Myopic Laser In Situ Keratomileusis Research Articles

Modified double-K method for intraocular lens power calculation after excimer laser corneal refractive surgery

To propose the new anterior-posterior method (A-P method) that does not require historical data to calculate intraocular lens (IOL) power after laser in situ keratomileusis (LASIK) and to compare the accuracy of the method with other IOL formulas after LASIK. Keio University Hospital, Tokyo, Japan. Case series. Eyes having phacoemulsification and IOL implantation after myopic LASIK were analyzed retrospectively. The A-P method is a modification of the double-K method using the SRK/T formula in which the estimated pre-LASIK keratometry (K) power calculated from the post-LASIK posterior sagittal power in the 6.0 mm zone is used for the preoperative K value in the double-K method and the post-LASIK anterior sagittal power is used for the postoperative K value. The accuracy of the A-P method was compared with that of other formulas that do not require preoperative data and with formulas that require preoperative data. The median values of the arithmetic and absolute prediction errors using the A-P method were 0.16 diopter (D) and 0.54 D, respectively. The prediction errors using the A-P method were within ± 0.50 D in 46.4% of eyes and within ± 1.00 D in 75.0%. The percentage of eyes within ± 1.00 D of the prediction errors with the A-P method was highest with the no-history methods. The A-P method may be a good option for calculating IOL power in eyes having cataract surgery after LASIK when preoperative LASIK data are unavailable.

A new central–peripheral corneal curvature method for intraocular lens power calculation after excimer laser refractive surgery

To propose the central-peripheral (C-P) method, which requires no data history to calculate intraocular lens (IOL) powers for eyes that underwent laser in situ keratomileusis (LASIK), and compare the accuracy of the C-P method with other IOL formulas for eyes after LASIK. Sixteen patients with cataract (25 eyes) who underwent myopic LASIK were analysed retrospectively. The C-P method is a modified double-K method using the SRK/T formula, in which the estimated pre-LASIK keratometric power calculated from the post-LASIK peripheral anterior sagittal power (also called the axial power) is used for the Kpre in the double-K method using the SRK/T formula, and the post-LASIK anterior sagittal power is used for the Kpost. We compared the accuracy of the C-P method with other popular IOL calculation formulas for use in eyes after LASIK. The median values of the arithmetic and absolute prediction errors with the C-P method were 0.11 diopter (D) (range, -1.67 to 1.97 D) and 0.55 D (range, 0.02-1.97 D), respectively. The prediction error using the C-P method was within ±0.5 D in 48% of eyes, within -1.0 to +0.5 D in 60% of eyes, and within ±1.0 D in 68% of eyes. The C-P method resulted in a significantly higher percentage of eyes within ±0.5 D than the BESSt formula, Shammas-PL formula, true net power method, double-K method using 43.5 D for Kpre, and Feiz-Mannis method. The C-P method may be a good option for calculating IOL powers in eyes undergoing cataract surgery after LASIK when the preoperative LASIK data are unavailable.

The role of presbyopia-correcting intraocular lenses after laser in situ keratomileusis

There is a growing number of patients who wish to remain spectacle independent after cataract surgery, and this number includes some of the millions of people worldwide who have undergone laser in situ keratomileusis (LASIK). This article reviews the evidence of the use of presbyopia-correcting intraocular lenses (IOLs) in patients who have previously undergone LASIK. Small studies have demonstrated that the use of hybrid refractive-diffractive multifocal IOLs in eyes with previous myopic or hyperopic LASIK can result in good refractive results. However, refractive surprise can be common and may require further intervention, such as laser surgery enhancement, to achieve satisfactory results. The use of these IOLs can also result in lost lines of vision, and visual quality may be poorer under mesopic or glare conditions. No reports were found regarding the use of accommodating IOLs in such patients. There is a surprising paucity of literature on this topic, given the millions that have undergone LASIK. Further and timelier research is needed to assess the use of newer multifocal and accommodating IOLs in post-LASIK eyes, the effect of IOL asphericity on visual quality, and patients' experience, satisfaction and level of spectacle independence after surgery.

