Corneal Wound Healing After Laser in situ Keratomileusis in Rabbits

Epithelial ingrowth following laser in situ keratomileusis (LASIK): prevalence, risk factors, management and visual outcomes

The number of laser in situ keratomileusis (LASIK) procedures is continuing to rise. Since its first application for correcting simple refractive errors over 25 years ago, the role of LASIK has extended to treat other conditions, including postkeratoplasty astigmatism/ametropia, postcataract surgery refractive error and presbyopia, among others. The long-term effectiveness, predictability and safety have been well established by many large studies. However, due to the creation of a potential interface between the flap and the underlying stroma, interface complications such as infectious keratitis, diffuse lamellar keratitis and epithelial ingrowth may occur. Post-LASIK epithelial ingrowth (PLEI) is an uncommon complication that usually arises during the early postoperative period. The reported incidence of PLEI ranged from 0%–3.9% in primary treatment to 10%–20% in retreatment cases. It can cause a wide spectrum of clinical presentations, ranging from asymptomatic interface changes to severe visual impairment and flap melt requiring keratoplasty. PLEI can usually be treated with mechanical debridement of the affected interface; however, additional interventions, such as alcohol, mitomycin C, fibrin glue, ocular hydrogel sealant, neodymium:yttriumaluminum garnet laser and amniotic membrane graft, may be required for recurrent or refractory cases. The aims of this review are to determine the prevalence and risk factors of PLEI; to describe its pathogenesis and clinical features and to summarise the therapeutic armamentarium and the visual outcome of PLEI.

Progress in corneal wound healing

Corneal wound healing is a complex process involving cell death, migration, proliferation, differentiation, and extracellular matrix remodeling. Many similarities are observed in the healing processes of corneal epithelial, stromal and endothelial cells, as well as cell-specific differences. Corneal epithelial healing largely depends on limbal stem cells and remodeling of the basement membrane. During stromal healing, keratocytes get transformed to motile and contractile myofibroblasts largely due to activation of transforming growth factor-β (TGF-β) system. Endothelial cells heal mostly by migration and spreading, with cell proliferation playing a secondary role. In the last decade, many aspects of wound healing process in different parts of the cornea have been elucidated, and some new therapeutic approaches have emerged. The concept of limbal stem cells received rigorous experimental corroboration, with new markers uncovered and new treatment options including gene and microRNA therapy tested in experimental systems. Transplantation of limbal stem cell-enriched cultures for efficient re-epithelialization in stem cell deficiency and corneal injuries has become reality in clinical setting. Mediators and course of events during stromal healing have been detailed, and new treatment regimens including gene (decorin) and stem cell therapy for excessive healing have been designed. This is a very important advance given the popularity of various refractive surgeries entailing stromal wound healing. Successful surgical ways of replacing the diseased endothelium have been clinically tested, and new approaches to accelerate endothelial healing and suppress endothelial-mesenchymal transformation have been proposed including Rho kinase (ROCK) inhibitor eye drops and gene therapy to activate TGF-β inhibitor SMAD7. Promising new technologies with potential for corneal wound healing manipulation including microRNA, induced pluripotent stem cells to generate corneal epithelium, and nanocarriers for corneal drug delivery are discussed. Attention is also paid to problems in wound healing understanding and treatment, such as lack of specific epithelial stem cell markers, reliable identification of stem cells, efficient prevention of haze and stromal scar formation, lack of data on wound regulating microRNAs in keratocytes and endothelial cells, as well as virtual lack of targeted systems for drug and gene delivery to select corneal cells.

Management of long-standing partially torn and flipped laser in situ keratomileusis flaps

We describe 2 cases of traumatized and torn laser in situ keratomileusis (LASIK) flaps, partially flipped anteriorly or posteriorly, fixed for 8 months or 4 months, and accompanied by epithelial ingrowth. The 2 patients had had uneventful bilateral LASIK 6 years and 1 year before the trauma. In Case 1, the anteriorly flipped flap was removed with transepithelial phototherapeutic keratectomy. Next, mitomycin-C 0.04% was applied for 30 seconds. In Case 2, the portion of the flap that was flipped posteriorly and buried under the remaining intact LASIK flap was restored to its original normal position and epithelial ingrowth was removed mechanically with a microcurette. Irrigation with 20% ethanol was performed to inhibit the recurrence of interfacial epithelial ingrowth. The stretched amniotic membrane overlay over the cornea and sclera was sutured tightly to the episclera as the biologic pressure patch for the inhibition of epithelial re-ingrowth. Good visual acuity was restored in both cases.

FINANCIAL DISCLOSURE

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

Traumatic flap dislocation 10 years after LASIK. Case report and literature review

We report a case of traumatic partial flap dislocation 10 years after uneventful laser in situ keratomileusis (LASIK). The patient was treated bilaterally for hyperopia and astigmatism with LASIK. A superior-hinged corneal flap was created using the Moria M2 microkeratome (Moria SA, Antony, France) and the surgery was uneventful. Ten years later, partial flap dislocation was diagnosed after mild trauma. This case suggests that flap dislocations can occur during recreational activities up to 10 years after surgery. Full visual recovery is achievable if the case is managed promptly. Further studies should evaluate the potential protective role of an inferior hinge during LASIK.

Surgical management of traumatic LASIK flap dislocation with macrostriae and epithelial ingrowth 14 years postoperatively

Fourteen years after uneventful laser in situ keratomileusis (LASIK), a 59-year-old woman presented after suffering blunt trauma to her left eye 5 weeks earlier. The injury resulted in traumatic flap dislocation, epithelial ingrowth, and significant macrostriae. Following epithelial removal, the flap was hydrated with sterile water, facilitating reduction of the macrostriae and reapproximation without the need for suture placement. The postoperative course was uneventful, and at 1 month, the epithelial ingrowth and macrostriae had resolved and the uncorrected distance visual acuity was 20/30. This case represents the longest documented interval from LASIK surgery to traumatic flap dislocation. We describe our surgical approach to the management of this type of injury and present a video illustrating the technique.

Traumatic Flap Striae 6 Years After LASIK: Case Report and Literature Review

Purpose:

To report a case of traumatic flap striae without flap dislocation 6 years after LASIK and provide a literature review of surgical flap striae, late traumatic flap striae, and their management.

Methods:

A 28-year-old man presented with late traumatic flap striae without concurrent flap dislocation, which closely approximated the longest reported interval between LASIK and the development of flap striae.

