Peripheral Melt of Flap after Laser in situ Keratomileusis

Incidence, Indications, and Outcomes of Eyes Needing Early Flap Lifting After LASIK

PURPOSE

To analyze the incidence, indications, and outcomes associated with early flap relifting after uncomplicated laser in situ keratomileusis (LASIK).

METHODS

All LASIK cases from a single surgical center between 2007 and 2015 were reviewed. Early postoperative flap lift cases (<15 d after surgery) were identified.

RESULTS

Overall, 25,712 eyes were included, of which 366 (1.42%) underwent early postoperative flap lifting. There was a significant reduction in early postoperative flap lifting rates from 2006 (2.46%) to 2015 (0.92%) (P = 0.001). Reasons for early flap lifting included striae (n = 301, 1.17%), diffuse lamellar keratitis (n = 62, 0.24%), flap dislocation (n = 20, 0.08%), epithelial ingrowth (n = 18, 0.07%), and interface debris (n = 15, 0.06%). There was a significant difference in rates and outcomes of flap relifting among high-volume surgeons (P < 0.001). The flap lift group had a significantly lower final safety index (0.95 ± 0.16 vs. 1.01 ± 0.15, P < 0.001), efficacy index (0.85 ± 0.26 vs. 0.94 ± 0.26, P < 0.001), and a higher distance from target refraction (0.39 ± 0.61 vs. 0.21 ± 0.46 D). In unilateral cases, the study eye had a lower safety index (P < 0.001), efficacy index (P < 0.001), and greater distance from target refraction (P = 0.003) compared with the fellow eye. After intervention, 81.1% of cases achieved full resolution, 10.1% achieved partial resolution, 4.1% required additional flap relifting, and 4.7% were nonresolved by the end of follow-up.

CONCLUSIONS

The main indication for early flap relifting after LASIK was striae, and most cases achieved full resolution. Although refractive and visual outcomes are lower in this group, they are, nevertheless, satisfactory.

Risk Factors for Epithelial Ingrowth Following Microkeratome-Assisted LASIK

PURPOSE

To analyze the incidence and risk factors associated with epithelial ingrowth following uncomplicated microkeratome-assisted LASIK.

METHODS

All patients who underwent microkeratome-assisted LASIK between January 2006 and December 2014 in a single surgical center were reviewed. Epithelial ingrowth cases were identified and associated factors were assessed.

RESULTS

Overall, 149 (0.49%) of 30,574 cases developed epithelial ingrowth. The epithelial ingrowth group was older compared to controls (35.3 ± 12.3 vs 31.7 ± 10.3 years, P = .001) and had a higher percentage of moderate to high hyperopia (13.7% vs 5.3%, P < .001), early postoperative flap slippage requiring flap repositioning (9.4% versus 2.8%, P < .001), or flap lifting for enhancement (48.6% vs 4.3%, P < .001), were treated with a smaller optic zone (6 mm) (37.7% vs 15.2%, P < .001), with a Moria M2 microkeratome (Moria SA, Antony, France) (70.1% vs 55.5%, P = .02), by low volume surgeons (n < 1,000) (5.8% vs 1.3%, P < .001), in a lower operating room temperature (22.3 ± 1.8 vs 22.8 ± 1.6, P = .005), and with a greater maximum ablation depth (67.3 ± 29.7 vs 57.3 ± 30.3, P < .001). There was a high incidence of epithelial ingrowth in the enhancement group compared to primary LASIK (4.8% vs 0.2%, P < .001). The time between treatments (primary and enhanced LASIK) was significantly greater in the epithelial ingrowth group (mean: 1,110 ± 870 vs 626 ± 662 days, P < .001). There was a significant rise in epithelial ingrowth rates as time between primary and enhancement LASIK increased, peaking at 4 to 5 years (P < .001). In multivariate analysis, flap lifting for enhancement (odds ratio [OR] = 19.5, P < .001), 6-mm optic zone (OR = 2.2, P < .001), moderate to severe hyperopia (OR = 2.4, P = .005), greater ablation depth (OR = 1.005, P < .001), and low volume surgeon (OR = 3.9, P = .01) were associated with epithelial ingrowth (total R² = 15.4).