Corneal endothelial cell changes 5 years after laser in situ keratomileusis: Femtosecond laser versus mechanical microkeratome

To compare corneal endothelial cell density (ECD) and morphology between flap creation with a femtosecond laser and flap creation with a mechanical microkeratome 5 years after laser in situ keratomileusis (LASIK). Mayo Clinic, Rochester, Minnesota, USA. Prospective randomized masked paired-eye study. In this study of LASIK for myopia or myopic astigmatism, fellow eyes were randomized by ocular dominance to flap creation by a femtosecond laser or by a mechanical microkeratome. Central endothelial images were analyzed before and 3 years and 5 years after LASIK; endothelial cell variables were compared between treatments at each examination. Relationships between endothelial cell loss and contact lens wear, residual bed thickness, and preoperative refractive error were evaluated. There were no differences in the ECD, percentage of hexagonal cells, or coefficient of variation of cell area between treatments at any examination (all P = .99); the smallest detectable differences were 120 cells/mm(2), 5%, and 2%, respectively. The mean annual rate of corneal endothelial cell loss was -0.1% ± 1.2% (SD) and -0.1% ± 1.0% for the femtosecond laser and the mechanical microkeratome, respectively. Endothelial cell loss was not associated with contact lens wear, residual bed thickness, or preoperative refractive error. The energy delivered to the cornea during femtosecond laser flap creation did not affect the corneal endothelium 5 years after LASIK when compared with flap creation with a mechanical microkeratome. Corneas that have had either method of flap creation could be accepted as donor tissue for endothelial keratoplasty from the standpoint of endothelial health. No author has a financial or proprietary interest in any material or method mentioned.

Transitioning from mechanical microkeratome to femtosecond laser flap creation: Visual outcomes of an experienced and a novice LASIK surgeon

To compare the visual outcomes of the first 200 myopic laser in situ keratomileusis (LASIK) cases between a mechanical microkeratome expert surgeon and a fellowship-trained surgeon transitioning to the femtosecond laser. London Vision Clinic, London, United Kingdom. Comparative case series. This analysis comprised the first 200 consecutive myopic LASIK procedures using the Visumax femtosecond laser and the MEL 80 excimer laser for an expert surgeon (11,637 previous microkeratome LASIK procedures) and a fellowship-trained surgeon (observed 1057, performed 155 supervised LASIK procedures) following a standardized surgical technique. Inclusion criteria were preoperative spherical equivalent (SE) refraction up to -8.50 diopters (D), cylinder up to 3.50 D, and corrected distance visual acuity (CDVA) of 20/20 or better. Follow-up was 1 year. There were no statistically significant differences in outcome measures between surgeons. Preoperatively, the mean SE was -4.00 D ± 1.83 (SD) and -3.97 ± 1.98 D and the mean cylinder was 0.81 ± 0.67 D and 0.79 ± 0.66 D for the expert surgeon and fellowship-trained surgeon, respectively. Postoperatively, the SE was ±0.50 D in 79% and 74%, uncorrected distance visual acuity was 20/20 or better in 96% and 96%, and 1 line of CDVA was lost in 3.5% and 1.5% for the expert surgeon and fellowship-trained surgeon, respectively. Contrast sensitivity increased or was unchanged. A fellowship-training program based on a standardized surgical protocol resulted in statistically comparable outcomes between an expert surgeon and a fellowship-trained surgeon when newly transitioned to a femtosecond laser device.