Results:

In the absence of flap dislocation, the finding of striae alone was subtle and went undetected initially. The flap was successfully refloated, stretched, and smoothed with recovery of 20/20 vision.

Conclusions:

Traumatic LASIK flap complications may occur many years after the original procedure. This report presents the first case of late traumatic flap striae without concurrent flap dislocation. Proper management can restore good visual function.

LASIK Induces Minimal Regrowth and No Haze Development in Rabbit Corneas

PURPOSE

To quantify central corneal regrowth and haze development after LASIK in rabbits.

METHODS

New Zealand White rabbits received an 89 microm (-8 diopters) myopic LASIK and were evaluated during 4 months using slit-lamp and in vivo confocal microscopy to monitor changes in central corneal morphology, epithelial and stromal thickness, flap and bed thickness, and corneal light backscattering (haze). At various time-points, corneas were processed for histology.

RESULTS

Using in vivo confocal microscopy, LASIK induced no detectable morphological changes besides a slightly elevated light backscattering at the interface. Correspondingly, all corneas remained clear with no haze development by slit-lamp biomicroscopy. Corneal thickness was stable by 8 weeks after an increase of 17 +/- 4 microm that consisted of a 13 +/- 3 microm stromal regrowth and a 4 +/- 2 microm epithelial hyperplasia. At the LASIK interface, less than 4 microm new extracellular matrix was deposited. Accordingly, all LASIK flaps were easily pulled off by 6 months.

CONCLUSIONS

LASIK induces a minimal wound healing response in rabbit corneas with no haze development and a regrowth (regression) of only 17 microm of an 89-microm photoablation. Three main factors contributed to the observed regrowth: epithelial hyperplasia (approximately 4 microm), matrix deposition at the LASIK interface (approximately 4 microm), and stromal growth outside the interface within the flap and wound bed (approximately 9 microm).

Immunohistochemical Evaluation of Two Corneal Buttons With Post-LASIK Keratectasia

PURPOSE

To examine immunohistochemically 2 human corneal buttons after corneal transplantation for post-laser in situ keratomileusis (LASIK) keratectasia.

METHODS

Two ectatic corneas after penetrating keratoplasty and 2 postmortem control corneas from a patient after uncomplicated LASIK were used. Cryostat sections were stained by immunofluorescence for >30 extracellular matrix (ECM) components and proteinases.

RESULTS

The ratios of distance between LASIK flap interface and the upper epithelial layer to total corneal thickness were 0.27-0.34 in all cases. The whole flap interface was positive only for total and cellular fibronectin. Stromal types VI and XIV collagen, fibrillin-1, tenascin-C, and vitronectin were unchanged with no evidence of fibrosis. In ectasia cases, keratocytes adjacent to the flap did not express nidogens. Staining for type IV collagen alpha5 chain, nidogen-2, chains of laminin-8, and laminin-10 was weak and discontinuous in the epithelial basement membrane (EBM). Type IV collagen alpha1/alpha2 chains were found in the EBM of ectasia cases only. Matrix metalloproteinase (MMP)-10 showed increase in the epithelium, and MMP-3, in some keratocytes near the flap interface of ectatic corneas. Also, cathepsin F was seen at the flap margin only. Staining for limbal basal epithelial marker, alpha-enolase, was mostly absent in the ectatic cases, suggesting largely normal epithelial differentiation.

CONCLUSIONS

Abnormal EBM structure similar to that previously observed in keratoconus and bullous keratopathy and an increase in certain proteinases suggest ongoing EBM lysis and remodeling. Immunohistochemical staining for fibronectin may be used to reveal the position of flap interface.

Ultrabiomicroscopy (UBM) in flap dislocation following LASIK: a case report

PURPOSE

To describe postoperative laser-assisted in situ keratomileusis (LASIK) flap dislocation occurred after trauma

METHODS

Ultrabiomicroscopy (UBM) is used to obtain a high-resolution imaging of the cornea.

RESULTS

The UBM results are presented and compared with histologic and confoscan findings

CONCLUSIONS

The technique is useful and easy to perform, offering more opportunities to study the anatomical changes in LASK flap dislocation occurred after trauma.

Confocal Microscopy and Histopathological Examination of Diffuse Lamellar Keratitis in an Experimental Animal Model

PURPOSE

To investigate the cell populations and structural alterations of the cornea in an experimental model of diffuse lamellar keratitis (DLK) using confocal microscopy and histopathology.

METHODS

A corneal flap was cut in 22 eyes of 11 New Zealand rabbits and the stromal interface was exposed to balanced salt solution (BSS, BSS group) and Pseudomonas aeruginosa lipopolysaccharide (LPS) endotoxin (5 mg/mL) (LPS 5 mg/mL group) and (3.5 mg/mL) (LPS 3.5 mg/mL group). Postoperatively, eyes were examined with a slit-lamp microscope (DLK grading) and confocal microscopy. Animals were sacrificed on day 3 (BSS group and LPS 5 mg/mL group) and day 4 (LPS 3.5 mg/mL group). Corneoscleral buttons were excised and processed for histopathologic examination.

RESULTS

Seven eyes were excluded. Slit-lamp microscopy revealed no cellular infiltration in the BSS group (five eyes). In the LPS groups, all eyes developed DLK, with iritis only observed in grade III eyes. In the LPS 5 mg/mL group, four eyes had DLK grade III, with iritis in three eyes. In the LPS 3.5 mg/mL group, three eyes had grade II and three eyes had grade III with iritis. On confocal microscopy, the BSS group had no cellular infiltration. Dense accumulation of inflammatory cells at the interface was noted in both LPS groups. Histopathology in the BSS group had a normal appearance. In the LPS groups, an inflammatory infiltrate was present at the interface that consisted of three cell populations--eosinophils, neutrophils, and lymphocytes.

CONCLUSIONS

Lipopolysaccharide endotoxin induced DLK in all exposed eyes, with iritis in a considerable proportion of eyes. The infiltrate consisted of three cell populations. Confocal microscopy showed the infiltrate in all affected eyes. Histopathological and confocal microscopic findings correlated well with the clinical appearance.

Traumatic Corneal Flap Dislocation One to Six Years After LASIK in Nine Eyes With a Favorable Outcome

PURPOSE

To report our experience treating eye trauma after LASIK refractive surgery.

METHODS

Nine eyes of eight patients (one woman and seven men) were treated for ocular trauma: blunt trauma (n=5), sharp instrument trauma (n=2,) and trauma from inflation of automobile air bags during a traffic accident (n=2). The time from LASIK varied between 3 months and 6 years. All patients were hospitalized as a result of severe decrease in visual acuity and pain.

