLR) group and conventional ablation line of sight (LOS) group. METHODS: In total, 243 eyes (122 patients) were treated with centration on the CSCLR (visual axis) and 238 eyes (119 patients) treated with centration on the pupil center (LOS). Postoperative outcomes [uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA)], safety index, efficacy index, refractive outcome, ablation center distance from the visual axis, corneal high-order aberrations, subjective discomfort glare and shadowing incidence rate, and contrast sensitivity at 1, 3, and 6mo were measured and compared. RESULTS: The mean age was 27.77±7.1y in the CSCLR group and 26.03±7.70y in the LOS group. Preoperatively, the manifest refraction spherical equivalent (MRSE) was -6.68±2.60 D in the CSCLR group and -6.65±2.68 D in the LOS group. The postoperative UCVA, BSCVA, MRSE (-0.03±0.263 D in the CSCLR group, -0.05±0.265 D in the LOS group), efficacy index (1.04, 1.03), and safety index (1.09, 1.08) were not significantly different between the groups (all P>0.05). In total, 3% lost one line and more of BSCVA in the CSCLR group, as 9% in the LOS group postoperatively (P<0.05). The ablation center deviation was 0.20±0.15 mm from the visual axis (Pentacam system default setting; range, 0-0.75 mm) in the CSCLR group, and 0.43±0.22 mm (range, 0-1.32 mm) in the LOS group (P<0.0001). Statistically significant greater augmentation of total corneal higher-order aberrations (0.15±0.10 µm and 0.20±0.12 µm respectively, P=0.03) and vertical and horizontal coma (P<0.0001) were noted in the LOS group. Subjective discomfort glare and shadowing incidence rates were 8.59% and 17.5% in the CSCLR and LOS groups, respectively (P<0.05). The 1-month postoperative contrast sensitivity visual acuity in the CSCLR group was significantly higher than that in the LOS group on contrast (100%, 25%, 10%) with a dark background, but there was no significant difference between the groups at 3 or 6m. CONCLUSION: Myopic LASIK centered on the CSCLR achieves significantly lower induction of loss of BSCVA, corneal high-order aberrations, and lower risk of subjective discomfort glare and shadowing, and lower decline in early contrast sensitivity by comparison with centration on the LOS, giving advantages in visual quality postoperatively.     

Comparison of ablation centration in initial and retreatment active eye-tracker-assisted laser in situ keratomileusis and the effect on visual outcome

PURPOSE: To evaluate the relationship between initial and retreatment ablation centers in active eye-tracker-assisted myopic laser in situ keratomileusis (LASIK) and determine whether the relationship between the 2 ablation centers influences the visual outcome after retreatment. SETTING: Department of Ophthalmology, China Medical University Hospital, Taichung, Taiwan. METHODS: This retrospective study comprised 21 eyes of 15 patients who had retreatment at least 3 months after primary myopic LASIK by lifting the initial flap. Corneal topography and best corrected visual acuity (BCVA) were evaluated preoperatively and 3 months postoperatively. The ablation centration was analyzed by corneal topography preoperatively and at 3 months. RESULTS: The mean decentration of the primary treatment was 0.43 mm +/- 0.21 (SD) and of the retreatment, 0.34 +/- 0.15 mm. There was no significant difference between them (P =.07). The 2 ablation centers were close each other. The mean distance between the 2 ablation centers was 0.29 +/- 0.18 mm and the mean angle between them, 39.7 +/- 46.2 degrees. The BCVA was unchanged after retreatment regardless of the relationship between the 2 ablation centers. CONCLUSIONS: With an active eye-tracking system, the retreatment center was not only close to the pupil center but also close to the primary ablation center. Regardless of the relationship between the 2 ablation centers, the BCVA did not change if the retreatment ablation was well centered.     