CONCLUSIONS

The potential risk factors described above may forewarn surgeons as to which individuals merit closer observation for this complication. [J Refract Surg. 2018;34(2):100-105.].

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.

Epithelial ingrowth within the interface following traumatic corneal lamellar laceration

A 45-year-old patient with a traumatic corneal lamellar laceration who was treated conservatively initially developed an epithelial ingrowth within the flap-stroma interface, causing diminished vision. Confocal microscopy revealed highly refractive bodies without cellular elements at the flap-stroma interface. Treatment comprised surgical debridement of the epithelial sheet from the interface with a thorough irrigation of the stromal bed followed by careful realignment of the flap. The diagnosis was confirmed by histologic examination of the scraped specimen. At the last follow-up examination, vision had improved and there was no recurrence of epithelial ingrowth. Proper primary management of a traumatic corneal lamellar laceration can provide good visual outcome and prevent rare complications such as epithelial ingrowth.

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.

Retreatment of LASIK

PURPOSE

To review the indications, techniques, and results of retreatment LASIK.

METHODS

Review of the literature and the authors' experience.

RESULTS

Patient selection is the key to successful LASIK enhancement. The enhancement procedure should generally be undertaken 3 months after the initial LASIK procedure. Relifting of the flap may be done easily within 1 year of previous LASIK surgery. A new LASIK flap is required in cases with previously complicated LASIK. LASIK retreatment by lifting the flap is an effective and safe procedure. Overall improvement is seen in uncorrected visual acuity (> or = 20/20 and > or = 20/40) and postoperative spherical equivalent refraction within +/- 0.5 D and +/- 1.0 D.

CONCLUSIONS

LASIK retreatment is an effective modality to treat regressions and residual refractive errors.

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.

Corneal Iron Line Following LASIK With Epithelial Ingrowth

PURPOSE

To report a new corneal iron line following keratorefractive surgery.

METHODS

Case report and review of the literature. A 51-year-old man developed epithelial ingrowth after otherwise uneventful LASIK surgery. The patient, satisfied with an uncorrected visual acuity of 20/25 and otherwise asymptomatic, declined to have his flap relifted to treat the ingrowth.

RESULTS

Six months postoperatively a corneal iron line was noted at the leading edge of the epithelial ingrowth. Vision remained stable.

CONCLUSIONS

: Epithelial iron lines have been reported with a number of conditions, including post-refractive procedures. This is the first report of an iron line associated with epithelial ingrowth following 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.

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.

Pathologic findings in postmortem corneas after successful laser in situ keratomileusis

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

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.

Laser-assisted subepithelial keratectomy and photorefractive keratectomy versus conventional treatment of myopic anisometropic amblyopia in children

PURPOSE

To evaluate the visual and refractive results of photorefractive keratectomy (PRK) and laser-assisted subepithelial keratectomy (LASEK) for high myopic anisometropia with amblyopia and contact lens (CL) intolerance in children.

SETTING

Department of Ophthalmology, Masaryk University Hospital, Brno, Czech Republic.

METHODS

This prospective comparative study comprised 27 children with high myopic anisometropia and amblyopia. The mean age of the children was 5.4 years (range 4 to 7 years). Multizonal PRK (13 eyes) or LASEK (14 eyes) was performed in the more myopic eye under general anesthesia using the Nidek EC-5000 excimer laser. After surgery, the dominant eye was patched. The postoperative visual and refractive outcomes were analyzed; all children had a 2-year follow-up. The 27 children (Group A) were compared with a control group of 30 children (mean age 5.1 years) (Group B) in whom myopic anisometropia and amblyopia were treated conventionally by CLs and patching the dominant eye. The visual acuity and binocular vision outcomes in both groups were analyzed and compared.