RESULTS

Seven of nine LASIK flaps had some degree of dislocation and were lifted, irrigated, and repositioned. Two flaps were edematous without dislocation. Intensive topical steroids and antibiotics were used in all patients up to 3 weeks after trauma. Three months after trauma, five eyes regained their pre-trauma visual acuity (between 20/20 and 20/40), and three eyes lost one line of best spectacle-corrected visual acuity.

CONCLUSIONS

Trauma occurring several months or years after LASIK may cause flap injury. Adequate and prompt treatment usually is successful.

Late-onset Traumatic Dislocation With Central Tissue Loss of Laser In Situ Keratomileusis Flap

PURPOSE

We report the occurrence and outcome of a severe late-onset traumatic dislocation of a laser in situ keratomileusis (LASIK) flap with loss of central flap tissue.

METHODS

Case report.

RESULTS

A 40-year-old woman underwent uncomplicated bilateral LASIK surgery, followed 5 years later by an enhancement procedure in both eyes. Ocular trauma with a power sander occurred 6 years after LASIK and 1 year after the enhancement procedure. The flap was found to have an almost complete tear from the nasal hinge and a central tissue defect. After irrigating, repositioning, and stabilizing the flap with 2 nylon sutures, a bandage contact lens was placed. The patient was treated with topical antibiotic and steroid drops. Stage 2 diffuse lamellar keratitis developed, which responded to topical treatment. Ten weeks after injury, the patient regained an uncorrected visual acuity of 20/20-1.

CONCLUSION

Late-onset trauma to the LASIK flap can result in flap dehiscence and tissue loss. Prompt and appropriate management can lead to an excellent visual outcome even in severely traumatized dislocated LASIK flaps.

Stability of the laser in situ keratomileusis corneal flap in rabbit eyes

PURPOSE

To quantify the force required to dislodge a laser in situ keratomileusis (LASIK) corneal flap in rabbits and correlate that force with sources of injury to LASIK corneal flaps in humans.

SETTING

Animal Vivarium and Department of Ophthalmology, Naval Medical Center, San Diego, California, USA.

METHODS

Corneal flaps were cut in 56 eyes of 30 rabbits. A -8.00 diopter excimer ablation was also performed in 32 of the eyes. Injury testing, using a burst of CO2 from a modified paintball gun, was conducted from 1 to 9 days postoperatively. Impact force was compared to that generated by mechanical trauma (fingers and a small tree branch) striking a force gauge.

RESULTS

Of 43 eyes tested for injury, flaps could not be dislocated in 11 eyes (26%). There was no significant difference between eyes treated with flap only and those that also had ablation. When flaps were dislodged, the required force generally resulted in extensive intraocular injury. There was no significant difference between the force required for flap dislocation on postoperative days 1 and 9.

CONCLUSIONS

In rabbits, LASIK corneal flaps were very resistant to high-speed wind trauma as early as 24 hours postoperatively. Flap stability was robust prior to the formation of collagen scar tissue, probably due to epithelial bridging at the edge of the flap and an osmotic gradient across the flap-stromal bed interface. Although this study used a rabbit model, it seems likely that both these flap adhesion mechanisms would also provide stability to the LASIK flap in humans.

Treatment of traumatic LASIK flap dislocation and epithelial ingrowth with fibrin glue

PURPOSE

To describe a case of a traumatic late dislocation of a laser-assisted in situ keratomileusis (LASIK) flap complicated by epithelial ingrowth.

DESIGN

Interventional case report.

METHODS

A 50-year-old woman presented 21 months after uncomplicated LASIK with painful vision loss in the right eye after minor trauma.

RESULTS

A dislocation of the LASIK flap was noted at examination and was repositioned. One week later, epithelial ingrowth was detected in the flap interface. The ingrowth was treated with flap lifting, debridement, and sealing of the flap with fibrin glue. Visual acuity returned to baseline, and there was no recurrence after 20 months of follow-up.

CONCLUSIONS

Traumatic dislocations of LASIK flaps may occur many months after uncomplicated surgery and may be associated with epithelial ingrowth after successful repositioning. The additional use of fibrin glue in conjunction with thorough debridement may be helpful in preventing the recurrence of epithelial ingrowth.

Immunohistochemical Findings After LASIK Confirm In Vitro LASIK Model

PURPOSE

To compare immunohistochemical findings in human donor corneas after successful laser in situ keratomileusis (LASIK) without clinical complications with a recently established human LASIK in vitro model.

METHODS

Donor corneas with prior LASIK treatment were investigated. Cryostat sections were stained immunohistochemically for collagen types I, III, and VI and laminin and fibronectin.

RESULTS

With light microscopy, the interface of the LASIK flap could hardly be detected. In all samples, fibronectin was consistently detected along the entire extent of the surgical wound. In contrast, collagen type III and laminin only stained the superficial portion of the LASIK incision site. Staining for collagen types I and VI showed no changes after LASIK.

CONCLUSION

Histologic findings in donor corneas with prior LASIK treatment confirm histologic observations in a recently introduced human organ culture LASIK model. This strengthens the reliability of the latter LASIK model for further studies concerning wound healing after LASIK surgery.

Absence of scar formation in human donor cornea with prior laser in situ keratomileusis

PURPOSE

To investigate transglutaminases (enzymes capable of cross-linking extracellular matrix proteins to proteolysis-resistant complexes during scar tissue formation) in a human donor cornea after successful laser in situ keratomileusis (LASIK) without clinical complications and to compare with the results in a human donor cornea with corneal scarring after corneal injury.

SETTING

Department of Ophthalmology, Ludwig-Maximilians University, Munich, Germany.

METHODS

A donor cornea with prior uneventful LASIK treatment and 1 with corneal scarring after penetrating injury were investigated. Cryostat sections were stained immunohistochemically for tissue transglutaminase (tTG), keratocyte transglutaminase (kTG), and their reaction product epsilon-(gamma-glutamyl)-lysine.

RESULTS

With light microscopy, the flap interface of the LASIK-treated eye could hardly be detected, while in the injured eye, infiltration of cells and a clear margin next to the scar formation were present. Immunohistochemistry demonstrated a distinct staining for tTG, kTG, and epsilon-(gamma-glutamyl)-lysine in the corneal scar. In contrast, neither transglutaminase nor epsilon-(gamma-glutamyl)-lysine staining could be observed at the flap margin or in the interface of the LASIK-treated donor eye.

