Incidence of diffuse lamellar keratitis after laser in situ keratomileusis associated with the IntraLase 15 kHz femtosecond laser and Moria M2 microkeratome

Central toxic keratopathy leading to epithelial ingrowth following femtosecond LASIK

We report a case of a woman in her 30s who underwent femtosecond LASIK (laser-assisted in situ keratomileusis) in both eyes to correct her simple myopic astigmatism. After the surgery, both eyes developed diffuse lamellar keratitis, and intensive topical steroids were initiated to control the same. Subsequently, central toxic keratopathy (CTK) developed bilaterally. Three weeks after the surgery, the right eye showed signs of progressive epithelial ingrowth involving the pupillary area. Surgical intervention in the form of flap relift followed by debridement of the epithelial cells and an alcohol interface wash were performed to treat the same. This is the first report of an epithelial ingrowth following CTK after femtosecond LASIK.

Delayed diffuse lamellar keratitis after small-incision lenticule extraction related to immunoglobulin A nephropathy: A case report

BACKGROUND

Diffuse lamellar keratitis (DLK) is a complication of laser-assisted in situ keratomileusis (LASIK). This condition can also develop after small-incision lenticule extraction (SMILE) with a distinctive appearance. We report the case involving a female patient with delayed onset DLK accompanied by immunoglobulin A (IgA) nephropathy.

CASE SUMMARY

A 22-year-old woman was referred to our department for DLK and a decline in vision 1 mo after undergoing SMILE. The initial examination showed grade 2 DLK in the flap involving the central visual axis of the right eye. She was immediately administered with a large dose of a topical steroid for 30 d. However, the treatment was ineffective. Her vision deteriorated from 10/20 to 6/20, and DLK gradually worsened from grade 2 to 4. Eventually, interface washout was performed, after which her vision improved. DLK completely disappeared 2 mo after washout. Six months after SMILE, the patient was diagnosed with IgA nephropathy due to a 4-year history of interstitial hematuria.

CONCLUSION

DLK is a typical complication of LASIK but can also develop after SMILE. Topical steroid therapy was ineffective in our patient, and interface washout was required. IgA nephropathy could be one of the factors contributing to the development of delayed DLK after SMILE.

Five-Year Incidence, Management, and Visual Outcomes of Diffuse Lamellar Keratitis after Femtosecond-Assisted LASIK

Femtosecond (FS) lasers initially had a higher incidence of diffuse lamellar keratitis (DLK) compared with microkeratome flap creation. It has been theorized that higher-frequency lower-energy (HFLE) FS lasers would reduce the incidence of DLK. Our study sought to evaluate the incidence of newer HFLE FS lasers with pulse frequencies above 60 kHz. It was a retrospective case-control study evaluating the incidence of DLK following flap creation with one of three FS lasers (AMO iFs, WaveLight FS200, Zeiss VisuMax). Uncomplicated LASIK cases were included as the control group (14,348 eyes) and cases of DLK were recorded in the study group (637 eyes). Of the 637 cases of DLK, 76 developed stage II, 25 progressed to stage III, and only three developed stage IV DLK. The overall incidence rate of DLK was 4.3%; it has fallen with the invention of newer HFLE FS lasers and is approaching the DLK incidence rates of DLK with microkeratome.

Diffuse lamellar keratitis after LASIK with low-energy femtosecond laser

PURPOSE

To evaluate the incidence, evolution, and prognosis of diffuse lamellar keratitis (DLK) in a large series of laser in situ keratomileusis (LASIK) with low-energy femtosecond laser.

SETTING

Private practice, Siena, Italy.

DESIGN

Retrospective, consecutive, noncomparative case series study.

METHODS

Single-use instruments, powder-free gloves, and no corneal marking were used. Flap was created by a low-energy femtosecond laser (Ziemer Z2 and Z4).

RESULTS

A total of 37 315 eyes of 19 602 patients were reviewed. DLK was observed in 236 eyes (0.63%) of 149 patients (0.76%). Grade 1 DLK was observed in 231 eyes of 142 patients, grade 2 in 1 eye: when treated with topical steroids, they had no visual consequences. Three patients had bilateral grade 3 to 4 DLK: one of them, with bilateral grade 3, despite flap lifting and irrigation worsened to stage 4 (central stroma thinning and flattening), partially recovered in 2 years, and underwent repeat femtosecond laser-assisted LASIK for hyperopic shift in 1 eye. In all the 5 eyes that developed grade 4 DLK, corneal thickness decreased until the first month and then partially recovered; mean final tissue loss at 1 to 2 years was 35 µm. Compensatory epithelial thickening was observed.

CONCLUSIONS

DLK after low-energy femtosecond laser-assisted LASIK is rare; severe DLK (stages 3 and 4) was found in only 6 eyes (0.016%). Flap lifting and irrigation might not prevent progression. Spontaneous reformation of stromal tissue and epithelial thickening improve visual acuity in the long term; residual hyperopic shift can be corrected by repeat femtosecond laser-assisted LASIK.