Topography-guided treatment of decentered laser ablation using LaserSight's excimer laser

PURPOSE: To assess the efficacy of topography-guided laser ablation for correction of previously decentered laser ablation using LaserSight's excimer laser. METHODS: Re-treatment was performed to correct decentered ablation using LaserSight's excimer laser for 18 patients who previously underwent LASIK surgery for myopia correction in both eyes. For each patient, only the decentered eye was re-treated while the other asymptomatic eye forms a control group for this study. Measurements were conducted on ablation center, best spectacle-corrected visual acuity (BSCVA), contrast sensitivity and corneal aberrations pre- and post-operatively. RESULTS: For the retreated 18 eyes, the mean decentration was significantly reduced from 1.32+/-0.28mm to 0.61+/-0.23mm post-operatively (t=16.24, p<0.001), and with a significant improvement in mean BSCVA from 0.08+/-0.09 logMAR to 0.01+/-0.11 logMAR (t=4.58, p<0.001). The post-operative contrast sensitivity at the spatial frequencies (SF) of 1.00 and 0.70 was significantly improved (p<0.05 for both SFs). Corneal higher-order aberrations (HOAs), including the coma-like aberrations and spherical aberration, were decreased. In comparing the measurements for the retreated group to those for the control group, no significant differencewas found either in decentration or in BSCVA, but the contrast sensitivity at 0.70 was lower and the level of corneal aberrations was higher. CONCLUSIONS: Topography-guided ablation with LaserSight excimer laser is effective to correct decentered ablation. However, the re-treated eye is still inferior to the eye with originally centered ablation in corneal optical quality or visual performance.     

Comparison of ablation centration after bilateral sequential versus simultaneous LASIK

PURPOSE: To compare ablation centration after bilateral sequential and simultaneous myopic LASIK. METHODS: A retrospective randomized case series was performed of 670 eyes of 335 consecutive patients who had undergone either bilateral sequential (group 1) or simultaneous (group 2) myopic LASIK between July 2000 and July 2001 at the China Medical University Hospital, Taichung, Taiwan. The ablation centrations of the first and second eyes in the two groups were compared 3 months postoperatively. RESULTS: Of 670 eyes, 274 eyes (137 patients) comprised the sequential group and 396 eyes (198 patients) comprised the simultaneous group. Three months post-operatively, 220 eyes of 110 patients (80%) in the sequential group and 236 eyes of 118 patients (60%) in the simultaneous group provided topographic data for centration analysis. For the first eyes, mean decentration was 0.39 +/- 0.26 mm in the sequential group and 0.41 +/- 0.19 mm in the simultaneous group (P = .30). For the second eyes, mean decentration was 0.28 +/- 0.23 mm in the sequential group and 0.30 +/- 0.21 mm in the simultaneous group (P = .36). Decentration in the second eyes significantly improved in both groups (group 1, P = .02; group 2, P < .01). The mean distance between the first and second eyes was 0.31 +/- 0.25 mm in the sequential group and 0.32 +/- 0.18 mm in the simultaneous group (P = .33). The difference of ablation center angles between the first and second eyes was 43.2 < or = 48.3 degrees in the sequential group and 45.1 +/- 50.8 degrees in the simultaneous group (P = .42). CONCLUSIONS: Simultaneous bilateral LASIK is comparable to sequential surgery in ablation centration.     

Ablation centration in myopic laser in situ keratomileusis. comparing the Visx S3 ActiveTrak and the Visx S2