Anterior corneal optical irregularity measured by higher‐order aberrations induced by a broad beam excimer laser

Background: The aim was to analyse anterior corneal optical irregularity in patients receiving photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with a conventional broad beam laser.Methods: Pre‐ and post‐operative anterior corneal aberrations including Zernike coefficients and root mean squares of higher‐order aberrations were measured and derived with a Placido‐ring‐based corneal topographer and wavefront software, respectively, from 768 right eyes of patients receiving either PRK or LASIK for myopia with a conventional broad beam excimer laser in National Taiwan University Hospital, Taipei, Taiwan. Multiple linear regression models selected by Mallows' Cp criteria were used to evaluate predictability of surgically induced aberrations and relevant factors.Results: Mean attempted spherical equivalent correction was ‐7.37 ± 2.33-D (range: ‐16.5 to ‐1.95). Root mean squares of higher‐order aberrations and variances of Zernike coefficients all increased significantly after surgery (p < 0.01). All post‐operative higher‐order aberrations increased with the amount of attempted myopic correction and secondary astigmatism increased with attempted cylindrical correction. LASIK surgery induced less coma and third‐order aberrations but more fifth‐ and sixth‐order aberrations than PRK, although squared partial correlation coefficients were low. Larger optic and transitional zones meant fewer higher‐order aberrations after surgery. Younger patients tended to have more surgically induced aberrations in the 3.0 mm pupil zone.Conclusions: Anterior corneal optical irregularity increased tremendously after refractive surgery by conventional broad beam lasers and correlated with greater attempted myopic correction, younger age and a smaller treatment zone. The effect of corneal flaps on post‐operative corneal irregularity differed trivially.

Response of the posterior corneal surface to myopic laser in situ keratomileusis with different ablation depths

To evaluate the posterior corneal surface response at a very early stage after myopic laser in situ keratomileusis (LASIK) with different ablation depths. Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. Cohort study. Healthy myopic eyes were divided based on the achieved ablation depth as follows: Group 1, more than 100 μm; Group 2, between 50 μm and 99 μm; Group 3, less than 50 μm. Posterior eccentricity and central (0.0 to 4.0 mm), paracentral (4.0 to 7.0 mm), and peripheral (7.0 to 10.0 mm) posterior corneal curvatures were measured with the Galilei system preoperatively and postoperatively after 1 day, 1 week, and 1 and 3 months. Eighty eyes were evaluated. Posterior surface steepening and a shift toward prolateness occurred in all groups, with a peak within the first week before returning toward the original level after 1 month. The maximum change in the central posterior cornea occurred after 1 day in Group 1 and reached -0.106 diopter (D). This change was statistically significant (P=.03) and statistically greater than the change in Group 2 (mean -0.042 D; P = 0.02) and Group 3 (mean -0.026 D; P<.01). This change was not significant after 3 months (P = .5). Posterior steepening and a shift toward prolateness of the posterior surface were observed very early after myopic LASIK, with a tendency to return toward the preoperative level between 1 month and 3 months. The degree of change was related to the amount of anterior tissue severed. No author has a financial or proprietary interest in any material or method mentioned.

Multiple regression analysis in myopic wavefront laser in situ keratomileusis nomogram development

To develop a systematic method for quantifying pretreatment adjustments to the treatment sphere in patients having myopic wavefront laser in situ keratomileusis (LASIK). Moorfields Eye Hospital, London, United Kingdom. Comparative case series. Preoperative and 3-month postoperative data from consecutive cases of myopic wavefront LASIK (<10.0 diopters [D] sphere; <4.5 D cylinder) treated in 2008-2009 were tabulated. Multiple regression modeling was used to derive a weighted relationship between the achieved manifest refraction spherical equivalent (MRSE) and several possible influences. A new nomogram was derived from the resultant regression equation in which the percentage treatment boost was based on the partial correlation coefficient for the 4.0 mm pupil wavefront refraction spherical equivalent (SE), and pretreatment adjustment to the treatment sphere was based on the sum of the other weighted independent variables. The MRSE results in eyes treated using the new nomogram in 2009-2010 were compared with those from the original data set. The variance in postoperative MRSE error was significantly reduced using the new nomogram (0.10 D in 2009-2010 versus 0.16 D in 2008-2009; P<.0001, Bartlett test). The R(2) measure of linear fit increased from 0.967 in 2008-2009 to 0.983 in 2009-2010. Multiple regression modeling can be used to take account of several possible influences in enhancing the accuracy of wavefront LASIK. Nomograms developed through multiple regression modeling can be used to derive eye-specific pretreatment adjustments to the treatment sphere. Neither author has a financial or proprietary interest in any material or method mentioned.

