Histological and immunohistochemical findings after laser in situ keratomileusis in human corneas

Bilateral post-LASIK exacerbation of granular corneal dystrophy with epithelial ingrowth

A male patient in his 30s, with a history of bilateral microkeratome-assisted myopic laser-assisted in situ keratomileusis (LASIK) 8 years ago at another centre, presented to us with gradually progressive diminution of vision and glare in both eyes for the last 4 years. On presentation, uncorrected distance visual acuity (UDVA) was 6/24 and 6/15 in the right eye and left eye, respectively, with normal intraocular pressures. Slit-lamp examination and anterior segment optical coherence tomography revealed well-defined white deposits, limited to an area within the LASIK flap. The deposits were confluent, at the level of the LASIK flap interface, and few discrete opacities were present in the posterior stroma. His father also had a similar clinical picture in both eyes. A diagnosis of both eyes post-LASIK exacerbation of granular corneal dystrophy with epithelial ingrowth was made. He underwent right eye femtosecond laser-assisted sutureless superficial anterior lamellar keratoplasty. At 6-month follow-up, UDVA improved to 6/12 with graft clarity of 4+ and coexistent grade 1 epithelial ingrowth.

Ectasia After Corneal Refractive Surgery: A Systematic Review

INTRODUCTION

The incidence of ectasia following refractive surgery is unclear. This review sought to determine the worldwide rates of ectasia after photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) based on reports in the literature.

METHODS

A systematic review was conducted according to modified Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Publications were identified by a search of eight electronic databases for relevant terms between 1984 and 2021. Patient characteristics and preoperative values including manifest refractive spherical refractive equivalent (MRSE), central corneal thickness (CCT), anterior keratometry, postoperative residual stromal bed (RSB), and percent tissue altered (PTA) were summarized. In addition, annual rates of each refractive surgery were determined, and incidence of post-refractive ectasia for each type was calculated using the number of ectatic eyes identified in the literature.

RESULTS

In total, 57 eyes (70 eyes including those with preoperative risk factors for ectasia) were identified to have post-PRK ectasia, while 1453 eyes (1681 eyes including risk factors) had post-LASIK ectasia, and 11 eyes (19 eyes including risk factors) had post-SMILE ectasia. Cases of refractive surgery performed annually were estimated as 283,920 for PRK, 1,608,880 for LASIK, and 96,750 for SMILE. Reported post-refractive ectasia in eyes without preoperative identifiable risk factors occurred with the following incidences: 20 per 100,000 eyes in PRK, 90 per 100,000 eyes in LASIK, and 11 per 100,000 eyes in SMILE. The rate of ectasia in LASIK was found to be 4.5 times higher than that of PRK.

CONCLUSION

Post-refractive ectasia occurs at lower rates in eyes undergoing PRK than LASIK. Although SMILE appears to have the lowest rate of ectasia, the number of cases already reported since its recent approval suggests that post-SMILE ectasia may become a concern. Considering that keratoconus is a spectrum of disease, pre-existing keratoconus may play a larger role in postoperative ectasia than previously accounted for in the literature.

Clinical evaluation of a new correction algorithm for dynamic Scheimpflug analyzer tonometry before and after laser in situ keratomileusis and small-incision lenticule extraction

PURPOSE

To compare a biomechanically corrected intraocular pressure (bIOP) algorithm provided by the dynamic Scheimpflug analyzer (Corvis ST) with Goldmann applanation tonometry IOP (Goldmann IOP) and standard dynamic Scheimpflug analyzer IOP measurements before and after laser in situ keratomileusis (LASIK) and refractive lenticule extraction small-incision lenticule extraction (SMILE) surgeries.

SETTING

Smile Eye Clinic, Munich, Germany, and University of Liverpool, Liverpool, United Kingdom.

DESIGN

Retrospective case series.

METHODS

Patients scheduled for LASIK and patients scheduled for small-incision lenticule extraction for myopia or myopic astigmatism were included. The preoperative and postoperative evaluations included Goldmann, Scheimpflug tomography, and dynamic Scheimpflug analyzer IOP measurements.

