Incidence of intraoperative flap complications in laser in situ keratomileusis

Flap Thickness and the Risk of Complications in Mechanical Microkeratome and Femtosecond Laser In Situ Keratomileusis: A Literature Review and Statistical Analysis

INTRODUCTION

A recent Cochrane review found no difference in visual acuity outcomes between femtosecond-assisted laser in situ keratomileusis (LASIK) and LASIK using mechanical microkeratomes (MMKs). This study compares the flap thickness and risk of complications related to flap creation using femtosecond lasers and MMKs.

METHODS

PubMed and the Web of Science are used to search the medical literature. An extensive search is performed to identify the flap thickness and complications of LASIK as reported up to 15 July 2021. The following keywords are used in various combinations: Corneal flap, femtosecond laser, laser in situ keratomileusis, laser-assisted in situ keratomileusis, LASIK, mechanical microkeratome.

RESULTS

After removing duplicates and irrelevant studies, 122 articles were included for review. Pooled differences for intended vs. postoperative flap thickness using MMKs and femtosecond laser were -4.07 μm (95% CI: -19.55, 3.24 μm) in studies on the MMK and 5.43 μm (95% CI: 2.30, 7.84 μm; p < 0.001), respectively. After removing the studies evaluating outcomes of the old generation Hansatome MMKs (which had a significantly greater variation of flap thickness), the pooled difference for newer MMKs was 4.97 μm (95% CI: 0.35, 9.58 μm; p < 0.001), but the results still favored the femtosecond laser. Uncommon and mild complications unique for the femtosecond LASIK are epithelial gas breakthrough, opaque bubble layer, transient light sensitivity syndrome, and rainbow glare. A single study reported a very low, but stastically different risk of postoperative flap slippage (0.033% for MMK LASIK, and 0.003% for femtosecond LASIK, respectively).

CONCLUSION

In both manual microkeratome and femtosecond LASIK, intra- and postoperative complications were uncommon. The evidence of the superiority of one technique in terms of complications over another cannot be indisputably stated.

Suction stability management in small incision lenticule extraction: incidence and outcomes of suction loss in 4000 consecutive procedures

PURPOSE

To report the incidence and outcomes of suction loss during small incision lenticule extraction (SMILE).

METHODS

The incidence of suction loss was measured over 4000 consecutive SMILE procedures and categorized by cause, the interface in which suction was lost and management (restart/continue SMILE, re-SMILE thinner cap, convert to laser in-situ keratomileusis [LASIK]). One-year outcomes were compared to the fellow eye where no suction loss occurred.

RESULTS

There were 20 cases of suction loss (0.50%): during the lenticule interface in seven eyes, lenticule side cut in one eye, cap interface in nine eyes and small incision for three eyes. Small incision lenticule extraction (SMILE) was continued in seven eyes, thinner cap SMILE in four eyes, LASIK in eight eyes, and the small incision was manually completed in one eye. Suction loss was caused by a Bell's reflex in 10 eyes, fixation light tracking in six eyes, patient anxiety in two eyes, a nociceptive reflex in one eye and false suction in one eye. There was no difference in results for suction loss and fellow eyes, respectively: uncorrected distance visual acuity was 20/20 or better in 100% in both groups, spherical equivalent was within ±0.50 D in 85% and 79%, one line loss of corrected distance visual acuity in 5% and 0%, and no eyes lost two lines.

CONCLUSION

Suction loss can be managed depending on the interface during which suction is lost. Treatment was completed on the same day in all instances. Visual and refractive outcomes were unaffected compared to the fellow eye in this series.

Hydrogel sealant to prevent recurrent epithelial ingrowth in the setting of a LASIK flap buttonhole

Purpose

To report the first case of hydrogel sealant to prevent the recurrence of epithelial ingrowth in a LASIK flap buttonhole.

Observations

A 67-year-old female presented ten years after undergoing bilateral LASIK with diffuse lamellar keratitis and flap dislodgement after blunt trauma to the right eye. She was found to have epithelial ingrowth with diffuse debris and striae, so her flap was lifted and the epithelial ingrowth was removed. However, a central buttonhole was noted intraoperatively. Once all the epithelium was removed, the flap was repositioned and hydrogel sealant (ReSure, Ocular Therapeutix, Bedford, MA) was used to fill the buttonhole as well as seal down the edges of the flap. Sixteen months postoperatively, the patient's uncorrected visual acuity was 20/50-2 and there was no recurrence of the epithelial ingrowth at the edges of the buttonhole.