Pathophysiology and Treatment of Diffuse Lamellar Keratitis

PURPOSE

To review cytokine- and chemokine-mediated mechanisms of diffuse lamellar keratitis (DLK) after lamellar corneal surgical procedures.

METHODS

Review of the basic science and clinical literature.

RESULTS

DLK can occur early or late (months to decades) after all lamellar corneal surgeries, including laser in situ keratomileusis, small incision lenticule extraction, anterior lamellar keratoplasty, and Descemet's stripping automated endothelial keratoplasty. It is most commonly triggered by epithelial injury during or after lamellar surgery, which leads to the release of interleukin (IL)-1α, IL-1β, and tumor necrosis factor (TNF)-α from the epithelium and into the stroma. These chemokines directly attract inflammatory cells into the cornea from the limbal blood vessels and also bind to receptors on keratocytes and corneal fibroblasts where myriad chemokines are upregulated that also chemotactically attract monocytes, macrophages, granulocytes, lymphocytes, and other bone marrow-derived cells into the corneal stroma. Other factors that can trigger DLK include retained blood in the interface, endotoxins and other toxins, and excessive keratocyte necrosis caused by femtosecond lasers. Infiltrating cells show a preference to enter any lamellar interface in the cornea, regardless of the time since surgery, because of the ease of movement toward the chemotactic attractants relative to the surrounding stroma with intact collagen lamellae and stromal cells that serve as relative barriers impeding motility. The mainstay of treatment is topical corticosteroids, but severe cases may also be treated with flap lift irrigation and systemic corticosteroids.

CONCLUSIONS

DLK can occur early or late after any lamellar corneal surgical procedure and is most commonly triggered by epithelial-stromal-bone marrow-derived cellular interactions mediated by corneal cytokines and chemokines. [J Refract Surg. 2020;36(2):124-130.].

Early Surface Ablation on Aborted LASIK Flaps

PURPOSE

To report the outcomes of a series of 16 patients who had secondary surface ablation within 4 weeks of an aborted femtosecond laser-assisted in situ keratomileusis (FS-LASIK) procedure.

METHODS

A retrospective chart review of electronic medical record data from 2011 to 2015 was performed to identify eyes of patients who had an aborted FS-LASIK procedure followed by secondary surface ablation (photorefractive keratectomy or laser epithelial keratomileusis) within 4 weeks of the primary procedure. Patients were required to have at least three postoperative visits to be included in the study.

RESULTS

The review identified 20 aborted FS-LASIK procedures of 7,142 eyes (0.003%), of which 16 met the inclusion criteria. The most common reasons for abortion were incomplete (10) and decentered (3) flaps. Thirteen of 16 eyes were treated within 2 weeks. A total of 11 of 16 eyes achieved uncorrected distance visual acuity (UDVA) of 20/20, 13 of 16 achieved UDVA of 20/25 or better, and 15 of 16 had a corrected distance visual acuity (CDVA) of 20/20. There were no intraoperative complications during the second procedure and there were no cases of diffuse lamellar keratitis. One patient developed postoperative haze with a CDVA of 20/25 and was lost to follow-up.

CONCLUSIONS

This case series indicates that early surface ablation (within 4 weeks) after an aborted FS-LASIK procedure may be performed with good visual outcomes. [J Refract Surg. 2019;35(2):121-125.].

Incidence and Outcomes of Sterile Multifocal Inflammatory Keratitis and Diffuse Lamellar Keratitis After SMILE

PURPOSE

To report the incidence outcomes of sterile multifocal inflammatory keratitis and diffuse lamellar keratitis (DLK) after small incision lenticule extraction (SMILE) in a large population.

METHODS

This was a retrospective review of a population of 4,000 consecutive eyes treated by SMILE at the London Vision Clinic using the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). The inclusion criterion was to have presented with inflammatory keratitis after SMILE. In some cases after SMILE, the inflammatory keratitis presented as sterile multifocal interface keratitis uncharacteristic of classic DLK. The incidence was measured and categorized as primary or secondary by presenting appearance, grade, and time to presentation. Patients were observed for 1 year after surgery and standard outcomes analysis was performed.

RESULTS

Of the 4,000 eye population, there were 18 cases (0.45%) of DLK grade 1 or 2. All cases were managed and resolved with topical steroid therapy. Of these, 12 cases (67%) were of classic appearance and 6 cases (33%) presented as sterile multifocal inflammatory keratitis. DLK was primary in nature in 11 cases (61%) and secondary in 7 cases (39%). Postoperative uncorrected distance visual acuity was 20/20 or better in 93% of eyes. No patients lost any lines of corrected distance visual acuity and there was no change in contrast sensitivity.

CONCLUSIONS

DLK occurred after SMILE with an incidence of 0.45% in this population. Topical steroid therapy resolved the DLK in all cases with no sequelae and no adverse effect on refractive or visual outcome at 1 year postoperatively. A unique type of DLK presentation can occur after SMILE, characterized by multiple focal sterile inflammatory spots. Management is the same as for classic DLK, but with a lower threshold for performing an interface washout. [J Refract Surg. 2018;34(11):751-759.].

