Long-term results of superficial laser in situ keratomileusis after ultrathin flap creation

Incidence and Risk Factors of Opaque Bubble Layer Formation According to Flap Thickness During 500-kHz FS-LASIK

PURPOSE

To present the incidence, risk factors, and effect of opaque bubble layer (OBL) formation during flap creation in laser-assisted in situ keratomileusis (LASIK) with a 500-kHz femtosecond laser on visual performance.

METHODS

In this retrospective study, preoperative characteristics (age, sex, keratometric value, spherical equivalent, and central corneal thickness) and intraoperative surgical factors (used energy, docking type, and flap thickness) were compared between eyes with and without OBL formation during flap creation. Possible risk factors for specific types of OBLs were analyzed.

RESULTS

One hundred thirty-five eyes of 71 patients underwent LASIK, and OBL developed in 98 eyes (72.59%). In the univariate analysis, the greater than 80-µm flap group was associated with a lower OBL occurrence than the 80-µm flap group (P = .0424, odds ratio [OR] = 0.481) and hard docking was associated with increased OBL formation (P = .0001, OR = 6.859). In the multivariate analysis, hard docking was a risk factor for OBL development (P = .0003, OR = 6.329). In the subgroup analysis, hard docking had a marginal effect on OBL occurrence in the 80-µm flap group (P = .086, OR = 3.564), but it had a strong effect in the greater than 80-µm flap group (P = .0018, OR = 10.210).

CONCLUSIONS

Hard docking is a risk factor for OBL development. However, hard docking had a small effect on OBL occurrence in the 80-µm flap group during LASIK. OBL formation did not affect visual performance. [J Refract Surg. 2019;35(9):583-589.].

Corneal flap thickness with the Moria M2 single-use head 90 microkeratome in 72 consecutive LASIK procedures

Purpose

This study aimed to evaluate the accuracy and consistency of corneal flap thickness in laser-assisted in situ keratomileusis (LASIK) with the Moria M2 single-use head 90 microkeratome.

Methods

The central corneal thickness of 72 (37 right, 35 left) eyes of 37 patients was measured by ultrasonic pachymetry preoperatively and intraoperatively after flap cut. The Moria M2 single-use head 90 microkeratome was used to create a superior hinged flap in all eyes. The right eyes were always operated on before the left eyes in each patient, using the same blade in all bilateral cases. All patients underwent LASIK for myopia and/or myopic astigmatism using VISX Star S4 platform.

Results

The mean preoperative spherical equivalent refraction was −3.55±2.30 D (range: −0.625 to −11.00 D), preoperative central corneal thickness by ultrasonic pachymetry was 541±26.82 µm (490–600 µm) and steepest K was 44.08±1.49 D (40–46.75 D) in all eyes. The mean flap thickness was 136.97±20.07 µm (106–192 µm), 131.2±19.5 µm (91–192 µm), and 134.16±19.85 µm (91–192 µm) in the right, left, and both eyes, respectively. A positive significant relationship was found between flap thickness and preoperative ultrasonic pachymetry thickness. No significant relationship was found between flap thickness and the age, preoperative spherical equivalent, and preoperative steepest K. The difference between the first and second eyes was not significant. There were no major intraoperative and postoperative complications in all eyes.

Conclusion

The Moria M2 single-use head 90 microkeratome cut relatively thicker flaps than were intended. The flap thickness range was quite wide. This was a disadvantage for the accuracy and consistency of corneal flap thickness.

Effects of silicone hydrogel contact lenses on ocular surface after Sub-Bowman's Keratomileusis

PURPOSE

To evaluate the efficacy of silicone hydrogel contact lenses on ocular surface after Sub-Bowman Keratomileusis (SBK).

MATERIALS AND METHODS

Forty-six patients suffered from myopia underwent a bilateral SBK. Post-operatively, one eye of each patient wore a PureVision contact lens for 24 h as a treated eye and the contralateral eye was as a blank control. Afterwards, corneal fluorescein (FL) staining, tear break-up time (TBUT), schirmer I test (SIT), central corneal thickness (CCT), ocular surface disease index (OSDI), corneal hysteresis (CH), corneal resistance factor (CRF) and corneal flap complications were assessed 1 d (except for CH and CRF), 1 week, 1 month and 3 months postoperatively.