Conclusions and importance

Preventing the recurrence of epithelial ingrowth is a challenging situation, especially in the setting of a LASIK flap buttonhole. The use of hydrogel sealant in the buttonhole and around the edges of the flap may offer an elegant and effective solution.

Short-term complications of femtosecond laser-assisted laser in situ keratomileusis cuts: Review of 1210 consecutive cases

PURPOSE

To evaluate short-term complications after femtosecond laser cuts for laser in situ keratomileusis (LASIK).

SETTING

Department of Ophthalmology, Goethe University, Frankfurt, Germany.

DESIGN

Retrospective consecutive case series.

METHODS

Consecutive femtosecond laser cuts (1210 cuts in 624 patients) from LASIK performed with the Intralase FS60 between 2006 and 2014 were analyzed. The analysis looked at intraoperative and postoperative complications at 1 day, 1 week, and 1 month and factors with potential impact on the complication rate, such as ablation depth.

RESULTS

No irregular, incomplete, or thin flaps, buttonholes, gas breakthrough, or free caps were observed. Intraoperatively, incomplete side cuts were observed in 4 cases (0.3%). Three of the 4 occurred during the first year of femtosecond laser usage and were explained by a software problem. Epithelial defects, limbal bleeding, and decentered flaps without negative impact on outcome were observed in 45 (3.7%), 12 (1.0%), and 5 (0.4%) eyes, respectively, on the treatment date. Diffuse lamellar keratitis (DLK) stage 1 was observed in 69 (5.7%), 36 (3.0%), and 3 (0.2%) eyes at 1 day, 1 week, and 1 month, respectively, and DLK stage 2 in 20 (1.7%), 6 (0.5%), and 2 (0.2%) eyes, respectively. An increase in total ablation depth resulted in a higher incidence of microstriae (P < .01 at 1 day, 1 week, and 1 month). An increase in the optical zone resulted in a significantly higher incidence of epithelial ingrowth at 1 day and 1 week (P < .01).

CONCLUSION

No major cut-related complications were observed. The femtosecond laser is a safe option to create a flap in LASIK.

FINANCIAL DISCLOSURE

Proprietary or commercial disclosures are listed after the references.

Risk Factors for Sporadic Diffuse Lamellar Keratitis After Microkeratome Laser-Assisted In Situ Keratomileusis: A Retrospective Large Database Analysis

PURPOSE

To determine the factors associated with sporadic diffuse lamellar keratitis (DLK) after microkeratome laser-assisted in situ keratomileusis (LASIK).

METHODS

This large database retrospective study included consecutive cases of LASIK performed between 2007 and 2016 at Care-Vision Laser Centers, Tel-Aviv, Israel. Patients were divided into 2 groups according to whether or not they subsequently developed DLK.

RESULTS

A total of 24,026 eyes of 12,013 patients with a mean age of 32.9 ± 10.3 years were included. Post-LASIK DLK developed in 464 eyes (1.9%), and the annual rate decreased from 7.1% (2007) to 1.7% (2016) (P < 0.001). The DLK group had a higher proportion of males (58.5% vs. 52.1%, P = 0.006), greater preoperative central corneal thickness (549.5 ± 32.6 vs. 545.3 ± 30.5 μm, P = 0.005), and a lower proportion of high astigmatism (>3 D) (0.4% vs. 1.6%, P = 0.05). The DLK group had a higher proportion of previous LASIK treatment (2.8% vs. 1.3%, P = 0.006), Moria M2 (rather than the SBK) microkeratome (71.1% vs. 34.0%, P < 0.001), smaller suction ring number (P < 0.001), greater stop size (P < 0.001), and greater flap thickness (119.2 ± 50.4 vs. 110.8 ± 22.2, P = 0.007). In multivariable analysis, a smaller suction ring number [odds ratio (OR) 0.89, P = 0.04], Moria M2 microkeratome (OR 5.26, P < 0.001), larger optical zone (OR = 2.04, P = 0.01), and higher spherical equivalent (OR = 1.08, P = 0.02) were associated with DLK.

CONCLUSIONS

In the modern LASIK era, the incidence of DLK continues to decrease. Higher preoperative ametropia, smaller suction ring number, an older type of microkeratome, and larger optical zones are associated with higher DLK rates after LASIK.

