Sloughing of corneal epithelium and wound healing complications associated with laser in situ keratomileusis in patients with epithelial basement membrane dystrophy

Clinical outcomes of epithelial basement membrane dystrophy after keratorefractive lenticule extraction

PURPOSE

To determine the clinical outcomes of keratorefractive lenticule extraction (KLEx) in eyes with epithelial basement membrane dystrophy (EBMD) that developed after surgery.

SETTING

Onnuri Smile Eye Clinic, Seoul, South Korea.

DESIGN

Retrospective single-center study.

METHODS

This study reviewed the medical records of 26 eyes of 16 patients who exhibited signs of EBMD after KLEx. Postoperatively, corneal findings and visual outcomes were evaluated. Statistical analyses were also performed on eyes without corneal complications after KLEx.

RESULTS

Signs of EBMD were first observed within 1 week postoperatively in 22 eyes (84.6%): 6 eyes (23.1%) showed epithelial defects, 10 eyes (38.5%) showed subepithelial corneal opacity, 5 eyes (19.2%) showed diffuse lamellar keratitis, and 1 eye (3.9%) showed epithelial ingrowth. Symptoms such as pain, while corneal lesions were present, occurred in 21 eyes (80.8%). At 3 months postoperatively, 21 eyes (80.8%) showed no specific findings on slitlamp microscopy after medical treatment, 2 eyes (7.7%) showed subepithelial corneal opacity, 2 eyes (7.7%) showed corneal scar, and 1 eye (3.9%) showed epithelial ingrowth. Uncorrected distance visual acuity was 20/25 or better in 24 eyes (92.3%), and spherical equivalent was within ±1.0 D in 20 eyes (76.9%). The efficacy index of the EBMD group did not significantly differ from the control group, while the safety index was significantly lower.

CONCLUSIONS

Manifestations of EBMD can occur after KLEx and can affect clinical outcomes. Most cases showed favorable results with appropriate nonsurgical treatment; however, some cases had long-term complications such as corneal scarring.

Management of Corneal Haze After Photorefractive Keratectomy

Photorefractive keratectomy (PRK) is a safe and popular corneal surgery performed worldwide. Nevertheless, there is potential risk of corneal haze development after surgery. Proper management of post PRK haze is important for good visual outcome. We performed a comprehensive review of the literature on the various risk factors and treatments for PRK haze, searching the PubMed, Google Scholar, SCOPUS, ScienceDirect, and Embase databases using relevant search terms. All articles in English from August 1989 through April 2023 were reviewed for this study, among which 102 articles were chosen to be included in the study. Depending on the characteristics of and examination findings on post PRK haze, different management options may be preferred. In the proposed framework, management of PRK haze should include a full workup that includes patient's subjective complaints and loss of vision as well as visual acuity, biomicroscopy, anterior segment optical coherence tomography, epithelial mapping, and Scheimpflug densitometry. Topical steroid treatment for haze should be stratified based on early- or late-onset haze. Mechanical debridement or superficial phototherapeutic keratectomy (PTK) may be used to treat superficial corneal haze. Deep PTK and/or PRK can be used to treat deep corneal haze. Mitomycin-C and topical steroids are prophylactic post-surgery agents to prevent recurrence of haze.

A Literature Review of the Incidence, Management, and Prognosis of Corneal Epithelial-Related Complications After Laser-Assisted In Situ Keratomileusis (LASIK), Photorefractive Keratectomy (PRK), and Small Incision Lenticule Extraction (SMILE)

Our purpose is to provide a comprehensive investigation into the incidence, treatment modalities, and visual prognosis of epithelial-related complications in corneal refractive surgeries, including laser-assisted in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and small incision lenticule extraction (SMILE). A systematic search of multiple databases was conducted by two independent examiners using various search terms related to epithelial-related complications and corneal refractive surgeries. A total of 91 research articles were included, encompassing a sample size of 66,751 eyes across the three types of surgeries. The average incidence of epithelial-related complications varied across the different types of corneal refractive surgeries. LASIK had an average incidence of 4.9% for epithelial defects, while PRK and SMILE had lower rates of 3.3% and 3.9%, respectively. Our findings indicate that SMILE has a lower incidence of epithelial defects compared to LASIK, potentially due to the less invasive nature of lenticule incision in SMILE. Visual prognosis after epithelial complications (EC) is generally favorable, with various supportive care and surgical interventions leading to significant improvements in postoperative visual acuity and full recovery. Understanding the incidence rates and management approaches for epithelial-related complications can guide clinicians in enhancing patient safety, refining surgical techniques, and optimizing postoperative outcomes in corneal refractive surgeries.

Optimization of the Ocular Surface Through Treatment of Ocular Surface Disease Before Ophthalmic Surgery: A Narrative Review

Ocular surface disease commonly exists in individuals requiring ophthalmic surgery and may compromise the structure and function of ocular surface components. Ophthalmic surgery may further affect the ocular surface by injuring the epithelium and sensory nerves, disrupting the tear film, or causing local inflammation. Medical management of ocular surface disease prior to ophthalmic surgery aids in reducing inflammation, resolving infection, improving epithelial pathology, stabilizing the tear film, and easing patient symptoms, promoting positive long-term outcomes and minimizing the incidence of postoperative complications. This review summarizes frequently encountered ocular surface diseases and available preoperative medical management options, discusses common ophthalmic surgeries and their effects on the ocular surface, examines potential postoperative complications, and defines recommendations for postoperative ocular surface maintenance.

Laser refractive surgery in corneal dystrophies

Twenty-eight case reports and case series published between 2000 and 2019 concerning laser refractive surgery in patients with corneal dystrophies, resulting in 173 eyes from 94 patients, were included in this systematic review. Best results were achieved in posterior corneal polymorphous and Cogan dystrophy. Unfavorable results were found in Avellino dystrophy and Fuchs endothelial corneal dystrophy (FECD). Photorefractive keratectomy was not indicated in Meesmann and Avellino dystrophy. Laser in situ keratomileusis was indicated in posterior polymorphous corneal dystrophy but not in FECD, Avellino, or Cogan dystrophy. Small-incision lenticule extraction and other dystrophies such as lattice, fleck, Lisch, or François did not achieve enough scientific evidence to report any recommendation.