PURPOSE: To compare ablation centration and outcome measurements in myopic laser in situ keratomileusis (LASIK) using the eye-tracking Visx S3 ActiveTrak and the nontracking Visx S2 excimer lasers. SETTING: University-based refractive surgery practice. METHODS: In a retrospective study, 71 consecutively treated myopic eyes that had LASIK with the Visx Star S3 ActiveTrak were compared to 71 control-matched eyes treated with the Visx Star S2 without pupil tracking. Primary outcome variables including ablation centration, uncorrected visual acuity, best spectacle-corrected visual acuity, manifest refraction, complications, and induced cylinder analyzed by vector analysis were evaluated 3 months postoperatively. RESULTS: The myopia ranged from -1.50 to -11.25 diopters (D) and the cylinder, from +0.25 to +2.75 D. Ninety-four of 142 eyes (66%) were available for analysis at 3 months; 50 eyes could be used to analyze ablation centration. At 3 months, the mean decentration of the ablation zone from the entrance pupil was 0.22 mm +/- 0.20 (SD) in tracked eyes (n = 25) and 0.21 +/- 0.26 mm in nontracked eyes (n = 25) (P =.88). Three eyes (12%) in the tracked group were decentered 0.5 to 1.0 mm, and 1 eye (4%) in the nontracked group was decentered more than 1.0 mm. All other eyes were decentered less than 0.5 mm. There was an association in the tracked group between greater decentrations and higher levels of myopia (r = 0.67), but this association did not exist in the nontracked group (r = -0.03). CONCLUSION: Comparable ablation centration as well as visual and refractive outcomes can be achieved with and without active eye tracking during myopic and astigmatic myopic LASIK.     

Comparison of corneal aberration changes after laser in situ keratomileusis performed with mechanical microkeratome and IntraLase femtosecond laser: 1-year follow-up

PURPOSE: To compare corneal aberration changes 1 year after myopic laser in situ keratomileusis (LASIK) performed with a mechanical microkeratome and IntraLase femtosecond laser. METHODS: Twenty four eyes of 15 patients underwent LASIK with the Hansatome microkeratome, and 23 eyes of 13 patients underwent LASIK with the IntraLase femtosecond laser. A standard ablation was performed with the Bausch & Lomb Technolas 217 excimer laser. Topography data were used to calculate corneal aberrations with a 3.0 mm and 5.00 mm pupil, before and 12 months after surgery. The increasing factor (IF), defined as the ratio between the postoperative and preoperative mean value of the optical aberration, was calculated. The method of Mulhern et al was used to evaluate the centration of ablation. The comalike aberration was correlated with the decentration of ablation. The Student t test was used for the statistical anaylsis. RESULTS: The postoperative mean decentration of ablation was <0.5 mm. The comalike aberration appeared to be positively correlated with the decentration of ablation in both groups with a 5.0-mm pupil (P < 0.05). With a 3.00-mm pupil, the comalike aberration changed in the Hansatome group, whereas with a 5.00-mm pupil, all aberrations statistically significantly changed in both groups (P < 0.05). The IF similarly increased in 2 groups for spherical-like aberration, whereas IF greatly increased for total and comalike aberrations in the Hansatome group. CONCLUSIONS: Wavefront corneal aberrations change significantly 1 year after myopic LASIK performed with the Hansatome microkeratome as well as with IntraLase femtosecond lasers. Both of the procedures induce higher-order aberrations in the anterior corneal surface, but the amount of comalike aberration increases more with the Hansatome mechanical microkeratome.     

Factors influencing flap and INTACS decentration after femtosecond laser application in normal and keratoconic eyes

PURPOSE: To compare accuracy of LASIK flap and INTACS centration following femtosecond laser application in normal and keratoconic eyes. METHODS: This is a retrospective case series comprising 133 eyes of 128 patients referred for refractive surgery. All eyes were divided into two groups according to preoperative diagnosis: group 1 (LASIK group) comprised 74 normal eyes of 72 patients undergoing LASIK with a femtosecond laser (IntraLase), and group 2 (INTACS group) consisted of 59 eyes of 39 patients with keratoconus for whom INTACS were implanted using a femtosecond laser (IntraLase). Decentration of the LASIK flap and INTACS was analyzed using Pentacam. RESULTS: Temporal decentration was 612.56 +/- 384.24 microm (range: 30 to 2120 microm) in the LASIK group and 788.33 +/- 500.34 microm (range: 30 to 2450 microm) in the INTACS group. A statistically significant difference was noted between the groups in terms of decentration (P < .05). Regression analysis showed that the amount of decentration of the LASIK flap and INTACS correlated with the central corneal thickness in the LASIK group and preoperative sphere and cylinder in the INTACS group, respectively. CONCLUSIONS: Decentration with the IntraLase occurred in most cases, especially in keratoconic eyes. The applanation performed for centralization during IntraLase application may flatten and shift the pupil center, and thus cause decentralization of the LASIK flap and INTACS. Central corneal thickness in the LASIK group and preoperative sphere and cylinder in the INTACS group proved to be statistically significant parameters associated with decentration.     