RESULTS

The study comprised 14 patients in the LASIK group and 22 patients in the small-incision lenticule extraction group. Preoperative Goldmann IOP and Scheimpflug analyzer IOP values showed significant positive correlation with central corneal thickness (CCT) (P = .05 for LASIK; P = .003 for small-incision lenticule extraction). No significant correlation was found between bIOP and CCT (P > .05). After both surgeries, there were significant decreases in Goldmann IOP (-3.2 mm Hg ± 3.4 [SD] and -3.2 ± 2.1 mm Hg, respectively; both P < .001) and Scheimpflug analyzer IOP (-3.7 ± 2.1 mm Hg and -3.3 ± 2.0 mm Hg, respectively, both P < .001) compared with preoperative readings, whereas bIOP did not differ significantly (0.1 ± 2.1 mm Hg and 0.8 ± 1.8 mm Hg, respectively; P = .80 and P = .273, respectively).

CONCLUSIONS

The bIOP readings before and after LASIK and small-incision lenticule extraction were neither significantly different nor correlated with CCT. In contrast, both Goldmann IOP and Scheimpflug analyzer IOP had significant reductions postoperatively and showed significant correlation with CCT preoperatively.

Superficial Anterior Lamellar Keratoplasty (SALK) for Trauma-induced Post Refractive Surgery Corneal Opacity

Purpose:

To report a case of post laser in situ keratomileusis (LASIK), nebulomacular corneal opacity following a trauma induced flap dehiscence and was managed with superficial anterior lamellar keratoplasty (SALK).

Case Report:

A 32-year-old female underwent LASIK 2.5 years back, with a postoperative unaided visual acuity (VA) of 6/6 in both eyes. She was involved in a road traffic accident and sustained blunt trauma to the right eye 5 months before. At the time of presentation, the VA was 1/60 in the right eye. Slit lamp examination revealed flap dehiscence, stromal scar and descemet folds in that eye. There was a small macular scar in the parafoveal area due to a resolved Berlin's edema. SALK was performed in the affected eye. Unaided VA of 6/36 was noted on post- operative day 1. After 4 weeks of SALK surgery, best corrected VA was 6/24.

Conclusion:

This case highlights that flap adhesions are not very strong even years after LASIK and SALK may be an effective treatment option for post refractive surgery corneal opacities.

Late post-traumatic flap dislocation and macrostriae after laser in situ keratomileusis

We report an unusual flap-related complication that occurred 4 years after uneventful laser in situ keratomileusis (LASIK) performed in the eye of a 20-year-old woman. She developed dislocation with partial infolding of the LASIK flap with macrostriae and epithelial ingrowth in her left eye after trauma by a wooden chip. The flap was refloated, stretched, smoothened, and hydrated on both under and outer surfaces after epithelial debridement. At 1 week, the uncorrected visual acuity was 20/20 with absence of flap striae. The present case highlights that flap adhesions are not very strong even months and years after LASIK. Flap refloatation and stretching with hydration on both sides of the flap are effective in removing flap striae.

Ultrastructural and three-dimensional study of post-LASIK ectasia cornea

INTRODUCTION

Post-laser in situ keratomileusis (LASIK) corneal ectasia is a serious late postoperative complication. Here, we report the ultrastructural features of the post-LASIK cornea of two patients.

METHODS

Two normal corneas (age 24 and 37 years old) and two post-LASIK ectaic corneas from two patients (A and B) were studied. The "patient A" (age 27 years) underwent penetrating keratoplasty and "patient B" (age 31 years) underwent deep-anterior lamellar keratoplasty. The excised corneas were processed for light and electron microscopy. A total of 120 images for three-dimensional (3D) reconstruction were taken by using the software "Recorder" and using a bottom mounted camera "Quemesa" attached to a JOEL 1400 transmission electron microscope. The 3D images were constructed using "Visual Kai" software.

RESULTS

In the post-LASIK cornea, the hemidesmosomes, the basement membrane, and Bowman"s layer were abnormal. The stromal lamellae were thin and disorganized. The collagen fibrils (CFs) diameter and interfibrillar spacing had decreased. Aggregated microfibrils were present in the Bowman's layer and all parts of the stroma. A large number of microfilaments were present at the detachment end of the flap and residual stroma. The 3D images showed the presence of collagen microfibrils and proteoglycans (PGs) within the CF of the normal and post-LASIK cornea. The collagen microfibrils and PGs within the CFs had degenerated in the post-LASIK cornea.

CONCLUSION

Collagen microfibrils and PGs within the CFs were degenerated, leading to the degeneration of CFs, followed by the disorganization of lamellae in post-LASIK cornea. The CFs diameter and interfibrillar spacing decreased.

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.

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.