Epithelial basement membrane dystrophy after femtosecond laser-assisted LASIK successfully treated with in vivo confocal microscopy-assisted photorefractive keratectomy

Photorefractive keratectomy (PRK) was performed to treat corneal epithelial basement membrane dystrophy (EBMD) found after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) in a 29-year-old man with previous silent cornea. The patient was diagnosed with post-FS-LASIK EBMD by slitlamp examination and in vivo confocal microscopy (IVCM). Initial treatment with topical lubricants and alcohol soaking was unsuccessful, and the patient continued to have blurred vision and discomfort. The patient underwent a PRK procedure, and the symptoms resolved dramatically; residual refractive errors were also corrected. IVCM revealed a characteristic presentation of EBMD before PRK and normal corneal epithelium after treatment. Patients with asymptomatic EBMD might suffer from recurrent corneal erosions after FS-LASIK. Surface ablation including PRK might lead to successful treatment outcomes, and IVCM might provide helpful information before and after treatment.

Effect of a hyperosmotic agent on epithelial disruptions during laser in situ keratomileusis

PURPOSE

To evaluate the incidence of epithelial disruptions during primary laser in situ keratomileusis (LASIK) with the use of a preoperative hyperosmotic treatment comprising sodium chloride 5% ophthalmic ointment (Muro-128) and to identify the incidence of epithelial disruptions in various demographic populations.

SETTING

TLC Laser Eye Center, McLean, Virginia, USA.

DESIGN

Comparative case series.

METHODS

Using a matched-pair design, hyperosmotic treatment was randomized to 1 eye of patients having bilateral LASIK. The primary outcome measure, epithelial integrity, was assessed in each eye. Epithelial integrity was evaluated in groups defined by characteristics that included age, sex, ethnicity, skin type, presence or absence of rosacea, eye color, and hair color.

RESULTS

The study evaluated 496 eyes of 248 patients. The preoperative hyperosmotic treatment was associated with significantly less corneal epithelial disruption, as indicated by an epithelial integrity score. Compared with control eyes, the rate of corneal epithelial disruptions in the population of treated eyes decreased by 40% (relative risk, 0.60; 95% confidence interval [CI], 0.38-0.95). Among the characteristics studied, age was the best predictor of corneal epithelial disruptions; every 1-year increase in age was associated with a 9.0% increase in the risk for corneal epithelial disruptions (odds ratio [OR], 1.09; 95% CI, 1.05-1.13). Eyes of patients older than 34 years had a 4.4 times greater odds of being associated with epithelial disturbances than eyes of patients 34 years or younger.

CONCLUSIONS

The preoperative use of hyperosmotic agents can reduce the risk for intraoperative epithelial disruptions during LASIK. An increase in epithelial disruptions was associated with increasing age.

LASIK and surface ablation in corneal dystrophies

Corneal dystrophies are a rare group of hereditary disorders, that are bilateral, non-inflammatory, and progressive. Clinically, they can be classified based on the anatomic layer of the cornea affected. Refractive surgery and phototherapeutic keratectomy (PTK) can be performed with caution in patients with certain corneal dystrophies, but should be avoided in others. For epithelial basement membrane dystrophy, photorefractive keratectomy (PRK) is the procedure of choice for treatment of refractive error, and PTK may be performed for the treatment of recurrent erosions or irregular astigmatism. PRK and laser-assisted in situ keratomileusis (LASIK) have been associated with exacerbation of combined granular-lattice corneal dystrophy. LASIK and PRK appear to be safe in mild forms of posterior polymorphous corneal dystrophy, whereas LASIK should be avoided in Fuchs dystrophy. The safety of refractive surgery and PTK in the remainder of epithelial, Bowman layer, and stromal dystrophies has yet to be established.

Laser in situ keratomileusis in 2012: a review

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

[Epithelial basement membrane dystrophy diagnosed following LASIK surgery]

A 48-year-old woman with no significant past history underwent bilateral simultaneous laser in situ keratomileusis for correction of her myopia. On the tenth postoperative day, the patient complained of visual decrease and photophobia. Slit lamp exam showed corneal epithelial irregularities. Confocal microscopy was performed and revealed a characteristic appearance of epithelial basement membrane dystrophy (EBMD). The patient was successfully treated with artificial tears and autologous serum eyedrops. EBMD may be missed before LASIK surgery, even after a careful pre-operative examination. Exacerbation of EBMD after LASIK surgery is rare. It should be considered when unexplained corneal epithelial defects or irregularities occur following LASIK. Confocal microscopy is very useful to confirm the diagnosis.

Corneal nerve architecture in a donor with unilateral epithelial basement membrane dystrophy

BACKGROUND

Epithelial basement membrane dystrophy (EBMD) is by far the most common corneal dystrophy. In this study, we used a newly developed method of immunofluorescence staining and imaging to study the entire corneal nerve architecture of a donor with unilateral EBMD.

METHOD

Two fresh eyes from a 56-year-old male donor were obtained; the right eye of the donor was diagnosed with EBMD and the left was normal. After slit lamp examination, the corneas were immunostained with anti-β-tubulin III antibody. Images were recorded by a fluorescent microscope equipped with a Photometrics digital camera using MetaVue imaging software.

RESULTS

The left cornea appeared normal as observed by slit lamp and stereomicroscope, but the right eye had numerous irregular geographic patches in the basement membrane. Immunofluorescence showed no difference in the stromal nerve distribution between the 2 eyes, but there were areas without innervations in the EBMD cornea. Subbasal nerve fibers also showed tortuous courses and fewer divisions. There was a significant decrease in the density of subbasal nerve fibers and the number of terminals in the right eye.

CONCLUSION

We show for the first time detailed nerve architecture in an EBMD cornea. Our results suggest that EBMD-induced abnormalities of basement membrane altered epithelial nerve architecture and decreased nerve density, contributing to the pathology of the disease.

Laser refractive surgery in diabetic patients: a review of the literature

BACKGROUND

The purpose of this study was to evaluate the current recommendations regarding laser refractive surgery in patients with diabetes mellitus and to assess whether these patients make appropriate candidates for laser vision correction.

METHODS

A literature search was conducted to identify current research on the ocular complications of diabetes and original publications on laser refractive surgery in diabetic patients.

RESULTS

Diabetes was associated with several ocular complications. Initially the US Food and Drug Administration listed these complications as justification to advise against refractive surgery in patients with diabetes. However, recent studies on laser in situ keratomileusis in diabetic patients indicate that this procedure may be safe in diabetic patients with very well controlled systemic disease and no ocular manifestations.

