Standard LASIK Research Articles

Corneal stromal roughness after VisuMax and Intralase femtosecond laser photodisruption: An atomic force microscopy study.

PurposeTo compare the induced corneal stromal bed roughness measured with atomic force microscopy (AFM) after LASIK flap creation with the IntraLase 60 kHz and the VisuMax femtosecond laser platforms.MethodsThree freshly enucleated porcine eyes were operated with each femtosecond laser in this experimental study. Standard LASIK treatment parameters were used for the experiment. After LASIK flap creation, the corneal stromal roughness was assessed using a JPK NanoWizard II® AFM in contact mode immersed in liquid. Olympus OMCL-RC800PSA commercial silicon nitride cantilever tips were used. Surface measurements were made in 10 regions of the central cornea of each sample measuring 20 x 20 microns, at 512 x 512 point resolution. Roughness was measured using the root-mean-square (RMS) value within the given regions.ResultsMeasurements from 30 regions of the 3 eyes (10 measurements per eye) in the Intralase (FS1) group, and 30 regions of the 3 eyes (10 measurements per eye) in the VisuMax (FS2) group were analyzed. There was a statistically significant difference in mean ± standard deviation RMS values between the FS1 and the FS2 groups (360 ± 120 versus 230 ± 100 nm respectively; P< 0.00001).ConclusionThis AFM study indicates that the surface of the stromal bed after LASIK flap creation is smoother in the FS2 group than the FS1 group.

Effects of femtosecond and excimer lasers on implanted KAMRA corneal inlay in animal models

To evaluate the effect of femtosecond laser and excimer laser on an intracorneal inlay (KAMRA®) implanted in animal models. Femtosecond laser was used to create corneal intrastromal pockets at 250μm depth in five porcine eyes. Four intact KAMRA inlays, examined by slit-lamp biomicroscopy and light microscopy, were implanted in the pocket of four eyes. A standard LASIK flap was created above each implanted inlay in the four eyes using a femtosecond laser with flap thicknesses of 150μm, 130μm, 110μm and 90μm. In the fifth porcine eye, a LASIK flap was created using femtosecond laser at 110μm depth, and a fifth inlay was then implanted in the 250μm pocket. Excimer laser ablation was performed under the flap targeting a -3.00 refraction. The inlay was then explanted, examined and reimplanted in the same pocket followed by a second similar excimer laser ablation. Significant burn, shrinkage and distortion of microholes were noted in all the first four inlays following the femtosecond laser flap creation at all the various flap thicknesses. The damage was noted to be more prominent as the distance between the flap and inlay decreased. No apparent effect was noted on the fifth inlay following repeated excimer laser ablations. Unlike excimer laser, femtosecond laser appears to be hazardous and damaging to the intracorneal KAMRA inlay when applied above it.

Re-Lifting the Lasik Flap 16 Years after Primary Surgery

A forty-six-year-old Bahraini male patient presented with diminished vision in both eyes; he had a history of standard LASIK surgery 16 years ago to treat myopia and astigmatism. The pre-operative refraction was -5.50 D sphere, -2.00 D cylinder × 180 ○ in the right eye and -5.00 D sphere, -2.00 D cylinder × 160 ○ in the left eye. The original LASIK flap was re-lifted successfully after 16 years of primary LASIK surgery. Therefore, this will save the cornea from further incision. Enhancement laser treatment was performed for residual myopia and astigmatism after lifting a 16-year-old LASIK flap at King Hamad University Hospital, Bahrain. Bahrain Med Bull 2014; 36(2):103-104

LASIK following Small Incision Lenticule Extraction (SMILE) Lenticule Re-Implantation: A Feasibility Study of a Novel Method for Treatment of Presbyopia

