Laser-assisted In Situ Keratomileusis Flap Research Articles

Crosslinking for post-laser-assisted in situ keratomileusis corneal ectasia: Transepithelial flap-on 30 minute and flap-lift 4 minute protocol.

To evaluate the outcomes of transepithelial corneal collagen crosslinking (CXL) for management of corneal ectasia after laser-assisted in situ keratomileusis (LASIK). CXL was performed on 18 eyes of 16 patients either with LASIK flap lift (n = 9; 365 nm, 30 mW/cm2, 4 minutes, pulse) or with transepithelial flap-on (n = 9 eyes; 365 nm, 3 mW/cm2, 30 minutes) technique. Postoperative change in maximum keratometry (Kmax), anterior elevation, posterior elevation, spherical equivalent (SE), logMAR uncorrected distance visual acuity (UDVA), aberrations, and central corneal thickness (CCT) were evaluated at 12 months postoperatively. A total of 18 eyes of 16 patients (11 males, 5 females) were included. Overall, Kmax flattened more after flap-on CXL (P = 0.014) compared to flap-lift CXL. The endothelial cell density and posterior elevation were stable throughout the follow-up period. Index of vertical asymmetry (IVA), keratoconus index (KI), and central keratoconus index (CKI) decreased after flap-on CXL at 12 months, postoperatively (P < 0.05), whereas there were no statistically significant changes in these parameters after flap-off CXL group. The spherical aberrations and total root mean square decreased after flap-lift CXL at 12 months, postoperatively (P < 0.05). In our study, transepithelial collagen crosslinking was successfully used to halt disease progression in post-LASIK keratectasia. We recommend flap-on surgical technique for these cases.

Surgical management of a calzone-like posttraumatic infolding of a 10-year-old LASIK flap

Introduction: The popularity of femtosecond laser–assisted in situ keratomileusis (LASIK) has increased, but flap-related complications such as trauma and possibility of displacement, even years after surgery with complications such as striae, diffuse lamellar keratitis, and epithelial ingrowth, may still be challenging. Patient and Clinical Findings: A 45-year-old woman was referred a week after trauma and flap displacement on a 10-year-long myopic LASIK correction. Corrected distance visual acuity was 20/30 (0, −2.25 at 35 degrees) due to epithelial ingrowth involving the visual axis. The external third of the flap was rolled inward (calzone-like), exposing the underlying edematous stroma associated with dense fibrosis at the level of the roll. Diagnosis, Intervention and Outcomes: Emergency flap surgical revision was performed using a technique of mechanical debridement and a 20% alcohol-dipped sponge application to help with epithelial cells lysis, and fibrin glue was applied on the flap. Uncorrected distance visual acuity was restored and examination revealed a stable, well-apposed flap, without epithelial cell ingrowth, and an otherwise unremarkable examination. Conclusions: This study showed the 10-month-efficacy of a combined approach of mechanical debridement, ethanol-based cell lysis, and fibrin glue in traumatic 10-year-old-flap management with infolding or invagination and extensive epithelial ingrowth.

Long-Term Observation of Deep Anterior Lamellar Keratoplasty in Patients with Post-LASIK Granular Corneal Dystrophy Type 2: Two Case Reports

IntroductionLaser-assisted in situ keratomileusis (LASIK) exacerbates granular corneal dystrophy type 2. Post-LASIK granular corneal dystrophy type 2 is treated by several surgical techniques. To the best of our knowledge, no report has addressed the results of deep anterior lamellar keratoplasty in affected patients. Here, we report our experience regarding deep anterior lamellar keratoplasty treatment of patients with post-LASIK granular corneal dystrophy type 2.MethodsWe describe two Japanese women who underwent deep anterior lamellar keratoplasty to treat corneal opacities that worsened after LASIK.ResultsOne patient had a family history of corneal dystrophies. During the initial visit to our clinic, numerous fine opacities were found at the LASIK flap interface in both patients. The clinical findings were compatible with post-LASIK granular corneal dystrophy type 2. Both patients underwent deep anterior lamellar keratoplasty by one of the authors (T.C.). In both procedures, the surgeon used a visco-dissection technique and successfully removed the whole corneal stroma. Histopathological examination of the excised corneal button from each eye revealed amyloid and hyaline deposits at the LASIK flap interface. Neither patient experienced recurrent corneal opacity during the follow-up visit at 8 years (patient 1) and 6 years (patient 2).ConclusionDeep anterior lamellar keratoplasty can be used for the treatment of post-LASIK granular corneal dystrophy type 2. Removal of the entire host stroma may be important for the prevention of recurrent corneal opacity.