Two-Year Outcome of a Patient Treated With Phototherapeutic Keratectomy and Autologous SMILE Lenticule Transplantation for Flap-Related Complications Following LASIK

PURPOSE

To describe a patient with flap complications after LASIK who was subsequently treated using phototherapeutic keratectomy (PTK) and an autologous lenticule transplant obtained via small incision lenticule extraction (SMILE).

METHODS

A 23-year-old man experienced free flap and partial flap loss in the left eye following LASIK, resulting in corneal stroma opacity 1 month later. The manifest refraction was -3.25 diopters sphere (DS)/-0.50 diopters cylinder (DC) × 100° in the right eye and +2.50 DS/-1.25 DC × 155° in the left eye. His left eye was treated with PTK and transplantation of an autologous lenticule obtained from his right eye using the SMILE procedure.

RESULTS

At the 2-year follow-up visit, the uncorrected distance visual acuity of the left eye had improved from 20/100 to 20/22 and the corrected distance visual acuity had improved from 20/25 to 20/18. Central corneal thickness had increased from 464 to 499 µm. The mean keratometry value had decreased from 45.00 diopters (D) at the 1-month follow-up visit to 39.40 D at the 2-year follow-up visit. Optical coherence tomography examination revealed that the lenticule remained transparent and exhibited a visible demarcation line.

CONCLUSIONS

The transplantation of an autologous lenticule obtained via SMILE combined with PTK improved uncorrected and corrected acuity in this patient with flap loss after LASIK. [J Refract Surg. 2018;34(4):281-285.].

Topography-guided neutralization technique for the management of flap complication in laser in situ keratomileusis

A 29-year-old male was referred following a flap loss after the creation of a thin, irregular flap with a visual acuity of logMAR 0.1 with -2.0 DS-2.75 DC × 175°. Corneal topography and anterior segment optical coherence tomography revealed an irregular corneal curvature and epithelial profile. Phototherapeutic keratectomy (PTK) followed by Topography - Guided Custom Ablation Treatment (TCAT), as a modification of the topographic neutralization technique protocol, was planned to regularize the corneal surface and treat the residual refractive error. Postoperatively, the patient showed a best-corrected visual acuity of logMAR 0 with a refractive error of -1 DC × 90°. Regularization of topography and epithelial thickness was seen along with a reduction in astigmatism and higher order aberrations. We report the use of PTK followed by TCAT as a novel method to treat a case of intraoperative flap loss during laser in situ keratomileusis.

Visumax femtolasik versus Moria M2 microkeratome in mild to moderate myopia: efficacy, safety, predictability, aberrometric changes and flap thickness predictability

Introduction

This is an interventional prospective clinical study which was conducted to evaluate the efficacy, safety, predictability, ocular aberrations, and flap thickness predictability of Visumax femtosecond laser (FSL) compared to Moria M2 microkeratome (MK) in mild to moderate myopia.

Methods

This study included 60 eyes who were divided into two groups. Thirty eyes in group (I) in which the flap was created with Visumax FSL, while in group II (30 eyes) the Moria M2 MK was used. Keratometric, refractive, and aberrometric measurements were compared preoperatively and 3 months postoperatively. The intraoperative subtraction pachymetry (the SP 100 Handy pachymeter (Tomey, Nagoya, Japan) was used for preoperative pachymetry and flap thickness measurement.

Results

No significant difference was found between the two groups in regards to postoperative manifest sphere, spherical equivalent, astigmatism, safety indices nor ocular aberrations. Twenty six eyes (86.6%) in group I and 23 eyes in group II (76.6%) were within ±0.5D of the intended correction and 23 eyes (76.6%) in group I and 15 eyes in group II (50%) were within ±0.25D of the intended correction. In group I, the mean postoperative actual flap thickness was 100.12 ± 16.1 μm (81 to 122 μm), while in group II, it was 104.6 ± 20.1 μm (62 to 155 μm). The difference was statistically significant (p = 0.001).

Conclusions

Both Visumax and Moria M2 MK are safe and effective in treating myopia with no statistically significant difference in induction of ocular aberrations but with potential advantage for Visumax regarding predictability. More accurate flap thickness is achieved with Visumax femtolasik.

Trial registration

This study was retrospectively registered on 19/6/2017. Trial registration number NCT03193411, clinicalTrials.gov.