CONCLUSION

Laser refractive surgery may be performed safely in a very selected group of patients with diabetes.

Femtosecond laser-assisted enhancements after laser in situ keratomileusis

We describe a technique of femtosecond laser-assisted enhancement after primary LASIK with a mechanical microkeratome-created flap. The vertical side-cut incision by the femtosecond laser creates a wound configuration that decreases mechanical trauma to the epithelium and prevents epithelial cell migration. These factors may decrease the risk for post-LASIK enhancement epithelial ingrowth.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Photorefractive Keratectomy in a Patient with Epithelial Basement Membrane Dystrophy

PURPOSE

To report a case of excimer laser photorefractive keratectomy (PRK) in a patient with epithelial basement membrane dystrophy (EBMD).

METHODS

Interventional case report.

RESULTS

A 36-year-old male with clinical manifestations of EBMD underwent bilateral, simultaneous PRK for low myopia correction. A delay (up to 17 days) in the epithelial healing process with unstable epithelium was observed. During the first three postoperative months a visually significant subepithelial haze was developed in both eyes. One year postoperative, an improvement in haze formation and visual acuity in both eyes was found.

CONCLUSIONS

PRK in patients with EBMD could result in favorable refractive and clinical outcome.

In vivo laser confocal microscopic findings in patients with epithelial basement membrane dystrophy

PURPOSE

To evaluate the corneal characteristics of patients with epithelial basement membrane dystrophy (EBMD) using an in vivo laser confocal microscope, Heidelberg Retina Tomograph II, Rostock Cornea Module (HRT II RCM).

METHODS

Sixteen women and 13 men who were diagnosed with or suspected to have EBMD were included in the study. The mean age of the patients was 56.4+/-17.2 years within a range of 25 to 81 years. Nine patients (31%) had a history of recurrent corneal erosions and 3 patients had been misdiagnosed with herpetic epithelial keratitis. The remaining 17 patients were asymptomatic and EBMD was diagnosed incidentally during routine eye examinations.

RESULTS

Confocal microscopy revealed highly reflective tissue in various configurations within the intermediate and basal epithelial cell layers corresponding to the abnormal basement membrane extending into the epithelium. There were thin, parallel hyperreflective lines and high contrast round lesions in sizes ranging between 10 and 250 microm within the epithelium. Basal epithelial cells around the abnormal basement membrane and cysts seemed to be highly distorted. In two subjects with bleb-like disorder, the authors observed circular or oval hyporeflective areas with a diameter ranging between 40 and 100 microm at the level of basal epithelium and the Bowman layer, accompanied by hyperreflective, linear structures extending into the epithelium.

CONCLUSIONS

EBMD is most commonly asymptomatic and undiagnosed; however, it might be associated with recurrent corneal erosions and lead to severe complications after LASIK surgery. The confocal images are highly characteristic for EBMD; therefore, confocal microscopy seems to be a valuable tool in the diagnosis of EBMD.

Delayed epithelial ingrowth caused by viral conjunctivitis after LASIK

To report a patient who presented with epithelial ingrowth caused by viral keratoconjunctivitis 3 months after LASIK surgery. A 41-year-old man presented with decreased visual acuity in the right eye, which had developed about 3 weeks before. He had undergone LASIK surgery 3 months prior without complications. Two months after the surgery, he was treated for viral conjunctivitis. During the treatment period, filamentary keratitis developed, and a therapeutic bandage contact lens was applied for 2 weeks. Upon presentation, examination revealed a corrected visual acuity of 20/100 and irregular epithelial sheets under the edematous flap. The flap was lifted, and the in-grown epithelium was removed. The flap was repositioned with double continuous 10-0 nylon sutures. Post-operatively, the patient developed a mild diffuse lamellar keratitis that resolved rapidly with topical corticosteroid treatment. At 2 months, the corrected visual acuity was 20/20 without interface opacities. As the patient showed no complications prior to viral conjunctivitis, we suspect that the viral infection caused edema of the corneal flap, which caused epithelial ingrowth under the flap. Patients who have viral conjunctivitis after LASIK surgery should be examined carefully and managed with consideration of flap complications.

Risk factors for epithelial defect formation during laser in situ keratomileusis

PURPOSE

To analyze the occurrence of epithelial defects during primary laser in situ keratomileusis (LASIK) and identify predictive preoperative risk factors.

SETTING

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

METHODS

The records of primary LASIK cases performed between January 2001 and May 2002 were retrospectively evaluated. Information abstracted included patient sex, age, and preoperative refraction (spherical equivalent) and the excimer laser used (Nidek EC-5000 or Alcon LADARVision). The primary outcome measure was the rate of intraoperative epithelial defect formation.

RESULTS

A total of 6984 primary LASIK cases were analyzed; these included 6067 cases with myopia and 917 cases with hyperopia. In all cases, the flaps were created with a Hansatome microkeratome (Bausch & Lomb). Most cases (75.6%) were performed with the Nidek EC-5000 excimer laser; all hyperopia cases were performed with the LADARVision laser. Overall, 647 cases (9.3%) had epithelial defects. There were 323 cases (9.5%) of epithelial defect in men and 319 (9.0%) in women (P = .4). The rate of epithelial defect increased with age; 124 (4.1%) occurred in patients younger than 40 years, and 523 (13.2%) occurred in patients older than 40 years (P<.0001). One hundred sixty cases (17.3%) were in hyperopic eyes and 487 cases (8.0%), in myopic eyes (P<.0001). Multivariate analysis of LADARVision cases showed that age older than 40 years and hyperopia were risk factors for epithelial defect (odds ratio 2.7 and 1.7, respectively; P<.0001 and P = .00002, respectively), while sex was not.

CONCLUSION

Risk factors for epithelial defect formation during LASIK included increasing patient age, especially older than 40 years, and preoperative hyperopia.

Outcome of LASIK in fleck corneal dystrophy

PURPOSE

To report the outcome of laser in situ keratomileusis (LASIK) in a patient with Fleck corneal dystrophy.

METHODS

Case report and literature review.