RESULTS

Following SBK, in contrast to the control, corneal fluorescein staining of treated eyes were significantly reduced and tear break-up time of treated eyes were significantly improved at 1 d and 1 week after SBK. However, Schirmer I test of treated and control eyes were not different after SBK. Central corneal thickness of treated eyes were significantly thinner than that of control at 1 d after SBK, however, there were no differences at other time points. Ocular surface disease index of treated eyes were obviously alleviated more than that of control at 1 d after SBK, but no differences were found at other visits. Moreover, Corneal hysteresis and corneal resistance factor of treated and un-treated eyes were not different after surgery. And also the rate of corneal flap complications were not different between treated and control eyes after SBK.

CONCLUSIONS

Silicone hydrogel contact lenses played a positive role in accelerating corneal epithelial healing, enhancing tear film stability and reducing discomfort of patients in the early stage after SBK.

Interfaces detection after corneal refractive surgery by low coherence optical interferometry

The detection of refractive corneal surgery by LASIK, during the storage of corneas in Eye Banks will become a challenge when the numerous operated patients will arrive at the age of cornea donation. The subtle changes of corneal structure and refraction are highly suspected to negatively influence clinical results in recipients of such corneas. In order to detect LASIK cornea interfaces we developed a low coherence interferometry technique using a broadband continuum source. Real time signal recording, without moving any optical elements and without need of a Fourier Transform operation, combined with good measurement resolution is the main asset of this interferometer. The associated numerical processing is based on a method initially used in astronomy and offers an optimal correlation signal without the necessity to image the whole cornea that is time consuming. The detection of corneal interfaces - both outer and inner surface and the buried interface corresponding to the surgical wound - is then achieved directly by the innovative combination of interferometry and this original numerical process.

Influence of flap thickness on visual and refractive outcomes after laser in situ keratomileusis performed with a mechanical keratome

PURPOSE

To study the effect of flap thickness on visual acuity and refractive outcomes after laser in situ keratomileusis (LASIK) using 2 blade types with a mechanical microkeratome.

SETTING

Emory Vision, Atlanta, Georgia, USA.

METHODS

This retrospective analysis was of LASIK cases performed between January 2005 and June 2006 using an Amadeus I microkeratome and an ML7090 CLB blade (blade A) or a Surepass blade (blade B). Outcomes analyzed included flap thickness, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), the enhancement rate, and surgical complications 3 months postoperatively.

RESULTS

Two hundred sixty-three eyes of 153 patients were analyzed; blade A was used in 158 eyes and blade B, in 105 eyes. The mean flap thickness was significantly thinner with blade A than with blade B (107 microm +/- 12 [SD] versus 130 +/- 20 microm) (P<.0001). There was no overall correlation with either blade between flap thickness and UDVA, CDVA, or MRSE (all r<0.2). At 3 months, there was no statistically significant difference in UDVA, CDVA, or MRSE between the 2 blade groups at 3 months (all P > .10), and there was no difference in the complication rates.

CONCLUSION

Flap thickness did not affect visual or refractive outcomes with a mechanical microkeratome with either blade type.

Interface Haze Formation After Ultra Thin Flap Laser in Situ Keratomileusis

In this case series, five patients (10 eyes) underwent laser in siter keratomileusis (LASIK) for the correction of moderate myopia and astigmatism with the Schwind Carriazo Pendular microkeratome 90 mum head. Flap (superior hinged) thickness measured intraoperatively was assessed less than 70 mum in all eyes. On first month's postoperative examination, subepithelial mild corneal haze with consequent myopic regression was found in all patients. A significant improvement of haze formation and residual refractive error were observed during the following postoperative months. In conclusion, post-LASIK subepithelial corneal haze after thin flap creation is a temporarily potential complication that could affect patient's refractive error during the first postoperative month.

Safety and effectiveness of thin-flap LASIK using a femtosecond laser and microkeratome in the correction of high myopia in Chinese patients

PURPOSE

To establish safety and effectiveness of thin-flap LASIK using a femtosecond laser and microkeratome in correcting high myopia in Chinese patients.

METHODS

Two hundred seventy-four eyes of 148 Chinese patients with high myopia whose spherical equivalent refraction (SE) ranged from -6.12 to -15.75 diopters (D) received thin-flap LASIK with the VISX S4 IR excimer laser system. Corneal flaps were created with a femtosecond laser (15-kHz IntraLase, 134 eyes of 76 patients, target flap thickness 100 microm) and Moria M2 microkeratome (90-microm head, 140 eyes of 72 patients, target flap thickness 110 microm). Clinical outcomes were assessed with uncorrected (UCVA) and best spectacle-corrected visual acuity (BSCVA), manifest refraction, wavefront aberrometry, Schirmer tests, and tear break-up time (TBUT) at 1 day, 1 week, and 1 and 3 months postoperatively.

