Femtosecond Laser In Situ Keratomileusis Research Articles

Opaque bubble layer: Incidence, risk factors, and clinical relevance

To assess the incidence, risk factors, and impact on visual outcomes of an opaque bubble layer (OBL) produced by an Intralase femtosecond laser (60 kHz) during laser in situ keratomileusis (LASIK). Laser Vision Center, Chang Gung Memorial Hospital, Keelung, Taiwan. Case series. Patients had femtosecond laser-assisted LASIK surgery. The surgical procedures were videotaped, and the patterns and sizes of the OBLs noted during the operations were analyzed. Preoperative and postoperative data included patient demographics, visual acuity, contrast sensitivity, refractive status, keratometry, and intraoperative data (eg, flap size, flap thickness, and docking times). The study analyzed 23 patients (40 eyes). Twenty-one eyes (52.5%) developed an OBL, 40.0% with a hard pattern and 12.5% with a soft pattern. The hard OBLs covered a mean area of 28.6% ± 10.1% (SD) and the soft OBLs, of 7.4% ± 5.6% (P = .002). The preoperative central cornea was significantly thicker in eyes that developed an OBL (P = .045). The visual outcomes 1 month postoperatively were comparable between the 2 groups except that eyes with an OBL had slightly decreased contrast sensitivity under scotopic conditions. Thicker corneas tended to develop an OBL during femtosecond laser-assisted LASIK surgery. An OBL did not affect postoperative visual acuity except for a mild decrease in scotopic contrast sensitivity.

Confocal Comparison of Corneal Reinnervation after Small Incision Lenticule Extraction (SMILE) and Femtosecond Laser In Situ Keratomileusis (FS-LASIK)

PurposeTo evaluate corneal reinnervation, and the corresponding corneal sensitivity and keratocyte density after small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK).MethodsIn this prospective, non-randomized observational study, 18 patients (32 eyes) received SMILE surgery, and 22 patients (42 eyes) received FS-LASIK surgery to correct myopia. The corneal subbasal nerve density and microscopic morphological changes in corneal architecture were evaluated by confocal microscopy prior to surgery and at 1 week, 1 month, 3 months, and 6 months after surgery. A correlation analysis was performed between subbasal corneal nerve density and the corresponding keratocyte density and corneal sensitivity.ResultsThe decrease in subbasal nerve density was less severe in SMILE-treated eyes than in FS-LASIK-treated eyes at 1 week (P = 0.0147), 1 month (P = 0.0243), and 3 months (P = 0.0498), but no difference was detected at the 6-month visit (P = 0.5277). The subbasal nerve density correlated positively with central corneal sensitivity in both groups (r = 0.416, P<0.0001, and r = 0.2567, P = 0.0038 for SMILE group and FS-LASIK group, respectively). The SMILE-treated eyes have a lower risk of developing peripheral empty space with epithelial cells filling in (P = 0.0005).ConclusionsThe decrease in subbasal nerve fiber density was less severe in the SMILE group than the FS-LASIK group in the first 3 months following the surgeries. The subbasal nerve density was correlated with central corneal sensitivity.

Small incision lenticule extraction (SMILE) and femtosecond laser LASIK: comparison of corneal wound healing and inflammation

AimTo evaluate and compare early corneal wound healing and inflammatory responses after small incision lenticule extraction (SMILE) versus femtosecond laser laser in situ keratomileusis (LASIK).MethodsThirty-six eyes of 36 rabbits underwent...

Comparative study of visual acuity and aberrations after intralase femtosecond LASIK: small corneal flap versus big corneal flap.

To study the effect of different flap sizes on visual acuity, refractive outcomes, and aberrations after femtosecond laser for laser in situ keratomileusis (LASIK). In each of the forty patients enrolled, 1 eye was randomly assigned to receive treatment with a 8.1mm diameter corneal flap, defined as the small flap, while the other eye was treated with a 8.6mm diameter corneal flap, defined as the big flap. Refractive errors, visual acuity, and higher-order aberrations were compared between the two groups at week 1, month 1 and 3 postoperatively. The postoperative refractive errors and visual acuity all conformed to the intended goal. Postoperative higher-order aberrations were increased, especially in spherical aberration (Z12) and vertical coma (Z7). There were no statistically significant differences between the two groups in terms of postoperative refractive errors, visual acuity, root mean square of total HOAs (HO-RMS), trefoil 30° (Z6), vertical coma (Z7), horizontal coma (Z8), trefoil 0° (Z9), and spherical aberration (Z12) at any point during the postoperative follow-up. Both the small and big flaps are safe and effective procedures to correct myopia, provided the exposure stroma meets the excimer laser ablations. The personalized size corneal flap is feasible, as we can design the size of corneal flap based on the principle that the corneal flap diameter should be equal to or greater than the sum of the maximum ablation diameter and apparatus error.