CONCLUSIONS

Irreversible protein cross-linking of transglutaminases via epsilon-(gamma-glutamyl)-lysine connections seem to be indicators for scarring in corneal wound healing. The absence of transglutaminases and their reaction product epsilon-(gamma-glutamyl)-lysine in a LASIK-treated cornea supports the idea of missing scar tissue formation after LASIK surgery.

Experimental Model of Laser in situ Keratomileusis in Hens

PURPOSE

To develop an experimental animal model of laser in situ keratomileusis (LASIK) in hens.

METHODS

One hundred adult hens underwent a 60-microm corneal flap followed by -4 diopter excimer laser ablation. Surgical technique, clinical course, and pathology correlations are presented.

RESULTS

Sixty percent of animals had a successful LASIK outcome according to clinical observations. Pathology showed the integrity of Bowman's layer and homogeneous flap in all eyes with good clinical outcomes. Flap complications such as buttonholes (5%), free-flaps (2%), and slipped flaps (3.4%) occurred with the surgical technique. Corneal abscess (2.9%) was also present. Loss of transparency was noted in 26.4%, which correlates with epithelial ingrowth detected by light histology study.

CONCLUSIONS

An experimental animal model of LASIK was successfully developed in adult hens. This model could be useful in the study of wound healing and pharmacological modulation after LASIK in an animal with Bowman's layer.

Pathologic findings in postmortem corneas after successful laser in situ keratomileusis

PURPOSE

To examine the histologic and ultrastructural features of human corneas after successful laser in situ keratomileusis (LASIK).

METHODS

Corneas from 48 eyes of 25 postmortem patients were processed for histology and transmission electron microscopy (TEM). The 25 patients had LASIK between 3 months and 7 years prior to death. Evaluation of all 5 layers of the cornea and the LASIK flap interface region was done using routine histology, periodic acid-Schiff (PAS)-stained specimens, toluidine blue-stained thick sections, and TEM.

RESULTS

In patients for whom visual acuity was known, the first postoperative day uncorrected visual acuity was 20/15 to 20/30. In patients for whom clinical records were available, the postoperative corneal topography was normal and clinical examination showed a semicircular ring of haze at the wound margin of the LASIK flap. Histologically, the LASIK flap measured, on average, 142.7 microm (range, 100-200). A spectrum of abnormal histopathologic and ultrastructural findings was present in all corneas. Findings at the flap surface included elongated basal epithelial cells, epithelial hyperplasia, thickening and undulations of the epithelial basement membrane (EBM), and undulations of Bowman's layer. Findings in or adjacent to the wound included collagen lamellar disarray; activated keratocytes; quiescent keratocytes with small vacuoles; epithelial ingrowth; eosinophilic deposits; PAS-positive, electron-dense granular material interspersed with randomly ordered collagen fibrils; increased spacing between collagen fibrils; and widely spaced banded collagen. There was no observable correlation between postoperative intervals and the severity or type of pathologic change except for the accumulation the electron-dense granular material.

CONCLUSIONS

Permanent pathologic changes were present in all post-LASIK corneas. These changes were most prevalent in the lamellar interface wound. These changes along with other pathologic alterations in post-LASIK corneas may change the functionality of the cornea after LASIK.

Recovery of Corneal Sensitivity to Mechanical and Chemical Stimulation After Laser in situ Keratomileusis

PURPOSE

To evaluate the time course of changes in corneal sensitivity to mechanical and chemical stimuli produced by laser in situ keratomileusis (LASIK) in humans.

METHODS

We performed a cross-sectional study of 17 LASIK-operated eyes (VisX S2, equipped with version 2.50-3.10 software) and 15 control eyes of 17 individuals to evaluate regeneration of corneal sensitivity after LASIK. Gas pulses of variable flow and compositions were applied to the cornea by a non-contact gas esthesiometer. Mechanical stimuli consisted of air puffs at flows from 0 to 200 ml/min. Chemical stimulation was made with gas pulses containing 0% to 80% CO2 in air at subthreshold flow. Mechanical and chemical thresholds and intensity-response curves for the evoked sensations were determined prior to surgery, and 7 to 9 days, 3 to 5 months, and 1.5 to 2.5 years after surgery.

RESULTS

Corneal sensitivity to mechanical stimulation was enhanced 7 to 9 days after surgery but subsequently dropped markedly and remained significantly below control levels 3 to 5 months after LASIK. Sensitivity to both mechanical and chemical types of stimuli was close to normal 2 years postoperatively.

CONCLUSIONS

Corneal sensitivity decreased immediately after LASIK but mechanical sensitivity showed a transient hyperesthesia 7 to 9 days afterward. Subsequently, a long-lasting and deep hypoesthesia to mechanical and chemical stimuli was observed. Gas esthesiometry revealed that disturbances of corneal sensation still exist at times when coarse mechanical sensitivity appeared to be normal.

Effect of Suturing on Iatrogenic Keratectasia After Laser in situ Keratomileusis

PURPOSE

To evaluate the influence of corneal suturing on the clinical course of iatrogenic keratectasia after laser in situ keratomileusis (LASIK), in order to improve quality of vision and to avoid progressive deterioration of visual acuity.

METHODS

Three patients (four eyes) who had a perforation during LASIK or became keratectatic after LASIK received corneal suturing with 10-0 nylon immediately or up to 11 days after LASIK. Sutures were left in place for 1 to 4 months. Patients were followed for 20 to 23 months after suturing.

RESULTS

All eyes had a significant improvement in uncorrected and best spectacle-corrected visual acuity after suturing. The improvements in visual acuity for all patients remained unchanged after suture removal. In patient 1, keratectatic changes were not detected in the sutured eye although they were detected in the contralateral unsutured eye. In patient 2, both eyes were sutured, one immediately and the other 11 days after LASIK; no keratectatic changes were noted in either eye. Slight progression of corneal protrusion was observed in patient 3, who had corneal suturing after development of prominent keratectasia 2 weeks after LASIK. This eye showed stable but moderate keratectatic change 9 months after suture removal.

CONCLUSIONS

Flap suturing in patients during the course of keratectasia after LASIK improved both aided and unaided visual acuity. Prompt suturing seemed to provide a means of preventive management for iatrogenic keratectasia in anticipation of keratoplasty.