Refractive lenticule extraction (ReLEx) through a small incision (SMILE) for correction of myopia and myopic astigmatism: current perspectives

Small-incision lenticule extraction (SMILE) is an alternative to laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for the correction of myopia and myopic astigmatism. SMILE can be performed for the treatment of myopia ≤−12 D and astigmatism ≤5 D. The technology is currently only available in the VisuMax femtosecond laser platform. It offers several advantages over LASIK and PRK; however, hyperopia treatment, topography-guided treatment, and cyclotorsion control are not available in the current platform. The working principles, potential advantages, and disadvantages are discussed in this review.

Chung's swing technique: a new technique for small-incision lenticule extraction

Background

To introduce the Chung’s swing technique for small-incision lenticule extraction (SMILE).

Methods

A total of 112 eyes of 56 patients were included in this study. Patients were divided into two groups: 52 eyes of 26 patients were treated with SMILE using a traditional method (traditional group) and 60 eyes of 30 patients were treated with SMILE using the Chung’s swing technique (swing group).

Results

At 1 month postoperatively, all eyes in both groups had an uncorrected distance visual acuity of 20/20 or better. The efficacy indices were 1.09 ± 0.17 and 1.02 ± 0.11 (p = 0.492), and the safety indices were 1.12 ± 0.14 and 1.09 ± 0.15 (p = 0.537), for the traditional and swing group, respectively. All eyes in both groups underwent successful lenticule extraction; all lenticules were intact and complete. The mean lenticule extraction times were 48.67 ± 4.9 and 39.8 ± 5.53 s, for the traditional and swing group, respectively (p < 0.001).

Conclusions

The Chung’s swing technique is efficient for lenticule separation and extraction. Our study results showed good clinical outcomes.

Trial registration

Trial registration number: KCT0001978. Registered 22 July 2016. Retrospectively registered.

Electronic supplementary material

The online version of this article (doi:10.1186/s12886-016-0321-2) contains supplementary material, which is available to authorized users.

Visual outcomes after femtosecond laser in situ keratomileusis flap complications

PURPOSE

To compare visual outcomes in normal and complicated laser in situ keratomileusis (LASIK) flaps constructed with a femtosecond laser.

SETTING

Wilford Hall Ambulatory Surgical Center, San Antonio, Texas.

DESIGN

Retrospective chart review.

METHODS

The main outcome measures were uncorrected distance visual acuity (UDVA) and best-corrected distance visual acuity (CDVA) at 1 month post-surgery, which were compared in patients with and without complications during flap creation.

RESULTS

This retrospective chart review identified 586 eyes of 293 consecutive patients who had bilateral simultaneous femtosecond LASIK for myopia. A normal flap was attained in 539 (91.8%) of patients. At 1 month postoperatively, the mean UDVA was 20/19.1, and the CDVA was 20/16.8. 3 (0.51%) of patients experienced an incomplete side cut or intraoperative flap tear (the mean 1-month uncorrected distance visual acuity [UDVA] was 20/17.5 and the corrected distance visual acuity [CDVA] was 20/16.9 in both groups). Microstriae were seen in 28 (4.8%) of patients (mean 1-month UDVA, 20/21.7; CDVA, 20/17.4). Diffuse lamellar keratitis appeared in 4 (0.68%) of patients (mean 1-month UDVA, 20/21.7; CDVA, 20/15.6). Epithelial ingrowth developed in 9 (1.5%) of patients (mean 1-month UDVA, 20/18.7; CDVA, 20/16.9). There was no statistically significant difference in UDVA or CDVA at 1 month postoperatively between complicated and uncomplicated flaps (P > .05), and complicated flaps did not lose a statistically significant amount of CDVA or low-contrast acuity (CDVA 5%) compared to preoperative values.

CONCLUSIONS

Intraoperative and postoperative complications of LASIK flaps created with the femtosecond laser were rare, and their visual outcomes were equivalent to those of normal flaps.

FINANCIAL DISCLOSURE

Charles D. Reilly is a consultant to Alcon Labs and Abbott Medical Optics at present, but was not at the time of the study. For the remaining authors none are declared.

Comparison of the femtosecond laser and mechanical microkeratome for flap cutting in LASIK

AIM

To compare refractive results, higher-order aberrations (HOAs), contrast sensitivity and dry eye after laser in situ keratomileusis (LASIK) performed with a femtosecond laser versus a mechanical microkeratome for myopia and astigmatism.

METHODS

In this prospective, non-randomized study, 120 eyes with myopia received a LASIK surgery with the VisuMax femtosecond laser for flap cutting, and 120 eyes received a conventional LASIK surgery with a mechanical microkeratome. Flap thickness, visual acuity, manifest refraction, contrast sensitivity function (CSF) curves, HOAs and dry-eye were measured at 1wk; 1, 3, 6mo after surgery.