Dry Eye After LASIK with a Femtosecond Laser or a Mechanical Microkeratome

Dry eye is the most common complication after LASIK procedure and is associated with corneal denervation. We conducted the study to compare dry eye parameters and corneal sensitivity (CS) after laser in situ keratomileusis (LASIK) with a femtosecond laser (FS) or microkeratome (MK). In this prospective, nonrandomized, comparative study, 87 consecutive patients with myopia were assigned to receive either LASIK surgery with an FS (n = 44) or MK-assisted LASIK surgery (n = 43). The groups were age and sex matched. Corneal sensitivity, Schirmer testing, tear breakup time (TBUT), conjunctival and corneal stainings, and a subjective questionnaire (Ocular Surface Disease Index [OSDI]) were evaluated preoperatively, at 1 week, and at 1, 3, and 6 months postoperatively. Preoperative spherical equivalent and sphere, calculated ablation depth, and suction time differed significantly between the two groups (p < 0.01, all comparisons). Postoperatively, CS decreased in both groups and gradually recovered. Schirmer test values were not significantly different throughout the postoperative time points between the groups. Laser in situ keratomileusis-induced corneal epitheliopathy was also increased after operation in both groups. However, there was no significant difference between the groups in corneal and conjunctival staining scores. The OSDI scores were increased postoperatively in both groups. After adjustment for the calculated ablation depth, TBUT was the only parameter that was statistically higher in the FS group than in the MK group (p = 0.03). Both FS- and MK-assisted LASIK reduced CS and TBUT and increased corneal staining and OSDI scores. However, TBUT was significantly higher in the FS group than in the MK group after operation.

Comparison of efficacy and safety of laser in situ keratomileusis using 2 femtosecond laser platforms in contralateral eyes

To compare the efficacy, predictability, and refractive outcomes of laser in situ keratomileusis (LASIK) using 2 femtosecond platforms for flap creation. Multisurgeon single center. Clinical trial. Bilateral femtosecond LASIK was performed using the Wavelight Allegretto Eye-Q 400 Hz excimer laser system. The Visumax femtosecond platform (Group 1) was used to create the LASIK flap in 1 eye, while the Intralase femtosecond platform (Group 2) was used to create the LASIK flap in the contralateral eye. The preoperative, 1-month, and 3-month postoperative visual acuities, refraction, and contrast sensitivity in the 2 groups were compared. The study enrolled 45 patients. Three months after femtosecond LASIK, 79.5% of eyes in Group 1 and 82.1% in Group 2 achieved an uncorrected distance visual acuity of 20/20 (P=.808). The mean efficacy index was 0.97 in Group 1 and 0.98 in Group 2 at 3 months (P=.735); 89.7% of eyes in Group 1 and 84.6% of eyes in Group 2 were within ± 0.50 diopter of emmetropia at 3 months (P=.498). No eye in either group lost more than 2 lines of corrected distance visual acuity. The mean safety index at 3 months was 1.11 in Group 1 and 1.10 in Group 2 (P=.570). The results of LASIK with both femtosecond lasers were similar, and both platforms produced efficacious and predictable LASIK outcomes. No author has a financial or proprietary interest in any material or method mentioned.