RESULTS

A 48-year-old Taiwanese man presented in November 2005, 6 years after bilateral myopic LASIK. He complained of loss of uncorrected distance visual acuity that was worse in the left eye. The patient did not report glare, halos, or other visual aberrations. Preoperative best spectacle-corrected visual acuity (BSCVA) was 20/25 OU, with a manifest refraction of -14 D OU. In November 2005, uncorrected visual acuity (UCVA) was 20/40 OD and 20/50 OS, and BSCVA was 20/25 in each eye with a manifest refraction of -1.00 sphere OD and -1.75 -1.25 x 115 OS. Slit-lamp examination was remarkable for several subtle, small, gray corneal opacities present throughout the corneal stroma. Confocal microscopy revealed refractile bodies within swollen keratocytes and normal surrounding stromal mileu. The clinical and confocal appearance was consistent with Fleck corneal dystrophy.

CONCLUSION

In this patient with Fleck corneal dystrophy, corneal clarity and BSCVA were maintained 6 years after bilateral myopic LASIK, suggesting that LASIK does not stimulate visually significant exacerbation of Fleck corneal dystrophy.

Thin Head and Single Use Microkeratomes Reduce Epithelial Defects During LASIK

PURPOSE

To evaluate the effect of microkeratome design and head dimension (flap thickness) on the rate of epithelial defects.

METHODS

A retrospective review of 4000 LASIK procedures performed between May 2000 and December 2003 was conducted. Intraoperative epithelial defects were identified in 326 cases. The microkeratome design (reusable vs disposable) and head dimensions (100, 130, and 150 micron) were recorded along with age, sex, central ultrasonic pachymetry, keratometry, preoperative refraction (sphere, cylinder, and axis), and Schirmer testing. The chi-square and Student t test were used in data analysis.

RESULTS

A total of 326 (8.2%) procedures had an associated epithelial defect. With the reusable microkeratome, heads that produced thinner flaps were associated with a lower incidence of epithelial defects (P<.05 for all three groups, 100, 130 and 150 micron head). When compared to a reusable head of the same dimension and to the entire population of reusable heads, the disposable 130 head exhibited a significantly lower rate of epithelial defects (P<.0001).

CONCLUSIONS

The results of this study support that both microkeratome design and head dimension (and resulting corneal flap thickness) play a role in the formation of epithelial defects. These are surgeon selectable factors, unrelated to technique or patient risk factors, which can be used to reduce the rate of epithelial defects and associated complications.

Laser in situ keratomileusis in patients with diabetes

PURPOSE

To study the outcomes of laser in situ keratomileusis (LASIK) in patients with well-controlled diabetes mellitus.

SETTING

Gimbel Eye Centres, Calgary and Edmonton, Canada.

METHODS

The charts of all patients with diabetes who had LASIK surgery at the Gimbel Eye Centres were reviewed retrospectively. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), final refraction, and complications were assessed.

RESULTS

Twenty-four patients (16 men and 8 women) were identified. Mean patient age was 42 years (range 24 to 57 years). Seventeen patients had diabetes type II, and 7 had diabetes type I. Mean preoperative spherical equivalent (SE) was -4.88 +/- 2.13 diopters (D) (range +1.625 to -9.00 D). Median follow-up was 6 months (range 4 to 44 months). No eye lost BSCVA. Twenty-nine eyes (63%) achieved UCVA 20/25 or better, and 31 eyes (67%) were within +/-0.5 D of the intended refraction after the first LASIK surgery. Retreatment was required in 13 eyes (28.3%) because initial surgery was not adequate to correct the refractive error. At the last follow-up visit, 40 eyes (87%) achieved UCVA of 20/25 or better and 43 eyes (93.5%) were within +/-0.5 D of the intended refraction. Three eyes (6.5%) developed an epithelial defect after surgery, and secondary epithelial ingrowth developed in 2 of these eyes. No advancement of diabetic retinopathy was noticed in any eye at the end of the follow-up period.

CONCLUSIONS

Laser in situ keratomileusis surgery was safely performed in patients with well-controlled diabetes. Enhancement may often be required for optimal correction.

Long-term Refractive Results of Myopic LASIK Complicated With Intraoperative Epithelial Defects

PURPOSE

To evaluate the long-term refractive results of LASIK for myopia complicated with intraoperative epithelial defects.

METHODS

Twenty-six eyes with epithelial defects on the LASIK flap were compared with the contralateral eye that had no intraoperative complications. Pre- and postoperative data were compared between the two groups including 3-, 6- and 12-month postoperative spherical equivalent refraction, amount of undercorrection, and complications.

RESULTS

Eyes with intraoperative epithelial defects showed more undercorrection at 3 and 6 months postoperatively (P < .05). No statistically significant difference was noted at 12 months. Twenty (76%) eyes in the epithelial defect group lost best spectacle-corrected visual acuity (BSCVA) at 3 months postoperatively compared with 2 (7%) eyes in the control group. By 1 year, however, only 2 (7%) eyes in the epithelial defect group and no eyes in the control group lost > 1 line of BSCVA. Diffuse lamellar keratitis was observed in 15 (58%) of 26 eyes with epithelial defects and these eyes had more undercorrections at 6 and 12 months (P < .05) and higher corneal irregularity index at 6 and 12 months compared with controls (P < .05). Eyes with small epithelial defects (> 1 mm2 to < 3 mm2) had more undercorrections at 6 months (-1.08 +/- 0.76 diopters [D]) compared with the control group (-0.46 +/- 0.87 D). Eyes with centrally located epithelial defects had more undercorrections and increased corneal irregularity index compared with controls (P < .05).

CONCLUSIONS

Intraoperative epithelial defects after LASIK should be considered a severe complication that may result in diffuse lamellar keratitis, induce loss of BSCVA, prolong recovery of visual acuity, and induce undercorrection.

Use of Autologous Serum in Corneal Epithelial Defects Post-Lamellar Surgery

PURPOSE

To evaluate the efficacy of an autologous serum treatment of post-LASIK (laser in situ keratomileusis) corneal epithelial defects in a rabbit model.

METHODS

Five milliliters blood samples from 10 New Zealand rabbits were obtained by venepuncture. The serum was aseptically separated and diluted with saline solution to 20%. The final preparation was placed into 3-mL bottles with ultraviolet protection and maintained at 4 degrees C. Corneas were de-epithelialized using a 7-mm optical zone marker. A 160-microm thick flap was created in both eyes of all rabbits using an automatic corneal shaper microkeratome. Right eyes were treated with serum drops 6 times per day. Left eyes were treated with preservative-free artificial tears. Vital staining of the ocular surface and the area of corneal epithelial defect was measured daily for 1 week. Rabbits were humanely euthanized at postoperative day 7, and corneas were fixed and sectioned. Hematoxylin and eosin staining and immunohistochemical analysis were performed.