RESULTS

At 6mo postoperatively, the mean central flap thickness in femtosecond laser procedure was 113.05±5.89 µm (attempted thickness 110 µm), and 148.36±21.24 µm (attempted thickness 140 µm) in mechanical microkeratome procedure. An uncorrected distance visual acuity (UDVA) of 4.9 or better was obtained in more than 98% of eyes treated by both methods, a gain in logMAR lines of corrected distance visual acuity (CDVA) occurred in more than 70% of eyes treated by both methods, and no eye lost ≥1 lines of CDVA in both groups. The difference of the mean UDVA and CDVA between two groups at any time post-surgery were not statistically significant (P>0.05). The postoperative changes of spherical equivalent occurred markedly during the first month in both groups. The total root mean square values of HOAs and spherical aberrations in the femtosecond treated eyes were markedly less than those in the microkeratome treated eyes during 6mo visit after surgery (P<0.01). The CSF values of the femtosecond treated eyes were also higher than those of the microkeratome treated eyes at all space frequency (P<0.01). The mean ocular surface disease index scores in both groups were increased at 1wk, and recovered to preoperative level at 1mo after surgery. The mean tear breakup time (TBUT) of the femtosecond treated eyes were markedly longer than those of the microkeratome treated eyes at postoperative 1, 3mo (P<0.01).

CONCLUSION

Both the femtosecond laser and the mechanical microkeratome for LASIK flap cutting are safe and effective to correct myopia, with no statistically significant difference in the UDVA, CDVA during 6mo follow-up. Refractive results remained stable after 1mo post-operation for both groups. The femtosecond laser may have advantages over the microkeratome in the flap thickness predictability, fewer induced HOAs, better CSF, and longer TBUT.

The evolution of corneal and refractive surgery with the femtosecond laser

The use of femtosecond lasers has created an evolution in modern corneal and refractive surgery. With accuracy, safety, and repeatability, eye surgeons can utilize the femtosecond laser in almost all anterior refractive procedures; laser in situ keratomileusis (LASIK), small incision lenticule extraction (SMILE), penetrating keratoplasty (PKP), insertion of intracorneal ring segments, anterior and posterior lamellar keratoplasty (Deep anterior lamellar keratoplasty (DALK) and Descemet's stripping endothelial keratoplasty (DSEK)), insertion of corneal inlays and cataract surgery. As the technology matures, it will push surgical limits and open new avenues for ophthalmic intervention in areas not yet explored. As we witness the transition from femto-LASIK to femto-cataract surgery it becomes obvious that this innovation is here to stay. This article presents some of the most relevant advances of femtosecond lasers to modern corneal and refractive surgery.

Complications of femtosecond-assisted laser in-situ keratomileusis flaps

Femtosecond-assisted laser in-situ keratomileusis flaps have revolutionized refractive surgery since their introduction. Although these lasers are exceedingly safe, complications still do occur. This review focuses specifically on examining the literature and evidence for flap complications during femtosecond-assisted laser in-situ keratomileusis as well as their management.

Development of the continuous curvilinear lenticulerrhexis technique for small incision lenticule extraction

PURPOSE

To develop and evaluate the new continuous curvilinear lenticulerrhexis (CCL) technique for small incision lenticule extraction.

METHODS

Thirty-one eyes of 20 patients with myopia were included in the study. The CCL technique for lenticule extraction was developed and used in 16 eyes of 10 patients (CCL group). The traditional technique of lenticule extraction was used in 15 eyes of 10 patients (traditional group). Uncorrected and corrected distance visual acuity, manifest refraction, lenticule quality, the duration of the extraction procedure, microdistorsions in Bowman's layer under optical coherence tomography (Optovue OCT; Optovue, Inc., Fremont, CA), and adverse events were evaluated at 1 day and 1 month postoperatively.

RESULTS

At the first postoperative month, all eyes in both groups had an uncorrected distance visual acuity of 1.0 or better. The safety indices were 1.12 and 1.09 for the CCL and traditional groups, respectively. The efficacy indices were 1.06 and 1.09 for the CCL and traditional groups, respectively. All lenticules in the CCL group had intact, round margins, whereas one lenticule in the traditional group had a microdefect margin. There was no statistically significant difference in duration of lenticule extraction or microdistorsions in Bowman's layer. No eyes in the CCL group developed diffuse lamellar keratitis, as compared to one eye in the traditional group.

CONCLUSIONS

The CCL technique exhibited excellent safety and efficacy for myopia correction, suggesting CCL is a promising technique that merits further development and study.

Central toxic keratopathy after laser in situ keratomileusis

PURPOSE

To review cases of central toxic keratopathy (CTK) occurring over a period of 46 days.

SETTING

Moorfields Eye Hospital, London, United Kingdom.

DESIGN

Retrospective consecutive case series.

METHODS

This was a review of patients with CTK after uneventful laser in situ keratomileusis (LASIK) performed by 1 of 5 surgeons at a single institute. The following parameters were analyzed: corrected distance visual acuity (CDVA), manifest refraction, and central corneal thickness from Scheimpflug pachymetry readings (Pentacam).

RESULTS

The cohort consisted of 15 eyes of 9 patients. Thirteen eyes were diagnosed within 7 days after LASIK, while the remaining 2 eyes developed CTK 12 days postoperatively. In 10 eyes, the time to resolution was 1 to 8 months. Five eyes still had residual signs at the last outpatient visit. At the final follow-up, 3 eyes (20%) had a CDVA worse than 0.0 logMAR.