Analysis of changes in stray light and relevant factors before and after femtosecond laser in situ keratomileusis

Background As a newly developed refractive surgery,femtosecond laser in situ keratomileusis (LASIK) receives more and more attention.Changes in ocular stray light after femtosecond LASIK is an important problem that impacts visual quality.Some relevant research has been performed before,but the outcomes are conflicting.Objective This primary study was to investigate the change of stray light values before and after femtosecond LASIK and analyze the relevant factors underlying the change.Methods Clinical data from 109 eyes of 55 myopic patients who underwent femtosecond LASIK in Tianjin Eye Hospital from December,2010 through February,2011 were included in this study.Stray light values were measured and recorded by C-Quant stray light meter preoperatively,and 1 day,1 week,1 month and 6 months postoperatively.The stray light data were compared by repeated measures ANOVA,and the correlations among the stray light values with preoperative factors,such as age,equivalent sphere,pupil diameter and central corneal thickness(CCT),as well as with postoperative factors,such as residual bed thickness(RBT),RBT/CCT,ablation depth,ablation ratio,flap thickness,flap diameter flap base width and exiting energy,were analyzed statistically.Written informed consent was obtained from each individual at initial of this study.Results The stray light values were 0.90±0.19,1.10±0.19,1.02±0.18,0.96±0.16 and 0.94±0.15 pre-operation,and 1 day,1 week,1 month and 6 months after femtosecond LASIK.The stray light values increased significantly 1 day,1 week,and 1 month after surgery,showing significant differences among the various time points (F=17.699,P=0.000).The mean stray light value was higher in 1 week than that in 6 months after operation (t=2.412,P=0.017).No significant differences were found in the stray light values between 6 months and 1 month or pre-operation (t =0.779,P =0.437 ; t =-1.877,P =0.062).No significant correlations were seen between preoperative and postoperative stray light values with age,preoperative refractive diopter,pupil diameter or CCT (P＞0.05).The changes in stray light values 1 week,1 month and 6 months after surgery were negatively correlated with ablation depth(r=-0.226,-0.228,-0.241 ;P＜0.05) and ablation ratio(r =-0.149,-0.219,-0.255 ;P＜0.05).Conclusions Stray light values increase within 1 month and return to normal 6 months after femtosecond LASIK.Stray light values may be related to multiple setting laser parameters and factors during femtosecond LASIK. Key words: Femtosecond; Laser in situ keratomileusis; Stray light

Cox proportional hazards model of myopic regression for laser in situ keratomileusis flap creation with a femtosecond laser and with a mechanical microkeratome

To compare predictive factors for postoperative myopic regression between laser in situ keratomileusis (LASIK) with a femtosecond laser and LASIK with a mechanical microkeratome. Nobel Eye Clinic, Taipei, Taiwan. Retrospective comparative study. Refractive outcomes were recorded 1 day, 1 week, and 1, 3, 6, 9, and 12 months after LASIK. A Cox proportional hazards model was used to evaluate the impact of the 2 flap-creating methods and other covariates on postoperative myopic regression. The femtosecond group comprised 409 eyes and the mechanical microkeratome group, 377 eyes. For both methods, significant predictors for myopic regression after LASIK included preoperative manifest spherical equivalent (P=.0001) and central corneal thickness (P=.027). Laser in situ keratomileusis with a mechanical microkeratome had a higher probability of postoperative myopic regression than LASIK with a femtosecond laser (P=.0002). After adjusting for other covariates in the Cox proportional hazards model, the cumulative risk for myopic regression with a mechanical microkeratome was higher than with a femtosecond laser 12 months postoperatively (P=.0002). With the definition of myopic regression as a myopic shift of 0.50 diopter (D) or more and residual myopia of -0.50 D or less, the risk estimate based on the mean covariates in all eyes in the femtosecond group and mechanical microkeratome group at 12 months was 43.6% and 66.9%, respectively. Laser in situ keratomileusis with a mechanical microkeratome had a higher risk for myopic regression than LASIK with a femtosecond laser through 12 months postoperatively.

Femtosecond (FS) laser vision correction procedure for moderate to high myopia: a prospective study of ReLEx® flex and comparison with a retrospective study of FS‐laser in situ keratomileusis

