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

Purpose: To assess the relationship between measures of light distortion and retinal straylight in normal and post-LASIK subjects. Design: Cross-sectional, non-randomized, masked observational case series Setting: Clinica Oftalmologica Novovision, Madrid, Spain. Methods: Thirty eyes from 30 healthy subjects (mean age 33.9 ± 8.3 years old; mean spherical equivalent (MSE) −2.06 ± 1.40 D) and thirty six eyes from thirty six refractive surgery patients (mean age 36.1 ± 7.7 years old; mean preop MSE −3.43 ± 2.23 D) were examined with the Starlights and the C-Quant straylightmeter in a case-control study. Results: The age of both treated and control groups was not statistically different ( p > 0.05). Statistically significant differences between controls and post-LASIK eyes were found for luminous distortion index (LDI), but not for retinal straylight. Correlation analysis yielded significant correlation between retinal straylight Log(s) values and BCVA measures ( r = 0.379, p = 0.002). Control subjects showed significant correlation between MSE and retinal straylight Log(s) values ( r = -0.650, p < 0.001), while post-LASIK eyes showed a significant correlation between LDI and Log(s) values ( r = 0.338, p = 0.044) and between Log(s) values and BCVA ( r = 0.460, p = 0.005). Correlation between measures obtained by both methods was higher after LASIK than in control eyes, although values were quite scattered in any case. Conclusion: Light distortion phenomena and retinal straylight measures are correlated in both normal and postsurgical eyes. Both parameters are increased in LASIK subjects compared to control non-operated subjects. [ABSTRACT FROM AUTHOR]

Purpose: To assess the relevance of the homogeneity of femtosecond laser flap thickness regarding induction of higher-order aberrations (HOAs). Setting: Clinica Rementeria & Clinica Novovision, Madrid, Spain. Design: Prospective observational study. Methods: Two hundred thirty-one patients underwent in situ keratomileusis using 5 different femtosecond lasers. The flap thicknesses were measured using anterior segment optical coherence tomography 3 months postoperatively. The same masked observer measured 6 symmetrical points nasally and temporally 1.0 mm, 2.0 mm, and 3.0 mm from the center of the flap in each case. HOAs induced in the cornea were measured using tomography. Results: Positive and significant correlations were found between HOA induction and the flap thickness heterogeneity 3.0 mm from the center of the flap. Pearson correlation coefficients for the induction of HOAs were third-order 0.17112 (P =.0224), fourth-order 0.22474 (P =.0026), fifth-order 0.16449 (P =.0282), coma-like 0.17370 (P =.0204), and total HOAs 0.18182 (P =.0151). Conclusions: The amount of flap-thickness heterogeneity at 3.0 mm from the center of the flap created using femtosecond lasers was correlated with the magnitude of the HOAs induced. [ABSTRACT FROM AUTHOR]

To measure intraocular pressure (IOP) elevations in porcine eyes during laser in situ keratomileusis (LASIK) performed using 3 femtosecond laser platforms. Clínica Novovisión, Madrid, Spain. Experimental study. Three femtosecond devices, the iFS 150 kHz, which is the newest-generation IntraLase with a flat interface, and the Victus and LenSx, which are both dual femtosecond lasers with curved interfaces, were used to create lamellar corneal flaps in freshly enucleated porcine eyes. The IOP was recorded during placement of the suction ring on the eye (suctioning phase) and during the intrastromal laser application for flap creation (cutting phase) using a manometric technique with direct cannulation to the anterior chamber. Twenty-one eyes were analyzed (7 per group). The mean IOP increase during suctioning was significantly higher with the iFS system (78.14 mm Hg ± 23.6 [SD]) than with the Victus system (20.28 ± 6.7 mm Hg) (P =.0001). The LenSx system performed the suctioning and applanation phases simultaneously, making it impossible to obtain the results of the suctioning phase alone. The mean IOP elevation during the cutting phase was significantly lower with the LenSx system (20 ± 5.3 mm Hg) than with the iFS (108.1 ± 17.0 mm Hg) and Victus (96.4 ± 16.8 mm Hg) systems (P =.0001). The total surgical time was significantly lower with the LenSx system (17.21 ± 0.7 seconds) than with the iFS (25.10 ± 4.3 seconds) and Victus (33.40 ± 0.7 seconds) systems (P =.0001). The preliminary results suggest that the iFS and Victus systems induced higher IOP increases and required longer surgical times to cut a LASIK flap than the LenSx system. [ABSTRACT FROM AUTHOR]