CONCLUSIONS

Although a rare entity, CTK can occur in clusters. Although a cause was not fully isolated, ultimately each eye achieved excellent CDVA (all better than 0.2 logMAR) at the last follow-up.

Long-term observation and evaluation of femtosecond laser-assisted thin-flap laser in situ keratomileusis in eyes with thin corneas but normal topography

PURPOSE

To evaluate the long-term outcomes of thin-flap laser in situ keratomileusis (LASIK) in eyes with thin corneas (central corneal thickness [CCT] <500 μm) but normal topography.

SETTING

Private center, Tokyo, Japan.

DESIGN

Retrospective randomized comparative study.

METHOD

The efficacy, safety, predictability, and topography of LASIK were evaluated in eyes with a CCT of less than 500 μm but with normal topography (thin-cornea group) to 6 years postoperatively. The LASIK outcomes in the thin-cornea group were compared with those in eyes with a CCT of 500 μm or greater (control group). Analysis was performed to determine whether there were differences between the groups at the last checkup 3 to 4 years postoperatively.

RESULTS

In the thin-cornea group (291 eyes; 146 patients), no significant differences were observed in LASIK outcomes when eyes were subdivided by the time of final checkup (3, 4, and ≥ 5 years). There was a significant difference in visual and refractive outcomes between 3 months postoperatively and the last checkup in the thin-cornea group and the control group (371 eyes; 193 patients). No significant difference in visual, refractive, or topography outcomes was observed between the 2 groups at the last checkup.

CONCLUSIONS

Laser in situ keratomileusis in eyes with thin corneas was as safe and effective as and showed similar long-term stability in eyes with a CCT of 500 μm or greater. No eye in either group had a postoperative complication.

FINANCIAL DISCLOSURE

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

Diffuse lamellar keratitis in the femtosecond-assisted LASIK flap tunnel

Here we report a case of a 29-year-old myopic female who underwent femtosecond laser-assisted in situ keratomileusis (LASIK) and, on the first postoperative day slit-lamp examination revealed a dense, white, granular reaction with the presence of some blood droplets (stage I diffuse lamellar keratitis [DLK]) in her left eye, specifically localized into the femtosecond LASIK flap tunnel (not extended to the flap interface). The patient received intensive treatment with topical corticosteroids and 5 days later the granular reaction had completely resolved. A new site of DLK, ie, the flap tunnel, in femtosecond-assisted LASIK is presented. DLK into the flap tunnel could be managed with corticosteroids if detected early, without affecting the flap interface.

Corneal backscatter analysis by in vivo confocal microscopy: fellow eye comparison of small incision lenticule extraction and femtosecond laser-assisted LASIK

Purpose. To evaluate and compare corneal backscatter from anterior stroma between small incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK (femto-LASIK). Methods. A cohort of 60 eyes of 30 patients was randomized to receive SMILE in one eye and femto-LASIK in the fellow eye. In vivo confocal microscopy was performed at 1 week and 1, 3, and 6 months after surgery. The main outcome measurements were maximum backscattered intensity and the depth from which it was measured, the backscattered light intensity 30  μ m below Bowman's membrane at the flap interface and 150  μ m below the superficial epithelium, and the number of refractive particles at the flap interface. Results. The mean backscattered light intensity (LI) at all measured depths and the maximum backscattered LI were higher in the SMILE group than the femto-LASIK group at all postoperative visits. LI differences at 1 week and 1- and 3-month visits were statistically significant (P < 0,05). LI differences at 6 months were not statistically significant. There was no difference in the number of refractive particles at the flap interface between the groups at any visit. Conclusions. SMILE results in increased backscattered LI in the anterior stroma when compared with femto-LASIK were evaluated.

Comparison of DLK incidence after laser in situ keratomileusis associated with two femtosecond lasers: Femto LDV and IntraLase FS60

Purpose

To compare the incidence of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK) with flap creation using the Femto LDV and IntraLase™ FS60 femtosecond lasers.0

Methods

A total of 818 consecutive myopic eyes had LASIK performed using either Femto LDV or IntraLase FS60 for flap creation. The same excimer laser, the Allegretto Wave® Eye-Q Laser, was used for correcting refractive errors for all patients. In the preoperative examination, uncorrected distance visual acuity, corrected distance visual acuity, and manifest refraction spherical equivalent were measured. At the postop examination, the same examinations were performed along with a slit-lamp biomicroscopic examination, and patients with DLK were classified into stages. For the statistical analysis of the DLK occurrence rate and the visual and refractive outcomes, the Mann-Whitney’s U-test was used.

Results

In the Femto LDV group with 514 eyes, 42 (8.17%) had DLK. In the IntraLase FS60 group with 304 eyes, 114 (37.5%) had DLK. There was a statistically significant difference in the DLK incidence rate between these groups (P < 0.0001). Both groups had excellent visual and refractive outcomes. Although low levels of DLK were observed for both groups, they did not affect visual acuity.

Conclusion

While there were significantly fewer incidences of low level DLK when using Femto LDV, neither femtosecond laser induced high levels of DLK, and any postoperative DLK cleared up within 1 week. Therefore, both lasers provide excellent results, with no clinical differences, and both excel at flap creation for LASIK.