Traumatic displacement of laser in situ keratomileusis flaps: an integrated clinical case presentation

BackgroundTraumatic dislocation of laser-assisted in situ keratomileusis (LASIK) corneal flaps is an uncommon postoperative complication that could occur any time after LASIK, and could be visually devastating. We evaluated the visual outcomes, corneal sensation, tear function, and dry eye questionnaire results of patients with traumatic dislocation of LASIK flaps, including one LASIK flap amputation.MethodsThis is a retrospective case series. Seven patients who were diagnosed with traumatic displacement of the LASIK flap and underwent flap replacement surgery between August 2014 and January 2019 were included.Patient’s visual acuity, refraction, corneal sensitivity, non-invasive tear breakup time (NIBUT), tear meniscus height (TMH), and ocular surface disease index (OSDI) results were evaluated.ResultsThe patients’ mean age was 35.86 ± 5.84 years, and 42.9 % (3/7) were male. The mean duration from LASIK to trauma was 8.86 ± 2.48 years.The mean preoperative and postoperative six-month corrected distance visual acuity (CDVA) were 0.55 ± 0.34 and 0.02 ± 0.03, respectively. The mean spherical equivalent and astigmatism at six months postoperatively was − 1.0 ± 0.95 D and − 0.5 ± 0.25 D, respectively. The corneal flap was clear and well-positioned at the final follow-up (mean: 28.57 ± 6.9 months). 85.71 % (6/7) of the patients showed worse corneal sensation in the injured eye. Interocular OSDI discrepancy was less in those whose last visit was more than 30 months after the trauma.ConclusionsPostoperative CDVAat six months was improved, and the refractive data also showed some improvement. The corneal nerve and tear function recovery peaked before 30 months, while the OSDI continued to show a strong trend of improvement beyond 30 months.

Measurement of the Intraocular Pressure Elevation During Laser-Assisted In Situ Keratomileusis Flap Creation Using a Femtosecond Laser Platform.

PurposeThe purpose of this study was to measure the intraocular pressure (IOP) elevation during laser assisted in situ keratomileusis (LASIK) flap creation using the WaveLight FS200 femtosecond (FS) laser platform.MethodsWe conducted an ex vivo experimental study in an animal model. The WaveLight FS200 FS laser platform was used to perform the corneal LASIK flap in freshly enucleated porcine eyes. We measured the changes in IOP from the application of the suction ring (suctioning phase) through the creation of the lamellar corneal flap (cutting phase). The IOP was recorded using a manometric technique with direct cannulation to the anterior chamber.ResultsNine freshly enucleated porcine eyes were included in the study. The mean baseline IOP before the procedure was 20.33 ± 5.9 mm Hg. The mean IOP increase over baseline IOP was 32.33 ± 11.3 mm Hg at the suctioning phase, and 38.22 ± 11.3 mm Hg at the cutting phase. The total surgical time needed to complete the procedure was 29.5 ± 4.4 seconds.ConclusionsThe WaveLight FS200 FS laser platform produces a low to moderate increase in IOP during LASIK flap creation.Translational RelevanceThe WaveLight FS200 is a safe FS laser platform because it induces a low to moderate IOP increase during LASIK flap creation.

Inadvertent inversion of corneal flap following microkeratome-assisted laser-assisted in situ keratomileusis.