Stability of posterior corneal elevation one year after myopic laser in situ keratomileusis

Purpose: The aim was to describe the forward shift of the posterior corneal surface one year after myopic laser in situ keratomileusis (LASIK) relative to the estimated residual stromal bed thickness (RBT) and to correlate RBT with the ablation percentage per total corneal thickness (CT) in eyes without significant changes in anterior best‐fit sphere (BFS) and corneal thickness one year after LASIK.Methods: The anterior and posterior BFS and central and peripheral corneal thickness were measured in 86 eyes from 43 patients (mean age 32.07 ± 7.01-years), who underwent uneventful LASIK for myopia using Orbscan before and one, six and 12-months after LASIK. The patients were divided into three groups based on estimated RBT (Group 1 with 16 eyes [19%], RBT less than 250 µm, Group 2 with 52 eyes [58%], RBT from 250 to 300 µm and Group 3 with 20 eyes [23%], RBT greater than 300 µm) and into two groups based on ablation percentage (Group A, 52 eyes [60%], less than 20% and Group B, 34 eyes [40%], more than 20%).Results: The mean posterior forward shifting was 9.4 ± 14.3 µm (range ‐27 to 80 µm) (p < 0.05), 4.0 ± 9.8 µm (range ‐34 to 24 µm) (p > 0.05) and 3.1 ± 8.8 µm (range ‐37 to 21 µm) (p > 0.05) at one, six and 12-months following LASIK, respectively. The posterior corneal forward shift was higher and showed an increasing trend in Group 1 (r2= 0.111), Group 2 (r2= 0.185) and Group B (r2= 0.156). Non‐significant (p > 0.05) posterior elevation was found in Group 3. The anterior BFS and central and peripheral corneal thickness did not show statistically significant differences (p > 0.05) for all post‐LASIK follow‐up visits.Conclusions: The posterior corneal displacement measured with Orbscan after LASIK was time dependent, with a different trend between estimated residual stromal bed thickness that protruded at an early stage but then returned to original levels 12-months after LASIK in eyes without post‐LASIK anterior topographic or pachymetric changes.

Visual and non-visual factors associated with patient satisfaction and quality of life in LASIK

The aim of this study was to determine how laser in situ keratomileusis (LASIK) affects quality of life (QOL) and to identify factors that may affect satisfaction after LASIK. A total of 104 patients with a mean age of 29±6, treated with LASIK for myopia and astigmatism, were enrolled in a prospective study. High (90%) and low (10%) contrast visual acuity (CVA) were measured under photopic and scotopic conditions before surgery and at 3 months later. A multidimensional QOL scale (Institute for Eye Research multidimensional QOL scale), which assesses psychological characteristics, personality traits, cosmesis, frequency, and tolerance to disturbing visual and ocular symptoms, and overall satisfaction with vision correction, was also used. Paired rank tests were used to compare preoperative and postoperative vision and QOL scores. Correlations and a multiple linear regression were used to describe the relationship between CVA, QOL, and satisfaction after LASIK. Significant postoperative changes included increased satisfaction following LASIK (P<0.001), reduced frequency of visual and ocular symptoms (P<0.001), and change in psychological characteristics (P=0.033). The change in satisfaction with LASIK can be predicted by a combination of preoperative satisfaction, postoperative frequency of disturbing visual and ocular symptoms, postoperative mean spherical equivalent, and postoperative scotopic high CVA (R (2)=0.725, P<0.05). Satisfaction with LASIK is related to visual function, preoperative expectations, psychological characteristics, and uncorrected CVA achieved. An increased sense of subjective well-being, adaptability, and self-efficacy was evident after LASIK. Patients reported a more optimistic attitude to life and increase perceived QOL after surgery.