Keratocyte phenotype mediates proteoglycan structure: a role for fibroblasts in corneal fibrosis

In pathological corneas, accumulation of fibrotic extracellular matrix is characterized by proteoglycans with altered glycosaminoglycans that contribute to the reduced transparency of scarred tissue. During wound healing, keratocytes in the corneal stroma transdifferentiate into fibroblasts and myofibroblasts. In this study, molecular markers were developed to identify keratocyte, fibroblast, and myofibroblast phenotypes in primary cultures of corneal stromal cells and the structure of glycosaminoglycans secreted by these cells was characterized. Quiescent primary keratocytes expressed abundant protein and mRNA for keratocan and aldehyde dehydrogenase class 3 and secreted proteoglycans containing macromolecular keratan sulfate. Expression of these marker compounds was reduced in fibroblasts and also in transforming growth factor-beta-induced myofibroblasts, which expressed high levels of alpha-smooth muscle actin, biglycan, and the extra domain A (EDA or EIIIA) form of cellular fibronectin. Collagen types I and III mRNAs were elevated in both fibroblasts and in myofibroblasts. Expression of these molecular markers clearly distinguishes the phenotypic states of stromal cells in vitro. Glycosaminoglycans secreted by fibroblasts and myofibroblasts were qualitatively similar to and differed from those of keratocytes. Chondroitin/dermatan sulfate abundance, chain length, and sulfation were increased as keratocytes became fibroblasts and myofibroblasts. Fluorophore-assisted carbohydrate electrophoresis analysis demonstrated increased N-acetylgalactosamine sulfation at both 4- and 6-carbons. Hyaluronan, absent in keratocytes, was secreted by fibroblasts and myofibroblasts. Keratan sulfate biosynthesis, chain length, and sulfation were significantly reduced in both fibroblasts and myofibroblasts. The qualitatively similar expression of glycosaminoglycans shared by fibroblasts and myofibroblasts suggests a role for fibroblasts in deposition of non-transparent fibrotic tissue in pathological corneas.

Stromal haze after laser in situ keratomileusis

PURPOSE

To report clinical and confocal microscopy characteristics of haze-like opacities in corneas after laser in situ keratomileusis (LASIK).

SETTING

Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.

METHODS

Eighteen eyes of 11 patients with clinically apparent corneal clouding were examined by slitlamp and confocal microscopy (Confoscan P4, Tomey) 1 to 9 months after primary LASIK or LASIK retreatment.

RESULTS

Postoperative slitlamp examination showed faint, white, snowflake-like clouding at the interface level in all patients. One patient had folds and rather diffuse haze-like opacities. Confocal microscopy revealed highly reflective structures in the flap stroma and at the interface level in all patients, probably due to numerous activated keratocytes and their processes. The confocal microscopy appearance was similar to that of photorefractive keratectomy haze.

CONCLUSION

Focal wound-healing reactions in the central flap stroma and interface resulting in significant keratocyte activation could be observed after LASIK.

Corneal flap complications in refractive surgery: Part 1: development of an experimental animal model

PURPOSE

To report the outcome, learning curve, and complication rates of an experimental animal model for corneal flaps in refractive surgery.

SETTING

Magill Research Center for Vision Correction, Storm Eye Institute, Charleston, South Carolina, USA.

METHODS

Corneal flaps with a nasal or a temporal hinge were created in 190 eyes of 95 Dutch Belted rabbits using the Automated Corneal Shaper microkeratome (Bausch & Lomb Surgical). Diffuse lamellar keratitis (DLK) was induced by inoculating the corneal interfaces with 1 of 7 substances. Postoperatively, the eyes were examined with a slitlamp. Special emphasis was placed on corneal flap complications and the relationship between slipped flaps and hinge position and/or inoculation agent.

RESULTS

A good corneal flap was achieved in 174 eyes (92%). The eyes with a nasal hinge had a lower incidence of slipped flaps (14%) than eyes with a temporal hinge (37%) (P =.02).

CONCLUSION

With the animal model described, corneal flaps were created in a precise and reproducible way in more than 90% of eyes. Nasal hinged flaps showed less postoperative displacements than temporal hinged flaps and are adequate for further study.

Laser in situ keratomileusis flap stability during simulated aircraft ejection in a rabbit model

PURPOSE

To determine the stability of the laser in situ keratomileusis (LASIK) flap in a rabbit model when subjected to vertical acceleration at nine times the force of gravity (+9 Gz) in an aircraft cockpit ejection simulator.

METHODS

Thirty-six eyes from 25 New Zealand white rabbits underwent LASIK flap creation without laser photoablation. One month after surgery, the rabbits were sedated and harnessed in a cockpit ejection seat simulator used to train United States Air Force pilots. They then underwent a controlled rapid-sequence ejection at +9 Gz. Subsequently, the rabbits were euthanized and the corneas harvested for microscopic examination. Refractive measurements and corneal examination were made before LASIK flap creation and prior to and after the +9 Gz ejections. Determination of LASIK flap dislocation was based on clinical observation of flap slippage or a significant shift in pre-ejection to postejection cylinder axis.

RESULTS

The average preoperative refraction of the rabbit eye was +1.83 D + 3.25 D x 086 degrees. The average change from pre-ejection to postejection was 0.04 D sphere, 0.02 D cylinder, 6.8 axis degrees, and 0.04 D spherical equivalent. The pre-ejection to postejection measurements were not statistically significantly different by a paired test. Laser in situ keratomileusis flap dislocation or ejection-induced corneal folds or striae were not clinically observed. Histologic examination revealed well-healed LASIK flaps but no reactive keratocytes at the central stromal-stromal interface.

CONCLUSIONS

Healed LASIK flaps as created in this rabbit model without laser ablation are stable when subjected to a rapid vertical ejection at nine times the force of gravity.

Late traumatic displacement of laser in situ keratomileusis flaps

PURPOSE

To report the occurrence, management, and outcome of late-onset traumatic dehiscence and dislocation of laser in situ keratomileusis (LASIK) flaps.

METHODS

Two interventional case reports of patients with late-onset LASIK corneal flap dislocation after ocular trauma occurring at 7 and 26 months after surgery, respectively.

RESULTS

The flaps were lifted, stretched, and repositioned after irrigation and scraping of the stromal bed and the underside of the flap. A bandage contact lens was placed, and topical antibiotic and corticosteroids were given postoperatively. The dislocated corneal flaps were successfully repositioned in both cases. The patient whose dislocated flap was repositioned 4 hours after the trauma recovered his uncorrected visual acuity (UCVA) of 20/20 1 week after the procedure and had a well-positioned flap with a clear interface. The patient who was managed 48 hours after the injury required repeat flap repositioning at 10 and 24 days after the initial procedure for treatment of persistent folds and striae in the visual axis. His uncorrected visual acuity 2 weeks after the third flap repositioning was 20/40 + 2. Diffuse lamellar keratitis developed in both patients that resolved with the use of topical corticosteroids.