To present our initial clinical experience with ReLEx(®) flex (ReLEx) for moderate to high myopia. We compare efficacy, safety and corneal higher-order aberrations after ReLEx with femtosecond laser in situ keratomileusis (FS-LASIK). Prospective study of ReLEx compared with a retrospective study of FS-LASIK. ReLEx is a new keratorefractive procedure, where a stromal lenticule is cut by a femtosecond laser and manually extracted. Forty patients were treated with ReLEx on both eyes. A comparable group of 41 FS-LASIK patients were retrospectively identified. Visual acuity, spherical equivalent (SE) and corneal tomography were measured before and 3 months after surgery. Preoperative SE averaged -7.50 ± 1.16 D (ReLEx) and -7.32 ± 1.09 D (FS-LASIK). For all eyes, mean corrected distance visual acuity remained unchanged in both groups. For eyes with emmetropia as target refraction, 41% of ReLEx and 61% of FS-LASIK eyes had an uncorrected distance visual acuity of logMAR ≤ 0.10 at day 1 after surgery, increasing to, respectively, 88% and 69% at 3 months. Mean SE was -0.06 ± 0.35 D 3 months after ReLEx and -0.53 ± 0.60 D after FS-LASIK. The proportion of eyes within ±1.00 D after 3 months was 100% (ReLEx) and 85% (FS-LASIK). For a 6.0-mm pupil, corneal spherical aberrations increased significantly less in ReLEx than FS-LASIK eyes. ReLEx is an all-in-one femtosecond laser refractive procedure, and in this study, results were comparable to FS-LASIK. Refractive predictability and corneal aberrations at 3 months seemed better than or equal to FS-LASIK, whereas visual recovery after ReLEx was slower.

Safety and efficacy of femtosecond LASIK with reverse side cut

Abstract Purpose Laser in situ keratomileusis has several advantages over photorefractive keratectomy when performed properly in appropriate eyes. These include faster visual recovery, less discomfort after surgery, and milder and more predictable wound healing with less risk for haze. Lamellar corneal flap formation is the critical step in successful LASIK surgery. In our study we used femtosecond lasik with 90° hinge and 100 µm thickness flap wi Methods We performed femtosecond lasik in 58 eyes of 30 patients (mean age 35 y.o.) with AMO's IntraLase™ FS and STAR S4 IR™ Excimer Laser System. Criteria for inclusion were spherical myopia of ‐2 to ‐8.00 D, hyperopia up to 5 D, astigmatism miopic/hyperopic up to 4.50 D; stable refraction for 2 years; a best‐spectacle corrected vision (BSCVA) of at least 20/25 in each eye. Corneal flap thickness was 100µm and hinge position was 90 degrees with reverse 120° side cut. The optical zone of the ablation was from 6.5 to 7 mm, transition zone from 8 to 9 mm. Results Controls were made at 1day, 1 and 3 months. No flap decentration was observed in any case, we had one case of epithelial sloughing and one slightly irregular flap border. Spherical equivalent was within +/‐ 0.50 D and the cylinder was 0.50 D or less in all patients. Only 5% of patients showed marked discomfort and avversion to light for several days. Conclusion Flap creation is probably the most important step during laser in situ keratomileusis (LASIK), and complications during it can affect the rest of the procedure and cause permanent visual loss. In our exeprience the use of 100µm thickness flap with oblique side cut demonstrated itself to be a safe procedure with a very low complications rate and good refractive results.

Scattered ultraviolet emissions during refractive surgery using a high-frequency, wavefront-optimized excimer laser platform

To evaluate occupational ultraviolet (UV) exposure during photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the Allegretto Wave Eye-Q 400 Hz excimer laser. Walter Reed Center for Refractive Surgery, Washington, DC, USA. Intraoperative UV measurements were performed during PRK with epithelial removal using an Amoils brush, PRK with epithelial removal using 20% ethanol, or femtosecond LASIK. A LaserStar power/energy meter with a silicone detector (model PD-10) was used for the measurements. The maximum pulse energy 25.4 cm from the corneal surface was recorded for each surgical procedure. Measurements were evaluated using a worst-case scenario for exposure of operating room personnel, and the results were compared with the occupational exposure limit set by the International Commission on Non-Ionizing Radiation Protection. Measurements were taken during 15 cases of each procedure. The mean maximum exposure was 129.38 nJ/pulse +/- 79.48 (SD) during brush PRK, 69.72 +/- 68.80 nJ/pulse during ethanol PRK, and 29.17 +/- 13.82 nJ/pulse during LASIK. The mean maximum exposure per eye was 0.085 mJ/cm(2), 0.046 mJ/cm(2), and 0.01 mJ/cm(2), respectively. The worst-case cumulative exposure during a heavy workday of 20 patients (40 eyes) was calculated at 3.92 mJ/cm(2), 1.51 mJ/cm(2), and 0.79 mJ/cm(2) for brush PRK, ethanol PRK, and LASIK, respectively. Results indicate that the excimer laser platform used in the study may yield greater UV exposure than previous systems; however, the levels did not exceed occupational exposure limits. No author has a financial or proprietary interest in any material or method mentioned.