Correlation between estimated and measured corneal ablation and refractive outcomes in laser in situ keratomileusis for myopia

PURPOSE

To evaluate the difference between the measured and the intended postoperative central corneal thickness (CCT) by optical low-coherence reflectometry (OLCR) for 3 months after myopic laser in situ keratomileusis (LASIK) and correlate it with refractive outcomes.

SETTING

Center for Refractive Therapy, Department of Ophthalmology, Ludwig-Maximilians-University Munich, Germany.

METHODS

The CCT was measured by OLCR before and 6 weeks and 3 months after myopic LASIK. The correlation between the difference in pachymetry and the difference in the measured and planned postoperative refraction was proven by linear regression and Pearson product moment correlation analysis (P<.05). In a subset of eyes with a 7.0 mm optical zone, the effect of the calculated ablation depth on the difference in pachymetry was evaluated. Based on the laser algorithm data, the intended ablation was 100 microm or less in Subgroup 1 and 100 microm or more in Subgroup 2.

RESULTS

Forty-three eyes of 25 patients were evaluated, with 25 eyes in the subset. The difference between the measured and intended postoperative CCT was 11.1 microm +/- 8.1 (SD) at 6 weeks and 13.8 +/- 7.5 microm at 3 months. The correlation between this difference and the difference in refraction was poor (r(2) = 0.005 microm and r(2) = 0.009, respectively). With greater ablation depth (Subgroup 2), the difference in pachymetry decreased by 3 months postoperatively.

CONCLUSION

The lack of correlation between differences in the measured and intended CCT and the final refraction shows the complexity of intraoperative variables in LASIK and the effect of individual wound healing.

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).

Keratectasia after laser in situ keratomileusis: a histopathologic and immunohistochemical study

OBJECTIVE

To examine histopathologic and immunohistochemical features of human corneal buttons from patients who developed keratectasia after laser in situ keratomileusis (LASIK).

METHODS

Five corneal buttons were obtained during penetrating keratoplasty from patients who developed keratectasia after LASIK. Histologic features were examined by hematoxylin-eosin staining using paraffin-embedded sections and by transmission electron microscopy. Immunostaining for alpha(1)-proteinase inhibitor, Sp1, and matrix metalloproteinases 1, 2, and 3 was performed with 2 healthy corneas and 2 corneas with keratoconus as controls.

RESULTS

Central stromal thinning was observed after hematoxylin-eosin staining in all corneas with keratectasia. No histologic features specific to keratoconus, including Bowman layer disruption, were identified in the corneas with keratectasia. By transmission electron microscopy, collagen fibril thinning and decreased interfibril distance were observed in the stromal bed. Immunostaining intensity and/or pattern for alpha(1)-proteinase inhibitor and Sp1 in the corneas with keratectasia was comparable to that of healthy corneas and differed from that in the corneas with keratoconus. No significant staining with anti-matrix metalloproteinases 1, 2, and 3 antibodies was observed in either the corneas with keratectasia or the healthy corneas.

CONCLUSIONS

Histologic findings suggest that post-LASIK keratectasia results in collagen fibril thinning and decreased interfibril distance within the residual stromal bed. Discrepant results between keratectasia and keratoconus suggest that the pathogenesis of the 2 conditions differ.

Management of slipped laser in situ keratomileusis flap following intrastromal corneal ring implantation in post-LASIK ectasia

Two cases of intrastromal corneal ring (Intacs, Addition Technology) implantation to treat post-laser in situ keratomileusis (LASIK) ectasia developed progressive slippage of the flap over the stromal bed, resulting in progressive flattening of the affected meridian. The flattening was thought to have occurred because the poorly healed flap edge could not withstand the change in corneal shape induced by the ring segments. The flap was lifted, debris was removed, and the flap was sutured to the residual stromal bed using interrupted 10-0 nylon sutures passed through two thirds of the cornea. The sutures induced a localized area of scarring that acted as "welding spots" and prevented further flap slippage. Refractive stability after suture removal supports the hypothesis that a sutured flap restores (at least partially) the biomechanical strength of post-LASIK corneas.

Alterations of extracellular matrix components and proteinases in human corneal buttons with INTACS for post-laser in situ keratomileusis keratectasia and keratoconus

PURPOSE

To perform an immunohistochemical evaluation of corneas with INTACS for post-laser in situ keratomileusis (LASIK) keratectasia and keratoconus, obtained after corneal transplantation.