CONCLUSION

Laser in situ keratomileusis corneal flaps are vulnerable to traumatic dehiscence and dislocation, which can occur more than 2 years after the procedure.

Late-onset traumatic flap dislocation and diffuse lamellar inflammation after laser in situ keratomileusis

PURPOSE

To report a case of traumatic flap partial dislocation and subsequent diffuse lamellar inflammation 14 months after laser in situ keratomileusis (LASIK) retreatment.

METHODS

Case report of a late flap dislocation that occurred during routine recreational activity (struck with a finger in the right eye while playing basketball).

RESULTS

The partially dislocated LASIK flap was reflected nasally, and the stromal surfaces of the flap and bed were thoroughly scraped to remove debris and epithelial cells. The flap was repositioned, and a bandage contact lens was placed. Diffuse lamellar inflammation, which developed on post-trauma day number two, was successfully treated with frequent topical steroids. Three weeks after the injury, the patient had regained 20/20 uncorrected visual acuity.

CONCLUSIONS

Patients should be appropriately warned of the possibility of late flap dislocation with traumatic forces encountered during routine recreational activities. Full visual recovery is possible if the dislocation is promptly diagnosed and appropriately managed.

Effect of myopic laser in situ keratomileusis on epithelial and stromal thickness: a confocal microscopy study

PURPOSE

To determine changes in central epithelial and stromal thickness in human corneas in vivo after laser in situ keratomileusis (LASIK).

DESIGN

Prospective, nonrandomized, comparative trial.

PARTICIPANTS

Eighteen eyes of 12 patients received LASIK (performed using the VISX Star laser [VISX, Santa Ana, CA]) with a planned 180- micro m flap (created using an automated Hansatome microkeratome [Bausch & Lomb, Irvine, CA]) to correct refractive errors between -2.0 diopters (D) and -11.0 D.

METHODS

Corneas were examined by using confocal microscopy in vivo before LASIK and at 1 week and 1, 3, 6, and 12 months after LASIK. Epithelial thickness was the distance between images of the surface epithelium and subbasal nerve plexus or, when nerves were not visible, the subbasal peak (if present in the light intensity profile). Total flap thickness was the distance between images of the surface epithelium and interface debris (or peak), and total stromal thickness was the distance between images of the most anterior keratocytes and endothelium.

MAIN OUTCOME MEASURES

Corneal epithelial and stromal thickness.

RESULTS

Epithelial thickness before LASIK was 46 +/- 5 micro m (mean +/- standard deviation) and increased 22% by 1 month after LASIK (56 +/- 5 micro m; P = 0.01). Thereafter, epithelial thickness did not change, but remained thicker at 12 months after LASIK (54 +/- 8 micro m) than before LASIK (P = 0.02). Total flap thickness at 1 month after LASIK was 160 +/-28 micro m and did not change thereafter. Changes in total stromal thickness between 1 and 12 months after LASIK were not significant.

CONCLUSIONS

The central corneal epithelium was thicker in the first year after LASIK than before LASIK. There was no change in central stromal thickness between 1 month and 12 months after LASIK.

Growth factors in corneal wound healing following refractive surgery: A review

The first part of this review article aims to provide important basic definitions of growth factor terminology, and to put forward a model for understanding the role of growth factors in a wound healing context. In the second part of the paper, we review the literature on growth factors in the cornea, including that on changes associated with wound healing following refractive surgery in the epithelial, stromal, and endothelial layers. The role of growth factors in stromal removal, corneal neovascularization, corneal innervation and wound healing is considered. The importance of the epithelial-stromal interaction is discussed, including the role of growth factors in keratocyte apoptosis. In the final section, we review the current literature on endogenous and exogenous modulation of growth factors in corneal wound healing. This includes important in vitro work but aims to emphasize clinically relevant results. Photorefractive keratectomy (PRK) may have short-term complications such as pain and haze, whereas laser in situ keratomilieusis (LASIK) may have longer-term adverse effects on corneal biomechanics. The emerging technique of laser epithelial keratomilieusis (LASEK) provides an interesting alternative wound which may be less susceptible to the inherent complications of PRK and LASIK. At present, the phenomenon of iatrogenic keratectasia following LASIK is not fully understood, but these features of wound healing following PRK may be amenable to growth factor modulation.

Cleaning Solutions as a Cause of Diffuse Lamellar Keratitis

PURPOSE

To assess the capability of two microkeratome cleaning solutions in causing diffuse lamellar keratitis (DLK) in a rabbit model of laser in situ keratomileusis (LASIK).

METHODS

Two cleaning solutions (Palmolive 2:100 and Cidezyme 2:250) were tested. These solutions were diluted with balanced salt solution according to directions from the Hansatome microkeratome manual. Two additional solutions were prepared using an additional ten-fold dilution, creating a total of four study solutions. A LASIK flap was created in one eye each of 25 rabbits using the ALK Chiron microkeratome. The rabbits were divided into five study groups. The flaps were reflected and a drop of one of the study solutions (or BSS, control group) was placed on the interface. After 1 minute, the solution was washed out from the interface and the flap was repositioned. The eyes were examined at the slit lamp on postoperative days 1, 2, 3, 5, and 7.

RESULTS

In 12 eyes, a flap displacement was identified. Four eyes showed flap retraction and five others, epithelial ingrowth in flap margins. The incidence of these events did not differ among groups. Thirteen eyes were then evaluated for DLK. No DLK-like interface inflammation was seen in the studied eyes.

CONCLUSION

The cleaning solutions, when diluted as recommended by the microkeratome manufacturer, when in contact with the corneal stroma, and provided that the interface was washed with BSS did not cause DLK interface inflammation in rabbit LASIK models.

Extracellular matrix and matrix metalloproteinase changes in human corneas after complicated laser-assisted in situ keratomileusis (LASIK)

PURPOSE

To characterize extracellular matrix (ECM) and nine matrix metalloproteinase (MMP) changes in two corneas that underwent a complicated laser-assisted in situ keratomileusis (LASIK) procedure.