Clinical characterization of corneal ectasia after myopic laser in situ keratomileusis based on anterior corneal aberrations and internal astigmatism

To evaluate and characterize the clinical features of corneal ectasia after myopic laser in situ keratomileusis (LASIK) considering internal astigmatism and corneal aberrations and their correlation with other clinical data. Vissum-Instituto de Oftalmológico de Alicante, Alicante, Spain. Retrospective comparative case series. In this multicenter study, eyes were divided into 2 groups. The study group comprised eyes that had corneal ectasia after myopic LASIK. The control group comprised eyes that had successful LASIK to correct high myopia. The clinical outcomes were analyzed and compared. Internal astigmatism was calculated using vectorial analysis. The study enrolled 91 eyes (48 study group; 40 control group) of 81 patients (age 18 to 67 years). Uncorrected and corrected (CDVA) distance visual acuities and the refractive status were significantly worse in the study group (P ≤ .01). Corneas in the study group had a significantly higher steepest keratometry (K) reading and a more negative central asphericity (P < .01). Internal astigmatism and corneal aberrations were also significantly higher in the study group (P < .01). The CDVA was significantly correlated with primary spherical aberration (r = -0.561, P =.01) and primary coma root mean square (r = 0.451, P =.04). Age was significantly correlated with mean K (r = -0.44, P =.01) and internal astigmatism (r = -0.34, P =.04). Larger levels of internal astigmatism and anterior corneal aberrations leading to a visual deterioration were present in eyes with corneal ectasia after myopic LASIK. No author has a financial or proprietary interest in any material or method mentioned.

Wavefront-Optimized Ablation Versus Topography-Guided Customized Ablation in Myopic LASIK: Comparative Study of Higher Order Aberrations

To compare the outcomes of wavefront-optimized ablation and topography-guided ablation in fellow eyes of patients undergoing laser in situ keratomileusis (LASIK) for myopia. This prospective study included 84 patients who underwent LASIK in both eyes: wavefront-optimized ablation in one eye (group I) and topography-guided ablation in the fellow eye (group II). The Moria2 microkeratome with a 110 single-use head (Moria, Antony, France) was used to create a superior hinged flap and the Allegretto Wave Excimer Laser (Alcon/Wavelight Light Laser Technologie GmbH, Erlangen, Germany) for photoablation. The Allegretto wave analyzer was used to measure the ocular aberrations before and 6 months after LASIK. Refractive visual outcomes and ocular aberration changes were compared between the two treatment modalities. Six months postoperatively, the mean uncorrected visual acuity of group II was statistically better than that of group I (P = .02). Seventy percent of group I and 83% of group II achieved a postoperative spherical equivalent refraction of ±0.5 diopters. The postoperative total root-mean-square of higher order aberrations (HOAs) of group II was smaller than that of group I, but the difference was not statistically significant (P = .51). There was a decrease in most of the individual terms of HOAs in group II, but it was only statistically significant in Z(3) (-1) (P = .04). The reverse occurred in group I, where most of the individual terms of HOAs increased, but it was not statistically significant. Significant improvement was only noted in Z(5) (3) (P = .05) and Z(5) (5) (P = .04). Both wavefront-optimized ablation and topography-guided ablation provided good refractive results, but the latter induced fewer HOAs.

Development of an Advanced Nomogram for Myopic Astigmatic Wavefront-Guided Laser in Situ Keratomileusis (LASIK)