Presbyopia remains a major visual impairment for patients, who have previously undergone laser refractive correction and enjoyed unaided distance vision prior to the onset of presbyopia. Corneal stromal volume restoration through small incision lenticule extraction (SMILE) lenticule re-implantation presents an opportunity for restoring the patients’ non-dominant eye to previous low myopia to achieve a monovision. In this study, we investigated the feasibility of performing LASIK after lenticule re-implantation as a method to create presbyopic monovision. A -6.00D SMILE correction was performed in 9 rabbit eyes. The lenticules were cryopreserved for 14 days and re-implanted. Five weeks later, 3 of these eyes underwent LASIK for -5.00D correction (RL group); 3 underwent LASIK flap creation, which was not lifted (RN); and no further procedures were performed on the remaining 3 eyes. These groups were compared with 3 eyes that underwent standard LASIK for a -5.00D correction (LO); 3 that underwent creation of non-lifted flap (LN); and 3 non-operated eyes. Rabbits were euthanized 1 day post-surgery. Tissue responses were analyzed by immunohistochemistry, slit lamp and in vivo confocal microscopy (IVCM). Intrastromal irregularities and elevated reflectivity levels of the excimer-ablated plane were observed on slit lamp and IVCM, respectively in the RL group. The results were comparable (P = 0.310) to IVCM findings in the LO group. RL and LO groups showed similar fibronectin expression levels, number of CD11b-positive cells (P = 0.304) and apoptotic cells (P = 0.198). There was no difference between the RN and LN groups in reflectivity levels (P = 0.627), fibronectin expression levels, CD11b-positive cells (P = 0.135) and apoptotic cells (P = 0.128). LASIK can be performed following lenticule re-implantation to create presbyopic monovision. The tissue responses elicited after performing LASIK on corneas that have undergone SMILE and subsequent lenticule re-implantation are similar to primary procedure.

Temporal evolution of ocular aberrations following laser in situ keratomileusis

To study the temporal evolution of ocular aberrations after standard LASIK to correct myopia. The ocular, corneal and internal aberrations for a 6-mm pupil were measured in 22 young myopic eyes (n = 12 subjects; range -2.0 to-7.6 D) before and during a 9-month follow-up after standard myopic LASIK. Ocular aberrations were measured with a Hartmann-Shack wavefront sensor, while corneal aberrations were estimated from the elevation data obtained by corneal topography. For every patient and condition the eye's modulation transfer function (MTF) and Strehl ratio (SR) were calculated. Compared to preoperative results, we found that standard myopic LASIK produced a significant increase of ocular high-order aberrations at 1 month after surgery. During the next 8 months, we found a small increase of ocular and corneal positive spherical aberration (SA), although with a large inter-subject variability. However, all eyes treated for myopia higher than -5 D showed a significant increase of positive SA during the first 6 months after surgery. Standard myopic LASIK decreases ocular optical quality. For most subjects, the increase in aberrations induced by the surgery was stable during the next 9 months after LASIK. However, further changes of the ocular SA after myopic LASIK are possible in patients treated for higher amounts of myopia. The changes in aberrations mainly appeared between the first and the sixth month after surgery, which suggests the need to wait at least 6 months after myopic LASIK before comparing outcomes, especially for patients treated for higher myopias.

Comparison of Q-value guide LASIK and standardized LASIK for the treatment of myopia:a meta-analysis

Background Nowadays,customized ablation is widely used in the excimer laser corneal refractive Burgery.And the Q-value guide LASIK is one of the research hotspots. Objective Present study was to evaluate and compare the effectiveness of Q-value guide LASIK and standardized LASIK for myopia.Methods A systematic literature retrieval from 2003 through 2010 was conducted in the MEDLINE,CNKI,Cochrane Library,EMBASE.The literature examine possible difierences in uncorrected visual acuity(UCVA),Q-value,higher order aberrations(HOAs),and spherical equivalent(SE) between Q-value guide LASIK and standardized LASIK for correcting myopia.Statistical analysis was performed using a Review Manager 5.0 software.The data was extracted,and the methodological quality was evaluated by two reviewers independently.The quality of included literature was scored according to the Jadad Scale. Results A total of 14 studies involving 1617 patients(2956 eyes)was included in the meta-analysis.Of these fourteen studies,six studies were randomized trials and the other eight studies were retrospective cohort studies.According to the Jadad Scale,2 studies scored 3 points,and the other 12 studies scored 1～2 points.The results showed that the Q-value guide LASIK group had a better postoperative effectiveness in uncorrective visual acuity(UCVA)(WMD=0.04.95% CI 0.00 to 0.08,P<0.05).Q-value(SMD=-1.52,95% CI -2.23 to-0.81,P=0.00),total HOAs (SMD=-1.63,95% CI-2.57 to-0.69,P<0.05) and spherical-like aberrations ( SMD =-1.49,95% CI-2.22 to-0. 76,P<0. 00) after surgery. However, the number of eyes achieved UCVA≥20/20 ( OR= 1.16,95% CI 0. 61 to 2. 19,P=0. 65) ,coma-like aberrations (SMD=-1. 02,95% CI-0. 36to 0.11,P=0.29) and SE (WMD=0.10,95% CI-0.11 to 0.31,P=0.34) after surgery were comparable.Conclusion The effectiveness of Q-value guide LASIK is superior to standardized LASIK for treatment of myopia.High-quality clinical randomized-controlled study should be performed to further evaluate the comparable outcome of Q-value guide LASIK with standard LASIK. Key words: Q-value guide; Laser in situ keratomileusis; Myopia; Meta analysis