A 21-year-old male with stable myopic astigmatism in OD (-1.50DS/-0.75 DCX900) and OS (-1.50DS/-0.75DCX900) underwent microkeratome-assisted laser-assisted in situ keratomileusis (LASIK). According to the referring surgeon, preoperative topography and pachymetry were normal. On postoperative day 1, UCVA in OD was 6/18 and 6/9 in OS. Slit-lamp biomicroscopy revealed the inferior epithelial defect. The patient was put on moxifloxacin 0.5%, prednisolone acetate 1% suspension, and sodium-hyaluronate eye drop 3 times a day. Epithelial defect healed after 24 h but UCVA remained 6/18 in OD. The patient was then referred for further management. On presentation, the patient had BCVA 6/6 (+2.00DS/-4.75DC × 980) in OD and UCVA 6/6 in OS. Slit-lamp biomicroscopy revealed a hvorizontal line in OD [Fig. 1a and b]. Tomography on Pentacam (OCULUS Optikgeräte GmbH Postfach, 35549 Wetzlar, GERMANY) showed corneal astigmatism and inferior steepening [Fig. 1c and d]. Clinical diagnosis of inadvertent inversion (inferior folding on itself) of the LASIK flap was considered. Lifting and repositioning of the LASIK flap were planned. The corneal epithelium between the horizontal line and peripheral cornea was removed. LASIK flap was lifted and repositioned with LASIK spatula. Interface irrigation was done. The margin of the flap was dried and uniformity of gutter width was ensured. A bandage contact lens (BCL) was placed. The lid speculum was removed carefully. The topical medication was continued as before surgery. On day 1, the LASIK flap was well apposed. On day 7, the patient achieved BCVA of 6/9 in OD (+0.75DS/-0.50DC × 930). After 4 weeks of flap repositioning, the patient achieved UCVA of 6/6 (-2). The horizontal line had disappeared, corneal astigmatism decreased considerably, and the area of steepening disappeared [Fig. 2a-d].Figure 1: Slit-lamp biomicroscopy and Scheimpflug corneal tomography of the right cornea with LASIK flap inversion. Diffuse illumination photograph shows an inferior horizontal line and irregularity of LASIK flap (a), these findings on retro-illumination suggestive of inadvertent inversion (b). The axial curvature map on Scheimpflug corneal tomography shows against the rule corneal astigmatism (c) and the area of inferior corneal steepening corresponding to inverted flap on anterior elevation map (d)Figure 2: Slit-lamp biomicroscopy and Scheimpflug corneal tomography of the right eye 4 weeks after flap lifting and reposition. The disappearance of the horizontal line and absence of inferior corneal irregularity on diffuse illumination (a) and retro-illumination suggestive of well-apposed LASIK flap (b). The axial curvature map on Scheimpflug corneal tomography shows a decrease in corneal astigmatism (c) and the absence of inferior corneal steepening on the anterior elevation map confirms proper apposition of LASIK flap (d)Discussion Inadvertent flap inversion occurs rarely. Inspection of the flap integrity and ensuring uniformity of gutter may prevent this complication. Prednisolone acetate 1% suspension being white has been advocated to enhance the visibility of gutter width.[1] Inadvertent flap inversion may occur if the patient squeezes the eyelids while removing the drapes and speculum.[2] Mechanical trauma due to forceful blinking, eyelid squeezing, and eye rubbing has been implicated to cause flap shift within 24 h of surgery.[3] In our case, most probably, this complication happened either due to squeezing during speculum removal or due to eyelids impinging on the flap margin, postoperatively in a flap that was not well adhered. Inadvertent flap inversion should be considered an emergency. Early repositioning of the flap should be done to prevent the development of fixed folds and epithelial ingrowth. Eyelid speculum and drapes should be removed carefully to prevent dislodgment of the flap. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Pressure-induced stromal keratopathy after laser-assisted In situ keratomileusis with high intraocular pressure in disguise

Here, we report the case of a 28-year-old male patient who underwent uncomplicated laser-assisted in-situ keratomileusis (LASIK) in both eyes 10 days earlier and came with complaints of blurring of vision in the left eye with vision of 20/20. The patient gave a history of not tapering steroids as advised. His intraocular pressure (IOP) measured with rebound tonometer was 15 mmHg in the right eye and 25 mmHg in the left eye. On slit-lamp examination, the LASIK flap was intact in both the eyes, but the cornea appeared hazy in the left eye. Optical coherence tomography shows a central thickness of 524 μ in the left eye. The patient was diagnosed to have pressure-induced stromal keratopathy. The patient was switched to low-potency steroids, and anti-glaucoma drugs were given. On follow-up on slit-lamp examination, there was a significant decrease in haze in the left eye clear vision of 20/20 in both the eyes. It is important to recognize and treat PISK appropriately, as untreated elevated IOP can lead to optic nerve damage even over a brief period of several weeks.