Microcapillary sign of flap alignment in femtosecond laser-assisted in situ keratomileusis

We present an observational sign that ensures perfect alignment during femtosecond laser-assisted in situ keratomileusis (FS LASIK). Alignment is assured when a microsponge is used to dry the flap and the area of dryness exceeds the area of direct touch of the microsponge. The area might even reach the whole circumference of the flap at the first touch. This sign of alignment can be explained by microcapillary action. This sign was not elicited in flaps created by a microkeratome.

Intraoperative Flap Complications in LASIK Surgery Performed by Ophthalmology Residents

Purpose:

To report the rate of flap-related complications in LASIK surgery performed by in-training ophthalmology residents and to analyze the risk factors for these complications.

Methods:

We analyzed 273 flap dissections in 145 patients from March 2013 to February 2014. We included all LASIK surgeries performed by 32 ophthalmology residents using a Moria M2 microkeratome. All the flap-related complications were noted. Comparison between both groups with and without complications was performed with an independent Student's t-test and relative risks were calculated.

Results:

There were 19 flap-related complications out of the 273 flap dissections (6.95%). The most common complication was incomplete flap dissection (n = 10; 3.66%), followed by free-cap (n = 5; 1.83%), and flap-buttonhole (n = 2; 0.73%). There was no significant difference between the complicated and uncomplicated cases in terms of the right versus the left eye, pachymetry results, white-to-white diameter, and spherical equivalent. But this difference was significant for mean keratometry (P = 0.008), K-min (P = 0.01), and K-max (P = 0.03) between these groups. Final visual acuity after rescheduling laser treatment was similar in both groups. Relative risks for flap-related complications were 2.03 for the first LASIK surgery (CI 95% 0.64 to 6.48; P = 0.22) and 1.26 (CI 95% 0.43 to 3.69; P = 0.66) for the surgeon's flap-related complications. Female gender presented an odds ratio of 2.48 (CI 95% 0.68 to 9.00; P = 0.16) for complications.

Conclusion:

Flap-related complications are common intraoperative event during LASIK surgery performed by in-training ophthalmologists. Keratometries and surgeon's first procedure represent a higher probability for flap related complications than some other biometric parameters of patient's eye.

Long-term evaluation of eyes with central corneal thickness <400 μm following laser in situ keratomileusis

Purpose

To study long-term refractive and visual outcomes of laser in situ keratomileusis (LASIK) in eyes with a postoperative thin central cornea.

Methods

In this retrospective observational case series, we studied 282 myopic eyes with a normal preoperative topographic pattern and postoperative thin corneas (<400 μm) that had at least 3 years of follow-up after LASIK in three private clinics. The main outcome measures were safety, efficacy, predictability, percent tissue altered, and complications.

Results

The mean postoperative central corneal thickness was 392.05 μm (range: 363.00–399.00 μm). After a mean follow-up of 6.89±2.35 years (standard deviation), the safety index was 1.17, the efficacy index was 0.94, and predictability (±1.00 diopter [D]) was 73.49. The mean residual stromal bed thickness was 317.34±13.75 μm (range: 275–356 μm), the mean flap thickness was 74.76±13.57 μm (range: 55–124 μm), and the mean percent tissue altered was 37.12%±3.62% (range: 27.25%–49.26%). No major complications were recorded.

Conclusion

LASIK with a resultant central cornea thickness <400 μm seems to be effective, safe, and predictable provided that preoperative topography is normal and the residual stromal bed thickness is >275 μm.

Artemis very high frequency digital ultrasound-guided femtosecond laser recut after flap complication

Incomplete flaps are a relatively uncommon complication of laser-assisted in situ keratomileusis (LASIK) that occur when creation of the corneal flap is interrupted. Further complications can arise if a second flap is created that intersects the original flap interface, resulting in tissue slivers that can lead to more complications and poor visual outcomes. We report the case of a 56-year-old man who underwent LASIK in which an incomplete flap occurred after 45% completion using a mechanical microkeratome with a 160 µm head. The maximum depth achieved by this incomplete flap was measured by very high-frequency (VHF) digital ultrasound as 182 μm peripherally. Two months later, a second flap was created beneath the incomplete flap, at a depth of 190 μm. The resulting flap had a central thickness of 196 μm and a minimum clearance of 30 μm beneath the incomplete flap. This demonstrates a method for creating secondary flaps that may significantly reduce the risk of flap interface intersection.