Contrast Sensitivity after Zyoptix Tissue Saving LASIK and Standard LASIK for Myopia with 6-Month Followup

This control-matched comparative study evaluated changes in contrast sensitivity after Zyoptix tissue-saving (TS) LASIK and Planoscan standard LASIK (Technolas 217z, Bausch & Lomb) for myopia 6 months postoperatively. 102 TS LASIK-treated eyes were matched with 102 standard LASIK-treated eyes (divided into low, moderate, and high groups). There were no significant differences in refraction outcomes between the groups postoperatively. In high group, a significant reduction in contrast sensitivity after TS LASIK was found at high spatial frequencies (P < .05) under photopic conditions and at middle to high spatial frequencies (P < .05) under mesopic conditions. And significant reduction was also found in standard LASIK at high spatial frequency (P < .05) under mesopic conditions. The reduction was significantly lower in TS LASIK than that in standard LASIK at high spatial frequencies (P < .05) under mesopic conditions. TS LASIK was prone to reduce mesopic contrast sensitivity of high myopia at high spatial frequencies.

Correção das aberrações oculares nos retratamentos de LASIK personalizado e convencional

To compare the correction of ocular aberrations between custom and standard LASIK retreatment. Prospective, randomized trial with paired eye control of 74 eyes from 37 patients who underwent LASIK retreatment. Each patient underwent retreatment using Zyoptix LASIK (Bausch & Lomb) in 1 eye and Planoscan LASIK (Bausch & Lomb) in the fellow eye. Correction of ocular aberrations was compared between custom and standard LASIK retreatments. At 6 months, there was a statistically significant reduction in defocus, astigmatism, coma, spherical aberration, second, third, higher-order and total aberration in Zyoptix eyes. There was a statistically significant reduction in defocus, second-order and total aberration in Planoscan eyes. Custom retreatment was statistically superior than standard retreatment for correction of lower and higher ocular aberrations.

Minor Influence of Myopic Laser In Situ Keratomileusis on the Posterior Corneal Surface

To check whether myopic LASIK induces changes on the posterior corneal surface. A Scheimpflug system (Pentacam; Oculus, GmbH, Wetzlar, Germany) was used to measure preoperative and postoperative posterior corneal topography in 27 eyes (of 14 subjects) that had undergone standard myopic LASIK surgery (attempted corrections between -1.25 and -8.50 D) and on 18 nonoperated eyes (9 subjects). A hybrid porcine-plastic eye model was developed to validate the measurement technique. Longitudinal displacement of the posterior corneal apex and changes of the apical radius of curvature and asphericity were computed. Measurements on a hybrid model eye of known posterior corneal geometry showed that the measured posterior corneal radius of curvature was minimally affected by the geometry of the anterior surface. The measurements on patients showed that, on average, the only relevant (though clinically unimportant) change in radius of curvature and asphericity occurred the first day after surgery (DeltaR = -28 +/- 34 microm and DeltaQ = -0.06 +/- 0.06). No statistically significant change was observed afterward. The change in radius was more pronounced in the vertical direction than in the horizontal direction. On average, there was no significant displacement of the posterior corneal apex. Individual changes over time did not show a systematic trend across patients, and control subjects experienced changes of the same order of magnitude. The Pentacam Scheimpflug system can be used reliably to assess changes in the posterior corneal radius of curvature after LASIK. There is no evidence of surgically induced changes in the corneal posterior surface beyond 1 week after surgery.