Predictors affecting myopic regression in \u2212\u20096.0D to \u2212\u200910.0D myopia after laser-assisted subepithelial keratomileusis and laser in situ keratomileusis flap creation with femtosecond laser-assisted or mechanical microkeratome-assisted

PurposeTo investigate the predictive factors of postoperative myopic regression among subjects who have undergone laser-assisted subepithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK) flap created with a mechanical microkeratome (MM), and LASIK flap created with a femtosecond laser (FS). All recruited patients had a manifest spherical equivalence (SE) from − 6.0D to − 10.0D myopia.MethodsThis retrospective, observational case series study analyzed outcomes of refraction at 1 day, 1 week, and 1, 3, 6, and 12 months postoperatively. Predictors affecting myopic regression and other covariates were estimated with the Cox proportional hazards model for the three types of surgeries.ResultsThe study enrolled 496 eyes in the LASEK group, 1054 eyes in the FS-LASIK group, and 910 eyes in the MM-LASIK group. At 12 months, from − 6.0D to − 10.0D myopia showed that the survival rates (no myopic regression) were 52.19%, 59.12%, and 58.79% in the MM-LASIK, FS-LASIK, and LASEK groups, respectively. Risk factors for myopic regression included thicker postoperative central corneal thickness (P ≦ 0.01), older age (P ≦ 0.01), aspherical ablation (P = 0.02), and larger transitional zone (TZ) (P = 0.03). Steeper corneal curvature (Kmax) (P = 0.01), thicker preoperative central corneal thickness (P < 0.01), smaller preoperative myopia (P < 0.01), longer duration of myopia (P = 0.02), with contact lens (P < 0.01), and larger optical zone (OZ) (P = 0.02) were protective factors. Among the three groups, the MM-LASIK had the highest risk of postoperative myopic regression (P < 0.01).ConclusionsThe MM-LASIK group experienced the highest myopic regression, followed by the FS-LASIK and LASEK groups. Older age, aspheric ablation used, thicker postoperative central corneal thickness, and enlarging TZ contribute to myopic regression; steeper preoperative corneal curvature (Kmax), longer duration of myopia, with contact lens, thicker preoperative central corneal thickness, lower manifest refraction SE, and enlarging OZ prevent postoperative myopic regression in myopia from − 6.0D to − 10.0D.

Accuracy of Alcon WaveLight® EX500 optical pachymetry during LASIK.

PurposeTo study the accuracy and reliability of optical pachymetry using the Alcon WaveLight EX500 during laser-assisted in situ keratomileusis (LASIK).Materials and methodsThis was a retrospective chart review of 90 eyes from 45 patients who had undergone LASIK (mean age 35.2±8.2 years; 19 males, 26 females). The WaveLight FS200 femtosecond laser was programmed to cut LASIK flaps at a desired depth of 120 μm. Optical low-coherence reflectometry (WaveLight EX500) was used to measure central corneal thickness prior to lifting the flap, and the residual stromal bed immediately after excimer ablation. Flap thickness (FT) was calculated using simple subtraction. Optical coherence tomography (OCT) was used to measure central corneal thickness, flap thickness, and residual stromal bed in the postoperative period and the results compared to intraoperative measurements.ResultsMean programmed FS200 FT was 119 μm. Mean FT using EX500 optical pachymetry was 109 μm. The difference between FS200- programmed and EX500-measured FT was 9 μm (P<0.001). There was also a significant difference between the EX500 and OCT FT (109 μm vs 119 μm, respectively; P<0.001).ConclusionFT values calculated using intraoperative EX500 optical pachymetry were significantly lower than programmed FS200 values or OCT measurements.

Comparison of self-reported quality of vision outcomes after myopic LASIK with two femtosecond lasers: a prospective, eye-to-eye study.