RESULTS

In Group A, the mean spherical equivalent refraction was -8.25 diopters (D) +/- 2.37 (SD) (range -6.00 to -11.25 D) preoperatively and -1.61 +/- 0.73 D (range +0.50 to -2.25 D) postoperatively. The mean best corrected visual acuity (BCVA) was 0.23 +/- 0.21 preoperatively and 0.78 +/- 0.19 at 2 years. In Group B, the mean BCVA was 0.16 +/- 0.19 at the start of CL correction and amblyopia therapy and improved to 0.42 +/- 0.15 after 2 years. The mean BCVA at the final examination was significantly better in Group A (P<.05). Binocular vision improvement expressed by the proportion of patients who gained fusion and stereopsis was better overall in Group A (78%) than in Group B (33%) (P<.05). There were no complications postoperatively.

CONCLUSIONS

Photorefractive keratectomy and LASEK were effective and safe methods for correcting high myopic anisometropia and improving amblyopia in children aged 4 to 7 years who were CL intolerant. Visual acuity and binocular vision outcomes were better in children who received permanent surgical correction of anisometropia than in those who were treated conventionally by CLs.

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.

The Effects of LASIK on the Ocular Surface

Laser in situ keratomileusis (LASIK) can affect corneal sensation, aqueous tear production, wound healing, and the incidence of corneal erosions. Virtually all patients experience dry eye at least transiently after LASIK. Because intact corneal sensation drives tear production, denervation associated with the LASIK procedure is the most significant cause of post-LASIK dry eye. To prevent symptomatic postoperative dry eye, it is crucial to identify and treat pre-existing dry eye before surgery. This review addresses the pathophysiology and management of dry eye, as well as the relationship between LASIK and corneal erosions, and suggests intra- and post-operative management techniques to minimize complications and maximize the stability of the ocular surface. Contraindications to LASIK and alternative refractive surgical procedures are discussed.

Penetrating keratoplasty for iatrogenic keratoconus after repeat myopic laser in situ keratomileusis: Histologic findings and literature review

We report a patient with a sufficiently thick cornea (593 microm) and no topographic signs of keratoconus preoperatively who developed iatrogenic keratoconus 2 months after repeat laser in situ keratomileusis (-4.00 -1.00 x 20) performed 5 months after the primary procedure (-10.50 -1.00 x 55). After penetrating keratoplasty, macrophotography showed severe multidirectional "macrostriae" of the stromal bed. On histologic evaluation, excessive thinning of the residual stromal bed to a minimum of 75 microm in the valleys and a maximum of 200 microm at the peaks of the macrostriae were documented. The flap thickness was 225 microm in the center. The thicker-than-intended flap (160 microm) is thought to be the cause of the severe complication of the LASIK procedure.

Laser-assisted subepithelial keratectomy and photorefractive keratectomy for the correction of hyperopia: Results of a 2-year follow-up

PURPOSE

To evaluate and compare the efficacy, safety, predictability, and stability of laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) for low to moderate hyperopia with a 2-year follow-up.

SETTING

Department of Ophthalmology, Masaryk University Hospital, Brno, Czech Republic.

METHODS

This prospective comparative single-surgeon study included 216 eyes of 108 patients with hyperopia who received PRK in 1 eye and LASEK in the contralateral eye. The mean patient age was 38.3 years (range 25 to 58 years). The mean preoperative spherical equivalent (SE) cycloplegic refraction was +3.67 diopters (D) +/- 1.15 (SD) (range +2.00 to +5.00 D), and astigmatism was less than 1.00 D. In each patient, PRK was performed in 1 eye (Group A) and LASEK was performed in the other eye (Group B) using the Nidek EC-5000 excimer laser. Postoperative uncorrected visual acuity (UCVA), best corrected visual acuity, contrast sensitivity, manifest and cycloplegic refractions, refractive stability and predictability, postoperative pain, and corneal haze were examined and statistically analyzed. A P value less than 0.05 was considered significant.