METHODS

Corneas from 1 patient with INTACS for post-LASIK keratectasia and 2 patients with INTACS for keratoconus were obtained within 3 hours after penetrating keratoplasty, and cryostat sections were analyzed by immunostaining for 35 extracellular matrix (ECM) components and proteinases.

RESULTS

In the stroma of all corneas next to an INTACS implant, ECM components typically associated with fibrosis were observed. These included tenascin-C, fibrillin-1, and types III, IV (alpha1/alpha2 chains), and XIV collagen. Also, significant deposition of perlecan, nidogen-2, and cellular fibronectin was revealed in the same locations. The keratoconus cases displayed typical Bowman layer breaks and subepithelial fibrosis with deposition of various ECM components. In all cases, some keratocytes around INTACS were positive for specific proteinases associated with stromal remodeling, including cathepsins F and H, matrix metalloproteinase (MMP)-1, MMP-3, and MMP-10. Staining for MMP-7 was variable; MMP-2 and MMP-9 were mostly negative. Patterns of type IV collagen alpha 3, alpha 4, and alpha 6 chains; types VI and VIII collagen; laminin-332, alpha 4, alpha 5, beta1, beta2, and gamma 1 laminin chains; vitronectin; thrombospondin-1; urokinase; EMMPRIN; and cathepsins B and L were unchanged around INTACS in all 3 cases compared with normal.

CONCLUSIONS

Abnormal accumulation of fibrotic ECM components and proteinases near INTACS suggests ongoing lysis and remodeling of corneal stroma. Specific changes observed in each case may be related to underlying pathology.

Five-Year Outcome of LASIK for Myopia

PURPOSE

To investigate the efficacy and safety of LASIK over a 5-year postoperative period.

DESIGN

Observational case series.

PARTICIPANTS

We examined 779 eyes in 402 patients with myopia or myopic astigmatism who underwent LASIK to correct their refractive errors and received regular postoperative assessments for 5 years.

METHODS

Postoperative examinations were performed 1 day; 1 week; 1, 3, and 6 months; and 1, 2, 3, 4, and 5 years after LASIK surgery.

MAIN OUTCOME MEASURES

We evaluated changes in uncorrected visual acuity (UCVA) (logarithm of the minimum angle of resolution [logMAR]), manifest refraction, best-corrected visual acuity (BCVA) (logMAR), intraocular pressure, corneal thickness, corneal endothelial cell counts, and complications.

RESULTS

Preoperative UCVA of 1.27 improved to -0.03 at 1 day after surgery and -0.08 at 1 month and revealed minimal but significant decreases thereafter. Postoperative manifest refraction was also improved by surgery, showing minimal but significant regression after 1 year. Final BCVA loss was seen in 10 eyes of 7 patients; in 7 cases, there were obvious reasons such as the progression of cataracts in 3 eyes, epithelial disintegrity due to dry eye in 2 eyes, irregular astigmatism due to flap striae in 1 eye, and age-related macular dystrophy in 1 eye. Intraocular pressure and corneal thickness decreased by 4.0 mmHg and 76.9 microm, respectively, due to surgery, but remained stable throughout the follow-up period. Corneal endothelial cell counts (2689.0+/-232.9 cells/mm(2) before surgery) showed a statistically significant decrease at 5 years after surgery (2658.0+/-183.1 cells/mm(2); 1.2% loss for 5 years), likely within the range due to physiological age-related loss. No serious, vision-threatening, irreversible complication such as keratectasia or progressive endothelial cell loss was observed.

CONCLUSION

LASIK surgery is an effective and safe procedure for correcting myopia/myopic astigmatism as long as inclusion and exclusion criteria are strictly respected. However, minimal regression occurred during the 5-year investigative period.

Visual rehabilitation and outcomes for ectasia after corneal refractive surgery

PURPOSE

To analyze the visual outcomes and method of final visual correction in eyes with corneal ectasia after laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK).

SETTING

Emory University Department of Ophthalmology and Emory Vision, Atlanta, Georgia, USA.

METHODS

This retrospective review comprised 74 eyes of 45 patients with corneal ectasia after LASIK (72 eyes) or PRK (2 eyes). Outcomes included postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), best corrected visual acuity (BCVA), and refraction; method of final visual correction; and time to rigid gas-permeable (RGP) contact lens failure.