PurposeTo compare self-reported quality of vision (QoV) outcomes after myopic LASIK (laser-assisted in situ keratomileusis) with two femtosecond lasers.DesignProspective, randomized, eye-to-eye study.MethodsConsecutive myopic patients were treated with wavefront-guided LASIK bilaterally. Eyes were randomized according to ocular dominance. The flap of one eye was made with the IntraLase FS 60 kHz femtosecond laser with a conventional 70° side-cut, and the flap of the fellow eye was made with the IntraLase iFS 150 kHz femtosecond laser with an inverted 130° side-cut. Patients completed the validated, Rasch-tested, linear-scaled 30-item QoV questionnaire preoperatively and at Months 1, 3, 6, and 12.ResultsThe study enrolled 120 fellow eyes in 60 patients. None of the measured QoV parameters exhibited statistically significant differences between the groups preoperatively or at any postoperative time point.ConclusionCreating LASIK flaps with an inverted side-cut using a 150 kHz femtosecond laser and with a conventional 70° side-cut using a 60 kHz femtosecond laser resulted in no significant differences in self-reported QoV assessed by the QoV questionnaire.

Opaque bubble layer incidence in Femtosecond laser-assisted LASIK: comparison among different flap design parameters.

The purpose of this study was to evaluate the incidence of opaque bubble layer (OBL) in femtosecond laser-assisted in situ keratomileusis (LASIK) flaps created with the support of Visumax Carl Zeiss femtosecond laser, planned with different flap diameters (7.90, 8.0, and 8.20mm) and the same laser energy and power settings. Incidence of intraoperative OBL in flaps of consecutive 108 patients (216 eyes) subjected to bilateral femtosecond-assisted LASIK was considered. Flap creation was performed with the same laser design parameters (spot distance and energy offset) and different presetting diameters of 7.90mm (72 eyes, group 1), 8mm (72 eyes, group 2), and 8.20mm (72 eyes, group 3). The incidence of OBL was considered and its extension was reported measuring involvement of different four corneal flap quadrants in which was theoretically divided the entire flap area; based on these data, OBL presence was classified as none (no evidence of OBL), minimal (minimal presence in not more that one quadrants corneal flap), mild (OBL presence in almost two or three quadrants without tendency to invade central cornea), and moderate (OBL presence in almost three quadrants with tendency to invade central cornea). In group 1, the incidence of OBL was of 23.6% (17 eyes) with a mild/moderate presence; in group 2, incidence was 20.8% (15 eyes) with mild presence. Group 3 presented a reduced OBL incidence (4.1%, 3 eye) with a minimal presence. No statistically significant difference was found between group 1 and 2 (p=0.8414).We found statistically significant differences between group 1 and group 3 (p=0.0012) and between groups 2 and 3 (p=0.0044). A significant reduction and extension of OBL incidence were evident when LASIK flap settings diameter was increased, and flap edge was closer to the contact glass border; this is probably consequent to a more effective gas dispersion outside of corneal flap.

Anterior chamber gas bubble emergence pattern during femtosecond LASIK-flap creation.

To characterise the emergence pattern of cavitation bubbles into the anterior chamber (AC) following femtosecond laser-assisted in situ keratomileusis (LASIK)-flap creation Retrospective review of patients undergoing femtosecond LASIK surgery at Boston Laser, a private refractive surgery practice in Boston, Massachusetts, between December 2008 and February 2014. Patient charts were reviewed to identify all cases with gas bubble migration into the AC. Surgical videos were examined and the location of bubble entry was recorded separately for right and left eyes. Five thousand one hundred and fifty-eight patients underwent femtosecond LASIK surgery. Air bubble migration into the AC, presumably via the Schlemm's canal and trabecular meshwork, occurred in 1% of cases. Patients with AC bubbles had an average age of 33±8 years with a measured LASIK flap thickness of 96±21 μm. The occurrence of gas bubbles impaired iris registration in 64% of cases. Gas bubbles appeared preferentially in the nasal or inferior quadrants for right (92% of cases) and left (100% of cases) eyes. This bubble emergence pattern is significantly different from that expected with a random distribution (p<0.0001) and did not seem associated with decentration of the femtosecond laser docking system. The migration of gas bubbles into the AC is a rare occurrence during femtosecond laser flap creation. The preferential emergence of gas bubbles into the nasal and inferior quadrants of the AC may indicate a distinctive anatomy of the nasal Schlemm's canal.