Comparison of visual acuity, refractive results and complications of femtosecond laser with mechanical microkeratome in LASIK

AIM

To compare the outcomes of laser in situ keratomileusis (LASIK) performed with a femtosecond laser (Femtec, Technolas Perfect Vision GmbH, Germany) versus a mechanical microkeratome (Hansatome, Bausch and Lomb, USA) for the correction of myopia and astigmatism.

METHODS

In this retrospective study, patients who had undergone LASIK using the 80-kHz Femtec femtosecond laser were compared to age- and refraction-matched patients in whom the Hansatome microkeratome was used. Refractive and visual results 1 month and 3 months postoperatively, and complication rates were compared between the two groups.

RESULTS

A total of 280 eyes were analyzed (140 in each group). At 3 months postoperatively in the Femtec vs Hansatome group, spherical equivalent refraction was within ±1.00D of emmetropia in 140 vs 138 eyes (P=0.498), the cylinder was within ±0.50D in 137 vs 139 eyes (P=0.622), and the UDVA was 20/20 or better in 136 vs 137 eyes (P=0.724), respectively. There was no statistically significant difference in the complication rates between the two groups (P=0.099).

CONCLUSION

LASIK performed both with Femtec femtosecond laser and Hansatome microkeratome achieved satisfactory refractive and visual results at 3 months postoperatively, without significant differences in efficacy, safety, and complication rates between the two procedures.

Femtosecond laser technology in corneal refractive surgery: a review

PURPOSE

To discuss current applications and advantages of femtosecond laser technology over traditional manual techniques and related unique complications in corneal refractive surgical procedures, including LASIK flap creation, intracorneal ring segment implantation, astigmatic keratotomy, presbyopic treatments, and intrastromal lenticule procedures.

METHODS

Literature review.

RESULTS

From its first clinical use in 2001 for LASIK flap creation, femtosecond lasers have steadily made a place as the dominant flap-making technology worldwide. Newer applications are being evaluated and are increasing in their frequency of use.

CONCLUSIONS

Femtosecond laser technology is rapidly becoming a heavily utilized tool in corneal refractive surgical procedures due to its reproducibility, safety, precision, and versatility.

Femtosecond lasers for LASIK flap creation: a report by the American Academy of Ophthalmology

OBJECTIVE

To review the published literature to assess the safety, efficacy, and predictability of femtosecond lasers for the creation of corneal flaps for LASIK; to assess the reported outcomes of LASIK when femtosecond lasers are used to create corneal flaps; and to compare the differences in outcomes between femtosecond lasers and mechanical microkeratomes.

METHODS

Literature searches of the PubMed and Cochrane Library databases were last conducted on October 12, 2011, without language or date limitations. The searches retrieved a total of 636 references. Of these, panel members selected 58 articles that they considered to be of high or medium clinical relevance, and the panel methodologist rated each article according to the strength of evidence. Four studies were rated as level I evidence, 14 studies were rated as level II evidence, and the remaining studies were rated as level III evidence.

RESULTS

The majority of published studies evaluated a single laser platform. Flap reproducibility varied by device and the generation of the device. Standard deviations in flap thicknesses ranged from 4 to 18.4 μm. Visual acuities and complications reported with LASIK flaps created using femtosecond lasers are within Food and Drug Administration safety and efficacy limits. Of all complications, diffuse lamellar keratitis is the most common after surgery but is generally mild and self-limited. Corneal sensation was reported to normalize by 1 year after surgery. Unique complications of femtosecond lasers included transient light-sensitivity syndrome, rainbow glare, opaque bubble layer, epithelial breakthrough of gas bubbles, and gas bubbles within the anterior chamber.

CONCLUSIONS

Available evidence (levels I and II) indicates that femtosecond lasers are efficacious devices for creating LASIK flaps, with accompanying good visual results. Overall, femtosecond lasers were found to be as good as or better than mechanical microkeratomes for creating LASIK flaps. There are unique complications that can occur with femtosecond lasers, and long-term follow-up is needed to evaluate the technology fully.

Corneal refractive surgery: past to present

There have been many historical corneal refractive techniques and procedures developed over the years. From early techniques of radial keratotomy to modern excimer laser techniques, the field of refractive surgery is one of the most rapidly developing in ophthalmology. This review details the historical aspects of the many early techniques up to current techniques used on millions of eyes around the world.

Diffuse lamellar keratitis after laser in situ keratomileusis with femtosecond laser flap creation

PURPOSE

To identify possible associations with the development of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK) with femtosecond laser flap creation.

SETTING

University-based academic practice, Ann Arbor, Michigan, USA.

DESIGN

Case-control study.

METHODS

Myopic LASIK was performed between October 2006 and December 2010 using an Intralase 60 kHz femtosecond laser for flap creation. Preoperative clinical characteristics, treatment parameters, and intraoperative and postoperative complications were recorded. Statistical comparisons were made using t, chi-square, and Fisher exact tests and repeated-measures logistic regression to adjust for inter-eye dependency.