Ablation centration after active eye-tracker-assisted photorefractive keratectomy and laser in situ keratomileusis

PURPOSE: To evaluate the ablation centration after active eye-tracker-assisted photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) and to investigate the effect of surgery, patient, and surgeon on the centration. SETTING: Department of Ophthalmology, China Medical College Hospital, Taichung, Taiwan, Republic of China. METHODS: This retrospective study comprised 177 eyes of 101 patients: 16 eyes had PRK and 161, LASIK. All laser treatments were performed with the aid of an eye tracker. The amount of decentration was analyzed by corneal topography. The factors influencing centration were divided into surgery related (PRK/LASIK), patient related (low/high myopia and effect of learning), and surgeon related (learning curve). RESULTS: The mean decentration was 0.33 mm in PRK eyes and 0.35 mm in LASIK eyes. For the surgery-related factor, there was no significant difference between the PRK and LASIK eyes. For the patient-related factors, centration was better in the second eye (effect of learning) and decentration was more severe in eyes with high myopia (low/high myopia). For the surgeon-related factor, there was no significant difference between eyes that had the first 50 LASIK procedures and those that had the last 50 procedures. CONCLUSIONS: An eye tracker, which makes the laser beam follow the eye's movements, helps to avoid severe decentration. This study showed, however, that an active eye-tracking system alone cannot ensure good centration. Patient cooperation and fixation are important.     

Changes in corneal topography after excimer laser photorefractive keratectomy for myopia

Computer-assisted analysis of corneal topography was performed in 17 normally sighted human eyes during the first year after excimer laser photorefractive keratectomy (PRK) for myopia. Laser ablation of the central cornea produced an optical zone with a smooth power transition to the peripheral cornea. Decentration of the ablation was noted in some eyes (less than 0.5 mm in 3 eyes, 0.5 to 1.0 mm in 10 eyes, 1 to 1.5 mm in 3 eyes, and 2.1 mm in 1 eye), suggesting that careful alignment of the laser beam is critical. Improved methods to align the ablation within the center of the entrance pupil are needed. In 12 of 17 eyes, the topographic pattern appeared to stabilize between 3 and 7 months after PRK. In the remaining five eyes, central ablation power changed by more than 0.5 diopters (D) between the 6- and 12-month examinations. Regression was more common and more pronounced in eyes with intended corrections more than 5 D, whereas the majority of eyes with intended corrections of 5 D or less showed good correspondence between the final change in central ablation power and the attempted correction. Two eyes had a loss of at least two lines of best spectacle-corrected visual acuity that was attributable to irregular astigmatism, decentration of the ablation, and/or corneal opacification.     

Tracker-assisted versus manual ablation zone centration in laser in situ keratomileusis for myopia and astigmatism

PURPOSE: Eye tracker systems have been developed concomitantly with small scanning beams to theoretically reduce ablation zone decentration and for accurate registration of all the laser pulses on the cornea. The purpose of the study was to compare the tracker-assisted with the manual centration method. METHODS: Twenty-five patients (48 eyes) with myopia and/or astigmatism had laser in situ keratomileusis (LASIK) between August 1998 and February 1999 with the Technolas 117C laser. Twenty patients (38 eyes, 80%) were available for follow-up at 3 months after surgery. Eyes were assigned randomly to one of two ablation zone centration methods: Group 1: Tracker-assisted (20 eyes), Group 2: Manual (18 eyes). RESULTS: Mean distance between the ablation zone center and the pupillary center in the tracker-assisted centration group was 0.55 +/- 0.30 mm (range, 0.10 to 1.4 mm), and in the manual centration group, 0.43 +/- 0.23 mm (range, 0.10 to 1.0 mm) (P = .177). There was no statistically significant difference in postoperative contrast sensitivity, glare, and Topographical Corneal Surface Regularity Index (SRI) between the two groups. CONCLUSIONS: We obtained good results with both centration methods. We did not find superiority of the tracker-assisted over manual regarding ablation zone centration, vision quality, or regularity of the ablation.     