Qualidade visual após retratamento de LASIK personalizado versus convencional

To evaluate visual quality after wavefront-guided LASIK versus standard LASIK in retreatment of primary LASIK for myopia and myopic astigmatism. A prospective study was performed with paired eye control of 74 eyes with LASIK retreatment. Each patient underwent retreatment using custom ablation (Zyoptix, Bausch & Lomb) in 1 eye and standard ablation LASIK (PlanoScan, Bausch & Lomb) in the contralateral eye. A complete ophthalmologic examination was performed, including evaluation of glare test and contrast sensitivity test, with a follow-up of 6 months. Zyoptix eyes showed better results of glare test and contrast sensitivity test than the contralateral eyes. Wavefront-guided LASIK produces better visual quality than standard LASIK in the retreatment of refractive errors after primary LASIK.

Resultados refracionais do retratamento de LASIK com ablação personalizada versus ablação convencional

To evaluate refractive outcomes of wavefront-guided LASIK (Zyoptix, Bausch & Lomb) versus standard LASIK (PlanoScan, Bausch & Lomb) in retreatment of primary LASIK for myopia and myopic astigmatism. A prospective, randomized trial with paired eye control of 74 eyes from 37 patients who underwent LASIK retreatment was performed. Each patient underwent retreatment using Zyoptix LASIK in 1 eye and Planoscan LASIK in the contralateral eye. A complete ophthalmologic examination was performed, including evaluation of high contrast visual acuity and manifest refraction, with a follow-up of 6 months. Both Zyoptix and Planoscan groups had similar values of high contrast visual acuity, gain and loss of best spectacle-corrected visual acuity, safety and efficacy indexes, percentage of eyes with spherical equivalent within +/- 0,50 D and +/- 1,00 D in the postoperative period of 6 months. In the Zyoptix group, the values of spherical component and spherical equivalent of manifest refraction were more hyperopic than in the Planoscan group in the postoperative periods of 1 week, 1, 3 and 6 months. The predictability of spherical equivalent correction was better for the Zyoptix group than for the Planoscan group at 6 months. Wavefront-guided LASIK with Zyoptix produces superior refractive outcomes than standard LASIK with Planoscan in retreatment of refractive errors after primary LASIK. High contrast visual acuity measures are not sensitive in showing the best technique.

Comparative study of multifocal LASIK for the correction of pre-presbyopic myopia

To evaluate the feasibility of multifocal LASIK for the correction of pre-presbyopic myopia In this prospective,comparative case series, thirty-two patients were recruited into the study,mean age was (38.5 +/- 2.7) years, standard LASIK using Planoscan was performed on the patient's dominant eye, while multifocal LASIK was performed on the nondominant eye. Routine examinations included distance and near vision, refraction, corneal topography, intraocular pressure, ultrasonic corneal pachymetry, contrast sensitivity function, amplitude of accommodation ,depth of defocus, wavefront aberration. The mean follow-up duration was 6.67 +/- 2.75 (range, 6 to 11 months). In the nondominant eyes,the near visual acuity was statistically significant difference, better in the postoperative visual acuity, however, there was no statistically significant difference between preoperation and postoperation in dominant eyes. The Q value of 6 mm diameter in the nondominant eyes was 0.081 +/- 0.274 (range, -0.53 to +0.53) and 0.464 +/- 0.266 (range, - 0.02 to +0.99) in the dominant eyes, significant difference were noted between two groups. Topography revealed high degree refractive power zone of (5.64 +/- 3.05) mm2 at central cornea in nondominant eyes. The wavefront analysis showed that after the multifocal procedure, a positive spherical aberration was induced ,which is opposite to that normally seen following a standard LASIK treatment for myopia. At 6 months, the nondominant eyes attained pseudoaccommodation of (0.84 +/- 0.61) diopters (range, 0 to 2.25 D), the amplitude of pseudoaccommodation are related to corneal multifocal index, spherical aberration. However, amplitude of accommodation was decreased (0. 10 +/- 0.67) diopters in dominant eyes at 6 months visit. The results of this study show that multifocal LASIK is safe and effective in preserving near vision for pre-presbyopic myopia patients . Multifocal LASIK are reasonably to induce pseudoaccommodation by decreasing negative spheric aberration.