RESULTS

Corneas treated with autologous serum had a statistically significant increase in the epithelial healing rate compared with those treated with artificial tears. Serum-treated corneas showed significantly less terminal transferase-mediated dUTP nick-end labeling (TUNEL) staining in the interface, minimal inflammatory cell infiltration, and less induced synthesis of stromal chondroitin sulfate than did corneas treated with preservative-free artificial tears.

CONCLUSIONS

Treatment with autologous serum could be an efficient way to provide essential components to the ocular surface in the treatment of post-LASIK epithelial defects. Autologous serum induces faster epithelial healing than do artificial tears, leading to (1) a decrease in keratocyte apoptosis and migration of fibroblasts and myofibroblasts in the wound site, (2) a decrease in the migration of inflammatory cells, and (3) a consequent inhibition of cytokine release. This treatment could improve long-term refractive results post-LASIK.

Severe corneal epithelial sloughing during laser in situ keratomileusis as a presenting sign for silent epithelial basement membrane dystrophy

PURPOSE

To report the occurrence of large intraoperative epithelial sloughing during laser in situ keratomileusis (LASIK) as a first diagnostic sign for silent epithelial basement membrane dystrophy (EBMD).

SETTING

Refractive Surgery and Cornea Unit, Alicante Institute of Ophthalmology, Alicante, Spain.

METHODS

In this retrospective case series, the medical records of all patients with large corneal epithelial sloughing/defects during LASIK from January 1995 to December 2004 were reviewed. All patients who presented normal corneas before LASIK and EBMD changes after LASIK were included in this study. The surgical procedures and postoperative course were recorded. The follow-up period was 12 months for all patients.

RESULTS

Eleven eyes of 6 patients were included. The mean age was 35 years +/- 6.1 (SD). Mean preoperative uncorrected visual acuity (UCVA) was 20/500 (0.04 +/- 0.02); 12 months after surgery, mean UCVA increased to 20/27 (0.74 +/- 0.21). There was a significant decrease in best spectacle-corrected visual acuity 1 month after surgery. One year postoperatively, 10 of 11 eyes (91%) were within +/-1.00 diopter of emmetropia. Postoperatively, clinical manifestations of EBMD were observed in all eyes and complications were common. In the early postoperative period, diffuse lamellar keratitis was observed in 6 of 11 eyes (54.5%) and flap microfolds were noted in 2 of 11 (18.2%). One year after surgery, epithelial ingrowth was present in 8 of 11 eyes (72.7%) and flap melting was noted in 4 of 11 (36.4%).

CONCLUSION

Occurrence of large intraoperative epithelium sloughing/defects during LASIK might be a diagnostic sign for subclinical EBMD. These patients are predisposed to multiple postoperative complications. Because of the high risk for epithelial sloughing in the second eye, LASIK should not be performed.

Incidence of Corneal Epithelial Defects With the Standard and Zero-Compression Hansatome Microkeratomes

PURPOSE

To evaluate the incidence of epithelial defects in patients who have had laser in situ keratomileusis (LASIK) surgery with the standard compression Hansatome microkeratome head in comparison to the modified (zero-compression) Hansatome microkeratome head (Bausch & Lomb, Rochester, NY).

METHODS

This study was a retrospective review of 404 consecutive patients who had LASIK surgery on both eyes between January 2002 and June 2002. The standard compression microkeratome head was used in 216 (53%) cases and the zero-compression microkeratome head was used in 188 (47%) cases. Epithelial defects were categorized as loose epithelium, or a break in the epithelium, within the area of the flap. An adverse outcome for a patient was defined as having an epithelial defect in at least one eye. Odds ratios were estimated using logistic regression.

RESULTS

When the standard compression microkeratome head was used, 19 (8.8%) patients had an epithelial defect in at least 1 eye. When the zero-compression microkeratome head was used, 5 (2.7%) patients had an epithelial defect in at least 1 eye. Logistic regression comparing the risk of epithelial defect in either eye with the standard compression head versus the zero-compression head resulted in an age-adjusted odds ratio of 0.2 (95% confidence interval, 0.07 to 0.58, P < .05).

CONCLUSIONS

These findings provide evidence that LASIK surgery with a zero-compression head reduces the risk of epithelial defect compared to the standard compression head of the Hansatome microkeratome.

Results of late flap removal after complicated laser in situ keratomileusis

PURPOSE

To evaluate the effect of flap removal on complications after laser in situ keratomileusis (LASIK).

SETTING

Three university-based referral centers and 1 private practice.

METHODS

This retrospective interventional case series comprised 6 eyes of 6 patients at 4 centers. Flap removal occurred 2 to 41 weeks after the LASIK procedure. The corneal flaps were excised by 2 methods: In 2 eyes, the flap was lifted and excised manually. In 4 eyes, the thin flap was removed by excimer ablation using phototherapeutic keratectomy and/or photorefractive keratectomy. Postoperative measurements included uncorrected visual acuity, best spectacle-corrected visual acuity (BSCVA), manifest refraction, slitlamp evaluation, and computerized videokeratography. All patients had an 8-month or longer convalescence to assess visual recovery.

RESULTS

After the initial flap complication, the BSCVA decreased in all 6 eyes (mean loss 3.0 lines +/- 1.5 [SD]). After flap removal, it improved in all eyes (mean gain 2.2 +/- 1.2 lines). All patients reported a reduction in or elimination of visual symptoms. Despite the improvements, a minor loss of BSCVA (mean -0.8 lines [range 0 to 2 lines]) remained in 4 patients.

CONCLUSION

In carefully selected patients, flap removal is a viable surgical option to improve visual function.

Triptans and the Incidence of Epithelial Defects During Laser in situ Keratomileusis

PURPOSE

To investigate whether the incidence of epithelial defects during laser in situ keratomileusis (LASIK) was different in patients who were taking sumatriptan (Imitrex, Glaxo Smith Kline, Pittsburgh, Pa) for migraine headaches than in those who were not.

METHODS

A retrospective chart review was performed on 54 eyes of 28 patients who had been identified as taking sumatriptan and had undergone LASIK at Minnesota Eye Consultants between 1999 and 2001. These patients were compared with 54 gender- and age-matched control eyes operated on with the same microkeratome at the same location during the same period of time. The incidence of epithelial defects during LASIK was compared between the two groups.