RESULTS

At 1 week, the UCVA was 20/40 or better in 58% of PRK eyes and 85% of LASEK eyes (P =.037); at 2 years, it was 20/40 or better in 81% and 91%, respectively (P =.076). At 2 years, the UCVA for near was N8 or better in 73% of PRK eyes and 89% of LASEK eyes (P =.064). No patient lost 2 or more lines of Snellen visual acuity. The safety index was 1.03 in PRK eyes and 1.08 in LASEK eyes. Refractive stability was achieved at 6 months in LASEK eyes and at 12 months in PRK eyes. The mean SE cycloplegic refraction decreased from +3.58 D (PRK eyes) and +3.76 D (LASEK eyes) at baseline to +0.74 D and +0.32 D, respectively, at 2 years; in 57% and 78% of eyes, respectively, the refraction was within +/-0.50 D of the targeted refraction. Peripheral corneal haze scores at 3 to 9 months and pain scores at 1 to 3 days were significantly lower in the LASEK group than in the PRK group.

CONCLUSIONS

Laser-assisted subepithelial keratectomy for hyperopia up to +5.00 D provided good visual and refractive results. It significantly reduced postoperative pain, grade of peripheral ring-shaped corneal haze, and regression of hyperopia. Hyperopic LASEK provided quicker visual recovery and achieved better efficacy, predictability, and refractive stability than hyperopic PRK.

Peripheral Keratitis Following Laser in situ Keratomileusis

PURPOSE

To report two different cases of sterile, peripheral keratitis following laser in situ keratomileusis (LASIK).

METHODS

A report of two cases (two eyes of two patients).

RESULTS

In two patients, peripheral infiltrates appeared 1 day after LASIK. One patient had a history of rheumatoid arthritis and both had peripheral corneal changes that may have represented prior inflammatory events. The presentations were quite different, with one occurring in association with an epithelial defect at the edge of the flap and the other occurring without an epithelial defect peripheral to the microkeratome cut. In the second case a similar infiltrate showed up in the unoperated fellow eye. Both patients were treated with aggressive antibiotic and corticosteroid therapy. Both patients recovered well with no loss of best spectacle-corrected visual acuity.

CONCLUSION

Peripheral keratitis can occur in patients following LASIK; preoperative evidence of previous inflammation may be a marker for patients at higher risk. Rheumatoid arthritis patients may be at increased risk for this complication. With careful and aggressive management excellent visual outcomes are still possible.

Fibrin glue for the prevention of epithelial ingrowth after laser in situ keratomileusis

We present 3 cases of recurrent epithelial ingrowth following laser in situ keratomileusis. All patients consented to flap lifting, epithelial ingrowth removal, and placement of fibrin glue (Tisseel(R) VH, Baxter) at the flap edges. Two of 3 eyes had no evidence of recurrent epithelial ingrowth within a relatively short follow-up. One eye that also had had radial keratotomy had a small nest of stable epithelial cells that had not progressed. Fibrin glue may be a useful adjunct to prevent recurrent epithelial ingrowth. There were no complications associated with its use.

Bilateral Marginal Sterile Infiltrates and Diffuse Lamellar Keratitis After Laser in situ Keratomileusis

PURPOSE

To report cases of acute bilateral catarrhal infiltrates in the early postoperative period after laser in situ keratomileusis (LASIK).

METHODS

Retrospective review of both eyes of two patients.

RESULTS

Two patients developed acute bilateral, marginal, catarrhal infiltrates in the early postoperative period after LASIK. Both patients had moderate to severe chronic meibomian gland dysfunction preoperatively. One patient (both eyes) developed grade 3 diffuse lamellar keratitis (DLK) that required both flaps to be lifted for irrigation and cleaning on postoperative day 5. Fungal and bacterial cultures were negative in both eyes of both patients. The condition resolved with intensive topical corticosteroids and fortified antibiotics. Regression of refractive error and the need for enhancement was encountered in all eyes. There was mild recurrence in one eye of each patient with pretreatment with topical corticosteroids prior to enhancement.

