Comparison of corneal flap thickness using a FS200femtosecond laser and a moria SBK microkeratome

AIMTo evaluate differences in flap thickness resulting from use of an Alcon Wavelight FS200 femtosecond laser and a MORIA SBK microkeratome when making a 110-µm-thick corneal flap and to identify the potential factors that affect corneal flap thickness.

Effect of microkeratome suction duration on corneal flap thickness and diameter in pigs

AIMTo determine the effect of suction duration on thickness and diameter of corneal flap created by microkeratome in porcine eyes in laser in situ keratomileusis (LASIK).

Comparisons of morphologic characteristics between thin-flap LASIK and SBK

AIM: To compare the morphologic characteristics between thin-flap laser in situkeratomileusis (LASIK) and Sub-Bowman keratomileusis (SBK), and to evaluate the uniformity of flap and to explore the correlative factors of corneal flap thickness. METHODS: A prospective, randomized, comparative clinical study was performed in Department of Ophthalmology, West Hospital of China, Chengdu, Sichuan Province, China. Totally 59 patients 114 eyes underwent LASIK or SBK to correct myopia, 29 patients 57 eyes underwent SBK, 30 patients 57 eyes underwent LASIK. Anterior optical coherence tomography (OCT) was used to measure corneal flap thickness in all the patients 1 week after surgeries, 16 positions were set to be measured in each eye. Comparisons of flap thickness in each group and between 2 groups were evaluated. Correlative factors of flap thickness were evaluated. RESULTS: Coefficient of variation(CV, s/((X) over bar)x%)in SBK group were lesser than that in LASIK group, ttest showed there was significant statistical difference between 2 groups (P=0.000). Comparisons of the difference of 2 paired positions (temporal-nasal; superior-inferior) showed there were no significant differences in each group, but between 2 groups, there were statistical significance of value of difference (D-value) of superior and inferior positions between SBK and LASIK group (P =0.036). Linear regression analysis of correlative factors of flap thickness showed there were no statistic significances related to central corneal thickness(CCT) (P =0.060, t=1.921)and corneal curvature( P=0.083, t=1.766). CONCLUSION: SBK is better than LASIK in a-eating much uniform corneal flap. There was no evidence showing correlations between flap thickness and CCT or corneal curvature.

Methods for measuring pre-,intra-,and postoperative skin thickness for cochlear implants

Objective:This study was conducted to determine whether there is a reliable method for measuring the thickness of the retroauricular skin before,during,and after cochlear implantation,which allows the assessment of the optimal force of the external magnet of the cochlear implant(CI).Methods:The retroauricular skin thickness of 83 patients who received a CI was measured using three different methods.The thickness was measured on pre-and postoperative CT images,as well as intraoperatively.The magnet category chosen by the surgeon was recorded when the implant was switched on and during the first follow-up visit.Correlation analyses were performed on the different skin thickness measurements and between the skin thickness and magnet strength categories.Results:Only six patients required an exchange of the magnet until the follow-up.Although the median absolute thickness differed significantly between the three measures(p<0.0001),their thickness values showed highly significant correlations(Pearson’s r=0.457-0.585;p<0.01).In addition,magnet strength,was significantly correlated with the flap thickness determined pre-,post-,and during surgery.The lowest correlation with magnet strength was found in the intraoperative needle method.Conclusion:All three measurements methods provided a suitable base for determining the ideal magnetic force.However,of particular interest were the pre-and postoperative CT measurements.The first enabled the early assessment of the required magnetic strength and thus a timely postoperative supply,whereas the latter helped to estimate the need for magnetic strength reduction during follow-up care and the feasibility of an early swith-on.

Comparison of Ziemer FEMTO LDV "Classic" and " Crystal Line" femtosecond laser flap quality by Fourierdomain optical coherence tomography

AIM:To compare the regularity and accuracy of laser in situ keratomileusis(LASIK) flaps created by the Ziemer FEMTO LDV 'Classic'(Ziemer 'Classic') and Ziemer FEMTO LDV Crystal Line femtosecond laser(Ziemer Crystal Line). METHODS:Fourier-domain optical coherence tomography(RTVue OCT) was used to measure the morphology of 200 LASIK flaps of 100 consecutive patients created with the Ziemer Classic(100 flaps) or the Ziemer Crystal Line(100 flaps) at one week postoperatively.Flap thickness was evaluated at 36 specified measurement points on each flap.For all procedures with both lasers,the nominal flap thickness was 110μm.RESULTS:The mean flap thickness of the Ziemer Crystal Line group(102.49±2.68μm) was thinner than that of the Ziemer Classic group(107.65±5.09μm)(P【0.01).Average thickness of all flaps was uniform within 4μm at all measurement points.The flaps in the Ziemer Crystal Line group were more regular than those in the Ziemer Classic group when measured from the center to the periphery.The maximum deviation from the nominal 110μm of 36 measurements was 8μm in the Ziemer Classic group,while in the Ziemer Crystal Line group it was 9μm.Within the 3 600 measurements on the 100 eyes,differences greater than 20μm were observed 0.14% in the Ziemer Classic group,and 0.04% in the Ziemer Crystal Line group. CONCLUSION:The flaps created with the Ziemer FEMTO LDV Crystal Line femtosecond laser are more uniform and thinner than those created by the Ziemer FEMTO LDV Classic femtosecond laser.

Comparison of the flaps made by femtosecond laser and automated keratomes for sub-bowman keratomileusis

Background Thin-flap laser in situ keratomileusis （LASIK） is the new trend of refractive error correction surgery, the formation of corneal flap is crucial for a success of LASIK surgery. This study aimed to assess and compare the variations of LASIK flap created by the IntraLase femtosecond laser, Moria One Use-Plus SBK and Moria M2 Single-Use 90 pm- head microkeratome using Anterior segment optical coherence tomography （Visante OCT）. Methods One hundred and sixty-one eyes of 81 consecutive patients were enrolled in this prospective study and randomly divided into three groups depending on the flap creation method： flap creation with the the IntraLase femtosecond laser （IntraLase group, 59 eyes）, flap creation with the Moria One Use-Plus SBK （SBK group, 44 eyes）, and flap creation with the Moria M2 Single-Use 90 pm-head microkeratome （M2SU90 group, 58 eyes）. The nominal flap thickness was 110 m for all patients and for the three devices. One month after surgery, Visante OCT was used to measure the flap thickness at 20 locations on each cornea and the results were assessed for uniformity, regularity, and accuracy. Results At 1 month after surgery, the mean central flap thickness was （111±3） pm in the IntraLase group, （114±8） pm in the SBK group, and （118±13） pm in the M2SU90 group respectively. The flaps in the IntraLase group and the SBK group were more regular, showing an almost planar configuration, than the meniscus-shaped flaps in the M2SU90 group. The maximum deviation from the intended flap thickness （110 pm） was 6 pm in the IntraLase group, 10 pm in the SBK group, and 20 pm in the M2SU90 group respectively. A difference greater than 20 pm was observed in 0.42% of measurements in the IntraLase group; 2.95% of the measurements in the SBK group and 21.12% of measurements in the M2SU90 group. Conclusions The flaps created by the IntraLase femtosecond laser and Moria One Use-Plus SBK are more uniform; more regular, and more accurate than those created by the Moria M2 Single-Use 90 pm-head microkeratome. The first two methods can make precise flaps for Sub-Bowman Keratomileusis.