RESULTS

In the sumatriptan group, 11.1% (6 of 54) of eyes developed epithelial defects as compared to 9.3% (5 of 54) of eyes in the non-triptan group (P=.75, chi square). More recent sumatriptan exposure did not increase the incidence of epithelial defect (P=.47). In patients in whom sumatriptan was stopped >1 month prior to LASIK, 6.3% (1 of 16 eyes) had epithelial defects; in patients in whom sumatriptan was stopped <1 month prior to LASIK, 14.3% (4 of 28 eyes) developed epithelial defects; and 9.3% (5 of 54 eyes) of patients in whom no triptans had ever been used had epithelial defects (P=.70).

CONCLUSIONS

There is no correlation between the use of sumatriptan for relief of migraine headaches and the generation of epithelial defects during LASIK. There appears to be no reason to stop triptans before proceeding with LASIK.

Complications associated with anterior basement membrane dystrophy after laser in situ keratomileusis

PURPOSE

To evaluate the complications associated with anterior basement membrane dystrophy (ABMD) after laser in situ keratomileusis (LASIK).

SETTING

Cornea Service, Wills Eye Hospital, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.

METHODS

In this noncontrolled retrospective case series, the medical records of all patients with LASIK complications seen in the Cornea Service at Wills Eye Hospital from January 1, 1998, to December 31, 2002, were reviewed. All patients who presented with ABMD changes after LASIK were included in the study. Patients with a history of trauma before or after surgery were excluded.

RESULTS

Thirty-five eyes of 18 patients were included. The mean age was 46.2 years. Thirteen eyes (37.1%) had a flap-lift procedure to remove epithelial ingrowth or for an enhancement. The most common reason for the visit was visual complaints, which were seen in 77.8% of patients. Seven patients (38.9%) had visual complaints alone; 27.8% had visual complaints associated with recurrent erosions and 11.1%, with dry eyes. Four patients (22.2%) had recurrent corneal erosions with no visual complaints. On examination, the most common finding was negative staining with fluorescein dye within the LASIK flap, which was seen in all patients. In addition to the ABMD changes, 25.7% had some degree of epithelial ingrowth and 45.7%, irregular astigmatism.

CONCLUSIONS

Anterior basement membrane dystrophy changes post LASIK were associated with visual complaints and/or recurrent erosions. Patients should be carefully screened for ABMD. Those who have ABMD signs or symptoms may not be ideal candidates for LASIK.

Automated superficial lamellar keratectomy augmented by excimer laser masked PTK in the management of severe superficial corneal opacities

AIM

To assess superficial lamellar keratectomy augmented by excimer laser smoothening with sodium hyaluronate 0.25%, for the management of superficial corneal opacities.

METHODS

Consecutive procedure performed in 14 eyes (13 patients) with an automated microkeratome and excimer laser phototherapeutic keratectomy (PTK) smoothening using sodium hyaluronate 0.25%.

MAIN OUTCOME MEASURES

UCVA, BCVA, pachymetry, degree of haze, ray tracing analysis, and complications. Mean follow up was 12 (SD 1.6) months.

RESULTS

Mean preoperative haze from previous corneal refractive surgeries was 3.5 (SD 0.5) (11/14 cases). In one case, opacity was caused by ocular trauma and in two by infectious keratitis. The mean preoperative UCVA was 0.7 logMAR (0.2 (SD 0.13) decimal value). BCVA was 0.4 logMAR (0.4 (SD 0.17) decimal value). Mean preoperative corneal pachymetry was 508 (SD 62.5) micro m and mean opacity depth measured by corneal confocal microscopy was 115.2 (SD 49.4) micro m. At 6 months, 71.4% of the eyes with previous corneal refractive surgery showed grade I haze or less. Mean postoperative corneal pachymetry at 6 months was 352.36 (SD 49.05) micro m.

CONCLUSIONS

Automated superficial lamellar keratectomy combined with excimer laser PTK smoothening assisted by sodium hyaluronate 0.25% induces a significant improvement of corneal transparency and visual acuity in cases of corneal opacity caused by previous refractive surgery, ocular trauma, and keratitis.

Clinical course of severe central epithelial defects in laser in situ keratomileusis

PURPOSE

To report the clinical outcome of laser in situ keratomileusis (LASIK) cases complicated by severe central intraoperative epithelial defects (EDs) caused by the microkeratome cut.

SETTING

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

METHODS

In a retrospective study of 1650 LASIK cases at 1 center, the preoperative data, surgical procedures, and postoperative course in 22 eyes of 14 patients who experienced severe central EDs during the LASIK procedure (1.3%) were reviewed. The surgery was performed using a Technolas C-LASIK 217 excimer laser (Bausch & Lomb) and a Hansatome microkeratome (Bausch & Lomb). A follow-up of at least 12 months was available in all but 1 case. The median follow-up was 13.5 months (range 12 to 25 months). In the postoperative period, the following parameters were reviewed: course of refraction, best spectacle-corrected visual acuity (BSCVA), slitlamp findings, and corneal topography.

RESULTS

The mean patient age was 42 years (range 27 to 61 years). Eight patients were affected bilaterally. Fifteen eyes (68%) had moderate to severe dry-eye symptoms preoperatively. Almost all eyes lost BSCVA in the postoperative period, and visual acuity improved slowly. By the last follow-up visit, no eye had lost more than 1 line of BSCVA. Diffuse lamellar keratitis (DLK) was observed in 20 eyes (91%), irregular astigmatism in 17 (77%), and microfolds in 12 (55%). In unilaterally affected patients, the refractive outcome was better in the nonaffected eye.

CONCLUSIONS

A large central ED is a severe intraoperative complication of LASIK that may lead to DLK, irregular astigmatism, flap microfolds, clearly prolonged visual rehabilitation, and temporary loss of BSCVA. The improvement in BSCVA may take several months.

Risk Factors in Interface Epithelialization After Laser in situ Keratomileusis

PURPOSE

To identify risk factors associated with primary and recurrent epithelial ingrowth after laser in situ keratomileusis (LASIK) requiring surgical debridement.

METHODS

Charts of patients who required single or multiple surgical debridements of epithelial ingrowth were reviewed retrospectively and analyzed to identify preoperative, intraoperative, and postoperative risk factors.