CONCLUSIONS

Endogenous factors such as chronic blepharitis and meibomian gland dysfunction may trigger inflammation resulting in sporadic cases of catarrhal infiltrates after LASIK. These patients may have chronic inflammatory milieus that can trigger sporadic cases of catarrhal infiltrates after LASIK, with accompanying diffuse lamellar keratitis.

An outbreak of Mycobacterium chelonae infection after LASIK

OBJECTIVE

To describe an outbreak of mycobacterial keratitis after laser in situ keratomileusis (LASIK), including the microbiologic investigation, clinical findings, treatment response, and outcome.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Patients (n = 10) who underwent LASIK surgery between August 22 and September 4, 2000, and developed mycobacterial infection.

METHODS

Patients were prospectively followed in relation to microbiologic investigation, clinical findings, treatment response, and outcome.

MAIN OUTCOME MEASURES

Most patients underwent bilateral simultaneous LASIK. Postoperative infection was signaled by the appearance of corneal infiltrates in the third postoperative week. The microbiologic workup was performed on cultures obtained either by direct scraping of the cornea or by lifting the flap. Medical therapy was instituted based on drug susceptibility testing. Surgical interventions such as corneal debridement and flap removal were performed during recurrences or when there was no satisfactory clinical response.

RESULTS

Cultures revealed Mycobacterium subspecies chelonae. Patients were treated with topical clarithromycin (1%), tobramycin (1.4%), and ofloxacin (0.3%). Oral clarithromycin (500 mg twice a day) was prescribed for those patients who did not respond clinically to topical treatment. Four eyes healed on this regimen. Flap removal was necessary in seven eyes.

CONCLUSIONS

This report highlights mycobacteria as an etiologic infectious agent after LASIK. Diagnosis can be difficult and is often delayed. The treatment mainstay is prolonged antibiotic therapy. Surgical debridement and flap removal may shorten the disease course.

The role of epithelial defects in intralamellar inflammation after laser in situ keratomileusis

BACKGROUND

A single factor responsible for diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK) has not yet been identified. Various theories have been proposed to explain what may trigger this condition. We evaluated the role of epithelial defects in interface inflammation and assessed the outcome of eyes with DLK with and without epithelial defects.

METHODS

We reviewed the records of all patients with DLK after LASIK performed at the Toronto Gimbel Eye Centre between September 1999 and May 2000. Patients with other epithelial problems, such as punctate epithelial erosions, were excluded. Patients with an epithelial defect and interface keratitis (group 1) were treated with a bandage contact lens and topical steroid therapy; those with interface keratitis alone (group 2) were treated with topical steroid therapy. Variables examined included the onset and duration of DLK, uncorrected visual acuity, best corrected visual acuity, refractive outcome and retreatment rate.

RESULTS

A total of 1,436 LASIK procedures were performed during the study period. Thirteen patients (20 eyes) had DLK after LASIK, in all cases of the sporadic type (i.e., nonepidemic). Of the 20 eyes, 8 had an epithelial disturbance. All the patients were followed for at least 3 months. Three eyes (37.5%) in group 1 had uncorrected visual acuity before retreatment of less than 20/25, compared with 2 eyes (16.7%) in group 2. The mean postoperative spherical equivalent was significantly higher in group 1 than in group 2 (-0.60 vs. -0.02 dioptres) (p = 0.01). The retreatment rate was 37.5% (3/8) in group 1 and 16.7% (3/12) in group 2, a nonsignificant difference. After retreatment the uncorrected visual acuity was 20/20 or better in all cases. There were no cases of recurrence of DLK after retreatment.

INTERPRETATION

Eyes with interface keratitis and an epithelial defect have a larger deviation from emmetropia before retreatment than eyes with interface keratitis alone. Patients with epithelial defects intraoperatively or who are at risk for such defects postoperatively must be monitored carefully, as they may be at increased risk for DLK.