To identify the relationship between preoperative parameters and postoperative overcorrection or undercorrection in eyes with myopic astigmatism treated with wavefront-guided laser in situ keratomileusis (LASIK), and to develop an advanced surgical nomogram. A retrospective chart review of 468 eyes that underwent wavefront-guided LASIK for myopia with astigmatism with the Alcon LADARVision 4000 (Alcon Laboratories, Fort Worth, TX), of which 235 had flaps created by microkeratome (OneUse; Moria Surgical, Doylestown, PA) and 233 by femtosecond laser (Intralase; AMO, Santa Ana, CA). Manifest sphere, cylinder, and spherical equivalent were recorded preoperatively and 3 months postoperatively. Various parameters from patient records were analyzed to identify which had greatest influence on outcomes. Manifest spherical equivalent was the most important predictor of surgical overcorrection, with the second being spherical aberration. In both groups, there was a statistically significant (P < .0001) correlation of spherical aberration with the amount of overcorrection. Using these two parameters, compensatory nomograms were derived. Surgical overcorrection in wavefront-guided LASIK for myopic astigmatism correlates positively with the amount of spherical equivalent treated and preoperative spherical aberration. Nomograms incorporating spherical aberration may improve accuracy of outcomes.

Estimation of preoperative corneal power in patients with myopic LASIK based on postoperative corneal data measured from Orbscan II

Compare the change of pre- and post-operative posterior corneal curvature measurements in peripheral fitting zones using the Orbscan II topographer in patients undergoing myopic laser in situ keratomileusis (LASIK). To establish a new ratio of the anterior and posterior corneal curvature for the calculation of preoperative total corneal power using postoperative corneal data alone in patients after LASIK. Retrospectively analyzed the changes of posterior corneal curvature in peripheral 7 to 10 mm fitting zones in 151 right eyes (151 individuals) 3 month after LASIK as measured by Orbscan II. The new ratio between the anterior and posterior corneal curvature was measured. The new ratio was used to estimate pre-operative total corneal refractive power in 30 eyes. The estimated total corneal refractive power was compared with the value measured from Orbscan II preoperatively. The accuracy of intraocular lens power estimated in 2 cases underwent cataract surgery after corneal refractive surgery was studied. The mean difference in estimated pre- and post-operative power of the posterior cornea was (-0.005 ± 0.154) mm (t = 0.417, P = 0.677). The ratio between the preoperative anterior central (0 - 7 mm) corneal curvature and the posterior peripheral (7 to 10 mm) corneal curvature was 1.167 ± 0.030. Estimated mean pre-operative total corneal power was (43.49 ± 1.79) D, whereas the value measuring from Orbscan II preoperatively was (43.77 ± 1.53) D. The mean difference between these two measurements was (-0.28 ± 1.00) D (t = -1.523, P = 0.139). The spherical equivalent refraction after cataract extraction of the two cases undertaken cataract surgery after corneal refractive surgery was 0.54 D and 0.69 D, respectively. The difference in posterior corneal curvature measurement following myopic LASIK using the peripheral fitting zone with the Orbscan II, as compared to the preoperative values, is clinically insignificant. The pre-LASIK corneal power can be estimated using post-LASIK data together with the new calculated ratio. This will be useful in post-LASIK patients requiring cataract surgery but without the availability of pre-LASIK corneal data for the estimation of the intraocular lens power.

Retinal detachment after laser In Situ keratomileusis

Purpose:To report characteristics and outcome of rhegmatogenous retinal detachment (RRD) after laser in situ keratomileusis (LASIK) for myopia.Materials and Methods:A retrospective chart review of patients who presented with RRD after myopic LASIK over a 10-year period.Results:Fourteen eyes were identified with RRD. Of these, two of 6112 LASIK procedures were from our center. The mean age of patients with RRD was 35.43 years. The mean interval of RRD after LASIK was 37.71 months (range, 4 months to 10 years). The macula was involved in eight eyes and spared in six eyes. Retinal breaks included a macular hole in two eyes, and giant tear in two eyes. Multiple breaks (>2 breaks) occurred in 6 cases. Pars plana vitrectomy (PPV) was performed in 3 (21.4%) eyes, a scleral buckle (SB) was performed in 4 (28.5%) eyes and 7 (50%) eyes underwent combined PPV and SB. Mean follow-up was 15.18 months (range, 1 month to 7 years). The retina was successfully attached in all cases. The final visual acuity was 20/40 or better in 7 (50%) eyes, 20/40 to 20/60 in 4 (28.5%) eyes, and 20/200 or less in 3 (21.4%) eyes. Poor visual outcome was secondary to proliferative vitreoretinopathy, epiretinal membrane, macular scar and amblyopia.Conclusion:The prevalence of RRD after LASIK was low at our institute. Anatomical and visual outcomes were acceptable in eyes that were managed promptly. Although there is no cause-effect relationship between LASIK and RRD, a dilated fundus examination is highly recommended before and after LASIK for myopia.