RESULTS

Corneal ectasia developed a mean of 19.2 months after surgery. Postoperatively, the mean UCVA was 20/400 and the mean BSCVA before ectasia management was 20/108. After ectasia management, the mean BCVA was 20/37 and the final BCVA was 20/40 or better in 78% of eyes. Final visual correction was achieved with RGP lenses in 77% of eyes, spectacles in 9%, collagen crosslinking in 3%, intracorneal ring segments in 1%, and penetrating keratoplasty (PKP) in 8%. Two eyes with intracorneal ring segments required segment explantation and subsequent PKP. One eye that had PKP had a graft-rejection episode; there were no graft failures. Two eyes (3%) did not require a visual device to improve visual acuity. The mean time for successful RGP lens wear was 24.8 months; 80% of cases initially managed with RGP lenses were successful with this form of treatment.

CONCLUSIONS

The majority of eyes developing postoperative corneal ectasia achieved functional visual acuity with RGP lens wear and did not require further intervention. Penetrating keratoplasty can usually be postponed or avoided by alternative methods of visual rehabilitation; however, PKP, when necessary, can provide good visual outcomes.

Risk Assessment for Ectasia after Corneal Refractive Surgery

PURPOSE

To analyze the epidemiologic features of ectasia after excimer laser corneal refractive surgery, to identify risk factors for its development, and to devise a screening strategy to minimize its occurrence.

DESIGN

Retrospective comparative and case-control study.

PARTICIPANTS

All cases of ectasia after excimer laser corneal refractive surgery published in the English language with adequate information available through December 2005, unpublished cases seeking treatment at the authors' institution from 1998 through 2005, and a contemporaneous control group who underwent uneventful LASIK and experienced a normal postoperative course.

METHODS

Evaluation of preoperative characteristics, including patient age, gender, spherical equivalent refraction, pachymetry, and topographic patterns; perioperative characteristics, including type of surgery performed, flap thickness, ablation depth, and residual stromal bed (RSB) thickness; and postoperative characteristics including time to onset of ectasia.

MAIN OUTCOME MEASURES

Development of postoperative corneal ectasia.

RESULTS

There were 171 ectasia cases, including 158 published cases and 13 unpublished cases evaluated at the authors' institution. Ectasia occurred after LASIK in 164 cases (95.9%) and after photorefractive keratectomy (PRK) in 7 cases (4.1%). Compared with controls, more ectasia cases had abnormal preoperative topographies (35.7% vs. 0%; P<1.0x10(-15)), were significantly younger (34.4 vs. 40.0 years; P<1.0x10(-7)), were more myopic (-8.53 vs. -5.09 diopters; P<1.0x10(-7)), had thinner corneas before surgery (521.0 vs. 546.5 microm; P<1.0x10(-7)), and had less RSB thickness (256.3 vs. 317.3 microm; P<1.0x10(-10)). Based on subgroup logistic regression analysis, abnormal topography was the most significant factor that discriminated cases from controls, followed by RSB thickness, age, and preoperative corneal thickness, in that order. A risk factor stratification scale was created, taking all recognized risk factors into account in a weighted fashion. This model had a specificity of 91% and a sensitivity of 96% in this series.

CONCLUSIONS

A quantitative method can be used to identify eyes at risk for developing ectasia after LASIK that, if validated, represents a significant improvement over current screening strategies.

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.

Wound instability and management after cataract surgery in a patient with prior laser in situ keratomileusis

We report a case of cataract wound instability and subsequent management after cataract surgery in a patient who had had hyperopic laser in situ keratomileusis (LASIK). Standard cataract surgery was performed through a nasal limbal incision. One day postoperatively, the uncorrected visual acuity (UCVA) was 20/20 and the wound was stable. Subsequent examinations revealed overlying corneal edema, cataract wound slippage with corresponding with-the-rule astigmatism, and decreased vision. Separating and resuturing the cataract wound resulted in significant and stable improvement in the UCVA to 20/40. At 18 months, the best corrected visual acuity was 20/20 with a refraction of -3.50 +0.25x155 and keratometry of 44.75/45.00@155. Understanding wound stability and its management in cataract surgery in patients with prior LASIK refractive surgery will become increasingly important as more of these patients present.