When case report became case series: 45 cases of late traumatic flap complications after laser-assisted in situ keratomileusis and review of Chinese literature

ObjectiveTo report 45 cases of late traumatic flap complications after laser-assisted in situ keratomileusis (LASIK) and discuss the continually increasing number of cases in China.MethodsA multicentre retrospective survey of eye...

Influence of microkeratome parameters on the stromal bed and flap edge quality in laser in situ keratomileusis

PurposeFemtosecond lasers have become the standard for laser-assisted in situ keratomileusis (LASIK) flap creation, but advanced mechanical microkeratomes are still an alternative, more cost-effective way to create the flap. The SCHWIND Carriazo-Pendular microkeratome is one of the most commonly used microkeratomes. The influence of different cutting parameters (head-advance speeds, cutting heads) on morphology of LASIK cuts was investigated.SettingExperimental study performed at the University Eye Hospital of the Martin Luther University Halle/Wittenberg, Halle (Saale), Germany.MethodsThe Carriazo-Pendular microkeratome was used on freshly enucleated porcine eyes for lamellar keratotomy. After flap removal, the cutting edge and stromal bed were evaluated from scanning electron micrographs using an individualized scoring system. Four different settings of microkeratome parameters were compared. For each setting, eight cuts were evaluated (n=32).ResultsDifferent oscillation frequencies and head-advance speeds did not influence the cutting qualities. A higher oscillation/feed rate ratio seemed to be advantageous for a smoother interface. Concerning different cuttings heads, a deeper keratotomy led to sharper cutting edges. The thinner the flap, the more irregularities in the stromal bed appeared. Complications did not occur.ConclusionThe Carriazo-Pendular microkeratome is a safe tool with which to create a LASIK flap and is a good alternative to a costly femtosecond laser. Deeper keratotomies, as well as the use of a higher oscillation/feed rate quotient, improve the cutting quality.

Essential opaque bubble layer elimination with novel LASIK flap settings in the FS200 Femtosecond Laser

BackgroundThe purpose of this study is to evaluate the extent and incidence of opaque bubble layer (OBL) using laser-assisted in situ keratomileusis (LASIK) flaps created with the Alcon/WaveLight® FS200 femtosecond laser as a result of a recent change in flap programming parameters aiming to reduce further the incidence and extent of OBL.MethodsIntraoperative digital images of flaps from 36 consecutive patients (72 eyes) subjected to bilateral femtosecond-assisted LASIK were analyzed using a proprietary computerized technique. The incidence and extent of OBL was measured and reported as a percentage of the entire flap area. Flap creation was performed with a 1.7 mm wide canal, implemented as an updated design intended to reduce the extent of OBL (group A). The same OBL parameters were investigated and compared in an age-matched and procedure-matched patients in whom the previous standard setting of a 1.3 mm wide canal was implemented (group B).ResultsIn group A, the average extent of OBL was 3.69% of the flap area (range 0%–11.34%). In group B, the respective values were 6.06% (range 0%–20.24%). We found the difference to be statistically significant (one-tailed P = 0.00452).ConclusionThis study suggests that there is a significant reduction in the incidence and extent of OBL when novel LASIK flap ventilation canal parameters of width and spot line separation are used.