Subbasal Nerve Density and Corneal Sensitivity After Laser In Situ Keratomileusis

To compare changes in subbasal nerve density and corneal sensitivity after laser in situ keratomileusis (LASIK) with the flap created by a femtosecond laser (bladeless) vs a mechanical microkeratome. In a randomized paired-eye study, 21 patients received myopic LASIK with the flap created by a femtosecond laser in one eye and by a mechanical microkeratome in the fellow eye. Eyes were examined before and at 1, 3, 6, 12, and 36 months after LASIK. Central subbasal nerve density was measured by using confocal microscopy. Corneal mechanical sensitivity was measured by using a gas esthesiometer and was expressed as the ratio of mechanical threshold in eyes that received LASIK to mechanical threshold in concurrent control eyes. Subbasal nerve density and corneal sensitivity did not differ between methods of flap creation at any examination. Mean (SD) nerve density was decreased at 1 month (bladeless, 974 [2453] μm/mm(2); microkeratome, 1308 [2881] μm/mm(2)) compared with the preoperative examination (bladeless, 10,883 [5083] μm/mm(2), P < .001; microkeratome, 12,464 [6683] μm/mm(2), P < .001) and remained decreased through 12 months (P < .001). Mechanical threshold ratios did not differ from that at the preoperative examination through 36 months for either LASIK treatment; when all LASIK eyes were combined, the mechanical threshold ratio was transiently higher (decreased sensitivity) at 1 month (1.29 [0.85]) compared with the preoperative examination (0.89 [0.73], P = .05). The planar configuration of the femtosecond laser flaps is not associated with faster reinnervation compared with the microkeratome flaps. The prolonged decrease in subbasal nerve density after LASIK is not accompanied by a prolonged decrease in corneal sensitivity. clinicaltrials.gov Identifier NCT00350246.

Long-term comparison of corneal aberration changes after laser in situ keratomileusis: Mechanical microkeratome versus femtosecond laser flap creation

To compute and compare visual acuity, refractive outcomes, and anterior corneal aberration changes after myopic laser in situ keratomileusis (LASIK) with flap creation by a mechanical microkeratome and by a femtosecond laser. Private practice refractive surgery center, Valencia, Spain. Comparative case series. Patients were assigned to have LASIK flap creation with a mechanical microkeratome (Carriazo-Barraquer) or a femtosecond laser (IntraLase). The Visx S2 excimer laser was used for myopic ablation in all cases. Main outcome measures included uncorrected and corrected distance visual acuities and the defocus equivalent. Higher-order aberrations (HOAs) were computed from the anterior corneal surface measured with topography for 4.0 mm and 6.0 mm pupil diameters before and 48 months after surgery. The study evaluated 50 patients (98 eyes). The root mean square of HOAs increased postoperatively by a factor of approximately 1.9 in both groups and with both pupil diameters. There were no statistically significant differences between the 2 groups in the increase in anterior corneal aberrations, mean postoperative visual acuity, or residual refraction. All visual and optical performance metrics remained stable throughout the 4-year follow-up. There were no complications with flap creation and no postoperative complications. The increase in anterior corneal aberrations after myopic LASIK was similar after mechanical microkeratome and femtosecond laser flap creation. Visual acuity, refraction, and the optical quality of the cornea after LASIK remained stable through 4 years postoperatively in both groups.