Femtosecond laser in situ keratomileusis versus conductive keratoplasty to obtain monovision in patients with emmetropic presbyopia

To compare visual outcomes, complications, and patient satisfaction after femtosecond laser in situ keratomileusis (LASIK) and conductive keratoplasty (CK). Private laser clinics, Reading and Southampton, United Kingdom. In this retrospective consecutive single-surgeon comparative study, presbyopic emmetropia was treated with femtosecond LASIK or CK to achieve monovision by targeting -1.50 diopters (D) of myopia in the nondominant eye after a successful monovision contact lens trial. The CK treatments were performed with a ViewPoint CK system using the light-touch technique. The femtosecond LASIK was performed using an IntraLase FS/FS30 and EC-5000 platform with OPDCAT wavefront treatment. The mean spherical equivalent 12 months postoperatively was -1.63 D +/- 0.68 (SD) in the femtosecond LASIK group and -0.97 +/- 0.82 D in the CK group (P<.001). The mean vector value of astigmatism at 12 months was 0.32 +/- 0.32 D and 1.00 +/- 0.75 D, respectively (P<.0001). The mean induced higher-order aberration (HOA) was 0.45 +/- 0.28 microm in the femtosecond LASIK group and 1.13 +/- 0.25 microm in the CK group (P<.0001). The retreatment rate was 3% after femtosecond LASIK and 50% after CK (P<.0001). On a questionnaire administered at 12 months, 20 patients (62.5%) in the femtosecond LASIK group and 11 patients (34.4%) in the CK group reported being satisfied (P = .02). In emmetropic presbyopic cases, femtosecond LASIK monovision provided stable correction with less induced astigmatism and HOA. Eyes with CK monovision had regression and induced astigmatism.

Femtosecond LASIK Combined With Astigmatic Keratotomy for the Correction of Refractive Errors After Penetrating Keratoplasty

To evaluate the outcomes of femtosecond laser in situ keratomileusis (LASIK) compared to combined LASIK and astigmatic keratotomy in the treatment of refractive errors following penetrating keratoplasty. A retrospective review was performed on 18 eyes of 16 patients who underwent LASIK for visual rehabilitation after penetrating keratoplasty. Seven eyes (38.8%) had undergone paired relaxing incisions with topographic guidance prior to LASIK performance. Preoperative uncorrected visual acuity was 20/100 or worse in 13 eyes (72.2%) and best-corrected visual acuity (BCVA) was 20/40 or better in 15 eyes (83.3%). After LASIK, uncorrected visual acuity was 20/40 or better in 10 eyes (55.5%) and BCVA was 20/40 or better in 17 eyes (94.4%). Three eyes (16.6%) had a loss of 1 to 2 lines of BCVA. No difference in visual outcomes was noted in eyes undergoing LASIK and astigmatic keratotomy versus LASIK alone. An increased complication rate was noted in patients who also underwent astigmatic keratotomy and was associated with flap creation. Femtosecond LASIK is effective in reducing ametropia after penetrating keratoplasty. Astigmatic keratotomy might complicate flap creation in LASIK; therefore, photorefractive keratectomy should be considered for patients who had previous astigmatic keratotomy to reduce astigmatism.