Three-dimensional LASIK flap thickness variability: topographic central, paracentral and peripheral assessment, in flaps created by a mechanical microkeratome (M2) and two different femtosecond lasers (FS60 and FS200)

To evaluate programmed versus achieved laser-assisted in situ keratomileusis (LASIK) flap central thickness and investigate topographic flap thickness variability, as well as the effect of potential epithelial remodeling interference on flap thickness variability. Flap thickness was investigated in 110 eyes that had had bilateral myopic LASIK several years ago (average 4.5 ± 2.7 years; range 2-7 years). Three age-matched study groups were formed, based on the method of primary flap creation: Group A (flaps made by the Moria Surgical M2 microkeratome [Antony, France]), Group B (flaps made by the Abbott Medical Optics IntraLase™ FS60 femtosecond laser [Santa Ana, CA, USA]), and Group C (flaps made by the Alcon WaveLight(®) FS200 femtosecond laser [Fort Worth, TX, USA]). Whole-cornea topographic maps of flap and epithelial thickness were obtained by scanning high-frequency ultrasound biomicroscopy. On each eye, topographic flap and epithelial thickness variability was computed by the standard deviation of thickness corresponding to 21 equally spaced points over the entire corneal area imaged. The average central flap thickness for each group was 138.33 ± 12.38 μm (mean ± standard deviation) in Group A, 128.46 ± 5.72 μm in Group B, and 122.00 ± 5.64 μm in Group C. Topographic flap thickness variability was 9.73 ± 4.93 μm for Group A, 8.48 ± 4.23 μm for Group B, and 4.84 ± 1.88 μm for Group C. The smaller topographic flap thickness variability of Group C (FS200) was statistically significant compared with that of Group A (M2) (P = 0.004), indicating improved topographic flap thickness consistency - that is, improved precision - over the entire flap area affected. The two femtosecond lasers produced a smaller flap thickness and reduced variability than the mechanical microkeratome. In addition, our study suggests that there may be a significant difference in topographic flap thickness variability between the results achieved by the two femtosecond lasers examined.

Removal of Epithelial Ingrowth via Central Perforating Wound Tract 6 Years Post LASIK

The purpose was to report a case of a novel approach for the removal of central interface epithelial ingrowth caused by a perforating corneal injury 6 years after laser-assisted in situ keratomileusis (LASIK). Access to a large central area of epithelial ingrowth under a LASIK flap was achieved through the wound tract from a perforating corneal injury. Suturing of the central LASIK flap in a similar manner commonly carried out peripherally was then performed to prevent recurrent epithelial ingrowth. The offending epithelial ingrowth was removed with no recurrence over a 1-year follow-up. This is, to our knowledge, the first reported case of central epithelial ingrowth removal from a LASIK interface by a perforating injury wound tract.

OCT visualization of corneal structural changes in traumatic dislocation of LASIK flap

A 45-year-old woman presented with a traumatic laser-assisted in situ keratomileusis (LASIK) flap dislocation in the right eye. Anterior segment optical coherence tomography (OCT) showed the presence of macrostriae, flap stromal edema, epithelial hyperplasia between the striae and epithelial ingrowth. The flap was surgically repositioned with optimal visual recovery. Anterior segment OCT can efficiently visualize corneal structural changes associated with LASIK flap dislocation.

LASIK operations with the Ziemer FEMTO LDV femtosecond laser flap creation after previous photorefractive keratometry or laser-assisted sub-epithelial keratomileusis