RESULTS

The study enrolled 801 eyes (419 patients). Ninety-nine eyes (12.4%) of 70 patients developed DLK; most cases comprised mild flap interface inflammation and were treated with a routine postoperative antiinflammatory regimen. Twenty-two eyes (2.7%) required more than 1 week of antiinflammatory treatment. There was a statistically significant increase in the incidence of DLK with larger flap diameter (P=.0171), higher side-cut energy (P=.0037), and higher raster energy (P=.0033). Patients with DLK were less likely to achieve corrected distance visual acuity of 20/20 or better 1 day postoperatively (P=.0453). The difference in acuity was no longer present at 1 week. There were no significant associations between the incidence of DLK and preoperative refractive error, flap thickness, ablation depth, or other treatment parameters.

CONCLUSIONS

Diffuse lamellar keratitis after LASIK with femtosecond laser flap creation tended to be mild with little effect on visual acuity. Higher energy level for flap creation and larger flap diameter were associated with an increased risk for DLK.

IntraLase femtosecond laser vs mechanical microkeratomes in LASIK for myopia: a systematic review and meta-analysis

PURPOSE

To evaluate the safety, efficacy, and predictability of IntraLase (Abbott Medical Optics) femtosecond laser-assisted compared to microkeratome-assisted myopic LASIK.

METHODS

A comprehensive literature search of Cochrane Library, PubMed, and EMBASE was conducted to identify relevant trials comparing LASIK with IntraLase femtosecond laser to LASIK with microkeratomes for the correction of myopia. Meta-analyses were performed on the primary outcomes (loss of ≥2 lines of corrected distance visual acuity [CDVA], uncorrected distance visual acuity [UDVA] 20/20 or better, manifest refraction spherical equivalent [MRSE] within ±0.50 diopters [D], final refractive SE, and astigmatism), and secondary outcomes (flap thickness predictability, changes in higher order aberrations [HOAs], and complications).

RESULTS

Fifteen articles describing a total of 3679 eyes were identified. No significant differences were identified between the two groups in regards to a loss of ≥2 lines of CDVA (P=.44), patients achieving UDVA 20/20 or better (P=.24), final UDVA (P=.12), final mean refractive SE (P=.74), final astigmatism (P=.27), or changes in HOAs. The IntraLase group had more patients who were within ±0.50 D of target refraction (P=.05) compared to the microkeratome group, and flap thickness was more predictable in the IntraLase group (P<.0001). The microkeratome group had more epithelial defects (P=.04), whereas the IntraLase group had more cases of diffuse lamellar keratitis (P=.01).

CONCLUSIONS

According to the available data, LASIK with the IntraLase femtosecond laser offers no significant benefits over LASIK with microkeratomes in regards to safety and efficacy, but has potential advantages in predictability.

LASIK interface keratitis: epidemiology, diagnosis and care

PURPOSE OF REVIEW

Diffuse lamellar keratitis (DLK) is one of the more common interface complications occurs after laser in-situ keratomileusis (LASIK). The diagnosis can sometimes be challenging, as the differential diagnosis includes infectious keratitis, which requires a completely different treatment compared to DLK. This review assesses our current knowledge of the epidemiology, diagnosis and treatment of DLK.

RECENT FINDINGS

DLK occurs during the immediate postoperative period, but there are also late-onset cases. Early cases can occur in outbreaks, related to exogenous factors. Late-onset cases are most often related to inciting factors. Over time, case reports and series have reported DLK onset occurring further after surgery. It is probable that additional inciting factors will also be reported over time. Visual outcomes following DLK tend to be good when the condition is diagnosed properly and treated with intensive topical or systemic steroids, possibly combined with interface irrigation.

SUMMARY

DLK is a well recognized and well described complication occurring after LASIK. Associated inciting and risk factors and treatment algorithms have been described, but additional questions remain. Our knowledge and our patients will benefit from further research and development of evidence-based treatments.

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.

Femtosecond laser vs mechanical microkeratome for hyperopic laser in situ keratomileusis

PURPOSE

To compare the outcomes of laser in situ keratomileusis (LASIK) performed with a femtosecond laser vs a mechanical microkeratome for the correction of low to moderate hyperopia.

DESIGN

Retrospective, nonrandomized, interventional, comparative case series.

METHODS

settings: Vissum Santa Hortensia, Madrid, Spain.study population and procedures: Patients who had undergone LASIK to correct their hyperopia using the 60-kHz IntraLase femtosecond laser were compared to age- and refraction-matched patients in whom the Moria M2 microkeratome was used. Visual and refractive results 3 months postoperatively were compared between both groups.

RESULTS

A total of 144 eyes were analyzed (72 in each group). Mean preoperative sphere was +3.45 ± 1.0 diopters (D) in the IntraLase group vs +3.18 ± 1.3 D in the M2 group (P = .1). Results 3 months postoperatively were: mean residual sphere, +0.44 ± 0.6D vs +0.72 ± 0.8 D (P = .02), respectively; uncorrected visual acuity (UCVA), 0.89 ± 0.2 vs 0.80 ± 0.2 (P = .04); best spectacle-corrected visual acuity (BSCVA), 0.96 ± 0.2 vs 0.92 ± 0.2 (P = .2); safety index, 0.97 ± 0.1 vs 0.98 ± 0.1 (P = .5); efficacy index, 0.89 ± 0.2 vs 0.84 ± 0.2 (P = .3).