Increased risk for flap dislocation with perioperative brimonidine use in femtosecond laser in situ keratomileusis

To determine whether brimonidine 0.2% minimizes the occurrence of subconjunctival hemorrhages without inducing postoperative flap complications in femtosecond laser in situ keratomileusis (LASIK). Centro Oftalmológico Marqués de Sotelo and Hospital NISA Virgen del Consuelo, Valencia, Spain. This prospective contralateral-eye interventional study evaluated consecutive patients who had bilateral simultaneous femtosecond LASIK for myopia (spherical equivalent [SE] range -1.00 to -8.00 diopters) performed with an IntraLase femtosecond laser and a Visx Star 2 excimer laser. One eye of each patient received a single drop of brimonidine tartrate 0.2% (brimonidine group) and the other eye, a single drop of a balanced salt solution (control group). The study evaluated 136 eyes (68 patients). The difference in the incidence of subconjunctival hemorrhages was statistically significantly lower in the brimonidine group (mean score 2.24 +/- 1.96 [SD]) than in the control group (mean score 7.61 +/- 2.72) (P<.001). However, no eye in the control group and 7 eyes (10.4%) in the brimonidine group had a dislocated flap with folds on the first postoperative day (P = .016). All eyes with dislocated flaps required surgical intervention. At 6 months, there was no significant difference between groups in the percentage of eyes achieving 20/20 or better uncorrected distance visual acuity, in the mean SE, or in the enhancement rate. Brimonidine prevented the formation of subconjunctival hemorrhages after femtosecond LASIK but increased the risk for flap dislocation. Thus, surgeons are cautioned against the use of perioperative brimonidine to decrease hemorrhagic complications in femtosecond LASIK.

Incidence of rainbow glare after laser in situ keratomileusis flap creation with a 60 kHz femtosecond laser

To report the incidence of and factors associated with rainbow glare after laser in situ keratomileusis (LASIK) flap creation with a 60 kHz femtosecond laser. Department of Refractive Surgery, Cleveland Clinic Cole Eye Institute, Cleveland, Ohio, USA. Consecutive patients having LASIK by the same surgeon were questioned during postoperative examinations or by telephone about postoperative rainbow glare (radiating colors around a white light at night). Femtosecond laser (IntraLase) settings included pulse frequency 60 kHz, flap thickness 90 to 110 mum, and spot/line separation 8 mum. Raster energy was 0.8 microJ (75% of eyes) and 1.0 to 1.1 microJ (25%). Excimer laser ablation was performed with the LADAR 4000 or 6000 platform using custom or conventional treatments. Of 260 consecutive patients, 256 (98.5%) were successfully contacted. Fifteen patients (28 eyes) reported postoperative rainbow glare (5.8%), described as 4 to 12 bands of color around a white light, with 6 bands most common. The symptom did not correlate with refractive error, age, or sex but was more frequent at 1.0 microJ or 1.1 microJ raster energy (11.6%) than at 0.8 microJ (4.1%). The incidence followed a bimodal distribution, with the first grouping due to inadequate alignment and higher energy just after laser installation and the second just before a later maintenance service call. Rainbow glare is a mild optical side effect of femtosecond LASIK. In this study, higher raster energy levels and length of time between service calls were associated with the occurrence of rainbow glare.

Thresholds for Interface Haze Formation After Thin-Flap Femtosecond Laser In Situ Keratomileusis for Myopia

To evaluate the risk factors for interface haze formation after thin-flap femtosecond laser--laser in situ keratomileusis (LASIK). Prospective case series. One hundred and ninety-nine consecutive eyes that underwent femtosecond laser LASIK with a LADAR 4000 excimer laser (Alcon Laboratories, Fort Worth, Texas, USA), were analyzed from January 1 to April 30, 2008. Treated eyes were divided into 2 groups according to desired flap thickness: 90 microm (106 eyes), and 100 to 110 microm (93 eyes). Cycloplegic refraction, spherical equivalent (SE), uncorrected visual acuity, best spectacle-corrected visual acuity (BSCVA), depth of ablation, central corneal thickness, flap thickness (optical coherence tomography), Scheimpflug images (Pentacam; Oculus Inc, Lynnwood, Washington, USA), and light scattering were assessed in all eyes that developed haze postoperatively. Haze was observed in 32 eyes treated for moderate to high myopia (SE -6.23 +/- 1.67 diopters and depth of ablation 94.6 +/- 22.9 microm) at 3 months postoperatively. Ultra-thin IntraLASIK flaps (<or=90 microm) and younger age were strongly associated with risk of postoperative haze (P = .003 and P = .01, respectively). SE, depth of ablation, and self-reported history of dry eyes were not independently associated with an increased risk of corneal haze. Patients who developed any degree of haze had significantly higher logarithmic value of scatter (log S) values (mean difference =0.24 units, P < .0005) compared with those who did not develop haze. The mean postoperative BSCVA was good in all eyes with haze (logarithm of the minimal angle of resolution 0.05 +/- 0.04). Interface haze is associated with an ultra-thin femtosecond laser flap setting of 90 microm and younger age among eyes following LASIK for myopia.