Patient Satisfaction and Visual Symptoms After Wavefront-guided and Wavefrontoptimized LASIK With the WaveLight Platform

To investigate patient satisfaction and visual symptoms after wavefront-guided LASIK. A prospective, randomized, double-masked, controlled study comprised 200 eyes of 100 young patients who underwent LASIK for myopia and astigmatism. Patients were randomly divided into two different treatment groups: standard ablation using wavefront-optimized profiles (wavefront-optimized group) and aberration customized aspheric treatment ablation (customized group) using the WaveLight ALLEGRETTO platform. Patients were asked to complete questionnaires regarding reasons for surgery, satisfaction, and visual symptoms. Patients were followed for 6 months. The most frequent motivating factor for surgery was to improve uncorrected visual acuity (UCVA) in the wavefront-optimized and customized groups (both 100%), followed by freedom from spectacles (86.9% vs 96.3%). At 6 months postoperatively, over 95% of patients in both groups reported their UCVA was as good as anticipated and they were satisfied with the surgery and would recommend the operation to a friend or family member. Satisfaction was not correlated with age, attempted refractive error, residual refractive error, postoperative UCVA, or root-mean-square higher order aberration. The rate of postoperative overall visual symptoms was reduced and the mean analog scores of the symptoms in both groups did not change significantly postoperatively (P > .05). The rate of visual symptoms such as glare (8.7% vs 7.4%), halo (0% vs 7.4%), and night driving difficulty (8.7% vs 3.7%) decreased after LASIK at 6 months postoperatively in the wavefront-optimized and customized groups, respectively. Patient satisfaction was achieved in young myopic patients who underwent wavefront-guided and standard ("wavefront-optimized") LASIK. The rate of visual symptoms such as glare, halo, and night driving difficulty decreased postoperatively after both treatment protocols.

Wavefront-optimized Versus Wavefront-guided LASIK for Myopic Astigmatism With the ALLEGRETTO WAVE: Three-month Results of a Prospective FDA Trial

To compare visual outcomes using the WaveLight ALLEGRETTO WAVE to administer either wavefront-optimized (standard LASIK) or wavefront-guided (custom LASIK) treatments in myopic eyes. In this prospective, open-label, multicenter study conducted in the United States, 374 eyes were randomized by alternating enrollment to receive either wavefront-optimized or wavefront-guided LASIK treatments with this laser platform. Bilateral treatments were administered, with both eyes of each patient receiving the same treatment. Corneal flaps were created using the IntraLase femtosecond laser. In this FDA clinical trial, results at 3 months postoperatively revealed that 93% of eyes in both cohorts receiving either wavefront-optimized or wavefront-guided treatments attained an uncorrected visual acuity (UCVA) of 20/20 or better. Seventy-six percent of eyes with the wavefront-optimized treatment and 64% of eyes with the wavefront-guided treatment achieved UCVA of 20/16 or better. None of the eyes that received either treatment lost two lines or more of best spectacle-corrected visual acuity (BSCVA). In addition, 58% of eyes with wavefront-optimized treatment and 62% of eyes with wavefront-guided treatment gained one line or more of BSCVA. None of the eyes in either treatment group underwent retreatment. In the majority of eyes, no statistically significant differences were found between either treatment group in regard to visual acuity and refractive outcomes. Wavefront-guided treatments are not required in most cases with this laser, but may be considered if the magnitude of preoperative root-mean-square (RMS) higher order aberrations is >0.35 microm. In this study population, 83% of eyes had preoperative RMS higher order aberrations of <0.3 microm.

Multizone model for postsurgical corneas: analysis of standard and custom LASIK outcomes

A multizone model for postsurgical corneal topography is presented and applied to a comparative analysis of the outcome of standard and customized myopic LASIK. The different zones are segmented automatically by a clustering algorithm. The algorithm uses a set of three local descriptors, which correspond to normalized physical magnitudes computed for each point of the corneal topography map: Gauss curvature, root-mean-square (RMS) fit error to an ellipsoid surface model, and distance to the center of the topographic map. Both presurgical and post-LASIK corneal topographies of 31 eyes were analyzed using monozone and multizone models. The patients were classified into three groups according to the different LASIK treatments applied: Allegretto, Zyoptix, and PlanoScan. For post-LASIK corneas, the multizone model provided a lower fit error, an average of 1.2+/-0.4 microm versus 2.4+/-0.7 microm (monozone). The comparative analysis of the three different LASIK treatments showed no improvement of custom over standard treatments. The outcomes of Zyoptix and PlanoScan were basically equivalent and consistent with previous findings: The higher-order aberration (HOA) increased by a factor of two. The increase in HOA was higher, by a factor of three, after the Allegretto treatment. The multizone model shows a higher-fidelity representation and permits a deeper understanding of the postsurgical cornea.