Intraoperative and early postoperative flap-related complications of laser in situ keratomileusis using two types of Moria microkeratomes

The purpose of this study is to describe the incidence, management, and visual outcomes of intraoperative and early postoperative flap-related complications of laser in situ keratomileusis (LASIK) surgery using two types of Moria M2 microkeratomes. This retrospective analysis was performed on 806 primary LASIK cases. The intraoperative and early postoperative flap-related complications were identified and categorized according to type of Moria microkeratome. There were 52 intraoperative and early postoperative complications--one case of partial flap (0.124 %), one case of free flap (0.124 %), one case of small flap (0.124 %), 13 cases of epithelial defect (1.61 %), 12 cases of flap striae (1.49 %), 10 cases of diffuse lamellar keratitis (1.24 %), 10 cases of interface debris (1.24 %), three cases of epithelial ingrowth (0.37 %), and one case of microbial infection (0.124 %). The overall incidence of flap complications was 6.45 %. There were 27 right eye (6.73 %) and 25 left eye (6.17 %) complications. The incidence of complications with the Moria automated metallic head 130 microkeratome was 4.22 % and with the Moria single-use head 90 microkeratome was 2.23 %. We observed one culture-negative interface abscess which was cured with surgical cleaning and intensive medical treatment. The most common complication encountered was epithelial defects, followed by flap striae. Our study showed that LASIK with a microkeratome has a relatively low incidence of intraoperative and early postoperative flap complications. The authors have no financial interest in any of the issues contained in this article and have no proprietary interest in the development of marketing of or materials used in this study.

Comparison of Ziemer FEMTO LDV "Classic" and "Crystal Line" femtosecond laser flap quality by Fourier-domain 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.

Laser in situ keratomileusis in 2012: a review

Laser in situ keratomileusis (LASIK) is a safe and effective treatment for refractive error. A combination of technological advances and increasing surgeon experience has served to further refine refractive outcomes and reduce complication rates. In this article, we review LASIK as it stands in late 2012: the procedure, indications, technology, complications and refractive outcomes.

Management of post-keratoplasty astigmatism

Post-keratoplasty astigmatism remains a challenge for corneorefractive surgeons. While maintaining a healthy graft is the most crucial issue in keratoplasty procedures, astigmatism is a limiting factor in the visual rehabilitation of otherwise successful corneal grafts. The management of post-keratoplasty astigmatism takes place at 2 stages: when sutures are still present at the graft-host junction and when all sutures have been removed. Excessive suture-in post-keratoplasty astigmatism is usually managed by selective suture manipulation, ie, suture adjustment and/or suture removal along the steep meridian of astigmatism. A small amount of suture-out post-keratoplasty astigmatism can be managed by spectacles. Higher magnitudes of astigmatism can be addressed by contact lenses or surgical intervention, such as relaxing and compressing procedures. Laser lamellar refractive surgery can also be used to manage post-keratoplasty astigmatism, and toric phakic intraocular lenses have recently been recommended. In this review, we discuss the etiology and management of post-keratoplasty astigmatism and provide recommendations and tips to minimize it.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Long-term comparison of laser in situ keratomileusis versus laser surface ablation in corneas thinner than 470 μm

PURPOSE

To compare long-term refractive and visual outcomes of laser in situ keratomileusis (LASIK) and laser surface ablation in eyes with corneas thinner than 470 μm.

SETTING

Private clinics, Spain.

DESIGN

Comparative case series.

METHODS

The study comprised eyes with myopic error and corneas thinner than 470 μm that had at least 2.9 years of postoperative follow-up between September 2001 and June 2007. The main outcome measures were safety, efficacy, predictability, and complications.

RESULTS

The mean central corneal thickness was 462.0 μm (range 440 to 469 μm) in the LASIK group (n = 40) and 458.1 μm (range 420 to 469 μm) in the laser surface ablation group (n = 88). All eyes had normal preoperative topography. In the LASIK group after a mean follow-up of 5.1 years ± 1.5 (SD), the safety index was 1.07, efficacy was 0.99, and predictability (± 1.00 diopter [D]) was 0.93. In the laser surface ablation group after a mean follow-up of 4.8 ± 1.3 years, the safety index was 1.01, efficacy was 0.93, and predictability (± 1.00 D) was 0.92. The mean residual corneal bed thickness in all eyes was 345 ± 25 μm (range 270 to 399 μm). No major complications occurred. The safety index was better in the LASIK group than in the laser surface ablation group.

CONCLUSION

Both techniques were effective, safe, and predictable in eyes with corneas thinner than 470 μm, normal preoperative topography, and a residual corneal bed thickness greater than 250 μm.