CONCLUSIONS

Hyperopic LASIK performed with the IntraLase femtosecond laser seems to achieve better refractive results 3 months after the surgery compared to the M2 microkeratome, without significant differences in safety between both procedures.

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.

Incidence of diffuse lamellar keratitis after LASIK with 15 KHz, 30 KHz, and 60 KHz femtosecond laser flap creation

PURPOSE

To compare the incidence of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK) with flap creation using the 15 kHz (FS15), 30 kHz (FS30), or 60 kHz (FS60) femtosecond laser.

SETTING

University-based academic practice, Ann Arbor, Michigan, USA.

DESIGN

Retrospective comparative case series.

METHODS

Consecutive myopic LASIK cases performed between January 1, 2005, and June 1, 2007, using the IntraLase FS15, FS30, or FS60 femtosecond laser for flap creation were reviewed. Preoperative clinical characteristics, treatment parameters, and intraoperative and postoperative complications were recorded. Statistical comparisons were made using repeated measures analysis, analysis of variance, chi-square, and Fisher exact tests.

RESULTS

Five hundred twenty eyes of 274 patients were included in the study. One hundred seventy-six eyes (93 patients) were treated with the FS15 laser, 180 eyes (93 patients) with the FS30 laser, and 164 eyes (89 patients) with the FS60 laser. Seventeen eyes (10%) in the FS15 laser group, 24 eyes (13%) in the FS30 laser group, and 23 eyes (14%) in the FS60 laser group developed DLK. There was no statistically significant difference in the incidence of DLK between the 3 groups (P = .68).

CONCLUSION

There was no significant difference in the incidence of DLK between the FS15, FS30, and FS60 groups.

Comparison between femtosecond laser-assisted sub-Bowman keratomileusis vs laser subepithelial keratectomy to correct myopia

PURPOSE

To compare femtosecond laser sub-Bowman keratomileusis (FSBK) vs laser subepithelial keratectomy (LASEK) to correct myopia.

DESIGN

Retrospective, nonrandomized, interventional, comparative case series.

METHODS

Two thousand one hundred and eight eyes were included in the study. We compared 1,072 eyes treated with FSBK vs 1,036 eyes treated with LASEK with or without mitomycin C (MMC). Visual and refractive results were evaluated 1 day, 1 week, and 1 and 3 months postoperatively.

RESULTS

Preoperative mean sphere and best spectacle-corrected visual acuity (BSCVA) were -3.93 diopters (D) vs -3.87 D (P = .5) and 1.12 vs 1.12 (P = .8) in FSBK and LASEK, respectively. Uncorrected visual acuity (UCVA) was 0.92 vs 0.62, 0.98 vs 0.78, 0.96 vs 0.91, and 1.06 vs 1.03 in FSBK and LASEK, respectively, at 1 day, 1 week, and 1 and 3 months after surgery (P < .01 for all comparisons). Three months postoperatively, BSCVA was 1.13 and 1.10, respectively (P = .001). At that moment, 20 eyes (1.93%) in the LASEK group vs 9 eyes (0.84%) in the FSBK group had lost 2 or more lines of BSCVA. Ten eyes (0.96%) in the LASEK group gained 2 or more lines of BSCVA, whereas 3 eyes (0.28%) in the FSBK group gained 2 lines. Six months postoperatively, only 2 LASEK eyes (0.19%) showed loss of 2 or more lines of BSCVA, compared to 3 FSBK-treated eyes (0.28%).

CONCLUSION

Both FSBK and LASEK are safe and effective procedures to correct myopia. Slightly better visual and refractive results were observed in FSBK-treated eyes in a 3-month follow-up.

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.

Femtosecond lasers in ophthalmology

PURPOSE

To provide an update and review of femtosecond (FS) lasers in clinical ophthalmology.

DESIGN

Perspective, literature review, and commentary.

METHODS

Selected articles from the literature and the authors' clinical and laboratory studies.

RESULTS

The FS laser employs near-infrared pulses to cut tissue with minimal collateral tissue damage. Although its major use at present is in the cutting of laser in situ keratomileusis flaps, the laser has proven its versatility in laser-assisted anterior and posterior lamellar keratoplasty, cutting of donor buttons in endothelial keratoplasty, customized trephination in penetrating keratoplasty, tunnel creation for intracorneal ring segments, astigmatic keratotomy, and corneal biopsy. Current laboratory studies include all-FS laser refractive keratomileusis sans flap, cutting corneal pockets for insertion of biopolymer keratoprostheses, noninvasive transscleral glaucoma surgery, retinal imaging and photodisruption, presbyopia surgery, and anterior lens capsulorrhexis.

CONCLUSIONS

Advances in ultra-fast laser technology continue to improve the surgical safety, efficiency, speed, and versatility of FS lasers in ophthalmology.