2005 ESCRS Ridley Medal Lecture

The literature on keratoconus and progressive post-laser in situ keratomileusis ectasia (PPLK) was studied after a retrospective review of 137 highly myopic eyes (mean -15.58 diopters) 5 to 9 years after LASIK. Only 2 eyes developed keratectasia, 1 after automated lamellar keratolasty for myopia and 1 after myopic LASIK. In neither case was intraoperative pachymetry carried out. In the PPLK case, a residual stromal bed thickness (RSBT) of 120 microm was discovered when a retreatment was attempted on lifting the flap. The PPLK developed 2 years later. The obvious discrepancy between reported cases of PPLK and the expected rate from the incidences in larger retrospective studies and our own 15-year experience suggests that PPLK is not a significant complication provided the standard rules applying to the preoperative total corneal thickness and RSBT are observed. However, newer techniques for the study of posterior corneal changes and those involving corneal biomechanics should be used in the future to study the long-term effects of LASIK on the cornea.

Surgical Correction of Hyperopia

Surgical attempts to correct hyperopia have yielded varying results over the last 130 years. These techniques include the reshaping of the cornea through incisions, burns, or lamellar cuts with removal of peripheral tissue; the addition of central inlays; laser ablations; and the replacement of the crystalline lens. By examining the success of each surgical technique, the refractive surgeon may be able to make an informed decision on its indications and limitations, based on the specific patient's characteristics. Reporting the outcomes and complications of hyperopic surgery will help refine our approach to the management of an increasingly hyperopic and presbyopic population.

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.

Wound Dehiscence After Penetrating Keratoplasty

PURPOSE

To assess the patient characteristics, risk factors, and outcomes of penetrating keratoplasty wound dehiscence.

METHODS

Retrospective chart review of 30 eyes of 29 patients with corneal grafts who underwent repair of penetrating keratoplasty wound dehiscence from January 1, 1998 to December 31, 2003, followed on the Cornea Service at Wills Eye Hospital.

RESULTS

The mean time from penetrating keratoplasty to wound dehiscence was 7.5 years (range 1 week to 31 years). The mean age at time of wound dehiscence was 66 years (range 28-98 years). One eye developed wound dehiscence following suture removal, whereas the remaining 29 eyes sustained trauma-induced dehiscences. Falls were the most common mechanism of trauma, especially in the elderly population. There was a wide range of visual outcomes in the 21 patients followed for 1 year, with 4 patients maintaining best corrected visual acuity between 20/20 and 20/40 and 5 patients with light perception vision at 1 year. There were no cases of endophthalmitis.

CONCLUSIONS

Patients with corneal transplants have a life-long risk for wound dehiscence. This complication may be reduced by the regular use of eye protection in all corneal transplantation patients.

Proteinase and growth factor alterations revealed by gene microarray analysis of human diabetic corneas

PURPOSE

To identify proteinases and growth factors abnormally expressed in human corneas of donors with diabetic retinopathy (DR), additional to previously described matrix metalloproteinase (MMP)-10 and -3 and insulin-like growth factor (IGF)-I.

METHODS

RNA was isolated from 35 normal, diabetic, and DR autopsy human corneas ex vivo or after organ culture. Amplified cRNA was analyzed using 22,000-gene microarrays (Agilent Technologies, Palo Alto, CA). Gene expression in each diabetic corneal cRNA was assessed against pooled cRNA from 7 to 9 normal corneas. Select differentially expressed genes were validated by quantitative real-time RT-PCR (QPCR) and immunohistochemistry. Organ cultures were treated with a cathepsin inhibitor, cystatin C, or MMP-10.

RESULTS

More than 100 genes were upregulated and 2200 were downregulated in DR corneas. Expression of cathepsin F and hepatocyte growth factor (HGF) genes was increased in ex vivo and organ-cultured DR corneas compared with normal corneas. HGF receptor c-met, fibroblast growth factor (FGF)-3, its receptor FGFR3, tissue inhibitor of metalloproteinase (TIMP)-4, laminin alpha4 chain, and thymosin beta(4) genes were downregulated. The data were corroborated by QPCR and immunohistochemistry analyses; main changes of these components occurred in corneal epithelium. In organ-cultured DR corneas, cystatin C increased laminin-10 and integrin alpha(3)beta(1), whereas in normal corneas MMP-10 decreased laminin-10 and integrin alpha(3)beta(1) expression.

CONCLUSIONS

Elevated cathepsin F and the ability of its inhibitor to produce a more normal phenotype in diabetic corneas suggest increased proteolysis in these corneas. Proteinase changes may result from abnormalities of growth factors, such as HGF and FGF-3, in DR corneas. Specific modulation of proteinases and growth factors could reduce diabetic corneal epitheliopathy.