Outcomes of Retreatment after Aborted Laser In Situ Keratomileusis due to Flap Complications

Purpose:

To determine the refractive outcomes and complications of retreatment after aborted primary laser in situ keratomileusis (LASIK) due to flap complications.

Materials and Methods:

This retrospective study evaluated 50 retreated eyes that had flap complications during primary LASIK at the Eye Consultants Center in Riyadh, Saudi Arabia. Data were analyzed for patients with at least 3 months follow-up post retreatment.

Results:

Thirty-three eyes of 31 consecutive patients with 3 months follow-up or later post retreatment were included. The primary LASIK was aborted due to incomplete flaps in 22 eyes (66.7%), buttonhole flaps in 7 eyes (21.2%), free partial flaps in 3 eyes (9.1%), and a free complete flap in 1 eye (3.0%). Twenty-two eyes (66.7%) were retreated with LASIK, and 11 eyes (33.3%) were retreated with surface ablation. The mean spherical equivalent (SE) was –0.23 ± 0.72 D, the mean astigmatism was –0.65 ± 0.89 D, and the mean loss of the best corrected visual acuity (BCVA) was 0.78 lines at the final postoperative visit. At the last postoperative visit, 20/30 or better BCVA was achieved in 90.1% of eyes that underwent retreatment with LASIK and in 91% of eyes that were retreated with surface ablation. There was no statistical difference in postoperative SE between eyes retreated with LASIK and eyes retreated with surface ablation (P = 0.610). There was no statistical difference in postoperative BCVA between eyes retreated with LASIK and those retreated with surface ablation (P = 0.756). There were no intraoperative complications and no eyes required a second retreatment.

Conclusion:

Creation of a flap after a previous intraoperative flap complication was not associated with any complications. The refractive outcomes of retreatment with LASIK or surface ablation were comparable and reasonably favorable.

Intraoperative and Postoperative Complications of Laser in situ Keratomileusis Flap Creation Using IntraLase Femtosecond Laser and Mechanical Microkeratomes

An essential step of laser in situ keratomileusis surgery is corneal flap creation, Femtosecond (FS)-assisted or mechanical microkeratome. Each type has rare intraoperative and postoperative complication rates. Several recent studies have identified risk factors and guidelines to help manage these complications. Fortunately, studies have shown no loss of best-corrected visual acuity (BCVA) after the management of intraoperative and postoperative complications in IntraLase FS and mechanical microkeratome. Refractive surgeons need to be aware of the types of complications that can occur, how to avoid them and how to manage them to ensure the best possible outcomes.

Intraoperative flap complications in laser in situ keratomileusis with two types of microkeratomes

PURPOSE

To determine the incidence and types of intraoperative flap complications in laser in situ keratomileusis (LASIK) encountered with the Hansatome microkeratome and the Moria microkeratome.

METHODS

In this retrospective case series, all patients with intraoperative flap complications who were treated between June 1999 and July 2008 at the Eye Consultants Center in Riyadh, Saudi Arabia, were identified and reviewed.

RESULTS

Of the 4352 subjects who underwent bilateral primary LASIK procedure, intraoperative microkeratome complications were detected in 89 eyes of 83 patients. The overall incidence of flap complications was 89/8704 (1.00%): incomplete flaps occurred in 53 eyes (0.60%), followed by buttonhole flaps in 17 eyes (0.19%), free complete flaps in 10 eyes (0.11%), free partial flaps in 6 eyes (0.07%), sluffed epithelium in 2 eyes (0.023%), and a splitted flap (vertical flap cut) in 1 eye (0.01%). The incidence rates of intraoperative flap complications with the Hansatome microkeratome and the Moria microkeratome were 1.21% (41/3378) and 0.90% (48/5326), respectively (P = 0.19). There was a statistically significant difference between the two microkeratomes with regard to the incidence of buttonhole flaps: 0.33% (11/3378) for the Hansatome microkeratome versus 0.11% (6/5326) for the Moria microkeratome (P = 0.04).

CONCLUSION

Generally, the incidence rates of intraoperative flap complications with the Hansatome microkeratome and the Moria microkeratome were similar. However, buttonhole flaps occurred more often with the Hansatome microkeratome (a type of microkeratome that produces larger flaps). The commonest complication encountered was the incomplete flap, followed by the buttonhole flap and free flap.