RESULTS

Fourteen of 22 patients had epithelial ingrowth that required a single surgical removal. These were mostly associated with the surgeon's learning curve, epithelial injury, and enhancement by lifting the flap. Multiple surgical debridements were required in eight patients and some of these were associated with epithelial basement membrane degeneration and a history of type I diabetes.

CONCLUSIONS

Refractive surgeons should be aware of surgical and non-surgical ocular and systemic risk factors associated with both primary and recurrent epithelial ingrowth after LASIK to appropriately consent patients seeking refractive surgery. Type I diabetes may increase the risk of epithelial downgrowth in LASIK.

Outcome of second surgery in LASIK cases aborted due to flap complications

PURPOSE

To describe the technique and timing of second refractive surgery after aborted laser in situ keratomileusis (LASIK) due to intraoperative flap complication and determine the final visual outcome.

SETTING

Outpatient ambulatory laser vision correction centers.

METHODS

This retrospective noncomparative case series included 16 patients (16 eyes) who had a second refractive surgery after initial LASIK surgery was aborted because of a flap complication. Charts were reviewed with attention to initial preoperative data, intraoperative details of the aborted LASIK, postoperative examination, possible causes of the flap complication, timing and technique of second refractive surgery, and final visual outcome.

RESULTS

Causes of the aborted LASIK were identified in 13 of 16 eyes (81.2%) and included eye squeezing (5 eyes), loss of suction or machine failure (5 eyes), steep corneas (2 eyes), and learning curve of the surgeon (1 eye). The mean time until the second surgery was 135 days (range 49 to 372 days). Repeat flaps were created deeper and larger than the initially attempted flaps when possible. No patient had a final uncorrected visual acuity (UCVA) worse than 20/30 after the second surgery. Two eyes (12.5%) lost 1 line of best spectacle-corrected visual acuity.

CONCLUSION

A planned delayed reoperation after sufficient corneal healing following an intraoperative flap complication can result in satisfactory recovery of UCVA.

Comparison of the IntraLase femtosecond laser and mechanical keratomes for laser in situ keratomileusis

PURPOSE

To compare laser in situ keratomileusis (LASIK) results obtained with the femtosecond laser (IntraLase Corp.) to those obtained using 2 popular mechanical microkeratomes.

SETTING

Private practice, Greensboro, North Carolina, USA.

METHODS

This retrospective analysis compared LASIK outcomes with the femtosecond laser to those with the Carriazo-Barraquer (CB) microkeratome (Moria, Inc.) and the Hansatome microkeratome (Bausch & Lomb, Inc.). The 3 groups were matched for enrollment criteria and were operated on under similar conditions by the same surgeon.

RESULTS

There were 106 eyes in the IntraLase group, 126 eyes in the CB group, and 143 eyes in the Hansatome group. One day postoperatively, the uncorrected visual acuity (UCVA) results in the 3 groups were similar; at 3 months, the UCVA and the best spectacle-corrected visual acuity results were not significantly different. A manifest spheroequivalent of +/-0.50 diopter (D) was achieved in 91% of eyes in the IntraLase group, 73% of eyes in the CB group, and 74% of eyes in the Hansatome group (P<.01). IntraLase flaps were significantly thinner (P<.01) and varied less in thickness (P<.01) than flaps created with the other devices. The mean flap thickness was 114 microm +/- 14 (SD) with the IntraLase programmed for a 130 microm depth, 153 +/- 26 microm with the CB using a 130 microm plate, and 156 +/- 29 microm with the Hansatome using a 180 microm plate. Loose epithelium was encountered in 9.6% of eyes in the CB group and 7.7% of eyes in the Hansatome group but in no eye in the IntraLase group (P =.001). Surgically induced astigmatism in sphere corrections was significantly less with the IntraLase than with the other devices (P<.01).

CONCLUSIONS

The IntraLase demonstrated more predictable flap thickness, better astigmatic neutrality, and decreased epithelial injury than 2 popular mechanical microkeratomes.

Influence of intraoperative epithelial defects on outcomes in LASIK for myopia

PURPOSE

To evaluate whether intraoperative epithelial defects have an adverse effect on achieving desired refractive outcomes following laser in situ keratomileusis (LASIK) for myopia.

DESIGN

Observational retrospective case control study.

METHODS

Thirty eyes that had intraoperative epithelial defects on the LASIK flap were compared with 60 randomly selected control eyes, matched for age, preoperative spherical equivalent, and preoperative cylinder, that had no intraoperative epithelial defects. Preoperative and postoperative clinical data were compared between the two groups. Statistical analyses were performed using analysis of means, analysis of variance, and the Student t test. Comparison variables included preoperative spherical equivalent, 3-month postoperative best-corrected visual acuity, attempted correction, amount of undercorrection at 3 months postoperatively, and whether LASIK enhancement was performed at 3 months postoperatively.

RESULTS

Eyes with intraoperative epithelial defects showed more undercorrection at 3 months (P =.005), were more likely to have lost lines of visual acuity (P =.003), and underwent more enhancement procedures at 3 months (P =.004) compared with control eyes.

CONCLUSIONS

Intraoperative epithelial defects during LASIK predispose eyes to increased wound healing, leading to myopic regression, irregular wound healing with loss of visual acuity, and increased need for enhancement procedures.

Keratocyte activation and inflammation in diffuse lamellar keratitis after formation of an epithelial defect

PURPOSE

To examine the inflammatory reaction in acute or late-onset post-laser in situ keratomileusis (LASIK) diffuse lamellar keratitis (DLK) associated with an epithelial defect.

SETTING

Department of Ophthalmology, Helsinki University Central Hospital, Helsinki, Finland.

METHODS

Six consecutive LASIK patients presented with stage 2 to 3 unilateral DLK 1 to 4 days after formation of an epithelial detachment (intraoperatively or up to 19 months postoperatively). Five corneas of 5 DLK patients, 1 eye twice, were examined by corneal in vivo confocal microscopy 1 to 8 days after the appearance of the epithelial defect. Confocal microscopy of conjunctival venules was performed in 2 of 6 DLK patients to quantify leukocyte rolling and extravasation. Corneas of 5 patients and conjunctival venules of 4 patients who had uneventful LASIK served as controls.