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.

Traumatic flap dislocation 4 years after laser in situ keratomileusis

We present a case of late traumatic flap dislocation 47 months after laser in situ keratomileusis (LASIK). This is the latest reported case of traumatic LASIK flap dislocation to date. The patient was examined 5 days after being struck in the face and found to have a flap dislocation. The flap was repositioned surgically, and postoperatively the patient had 20/20 visual acuity and no visual complaints.

Clinical manifestation and pathologic finding of unilateral acute hydrops after bilateral laser in situ keratomileusis

We present a case of unilateral acute hydrops that developed in 25-year-old man 6 years after bilateral laser in situ keratomileusis (LASIK) for the correction of 2.75 diopters (D) of myopia. Preoperative corneal thickness using ultrasound pachymetry were 556 microm in the right eye and 554 microm in the left eye. Preoperative corneal topography of both eyes showed an asymmetric bow-tie pattern with inferior steepening. Forty-seven months after LASIK, the left eye developed astigmatism and enhancement excimer ablation was performed. Sixteen months after enhancement, a definite sign of keratectasia was detected in the left eye. Twenty-six months after enhancement, acute hydrops occurred in the left eye. The interface of the LASIK wound was separated and filled with aqueous humor. Penetrating keratoplasty was performed to avoid perforation. The keratocytes at the edge between the peripheral flap and remaining stroma showed mixoid degeneration and edematous change suggesting dying cells.

Évaluation en microscopie confocale des modifications morphologiques cornéennes induites après LASIK et découpe du volet stromal par laser femtoseconde IntraLase®

PURPOSE

To assess stromal modifications occurring after IntraLase femtosecond laser for laser in situ keratomileusis (LASIK) using the Heidelberg retina tomograph II/Rostock cornea module.

MATERIAL AND METHODS

Twelve eyes from six patients were examined using the Heidelberg retina tomograph II cornea module after IntraLase femtosecond laser: ten eyes were examined at 1 week and 2 months after laser surgery, including four eyes examined at day 1, and two eyes examined at day 2. Morphological modifications of the corneal stroma, flap interface, and flap margin were evaluated at these different times and compared with the mechanical microkeratome interfaces of five patients (ten eyes), using the same technique at the same periods after the surgical intervention.

RESULTS

Evaluations at days 1 and 7 showed simultaneous depletion and activation of keratocytes on both sides of the interface. We also observed some brightly reflecting particles together with scattered, less bright dots, from day 7 and increasing after 2 months. Some clinically visible deposits at the level of the interface were observed at the periphery of the flap at day 1 and could represent cell-degradation products. With confocal microscopy, they appeared as homogeneous reflective deposits with a larger size than that of particles; they had decreased at month 2. The flap margin appeared microscopically as a very clear-cut edge, including epithelial cells, while those performed with a mechanical microkeratome appeared more like a poorly limited fibrotic scar. We also observed a secondary fibrotic reaction at month 2, adjacent to the still well-defined IntraLase flap edge.

CONCLUSION

This study showed substantial morphological similarity between the interfaces obtained with femtosecond laser and mechanical microkeratome. The discovery of brightly reflecting particles in the IntraLase interface goes against the hypothesis of the metallic origin of these deposits. The flap margin microscopically looked extremely well delimited, but seemed to provoke an adjacent secondary fibrotic reaction, both microscopically and macroscopically, greater at 2 months than after a mechanical microkeratome cut.

Korneale Wundheilungsreaktionen nach hyperoper PRK und LASIK

BACKGROUND

The purpose of this study was to investigate the influence of different postoperative treatments on the wound healing reaction in the anterior stroma after PRK and in the interface area after LASIK.

METHODS

Seventy-two corneal buttons of refractively treated rabbit eyes underwent different postoperative eyedrop regimens with antibiotics and/or steroids or additional UV-B irradiation. Morphological and immunohistological investigations were performed 6 months postoperatively by light and transmission electron microscopy.

RESULTS

PRK eyes showed interdigitations between the epithelia and the anterior stroma. LASIK-treated eyes showed only minor changes between epithelia and stroma in the incisional region. Only a slight increase in deposits of fibrillar extracellular matrix components were detectable in the interface region.

CONCLUSIONS

The clinically important problem of haze after PRK is caused by the interdigitations between epithelia and anterior stroma. The delicate wound healing reactions in the interface region in LASIK eyes corresponded to the clinically visible minor changes in these corneas.