METHODS

The first patient underwent bilateral LASIK. The flap on the left eye was transected in several locations and placed back. This cornea later developed edema, and the removed flap was analyzed after lamellar keratoplasty. The second patient had a LASIK flap lifted, replaced twice, and then completely removed. The epithelium grew over the stroma, but haze and severe ectasia occurred. After penetrating keratoplasty, the recipient cornea was analyzed. An autopsy cornea from a person who underwent uneventful LASIK and ten normal autopsy corneas served as controls. Corneas were analyzed by immunohistochemistry.

RESULTS

Both flap regions in the treated corneas had marked alterations of ECM components and MMPs. Stromal deposits of various ECM proteins, including those normally absent in the central cornea (tenascin-C, fibrillin-1, type XIV collagen), were found. Rare myofibroblasts and inflammatory cells were present. The epithelial basement membrane (BM) was altered in both cases. The most dramatic change was poor or no staining for alpha3-alpha6 type IV collagen chains and thrombospondin. The limbal alpha1-alpha2 type IV collagen and laminin-2 (alpha2beta1gamma1) appeared in the central epithelial BM. Other components were altered to a lesser extent. The anterior stroma was positive for MMP-1 and MMP-2, and some MMP-7 was seen in the epithelium. These ECM and MMP patterns were not seen in uneventful LASIK or normal corneas.

CONCLUSIONS

In the flaps of LASIK-treated corneas, fibrosed areas of anterior stroma had increased levels of MMP-1 and MMP-2 that may have caused loss of specific type IV collagen isoforms in the epithelial BM. These changes may reflect an ongoing wound healing process and contribute to the development of ectasia.

Relation between corneal haze and transforming growth factor-beta1 after photorefractive keratectomy and laser in situ keratomileusis

PURPOSE

To investigate the relation between corneal haze formation and transforming growth factor-beta (TGF-beta) after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

SETTING

Department of Ophthalmology, University of Tokyo Graduate School of Medicine, Tokyo, Japan.

METHODS

White rabbits were divided into 4 groups, with each group receiving 1 of the following surgeries: manual epithelial abrasion, PRK, lamellar keratotomy, or LASIK. The degree of corneal haze was quantitatively analyzed by measuring the light scattering intensity of corneas before and 4 and 12 weeks after surgery. The expression of type IV collagen and TGF-beta1 in the corneas at baseline and at 4 weeks was examined immunohistochemically.

RESULTS

The light scattering intensity was significantly greater 4 and 10 weeks after PRK. In contrast, epithelial abrasion, lamellar keratotomy, and LASIK did not influence the light scattering intensity of the corneas. Type IV collagen was detected in the basal lamina of the corneal epithelium and in Descement's membrane in the normal cornea. After epithelial abrasion, there was no change in the distribution of type IV collagen. Four weeks after PRK, the expression of type IV collagen was detected in the subepithelial layer of the laser-ablated area. Four weeks after lamellar keratotomy, type IV collagen was linearly and fragmentarily detected in the corneal stroma. Four weeks after LASIK, type IV collagen was linearly and continuously detected in the corneal stroma and was detected slightly in the subepithelial region of the laser-ablated area. In the normal corneas, the expression of TGF-beta1 was not detected in the keratocytes. Four weeks after PRK, the expression of TGF-beta1 increased in the keratocytes that proliferated in the subepithelial fibrous layer. In contrast, epithelial abrasion, lamellar keratotomy, and LASIK did not change the expression pattern of TGF-beta1 in the keratocytes.

CONCLUSION

The multiplier effect of epithelial abrasion and excimer laser ablation in PRK may increase the expression of TGF-beta1 in keratocytes and induce corneal haze.

Haze after laser in situ keratomileusis in eyes with previous photorefractive keratectomy

In cases with previous photorefractive keratectomy (PRK), there is a risk of developing severe haze after laser in situ keratomileusis (LASIK). We report 3 patients (4 eyes) who developed severe haze after LASIK treatment for residual myopia following PRK. Both PRK and LASIK procedures were performed using the VISX 20/20 excimer laser. We report the grade of haze, amount of regression, and visual acuity after the patients were treated with topical steroids. In 2 eyes, the uncorrected visual acuity was 1.0 after 1 year with grade I haze. In the other 2 eyes, there was a residual refractive error, and the best spectacle-corrected visual acuity was 0.7 with grade II haze.

LASIK complications: etiology, management, and prevention

Laser in situ keratomileusis (LASIK) is a rapidly evolving ophthalmic surgical procedure. Several anatomic and refractive complications have been identified. Anatomic complications include corneal flap abnormalities, epithelial ingrowth, and corneal ectasia. Refractive complications include unexpected refractive outcomes, irregular astigmatism, decentration, visual aberrations, and loss of vision. Infectious keratitis, dry eyes, and diffuse lamellar keratitis may also occur following LASIK. By examining the etiology, management, and prevention of these complications, the refractive surgeon may be able to improve visual outcomes and prevent vision-threatening problems. Reporting outcomes and mishaps of LASIK surgery will help refine our approach to the management of emerging complications.

Laser in situ keratomileusis for treatment of residual myopia after photorefractive keratectomy

PURPOSE

To evaluate the results of laser in situ keratomileusis after photorefractive keratectomy.

METHODS

Eighty eyes of 80 patients with residual myopia after photorefractive keratectomy were reoperated with laser in situ keratomileusis. The study was retrospective. Laser in situ keratomileusis was performed using the automated corneal shaper microkeratome and Chiron Technolas 217-C d1 excimer laser. Data measured after laser in situ keratomileusis included uncorrected visual acuity, best-corrected visual acuity, refraction, haze, pachymetry, and keratometry. The follow-up was at least 12 +/- 1.6 months (range, 12 to 15 months).

RESULTS

After laser in situ keratomileusis the mean spherical equivalent was -0.24 diopters +/- 0.78. (range, -3 to +1.5) at 12 months, and the mean uncorrected visual acuity was 0.76 diopters +/- 0.24 (range, 0.1 to 1). Sixty-five eyes (81.3%) had various degrees of haze after laser in situ keratomileusis. One eye (1.2%) lost 2 lines of best-corrected visual acuity.

CONCLUSIONS

Laser in situ keratomileusis enhancement may be a good alternative to correct residual myopia and astigmatism after primary photorefractive keratectomy. Corneal haze is a common problem in these eyes, and the treatment after laser in situ keratomileusis enhancement should be the same as the treatment after primary photorefractive keratectomy.

Late traumatic flap dislocation after laser in situ keratomileusis

Three patients who had laser in situ keratomileusis (LASIK) experienced severe direct corneal trauma 3 to 38 months postoperatively. Flap dislocation resulted in all 3 patients. Presentation following trauma ranged from a few hours to 9 days. All patients were successfully managed by surgical flap repositioning, and all maintained a best corrected visual acuity of 20/20. A literature review of traumatic flap dislocation cases and the most recent methods of diagnosis and management are included.