Laser in situ keratomileusis flap complications using mechanical microkeratome versus femtosecond laser: retrospective comparison

PURPOSE

To compare the incidence of flap complications after creation of laser in situ keratomileusis (LASIK) flaps using a zero-compression microkeratome or a femtosecond laser.

SETTING

John A. Moran Eye Center, Department of Ophthalmology, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Evidence-based manuscript.

METHODS

The flap complication rate was evaluated during the initial 18 months of experience using a zero-compression microkeratome (Hansatome) or a femtosecond laser (IntraLase FS60) for flap creation.

RESULTS

The flap complication rate was 14.2% in the microkeratome group and 15.2% in the femtosecond laser group (P = .5437). The intraoperative flap complication rate was 5.3% and 2.9%, respectively (P = .0111), and the postoperative flap complication rate, 8.9% and 12.3%, respectively (P = .0201). The most common intraoperative complication in the microkeratome group was major epithelial defect/sloughing; the rate (2.6%) was statistically significantly higher than in the femtosecond laser group (P = .0006). The most common postoperative complication in both groups was diffuse lamellar keratitis (DLK) (6.0%, microkeratome; 10.6%, femtosecond laser) (P = .0002).

CONCLUSION

Although the total complication rates between the 2 groups were similar, the microkeratome group had significantly more epithelial defects intraoperatively and the femtosecond laser group had significantly more DLK cases postoperatively.

Efficacy, safety, and flap dimensions of a new femtosecond laser for laser in situ keratomileusis

PURPOSE

To evaluate the clinical results of a preproduction femtosecond laser for flap creation in laser in situ keratomileusis (LASIK).

SETTING

Private practice, Brussels, Belgium.

METHODS

This study comprised myopic eyes with a plano target refraction and a target flap thickness of 110 microm. The LASIK flap was created with a Ziemer LDV femtosecond laser. Prospective evaluation included flap dimensions, intraoperative and postoperative complications, and visual outcomes.

RESULTS

Sixty-three patients (111 eyes; mean age 37.2 years) were evaluated. Preoperatively, the mean corrected distance visual acuity (CDVA) was 1.34 (Snellen) and the mean manifest refraction spherical equivalent (MRSE), -4.91 diopters (D) +/- 2.45 (SD). Six months postoperatively, the mean CDVA was 1.33; the mean MRSE, -0.05 +/- 0.3 D; and the mean uncorrected distance visual acuity (UDVA), 1.27. The UDVA was 20/25 or better in 98.2% of eyes and 20/20 or better in 94.6% of eyes. The MRSE was within +/-0.50 D in 95.5% of eyes and within +/-1.00 D in 99.1% of eyes. The cylinder was 0.50 D or less in 99.1% of eyes. The mean flap thickness was 106.6 +/- 12.6 microm. The most frequent complications were epithelial sloughing (10.8%), a decentered cut (4.5%), flap adhesions (5.4%), a slightly irregular flap border (5.4%), and microstriae (5.4%); all were mild.

CONCLUSIONS

Overall, the flap dimensions and refractive results were predictable and the complication rate was acceptable after LASIK using the new femtosecond laser for flap creation.

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.

Comparison of laser in situ keratomileusis reoperation outcomes with the Moria M2 head 90 and 130 following previous photorefractive keratectomy or laser in situ keratomileusis

PURPOSE

To compare the Moria Model Two (M2) automated microkeratome with the head 90 (intended to create a 120-microm flap) to the head 130 (intended to create a 160-microm flap) in reoperations following previous photorefractive keratectomy (PRK) or laser-assisted in situ keratomileusis (LASIK) in terms of accuracy, predictability, safety and complications of the procedure.

METHODS

Eighty-five eyes of 70 consecutive patients received LASIK with the Moria M2 microkeratome. Nine previously PRK-operated eyes were reoperated with the head 90 and 37 eyes were reoperated with the head 130. Repeated LASIK was performed on 16 eyes with the head 90 and on 23 eyes with head the 130. Flap dimensions were measured and correlated to preoperative parameters.

RESULTS

The average flap thickness in the previously PRK-operated eyes was 115.1 microm [range 82-137 microm, standard deviation (SD) 17.9] with the head 90 and 131.2 microm (range 105-171 microm, SD 19.8) with the head 130. In the previously LASIK-operated eyes, the mean flap thickness was 139.2 microm (range 92-182 microm, SD 23.8) with the head 90 and 141.9 microm (range 109-179 microm, SD 15.2) with the head 130. There were no free or incomplete flaps or flaps with buttonholes in the study. There was no statistically significant difference in postoperative uncorrected visual acuity (UCVA) between the groups.