RESULTS

At 3 months, both groups showed comparable clinical outcomes in most parameters assessed, including the percent of postoperative UCVA better than or equal to preoperative BSCVA (P=.642), mean residual spherical equivalent refraction (P=.448), mean Schirmer test (P=.950), and mean TBUT (P=.867). Postoperative coma, trefoil, and spherical aberration were similar in both groups (P=.202, P=.898, and P=.890, respectively). Both groups had a similar percent of eyes with a change of SE of <1.00 D (P=.284).

CONCLUSIONS

Thin-flap LASIK with a femtosecond laser and microkeratome are both safe and effective for the correction of high myopia in Chinese patients. Femtosecond laser shows similar predictability, stability, and induction of higher order aberrations to the microkeratome.

Thin-flap (sub-Bowman keratomileusis) versus thick-flap laser in situ keratomileusis for moderate to high myopia: case-control analysis

PURPOSE

To compare the refractive and visual outcomes of sub-Bowman keratomileusis (SBK) and thick-flap laser in situ keratomileusis (LASIK) for moderate to high myopia and evaluate the effect of corneal flap thickness on outcomes.

SETTING

Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA.

METHODS

Two studies were performed. In the first study, the refractive and visual outcomes in 33 eyes that had SBK (flap thickness 82 to 120 microm) and 62 eyes that had thick-flap LASIK (flap thickness >or=160) were retrospectively analyzed. Inclusion criteria were spherical equivalent -4.0 to -10.0 diopters (D), astigmatism 3.0 D or less, and follow-up 3 months or more. In the second study, the influence of flap thickness was evaluated. A case-control matched study (21 pairs) that controlled for residual stromal bed (RSB) thickness was performed.

RESULTS

The mean flap thickness was 110.2 microm+/-9.2 (SD) in the SBK group and 179.2+/-19.5 microm in the thick-flap LASIK group. There were no significant differences in visual outcomes. In the second study with equivalent RSB thickness, case-control matched comparisons between SBK (mean 108.6+/-8.0 microm) and thick-flap LASIK (mean 165.7+/-12.6 microm) showed no differences in preoperative and postoperative refractive and visual outcomes. Comparison of the intended versus achieved correction showed no significant differences between the 2 groups.

CONCLUSION

Retrospective analyses showed that the safety, efficacy, and predictability of SBK were similar to those of conventional thick-flap LASIK in corneas with equivalent RSB thickness.

Comparison of higher-order aberrations after LASIK using disposable microkeratome 130 and 90 micron heads

PURPOSE

To analyze and compare higher-order aberrations (HOAs) in cases of laser in situ keratomileusis (LASIK) flaps made using the Moria M2 disposable 130-micronm head with those made using the 90-micronm head.

METHODS

Consecutive prospective comparative clinical trial. Ninety-four consecutive eyes of 48 patients were enrolled in this study. They were divided into two equal groups of 47 eyes that underwent wavefront-guided LASIK using VISX CustomVue (VISX, Santa Clara, CA) system. Corneal flap was created using the disposable Moria M2 130 micronm in the first group and the 90 micronm head in the second one. All patients were followed up for 6 months. Wavefront aberrations were measured at baseline, 1 month, and 6 months after surgery using the WaveScan (VISX Inc.) aberrometer. Root mean square (RMS) of HOAs, coma, and spherical aberration (SA) values were analyzed and compared in the two groups.

RESULTS

At 6 months, values of RMS of HOAs, coma, and SA obtained from the 130-micronm head group were 0.32+/-0.10 micronm, 0.20+/-0.11 micronm, and 0.18+/-0.08 micronm, respectively. Values of RMS of HOAs, coma, and SA obtained from 90-micronm head group were 0.33+/-0.12 micronm, 0.19+/-0.10 micronm, and 0.15+/-0.08 micronm, respectively. Analyzing the data obtained revealed no statistically significant differences between the two groups. In each group, there was a significant decay of higher-order RMS and coma values from 1 month to 6 months.

CONCLUSIONS

HOAs following use of Moria M2 disposable 90 micronm head are similar to those arising following use of the 130 micronm.