Editor, Enhancement procedures may be needed after previous refractive surgery in the cases of under or over correction and regression. Enhancement procedures can be performed by photorefractive keratometry (PRK) or laser-assisted in situ keratomileusis (LASIK). LASIK is an attractive option for retreatment after previous surface ablations such as PRK or laser-assisted sub-epithelial keratomileusis (LASEK). Main reasons for choosing LASIK are a quick recovery and the absence of haze. Previously, in LASIK, corneal flaps have been recreated using various microkeratomes (Comaish et al. 2002; Pitkänen et al. 2010). In recent years, femtosecond lasers have emerged as alternatives to the traditional microkeratome-based LASIK. Femtosecond laser technology has some advantages, such as less variation in flap thickness and a more uniform flap thickness throughout the whole flap, compared to microkeratome-based flaps. However, reports published on reoperations performed with the femtosecond laser technology after previous refractive surgery are still scarce and limited to Intralase (Tran et al. 2008). This study presents the outcomes of the first 89 consecutive reoperated eyes of 71 patients, previously treated with PRK (87 eyes) or LASEK (two eyes), which now underwent LASIK flap creation with the FEMTO LDV (Ziemer Ophthalmic Systems, Port, Switzerland) femtosecond laser and excimer laser treatment with the Allegretto Wave Concerto 500 Hz excimer laser (Wavelight AG, Erlangen, Germany). The patients were operated in the two Finnish Mehiläinen Hospitals, in Tampere and in Helsinki. In all the eyes operated, a superior hinge was used and the intended flap thickness was 90 μm. The diameter of the suction ring was chosen according to the preoperative keratometric K1 value measured before the primary operation. The study included 64 myopic eyes (residual spherical equivalent of refraction, SE, range −6.63 D to −0.25 D, mean SE −1.45 ± 1.01 D) and 25 hyperopic eyes (range SE +0.00 D to +2.88 D, mean SE +1.31 ± 0.91 D). Flap dimensions and the best-corrected visual acuities were measured and intra- and postoperative complications recorded. Mean flap thickness was 90.5 ± 5.4 μm (range, 74–104; Fig. 1) and mean flap diameter was 9.1 ± 0.2 mm (range, 8.8–9.7). Flap thickness was positively correlated with corneal thickness both in myopic (r = 0.33, P < 0.01) and in hyperopic previously surface-ablated eyes (r = 0.51, P < 0.01). The distribution of flap thickness in 89 previously surface-ablated eyes now reoperated with the FEMTO LDV using the intended flap thickness of 90 μm. Complications occurred in six eyes (5.9%). They all were observed in the previously PRK-treated eyes. Most of the complications were very mild, and none of them prevented further treatment with excimer laser. There were no changes in the Snellen lines of BSCVA in 73 eyes (94.8%), and one line was gained in four eyes (5.2%). The mean flap thickness in the previously surface-ablated eyes was equivalent to the one we obtained in our previous study evaluating 787 primary operations with the FEMTO LDV (Pietilä et al. 2010). In this study, flap thickness was affected by corneal thickness just as in our previous study (Pietilä et al. 2010). Although the reason for this positive correlation is unknown, it is, if anything, a clinically advantageous phenomenon. Corneal changes in the previously PRK- or LASEK-treated eyes are mainly ultrastructural (changes in keratocytes in anterior stroma, absence of Bowman’s membrane, subclinical haze in wound healing process). LASIK revision in these eyes poses potentially more risks, and the previously operated corneal tissue is likely to behave in a different way than in the primary LASIK procedure. It is, however, evident that LASIK revisions with the femtosecond technology can be safely performed in most of these cases. Although in general retreatment of previously operated eyes offers greater risks in refractive surgery, the FEMTO LDV femtosecond laser can be successfully used for corneal flap creation in previously surface-ablated eyes.

Evaluation of transcutaneous electrical simulation to improve recovery from corneal hypoesthesia after LASIK

To evaluate the efficacy, and safety of transcutaneous electrical stimulation (TES) to accelerate corneal nerve regeneration and improved recovery from corneal hypesthasia after laser-assisted in situ keratomileusis (LASIK). Khodadoust Eye Hospital, Shiraz, Fars, Iran This prospective, randomized, clinical study comprised 40 eyes of 20 patients scheduled to undergo bilateral LASIK. In each patient, one eye was randomly assigned to receive transcutaneous electrical stimulation (20 HZ) for 60 minutes, and the other eye allocated as control. Corneal sensitivity was measured using the Cochet-Bonnet esthesiometer in four areas outside and five areas inside the LASIK flap preoperatively, and at 1 day, 1 week, 1 month, and 3 months postoperatively. Best-corrected visual acuity and the incidence of adverse events were noted at each visit. For all four points outside the LASIK flap, normal corneal sensitivity was maintained throughout the study; no significant difference was found between the study eyes and the control eyes at these points (P > 0.05). All points within the LASIK flap except the point closest to the hinge demonstrated profound corneal hypoesthesia at 1 day, 1 week, and 1 month postoperatively, with no differences noted between the control and study eyes (P > 0.05). After 3 months, points within the flap had statistically significantly better corneal sensitivity in the study group than in the control group (P < 0.05). Transcutaneous electrical stimulation significantly improves corneal sensitivity at 3 months after LASIK. This may be due to accelerated corneal nerve regeneration by electrical stimulation.