Ablation centration after active eye tracker-assisted LASIK and comparison of flying-spot and broad-beam laser

PURPOSE: To evaluate ablation centration of flying-spot LASIK, investigate the effect of patient- and surgeon-related factors on centration, and compare flying-spot and broad-beam laser results. METHODS: This retrospective study comprised 173 eyes of 94 patients who underwent LASIK with the Alcon LADARVision4000 with an active eye-tracking system. The effective tracking rate of the system is 100 Hz. The amount of decentration was analyzed by corneal topography. Patient- (low, high, and extreme myopia; effect of learning) and surgeon-related (learning curve) factors influencing centration were identified. Centration was compared to the SCHWIND Multiscan broad-beam laser with a 50-Hz tracker from a previous study. RESULTS: Mean decentration was 0.36+/-0.18 mm (range: 0 to 0.9 mm). Centration did not differ in low, high, and extreme myopia or in patients' first and second eyes. There were no significant differences in centration between the first 50 LASIK procedures and the last 50 procedures. Comparing flying-spot and broad-beam laser results, there were no differences in centration in low myopia. However, the LADARVision4000 yielded better centration results in high and extreme myopia. CONCLUSIONS: The Alcon LADARVision4000 active eye tracking system provides good centration for all levels of myopic correction and better centration than the Schwind broad-beam Multiscan in eyes with high and extreme myopia.     

Measurement of the spatial shift of the pupil center

PURPOSE: To evaluate the effectiveness of the pupil center as an anatomic landmark for excimer laser treatments. SETTING: Sekal-Microchirurgia-Rovigo Centre, Rovigo, Italy. METHODS: Pupillometry with the Costruzione Strumenti Oftalmici S.R.L. (CSO) pupil-measuring module (incorporated in Eye Top videokeratoscope) was performed in 52 patients with a diagnosis of myopia and in 25 patients with a diagnosis of hyperopia. Measurements both in mesopic and photopic conditions consisted of pupil diameters, spatial shift of the pupil center, and the distance between the pupil center and keratoscopic axis. RESULTS: The mean pupil diameter in photopic conditions of illumination in myopic eyes was 3.52 mm +/- 0.56 (SD), while in mesopic conditions it was 5.37 +/- 0.78 mm; in hyperopic eyes the mean photopic pupil diameter was 3.01 +/- 0.46 mm, while the mean mesopic diameter was 5.12 +/- 0.48 mm. The mean spatial shift of the pupil center in myopic eyes was 0.086 mm (maximum 0.269 mm), while in the hyperopic eyes it was 0.095 mm (maximum 0.283 mm). The mean distance between the pupil center and keratoscopic axis in myopic eyes was 0.226 +/- 0.13 mm (maximum 0.75 mm), while in hyperopic eyes it was 0.45 +/- 0.19 mm (maximum 0.8 mm). CONCLUSIONS: The mean of the measured pupil sizes was greater in myopic eyes than in hyperopic eyes. The spatial shift of the pupil center, as the pupil dilates, was relatively small in all groups; therefore, the pupil center is a good anatomic landmark for both traditional refractive surgery and wavefront-guided treatments. The mean distance between the keratoscopic axis and pupil center was greater in the hyperopic group than in the myopic group. Therefore, centration of any laser treatment on the basis of the keratoscopic analysis should be done carefully, especially in hyperopic eyes and in cases in which the pupil center is meaningfully shifted from keratoscopic axis, even in photopic conditions of illumination.     