Monitoring corneal structures with slitlamp-adapted optical coherence tomography in laser in situ keratomileusis

PURPOSE

To monitor corneal structures with slitlamp-adapted optical coherence tomography (OCT) in laser in situ keratomileusis (LASIK).

SETTING

Department of Ophthalmology, Vivantes Klinikum Neukölln, Berlin, Germany.

METHODS

In this prospective, nonrandomized, comparative clinical case series of consecutive patients who had LASIK for myopia and myopic astigmatism, the corneal structures were studied with slitlamp-adapted OCT at a wavelength of 1,310 nm. The central corneal thickness (CCT) and epithelial, flap, and residual stromal thicknesses were assessed preoperatively, immediately after surgery, on postoperative day 1, and then, on average, after 8, 35, and 160 days.

RESULTS

Twenty-five eyes of 13 patients were included. The attempted mean spherical equivalent correction was -6.11 diopters (D) +/- 2.16 (SD) with a mean calculated stromal ablation depth of 92 +/- 24 microm. The CCT was 516 +/- 26 microm preoperatively and 453 +/- 40 microm postoperatively (P<.001). The epithelial thickness increased from 57.0 +/- 7.7 microm preoperatively to 61.0 +/- 7.5 microm postoperatively (P =.04). Imaging of the hyperreflective interface was possible in all patients for up to 15 months. The flap and residual stromal thickness was 211 +/- 28 microm and 344 +/- 48 microm, respectively, immediately after LASIK and 164 +/- 21 microm (P<.001) and 284 +/- 32 microm (P<.001), respectively, on postoperative day 1. There were no further significant changes during the follow-up. The overall mean reproducibility was +/-4.50 microm (coefficient of variation [CV] 0.94%) for CCT, +/-4.99 microm (CV 8.57%) for epithelial thickness, +/-6.25 microm (CV 3.55%) for flap thickness, and +/-7.09 microm (CV 2.42%) for residual stromal thickness.

CONCLUSION

Slitlamp-adapted OCT can be used to longitudinally monitor the variable structures of the cornea, epithelium, flap, and residual stroma in LASIK.

Pupil size and night vision disturbances after LASIK for myopia

PURPOSE

To examine whether standardized, preoperative evaluation of pupil sizes can predict the risk of night vision visual disturbances after bilateral laser in situ keratomileusis (LASIK) for myopia.

METHODS

A prospective study was carried out involving 46 patients who underwent bilateral LASIK for myopia. Pupil sizes were measured before surgery using an infrared pupillometer under standardized settings. Pre- and postoperative refraction and best spectacle-corrected visual acuity (BSCVA) were registered. At the 3-month follow-up visit, the patients completed a questionnaire regarding night vision pre- and postoperatively.

RESULTS

The mean bilateral, spherical equivalent refraction (SE) was - 8.76 D (range 6.32 to - 12.0 D) preoperatively, and - 1.69 D (range 0 to - 4.38 D) postoperatively. The mean bilateral BSCVA was not changed by the operations. We found a significant correlation between large scotopic pupil sizes and the impression of worsened night vision (p < 0.01). A significant correlation between gender (males) and subjectively reduced night vision postoperatively was also found (p < 0.05).

CONCLUSION

Large pupil size measured preoperatively is correlated with an increased frequency of subjectively experienced post-LASIK visual disturbances during scotopic conditions. We recommend preoperative evaluation of pupil size in all patients prior to LASIK surgery.

Accommodating intraocular lenses

PURPOSE OF REVIEW

With the advent of interest in accommodative lenses as a solution for presbyopia and the growing baby-boomer demographic, ophthalmic surgeons will have the opportunity to provide this technology to facilitate near, intermediate, and distance vision for their patients.

RECENT FINDINGS

At present, six corporate entities and lens designs are attempting to commercialize accommodative intraocular lens devices. One Food and Drug Administration (FDA) clinical trial has been completed and the first FDA-approved accommodating lens is available.

SUMMARY

For the first time, ophthalmic surgeons will be able to provide a full range of visual focus in each eye of a patient to maintain binocular function while also avoiding the unwanted mesopic and scotopic visual disturbances that are experienced with monovision and multifocal lens technologies. Accommodative intraocular lenses could revolutionize not only cataract visual rehabilitation but also the surgical approach to presbyopia.