Matched Population Comparison of the Visian Implantable Collamer Lens and Standard LASIK for Myopia of -3.00 to -7.88 Diopters

To compare matched populations of LASIK and Visian Implantable Collamer Lens (ICL) cases in the correction of myopia between -3.00 and -7.88 diopters (D). One hundred sixty-four LASIK eyes with prospective data collected from a single center and 164 ICL eyes from the multicenter US ICL Clinical Trial were compared in this observational non-randomized study. The LASIK and ICL groups were well matched for age, gender, and mean level of preoperative spherical equivalent refraction. At 6 months, best spectacle-corrected visual acuity (BSCVA) > or = 20/20 was 85% with LASIK and 95% with ICL (P = .003) compared to preoperative values of 93% and 88%, respectively (P = .292). Loss of > or = 2 lines of BSCVA was significantly lower with the ICL at 1 week (0.6% vs 10%, P < .001) and 1 month (7% vs 0%, P = .001) with comparable outcomes at 6 months (0% vs 1%). At 6 months postoperatively, uncorrected visual acuity (UCVA) > or = 20/15 (11% vs 25%, P = .001) and > or = 20/20 (49% vs 63%, P = .001) was better in the ICL cases. Predictability within 0.50 D at 6 months for ICL cases was 85% (67% LASIK, P < .001); 97% of ICL cases were within 1.00 D (88% LASIK, P = .002). Refractive stability (+/- 0.50 D) between 1 and 6 months was 93% with ICL compared to only 82% with LASIK (P = .006). The ICL performed better than LASIK in almost all measures of safety, efficacy, predictability, and stability in this matched population comparison, supporting the ICL as an effective alternative to existing refractive laser surgical treatments for the range of myopia studied.

Femtosecond Laser versus Mechanical Keratome LASIK for Myopia

To assess efficacy, safety, predictability, stability, and changes in corneal higher-order aberrations (CHOAs) and contrast sensitivity (CS) after a femtosecond laser for LASIK and standard LASIK for myopia. Prospective, randomized, comparative clinical study. Two hundred eyes of 100 consecutive patients who underwent LASIK treatment using the VISX S2 laser system. A femtosecond laser for flap creation was used in 100 eyes (50 patients; spherical equivalent [SE], -2.85+/-1.79 diopters [D]), and a mechanical microkeratome was used in 100 eyes (50 patients; SE, -2.90+/-1.63 D). Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, CS by means of the Functional Acuity Contrast Test, and CHOAs by means of custom software linked to topography were evaluated preoperatively and 6 months after treatment. Efficacy, safety, predictability, stability, CHOAs, and CS were evaluated before and after surgery at 6 months' follow-up. At 6 months postoperatively, UCVA was 1.0 or better in 100% of the eyes. Efficacy indexes were 1.07 for the femtosecond laser for LASIK patients and 1.00 for LASIK patients. No eye lost > or =1 lines of BCVA; for the femtosecond laser for LASIK group, 24 eyes gained 1 line, and 18 eyes gained > or =2 lines; for the LASIK group, 18 eyes gained 1 line. The femtosecond laser for LASIK group showed a percentage of eyes (98%) within the 0.5-D range in SE higher than that of the LASIK group (92%). For a 3.5-mm pupil, CHOAs' root-mean-square (RMS) increased for both the femtosecond laser for LASIK (2.21-fold) and LASIK (2.81-fold) groups. For a 6-mm pupil, CHOA RMSs were increased significantly after femtosecond laser for LASIK (4.18-fold) and LASIK (5.07-fold) surgeries (P<0.01). Contrast sensitivity improved only in the femtosecond laser for LASIK group at the highest spatial frequency (18 cycles/degree; P<0.01) after surgery. A femtosecond laser for LASIK surgery is an effective and, in this series, safe procedure for treatment of myopia. The improvements in UCVA and CS after the femtosecond laser for LASIK are related to the differences in postoperative CHOAs found with femtosecond and microkeratome flap creation.