Topographic and biomechanical differences between hyperopic and myopic laser in situ keratomileusis

PURPOSE: To evaluate the size, shape, and uniformity of the videokeratographic functional optical zone (FOZ) after laser in situ keratomileusis (LASIK) in 2 cohorts of patients with equivalent amounts of preoperative myopic or hyperopic astigmatism. SETTING: Pepose Vision Institute, St. Louis, Missouri, USA. METHODS: Eyes with myopic or hyperopic astigmatism (n=27 in each group) that had LASIK with the Visx Star S3 laser were retrospectively selected to match for level of preoperative refractive error. Slit-scanning videokeratography was performed preoperatively and 6 months postoperatively and analyzed using custom software. The FOZ was calculated by analyzing refractive power maps using a region-growing algorithm. Difference maps were generated from slit images and compared for interval change in corneal elevation, tangential curvature, and refractive power. The difference maps were also averaged (mean difference maps) for each target population. A Zernike decomposition of corneal first-surface elevation was performed to compare postoperative values with baseline parameters. RESULTS: The mean postoperative refractive sphere at 6 months was -0.17 diopter (D) +/- 0.66 (SD) and +0.25 +/- 0.85 D in the myopia group and hyperopia group, respectively, and the mean postoperative astigmatism, -0.49 +/- 0.32 D and -0.65 +/- 0.52 D, respectively (P=.11). Based on the refractive power maps, the mean preoperative and postoperative myopic FOZ was 33.09 +/- 7.30 mm(2) and 30.94 +/- 5.43 mm(2), respectively, and the mean hyperopic FOZ, 33.19 +/- 7.96 mm(2) and 37.99 +/- 6.88 mm(2), respectively. After LASIK, there was an increase in magnitude of negative anterior corneal surface spherical-like Zernike values in the myopia group (P<.0001) and an increase in magnitude of positive spherical-like Zernike values in the hyperopia group. Postoperatively, significant induction of corneal surface horizontal coma was noted in hyperopic eyes (P<.0001). Hyperopic eyes, on average, had larger topographic FOZs after LASIK, but with less uniformity of curvature and power change than myopic eyes. CONCLUSIONS: Hyperopic LASIK, which involves more transition points along the ablation diameter, produced a less uniform topographic FOZ than typical myopic treatments. Less predictable biomechanical changes from the circumferential release of tension on collagen bundles after midperipheral hyperopic ablation and greater variation in beam centration and the angle of incidence may contribute to the greater variability in corneal curvature and power in hyperopic LASIK than in myopic LASIK.     

Intraocular lens centration and visual outcomes after bag-in-the-lens implantation

PURPOSE: To examine the centration and visual outcomes after cataract surgery using the bag-in-the-lens (BIL) implantation technique. SETTING: University Hospital Antwerp, Department of Ophthalmology, Edegem, Belgium. METHODS: This study comprised 180 eyes of 125 patients who had cataract surgery with implantation of the BIL intraocular lens (IOL) between March 2002 and September 2005. Postoperative data at 5 weeks, 6 months, and 1 year were evaluated. The geometric center of the IOL, measured on a red reflex slitlamp photograph, was compared with the geometric center of the pupil and the limbus. RESULTS: The mean decentration compared with the limbus was 0.304 mm+/-0.17 (SD) at a mean angle of -24.9+/-113.3 degrees. Compared with the dilated pupil, the mean deviation was 0.256+/-0.15 mm at a mean angle of -5.2+/-119.0 degrees. The amount of decentration was stable during the postoperative follow-up period. There was no correlation between the amount of decentration and the visual outcomes (pupil: r=-0.07, P=.494; limbus: r=0.11, P=.304). CONCLUSIONS: Surgeon-controlled BIL centration was predictable 5 weeks and unchanged 6 months and 1 year postoperatively. It can therefore be concluded that capsular bag healing has no influence on BIL IOL centration over time.