CONCLUSION

In eyes with previous PRK or LASIK, LASIK reoperation offers a safe alternative for improving refractive outcomes. The Moria M2 head 90, especially in LASIK-operated eyes, does not cut thinner flaps compared to the head 130.

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.

Corneal flap thickness with the Moria M2 microkeratome and Med-Logics calibrated LASIK blades

PURPOSE

 This study aimed to compare and study potential factors that affect the accuracy of corneal flap thickness created in laser-assisted in situ keratomileusis (LASIK) using the Moria model 2 (M2) head 130 microkeratome with the Med-Logics calibrated LASIK blades Minus 20 (ML -20) and Minus 30 (ML -30).

METHODS

 Corneal thickness in 200 (164 myopic and 36 hyperopic) eyes (100 patients) was measured by ultrasonic pachymetry preoperatively and intraoperatively after flap cutting. A total of 100 eyes were treated with the ML -20 and 100 with the ML -30. The right eye was operated before the left eye in each patient, using the same blade. In an additional group of 40 eyes, the left eye was operated first.

RESULTS

 Mean corneal flap thickness using the ML -20 blade for an intended flap thickness of 140 μm was 129.1 μm (standard deviation [SD] 15.6, range 104-165 μm) in right eyes and 111.5 μm (SD 14.5, range 78-144 μm) in left eyes. Mean corneal flap thickness using the ML -30 blade for an intended flap thickness of 130 μm was 127.1 μm (SD 16.6, range 90-168 μm) in right eyes and 109.9 μm (SD 16.8, range 72-149 μm) in left eyes.

CONCLUSIONS

Both microkeratome blade types cut thinner flaps than were intended. There was substantial variation in flap thickness. The first flap to be cut with a particular blade was considerably thicker than the second flap cut with the same blade. Based on these data, we recommend the use of disposable single-use microkeratomes rather than these ML blades.

Microkeratome complications

PURPOSE OF REVIEW

Complications from laser in-situ keratomileusis surgery are extremely rare. However, most of the complications involve construction of the corneal flap, which is fashioned using various mechanical or femtosecond laser microkeratomes. Here, we review and discuss complications of microkeratome flaps.

RECENT FINDINGS

Several large studies of microkeratome laser in-situ keratomileusis cases report a similar set of complications: partial or irregular flaps, buttonholes, and free flaps. Risk factors for these complications include increased age, preoperative hyperopia, and years of contact lens wear. Numerous animal and clinical studies have shown that the femtosecond platform produces flaps with greater stability with more consistent and accurate dimensions than the mechanical microkeratome. However, there is no significant difference in final visual outcome.

SUMMARY

The aim of this review is to report complications associated with mechanical microkeratomes in the construction of laser in-situ keratomileusis flaps and to see whether there is a significant disadvantage compared with the femtosecond laser.

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.

Corneal flap thickness with the Moria M2 single-use head 90 microkeratome

PURPOSE

To analyse the accuracy of corneal flap thickness created in laser-assisted in situ keratomileusis (LASIK) using the Moria Model 2 (M2) single-use head 90 microkeratome.

METHODS

The corneal thickness of 300 (266 myopic and 34 hyperopic) eyes of 150 patients was measured by ultrasonic pachymetry preoperationally and intraoperationally after flap cut. The Moria M2 single-use head 90, intended to create a flap with a thickness of 120 microm, was used in all eyes. The right eye was always operated first and the left eye second, using the same blade.

RESULTS

Mean corneal flap thickness was 115.4 microm (standard deviation [SD] 12.5) in the two eyes, 115.7 microm (SD 12.4, range 73-147 microm) in right eyes and 115.1 microm (SD 12.6, range 74-144 microm) in left eyes. Mean horizontal flap diameter was 9.1 mm (SD 0.2) and mean hinge length 4.1 mm (SD 0.1). There were no free flaps, incomplete flaps or flaps with buttonholes in the study. Occasional iron particles were observed in three (1.0%) eyes.

CONCLUSIONS

As with most microkeratomes, the single-use head 90 microkeratome cut thinner flaps than were intended. The range of the cuts was relatively wide. However, thin flaps did not increase the rate of flap-related complications. The difference between the first and second eyes was not significant.