Effect of laser in situ keratomileusis on vision analyzed using preoperative optical quality

To evaluate the effect on vision of laser in situ keratomileusis (LASIK) based on preoperative optical quality. Universitat Politècnica de Catalunya, Terrassa, and Barcelona Institute of Ocular Microsurgery, Barcelona, Spain. Comparative case series. The relative change in optical quality and visual acuity were evaluated in eyes that had LASIK for myopia. The optical quality was assessed before and 3 months after surgery using parameters provided by a double-pass system. Patients were classified into 4 groups by preoperative optical quality: low (Group 1), moderate (Group 2), high (Group 3), and very high (Group 4). The study evaluated 25 patients (50 eyes). The optical quality parameters improved postoperatively in Group 1 and Group 2, with the improvement ranging from 15% to 21% and from 13% to 17%, respectively. The preoperative and postoperative optical quality in Group 3 was similar. The optical quality in Group 4 worsened significantly by percentages ranging from -20% to -26%. Although visual acuity had the same trend, there were no statistically significant changes. The changes in optical quality after LASIK surgery depended on the patient's preoperative optical quality; visual acuity showed the same trend, although no change was significant.

Incidence of diffuse lamellar keratitis after LASIK with 15 KHz, 30 KHz, and 60 KHz femtosecond laser flap creation

To compare the incidence of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK) with flap creation using the 15 kHz (FS15), 30 kHz (FS30), or 60 kHz (FS60) femtosecond laser. University-based academic practice, Ann Arbor, Michigan, USA. Retrospective comparative case series. Consecutive myopic LASIK cases performed between January 1, 2005, and June 1, 2007, using the IntraLase FS15, FS30, or FS60 femtosecond laser for flap creation were reviewed. Preoperative clinical characteristics, treatment parameters, and intraoperative and postoperative complications were recorded. Statistical comparisons were made using repeated measures analysis, analysis of variance, chi-square, and Fisher exact tests. Five hundred twenty eyes of 274 patients were included in the study. One hundred seventy-six eyes (93 patients) were treated with the FS15 laser, 180 eyes (93 patients) with the FS30 laser, and 164 eyes (89 patients) with the FS60 laser. Seventeen eyes (10%) in the FS15 laser group, 24 eyes (13%) in the FS30 laser group, and 23 eyes (14%) in the FS60 laser group developed DLK. There was no statistically significant difference in the incidence of DLK between the 3 groups (P = .68). There was no significant difference in the incidence of DLK between the FS15, FS30, and FS60 groups.

Apodized diffractive intraocular lens implantation after laser in situ keratomileusis with or without subsequent excimer laser enhancement

To evaluate the long-term refractive and visual outcomes of apodized diffractive multifocal intraocular lens (IOL) implantation after myopic laser in situ keratomileusis (LASIK) with or without subsequent excimer laser enhancement. University of Texas Southwestern Medical Center at Dallas, Texas, USA. Comparative case series. This study comprised consecutive patients who had implantation of an AcrySof ReSTOR multifocal IOL after previous LASIK. Included were eyes that had refractive surgery enhancement with a Visx Star S4 excimer laser for residual refractive error correction and eyes that had neodymium:YAG (Nd:YAG) capsulotomy. Of the 49 eyes (38 patients), 21 (42.9%) had laser enhancement and 25 (51.0%) had an Nd:YAG capsulotomy. The mean follow-up was 14.2 months ± 7.23 (SD) (range 9 to 29 months). Although the uncorrected distance visual acuity (UDVA) was significantly worse in eyes with enhancement than in those with no enhancement at 1 month and 6 months (P<.05), there was no significant difference in UDVA between the 2 groups at the last follow-up (P>.05). At the last follow-up, 36 (73.5%) of the 49 eyes had a UDVA of 20/25 or better and an uncorrected near visual acuity of Jaeger 1 or better concurrently; 46 eyes (93.9%) were within ±1.00 diopter (D) of emmetropia, and 41 (83.7%) were within ±0.50 D. Apodized diffractive multifocal IOL implantation and excimer laser enhancement in eyes with previous myopic LASIK provided good results.