Retreatment after Wavefront-Guided and Standard Myopic LASIK

To assess and compare the clinical outcomes of conventional LASIK retreatments after primary wavefront-guided and standard myopic LASIK. Retrospective review of interventional case series. One hundred fifty-four eyes of 114 consecutive patients underwent a conventional LASIK retreatment after previous wavefront-guided and standard myopic LASIK. The eyes were divided into two groups: standard conventional myopic LASIK (SM) (n = 101) and wavefront-guided myopic LASIK (WM) (n = 53). Retreatment LASIK was performed by lifting the original flap and using an excimer laser. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, and complications were evaluated at a mean follow-up of 7.8+/-5.5 months after retreatment (range, 3-26). At the last visit, mean spherical equivalents (SEs) were -0.17+/-0.42 diopters (D) in the SM group and -0.11+/-0.34 D in the WM group (P = 0.394). An SE of +/-0.50 D was achieved in 87% (88/101) of SM eyes and 91% (49/53) of WM eyes. Seventy-five percent of eyes in both groups had UCVA> or =20/20. All eyes in the WM group and 98% of eyes in the SM group had 20/30 or better UCVA. All eyes in both groups had a postoperative BSCVA of 20/25 or better. No eyes lost 2 lines of BSCVA in either group. No sight-threatening complications were encountered. The number of eyes with pre-retreatment optical symptoms was reduced to half after retreatment. Our results suggest that retreatment with conventional LASIK is a safe, effective, predictable way of dealing with different types of residual refractive errors after both wavefront-guided and standard myopic LASIK.

Wavefront-guided Enhancements Using the WaveLight Excimer Laser in Symptomatic Eyes Previously Treated With LASIK

To describe our clinical experience in wavefront-guided LASIK enhancements using the WaveLight ALLEGRETTO system (WaveLight Technologie AG, Erlangen, Germany) for symptomatic eyes previously treated with standard LASIK. Twenty-six eyes of 20 patients with residual myopia, hyperopia, or mixed astigmatism and/or night vision symptoms after primary standard LASIK were considered for wavefront-guided customized retreatment using the WaveLight ALLEGRETTO WAVE 200 Hz excimer laser system (model 106). Preoperative best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity, topography with the ALLEGRETTO Topolyzer, wavefront analysis using the ALLEGRETTO WAVE Tscherning Analyzer, and contrast sensitivity were compared to postoperative (enhancement) measurements. Twenty-two of the original 26 eyes underwent wavefront-guided enhancement, 4 were excluded because they did not meet wavefront-guided treatment inclusion guidelines of this study. Mean follow-up was 8 months (range: 6 to 13 months, standard deviation [SD] 2). All patients were within +/- 0.50 diopters (manifest refraction) of intended postoperative refraction. The mean preoperative BSCVA improved from 20/25 (SD +/- 0.12) to 20/18 (SD +/- 0.1) postoperatively. All patients gained at least one line of BSCVA, and a maximum of three lines. There was no loss of BSCVA in any patient. The total amount of high order aberrations (RMSH) decreased from an average of 1.04 (SD +/- 0.22) to 0.46 (SD +/- 0.14) microm. Patients also had a mean improvement in low contrast sensitivity of 59%. Based on this small series, customized wavefront-guided enhancements using the WaveLight ALLEGRETTO system in patients who underwent previous LASIK appear to be safe and effective in correcting residual refractive error, reducing high order aberrations, and improving visual symptoms when reliable and reproducible measurements are achieved.

Centration on the Cornea Vertex Normal During Hyperopic Refractive Photoablation Using Videokeratoscopy

To evaluate a method for centering the ablation in standard hyperopic LASIK using an excimer laser with a video-based eye tracker system. Results of 52 consecutive hyperopic eyes treated with the ESIRIS excimer laser were retrospectively reviewed. Ablation was shifted from the pupil center to the vertex normal of the cornea using pupillary offset measured with the Keratron Scout videokeratoscope. Outcomes were assessed 3 months postoperatively. All eyes preoperatively had a nasally oriented vertex normal in relation to the pupil center. Three months postoperatively a refractive outcome of < 0.50 diopters of spherical equivalent was achieved in 94% (49/52) of eyes. No eye lost more than one line of best spectacle-corrected visual acuity. Standard hyperopic LASIK with the ESIRIS laser system leads to good predictable efficacy and safety results when the ablation center is shifted to the cornea vertex normal based on videokeratoscopy data.