Measurement of corneal curvature change after mechanical laser in situ keratomileusis flap creation and femtosecond laser flap creation

To compare the change in corneal curvature from the predicted surgical radius (sculpted in the corneal stroma) and the measured postoperative radius of the first surface of the cornea after laser in situ keratomileusis (LASIK) for myopia correction using 2 methods of flap creation: mechanical microkeratome and femtosecond laser. Vissum-Instituto Oftalmológico de Alicante, Alicante, Spain. This retrospective consecutive nonrandomized comparative interventional case series included 85 eyes with myopia or myopic astigmatism treated using the Esiris excimer laser (Schwind). Patients were divided into 2 groups. One group had LASIK with an M2 microkeratome (Moria) (mechanical LASIK group) and the other, with a femtosecond laser (IntraLase FS, IntraLase Corp.) (femtosecond LASIK group). The relationship between the postsurgical corneal radius and the predicted sculpted radius as well as the mean value of the percentage change in the curvature radius were analyzed to obtain the effect on the refractive defect in each group. There were 44 eyes in the mechanical LASIK group and 41 eyes in the femtosecond LASIK group. A high correlation was found between the final corneal radius and the predicted sculpted radius in both groups (r(2) = 0.85). The mean percentage change in the curvature radius was -3.6% in the mechanical LASIK group and -1.6% in the femtosecond LASIK group (P<.001). The mean estimated refractive change was 1.2 diopters (D) and 0.8 D, respectively. The refractive change in corneal curvature, which related to the biomechanical response of the corneal surface after the flap cut and repositioning, was lower after femtosecond laser LASIK than after LASIK performed using a mechanical microkeratome. Estimations of refractive change induced by this response should be taken into account in surgery design.

Flap thickness reproducibility in laser in situ keratomileusis with a femtosecond laser: Optical coherence tomography measurement

To compare ultrasound (US) pachymetry, Orbscan, and optical coherence tomography (OCT) measurements of the central corneal thickness (CCT) before laser in situ keratomileusis (LASIK) and evaluate the reproducibility of flaps created with the IntraLase femtosecond laser (IntraLase, Inc.) using OCT. Department of Ophthalmology, IIsan Paik Hospital, Goyang, Korea. Central corneal thickness was measured using OCT, US pachymetry, and Orbscan in 59 eyes of 30 patients before femtosecond laser LASIK. The postoperative corneal flap thickness, measured using OCT, was compared with the preoperative intended thickness. Optical coherence tomography, US pachymetry, and Orbscan measurements provided similar CCT values (P>.05). Corneal thickness values obtained using US or Orbscan correlated well with those obtained by OCT, with the correlation coefficient ranging from 0.804 to 0.889 (P<.05). The OCT measurements showed no significant difference between the postoperative flap thickness and the intended flap thickness (P>.05). Optical coherence tomography was comparable to US pachymetry and Orbscan in cornea thickness measurement. Optical coherence tomography was easy and relatively accurate to use preoperatively and in the early postoperative period. The femtosecond laser created highly reproducible flaps that corresponded with the preoperative intended thickness.

Femtosecond laser LASIK flap preparation with conical incision and positional spikes

Purpose: To describe the creation of corneal flaps for laser in situ keratomileusis (LASIK) with conical incisions and positional spikes that may increase postoperative rotational flap stability. Setting: University Eye Department. Methods: A corneal flap was prepared in 5 freshly enucleated porcine eyes using a femtosecond laser. In the first step, the flap bed with a diameter of 8.0 mm was created by an intrastromal incision running parallel to the corneal surface. In the second step, a posterior-anterior incision was created with a diameter of 8.0 mm at the level of the first incision and 7.0 mm at the corneal surface. In addition, a hinge and 3 spikes were prepared in the flap with corresponding notches in the surrounding tissue. Results: In all eyes, the corneal flaps were prepared easily within 5 minutes. Conclusion: Femtosecond laser technology allowed a new type of LASIK flap formation with conical incisions and positional spikes.