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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 describe the postoperative evolution of visual acuity, flap morphology, and stromal optical density femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Setting: Clinica Rementeria, Madrid, Spain. Design: Prospective case series. Methods: The study comprised 44 consecutive eyes that had FS-LASIK performed with the WaveLight FS200 and the Allegretto excimer laser to correct myopia. Visual outcomes, flap thickness, and stromal optical density were assessed 1 day, 1 week, 1 month, and 3 months postoperatively. Results: A statistically significant improvement in the mean uncorrected distance visual acuity at 1 day (0.94 +/- 0.2) and 1 week (0.93 +/- 0.2) to 1 month (1.04 +/- 0.2) and 3 months (1.11 +/- 0.1) postoperatively (P <.05). At 3 months postoperatively, the femtosecond laser had good outcomes in efficacy (0.98 +/- 0.1), safety (0.98 +/- 0.1), and predictability (100% of eyes were within +/- 0.5 D of emmetropia). The femtosecond-created flaps were slightly thicker than intended, the mean SD intraflap was 7.1 [mu]m, the range between the thickest and thinnest points in each flap was 25.4 [mu]m, and the mean flap thickness homogeneity was 7.6 [mu]m at 3 months postoperatively. A progressive decrease in the optical density of the flap stroma and the residual stromal bed was detected during follow-up. Conclusions: The femtosecond laser study appears to be a safe, effective, and predictable platform to obtain LASIK flaps. The flaps were planar and homogeneous but slightly thicker than intended. The optical density of the flap stroma was slightly higher at early follow-up and decreased over time. [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]

To analyze the recovery of the subbasal nerve plexus in corneas treated with laser in situ keratomileusis (LASIK) at least 10 years prior compared with nonoperated corneas. Clínica Novovisión, Madrid, Spain. Prospective nonrandomized observational study. Eyes that had LASIK surgery at least 10 years before (LASIK group) were compared with nonoperated healthy eyes (control group). The subbasal nerve plexus morphology (main nerves density, nerve length, nerve branches density, grade of nerve tortuosity, and reflectivity) and the dendritic cell density from the confocal images obtained with the Heidelberg Retina Tomograph II were analyzed. The study comprised 47 eyes (27 eyes in the LASIK group and 20 eyes in the control group). The values were significantly lower in the LASIK group compared with the control group in main nerves density (9.15 nerves/mm2 ± 3.46 [SD] versus 11.75 ± 2.86 nerves/mm2; P =.009) and nerve branches density (2.96 ± 1.99 nerves/mm2 versus 5.35 ± 3.05 nerves/mm2; P =.002). No significant differences were found in nerve length, grade of nerve tortuosity, dendritic cell density, or subbasal nerve plexus reflectivity between the two groups. The outcomes suggested that the subbasal corneal nerve plexus did not completely recover its preoperative pattern at least 10 years after LASIK. Both main nerves density and nerve branches density continued to be significantly lower compared with virgin corneas after a mean 13-year follow-up, although other parameters of nerve morphology (nerve length, tortuosity, and reflectivity) returned to normal levels. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate binocular visual acuity (VA), contrast sensitivity, and stereopsis in myopic patients after laser in situ keratomileusis (LASIK)-induced monovision. Design: Prospective, observational study. Methods: We performed a prospective study of 37 consecutive patients older than 45 years who underwent bilateral myopic LASIK with planned monovision. At the 6-month postoperative visit, we evaluated distance and near binocular visual acuity, contrast sensitivity, and stereopsis. Binocular tests were done without spectacles (in monovision condition) and compared with the results obtained by repeating the same binocular tests with the same patients (serving as a control group) after spectacle correction of the residual myopic defect in the nondominant eye for distance tests (reverting monovision) and after spectacle correction of the presbyopia bilaterally for near tests (near best spectacle-corrected VA). Results: By inducing a mean residual spherical equivalent defect of -0.97 diopter in the nondominant eye, the patients achieved a mean near binocular uncorrected visual acuity (UCVA) of 0.74, a mean reading test binocular UCVA of 0.88 using an acceptable spontaneous reading distance (48 cm), and a mean distance binocular UCVA of 1.08. A slight decrease in contrast sensitivity and stereopsis was observed in monovision compared to full distance correction. Conclusions: Monovision is a valid option for myopic patients with presbyopia who are considering LASIK. Good distance and near UCVAs can be obtained with this procedure. [ABSTRACT FROM AUTHOR]

A 52-year-old man had uneventful bilateral myopic laser in situ keratomileusis (LASIK) with planned monovision. Three months later, the left eye was retreated to improve the near vision. On postoperative day 1, the uncorrected distance visual acuity (UDVA) was 0.95 and the patient reported mild ocular pain. Stage 2 diffuse lamellar keratitis was observed. Despite hourly prednisolone instillation, the UDVA decreased to 0.1 and central flap necrosis syndrome was diagnosed. The flap was lifted and stromal bed irrigation performed. One month later, the UDVA was 0.05 with a hyperopic shift of +3.25 diopters and the flap, which had central haze and several striae, was amputated. Four months later, the UDVA was 0.05 with residual irregular astigmatism. Customized transepithelial photorefractive keratectomy (PRK) was performed; there were no postoperative complications. Three months after PRK, the UDVA was 0.8 with no refractive defect. [Copyright &y& Elsevier]

Phototherapeutic keratectomy (PTK) was performed to treat preexisting silent epithelial basal membrane dystrophy 1 month after laser in situ keratomileusis in 2 patients (4 eyes). The symptoms resolved dramatically during the follow-up period, with the patients reporting an immediate subjective visual improvement. At the last follow-up visit, 3 months after PTK, the eyes were asymptomatic, the epithelium was regular, no corneal erosions recurred, and the visual acuity was normal with no fluctuations. No eye developed haze greater than grade 1. There was no postoperative hyperopic shift, and no eye lost lines of best spectacle-corrected visual acuity. [Copyright &y& Elsevier]

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]