Complications of Laser in situ Keratomileusis: Etiology, Prevention, and Treatment

PURPOSE

To review the etiology, prevention, and management of laser in situ keratomileusis (LASIK) complications.

METHODS

Review of literature and the experience of the authors.

RESULTS

Careful preoperative screening is critical to prevention of many potential complications of LASIK. Flap complications that occur during surgery are typically managed by replacement of the flap and repeating the surgery or applying special methods such as transepithelial photorefractive keratectomy weeks to months following the initial procedure. A common source of serious complications is the use of a microkeratome that functions after improper assembly. Timely treatment of postoperative complications such as diffuse lamellar keratitis, flap striae, and infection is critical to an optimal outcome.

CONCLUSION

Most complications of LASIK can be treated effectively and have minimal effect on the final outcome after surgery, if appropriate methods are used for management.

Laser in situ keratomileusis flap margin: wound healing and complications imaged by in vivo confocal microscopy

PURPOSE

To examine the healing response of laser in situ keratomileusis flap margin in vivo.

METHODS

Forty-three eyes of 43 patients who had undergone myopic (n = 39) or hyperopic (n = 4) laser in situ keratomileusis were examined once after surgery. The flap margin was imaged by in vivo confocal microscopy at various depths, and the wound healing response, flap alignment, and complications were evaluated. Ten eyes were examined on day 3 postoperatively, 13 eyes at 1 to 2 weeks, 10 eyes at 1 to 2 months, five eyes at 3 months, and five eyes at 6 months or later.

RESULTS

At 3 days after laser in situ keratomileusis, the surface epithelium and basal epithelium appeared normal. Keratocyte activation was strongest at 1 to 2 weeks and 1 to 2 months, and an increased amount of haze was observed correspondingly. Intrastromal epithelial cells forming a plug could occasionally be perceived in the wound gape. Wound constriction was completed in most cases by 3 to 6 months or later. Good alignment was observed in 12 of 43 flaps (27.9%) and moderate and poor alignment in 17 of 43 flaps (39.5%) and 13 of 43 flaps (30.2%), respectively. Poor alignment was not associated with lamellar epithelial ingrowth. Epithelial ingrowth was associated with dense haze at the interface. Diffuse lamellar keratitis was imaged in two corneas after hyperopic laser in situ keratomileusis.

CONCLUSIONS

The laser in situ keratomileusis incision wound at the flap margin appears to heal after the sequence observed in incisional wounds in nonhuman primates. Complications, such as lamellar epithelial in growth and diffuse lamellar keratitis, were often observed, particularly after hyperopic laser in situ keratomileusis.

Postoperative Inflammation, Microbial Complications, and Wound Healing Following Laser in situ Keratomileusis

Although the biology of corneal wound healing is only partly understood, healing after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) differs in many respects, and the mechanisms appear to be differently controlled. There is less of an inflammatory and healing response after LASIK, but a longer period of sensory denervation. The cellular, molecular, and neural regulatory phenomena associated with postoperative inflammation and wound healing are likely to be involved in the adverse effects after LASIK, such as flap melt, epithelial ingrowth, and regression. Interface opacities in the early postoperative period include diffuse lamellar keratitis (DLK), microbial keratitis, epithelial cells, and interface opacities. Diffuse lamellar keratitis (sands of the Sahara syndrome) describes an apparently noninfectious diffuse interface inflammation after lamellar corneal surgery probably caused by an allergic or a toxic inflammatory reaction. Noninfectious keratitis must be distinguished from microbial keratitis to avoid aggressive management and treatment with antimicrobial drugs. Microbial keratitis is a serious complication after LASIK, but a good visual outcome can be achieved following prompt and appropriate treatment.

Confocal microscopy of a patient with irregular astigmatism after LASIK reoperations and relaxation incisions

PURPOSE

Laser-assisted in situ keratomileusis (LASIK) is widely used for correcting refractive errors. If the predicted refractive result is not achieved after the first operation, a re-operation can be performed by ablating more stromal tissue after reopening the flap. The goal of this study was to analyze, by using in vivo confocal microscopy, the morphologic changes associated with repeated LASIKs.

METHODS

Clinical examination, computed corneal topography, and real-time in vivo confocal microscopy were performed on both eyes of a 50-year-old patient with induced irregular astigmatism leading to decreased best-corrected vision in the left eye after LASIK. The left cornea had been operated on 5 times (LASIK with two reoperations followed by two relaxing incisions), and the right cornea twice (LASIK with one reoperation).

RESULTS

Microfolds at the level of the Bowman's layer and highly reflective particles at the flap interface were observed in both corneas. The subbasal nerve plexus was severed in the left eye. In addition, we identified epithelial material in the flap margin and inside one of the two relaxing incisions placed inferotemporally.

CONCLUSION

Repeated LASIKs may stretch the flap and result in microfolding at the Bowman's layer. This and deposition of particles in the flap interface may increase with the number of reoperations, challenging the healing response. Microfolding and occurrence of foreign material in the interface may add to the irregular astigmatism and poor visual outcome after LASIK. Clinical in vivo confocal microscopy offers new possibilities for the assessment of ultrastructural changes after corneal refractive surgery.

Epithelial ingrowth in a corneal graft treated by laser in situ keratomileusis: light and electron microscopy

PURPOSE

To demonstrate progressive epithelial ingrowth histopathologically in a human cornea after laser in situ keratomileusis (LASIK) and review its pathophysiology.

SETTING

Department of Ophthalmology, Medical College of Virginia Campus, Virginia Commonwealth University, and the Veterans Affairs Medical Center, Richmond, Virginia, USA.

METHODS

Tissue from a corneal transplant specimen was examined 6 weeks after LASIK by light and transmission electron microscopy.

RESULTS

Epithelial ingrowth in the flap interface with connection to the surface corneal epithelium was evident on light microscopy. In areas without epithelial ingrowth, the flap interface was imperceptible. Electron microscopy revealed minimal disruption of the stromal collagenous lamellae.

CONCLUSION

Progressive epithelial ingrowth occurred with a continuous sheet of epithelium to the flap edge. Location of epithelial ingrowth and cytokine epithelial-stromal interaction appear to be important factors in this complication. Histopathological changes in the cornea after LASIK are difficult to detect in areas with normal wound healing.