RESULTS

Two of the 4 patients examined 0 to 1 day after the onset of DLK presented with small objects, presumably inflammatory cells (diameter 6.0 to 10.0 microm), in the LASIK flap interface. A third patient examined 1 day after the onset of DLK had larger objects (approximately 13.0 microm in diameter) in the interface. Three other cases (1 to 7 days after the onset of DLK) showed changes typical of keratocyte activation and altered extracellular matrix. All cases healed completely following treatment with steroids. Control LASIK subjects showed some keratocyte activation on day 5.

CONCLUSIONS

Neither uneventful LASIK nor DLK induced an inflammatory reaction displaying leukocyte rolling in conjunctival venules or extravasation into the conjunctival stroma. Diffuse lamellar keratitis related to an epithelial defect does not always lead to the appearance of inflammatory cells in the flap interface. The corneal manifestations of epithelial defect-related DLK may originate from sterile epithelial-stromal or inflammatory cell-stromal cell interactions, leading to alteration of the keratocyte phenotype.

Corneal epithelial adhesion abnormalities associated with LASIK

PURPOSE

To assess the clinical characteristics, incidence, and pathologic correlation of corneal epithelial adhesion abnormalities encountered during LASIK.

DESIGN

Prospective noncomparative interventional case series.

PARTICIPANTS

Five hundred consecutive eyes of 268 patients undergoing primary LASIK procedures by one surgeon utilizing the Moria LSK One microkeratome and VISX Star S-2 excimer laser.

METHODS

Corneal epithelial adhesion was assessed immediately preoperatively using a cellulose surgical sponge (adhesion test), and the incidence, extent, and location of epithelial defects occurring during the microkeratome incision of the corneal flap were recorded. Epithelial specimens from 7 corneas requiring debridement of dysadhesive epithelium were examined by transmission electron microscopy.

MAIN OUTCOME MEASURES

The characteristics of the study population (age, gender, contact lens use, relevant ocular surface or systemic disease, refractive error, keratometry, pachymetry) and the microkeratome-related variables (head selection and vacuum level) were compared with the results of the preoperative epithelial adhesion test, the development of intraoperative epithelial effects (size and location), and the postoperative outcome.

RESULTS

Epithelial defects were sustained by 51 corneas (10.2%), and among these, 31 (6.2%) were microdefects and 20 (4.0%) were macrodefects. The adhesion test was positive (indicative of compromised adhesion of epithelium to stroma) in 20 (64.5%) corneas with microdefects, but false negatives (epithelial defect despite negative adhesion test) occurred in 11 cases (35.4%). The adhesion test was positive in 16 (80%) of corneas having macrodefects, with 4 (20%) false negatives. Thus, the overall positive predictive value of the adhesion test was 59%, and the percentage of positive prediction was 92% (Bayes' theorem). Among all other outcome measures assessed, only corneal flap thickness seemed a potential risk factor, as 40 (78.4%) epithelial defects were associated with the creation of a 180- micro m-thick flap, whereas 10 (19.6%) were associated with a 160- micro m-thick flap and only 1 (2%) occurred with a 130- micro m flap. These trends were not, however, statistically significant (P = 0.15, Fisher exact test). Transmission electron microscopy of all epithelial debridement specimens disclosed consistent abnormality of the basement membrane adhesion complex, as thickened and multilaminated basement membrane remained adherent to the intact epithelial sheet.

CONCLUSIONS

: Corneal epithelial dysadhesion and defects occurring in the course of LASIK surgery may be associated with an intrinsic compromise of the basement membrane adhesion complex, as evidenced clinically by the adhesion test and demonstrated pathologically by duplicated basement membrane.

Management of the Ocular Surface and Tear Film Before, During, and After Laser in situ Keratomileusis

PURPOSE

To identify evidence-based, best practice strategies for managing the ocular surface and tear film before, during, and after laser in situ keratomileusis (LASIK).

METHODS

After a comprehensive review of relevant published literature, evidence-based recommendations for best practice management strategies are presented.

RESULTS

Symptoms of ocular irritation and signs of dysfunction of the integrated lacrimal gland/ocular surface functional gland unit are common before and after LASIK. The status of the ocular surface and tear film before LASIK can impact surgical outcomes in terms of potential complications during and after surgery, refractive outcome, optical quality, patient satisfaction, and the severity and duration of dry eye after LASIK. Before LASIK, the health of the ocular surface should be optimized and patients selected appropriately. Dry eye before surgery and female gender are risk factors for developing chronic dry eye after LASIK. Management of the ocular surface during LASIK can minimize ocular surface damage and the risk of adverse outcomes. Long-term management of the tear film and ocular surface after LASIK can reduce the severity and duration of dry eye symptoms and signs.

CONCLUSIONS

Strategies to manage the integrated ocular surface/lacrimal gland functional unit before, during, and after LASIK can optimize outcomes. As problems with the ocular surface and tear film are relatively common, attention should focus on the use and improvement of evidence-based management strategies.

Intraindividual comparison of epithelial defects during laser in situ keratomileusis using standard and zero-compression Hansatome microkeratome heads

PURPOSE

To determine the difference between the standard and a modified (zero-compression) Hansatome microkeratome head (Bausch & Lomb) in the incidence of epithelial defects.

SETTING

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

METHODS

Ninety-three patients (186 eyes) with a mean age of 39.1 years +/- 9.5 (SD) having laser in situ keratomileusis (LASIK) in both eyes were enrolled in a prospective randomized study using intraindividual comparison. In 1 eye, the flaps were created with the Hansatome microkeratome using the standard Hansatome head and in the other eye, the flaps were created with a microkeratome head with a modified design (zero-compression head). Intraoperative evaluation of epithelial defects was done using a standardized protocol. Statistical evaluation was performed with McNemar and Bowker tests.

RESULTS

Epithelial defects occurred in 21 eyes (22.6%) in which the standard head was used and in 2 eyes (2.1%) in which the zero-compression head was used. In the former group, 15 (16.1%) of the epithelial defects were larger than 1.5 mm(2); the remaining 6 (6.4%) were smaller than 1.5 mm(2). In the latter group, both epithelial defects were smaller than 1.5 mm(2); both patients also had an epithelial defect in the eye in which the standard Hansatome head was used. The difference between the 2 Hansatome heads in the incidence (P<.001, McNemar) and size (P<.001, Bowker) of the epithelial defects was statistically significant.

CONCLUSIONS

The Hansatome microkeratome with a zero-compression head significantly reduced the occurrence of intraoperative epithelial defects. The change in the construction of the Hansatome head is a useful improvement in LASIK technology.