Epithelial ingrowth after laser in situ keratomileusis: clinical features and possible mechanisms

PURPOSE

To analyze the incidence, clinical course, and possible mechanisms of epithelial ingrowth after laser in situ keratomileusis (LASIK).

DESIGN

Interventional case series.

METHODS

Retrospective evaluation of 4,867 eyes of 2,502 patients who had LASIK. The type of microkeratome (LSK-One or MK-2000), corneal flap thickness, and clinical course were analyzed. We also compared the cutting characteristics of both microkeratomes in pig cadaver eyes by scanning electron microscopy.

RESULTS

The frequency of epithelial ingrowth was significantly greater in the MK-2000 (34 of 1,680 eyes; 2.0%) than the LSK-One group (30 of 3,187 eyes; 0.94%; P =.001). In 24 eyes (37.5%), blood, cell infiltration, ointment under the corneal flaps, or epithelial defect were detected at the area of epithelial ingrowth postoperatively. The incidence of epithelial ingrowth was correlated with the incidence of epithelial defect during surgery (P <.001) and with incidence of diffuse lamellar keratitis after surgery (P =.003). Flap thickness was thinner in eyes with epithelial ingrowth (126.0 +/- 29.1 microm) compared with flap thickness in eyes without epithelial ingrowth (133.8 +/- 27.3 microm; P <.001). Scanning electron microscopy showed clear differences in the appearance of flap edges created by the two types of microkeratomes. Epithelial ingrowth disappeared or remained unchanged in 54 eyes (90%) and progressed in six cases (10%).

CONCLUSIONS

Poor adhesion caused by excessive hydration due to epithelial defect as well as by foreign bodies between the flap stromal bed and thickness and morphologic characters of the corneal flap, depending on the type of microkeratomes, are related factors for development of epithelial ingrowth.

Risk factors for epithelial erosions in laser in situ keratomileusis

PURPOSE

To determine the risk factors for an epithelial defect during laser in situ keratomileusis (LASIK).

SETTING

LASIK Vision, Toronto, Ontario, Canada.

METHODS

In this prospective cohort study, 926 patients (1852 eyes) presenting for LASIK over a 6-month period were evaluated for age, sex, Fitzpatrick Skin Type (FST), eye color, hair color at 3 years of age, facial skin wrinkling, ethnicity (Lancer Ethnicity Scale [LES]), keratometry, Schirmer I reading, corneal thickness, and preexisting signs of corneal epithelial dystrophy. In all patients, LASIK was performed using the Technolas 217 laser (Bausch & Lomb), the Hansatome(R) microkeratome (Bausch & Lomb), and the same nomogram settings.

RESULTS

Fourteen percent of patients had significant epithelial fragility. In patients with FST I or II or LES 1 or 2, the relative risk of an epithelial defect was 10 times greater than in other patients; in those older than 40 years, it was 6 times greater than in other patients; in those with lighter hair or eye color, it was 2 to 3 times greater than in patients with darker hair or eyes. There was no significant difference in pachymetry, vertical or horizontal keratometry, or Schirmer readings between eyes with epithelial defects and eyes without.

CONCLUSIONS

The risk of epithelial erosions during LASIK strongly correlated with patients' skin type and age.

Laser-assisted subepithelial keratectomy for low to high myopia and astigmatism

PURPOSE

To evaluate the safety and efficacy of laser-assisted subepithelial keratectomy (LASEK) for the treatment of low to high myopia and astigmatism.

SETTING

Solo private practice, Mountain View, California, USA.

METHODS

Laser-assisted subepithelial keratectomy was performed in 146 eyes of 83 consecutive patients with myopia or myopic astigmatism using a VISX Star S2 excimer laser (72 eyes) or a Nidek EC-5000 excimer laser (74 eyes). The mean preoperative myopic spherical equivalent was -5.32 diopters (D) (range -1.25 to -14.38 D). Data were collected prospectively with a follow-up of 1 to 12 months. Outcome measurements included uncorrected visual acuity (UCVA), manifest refraction, best spectacle-corrected visual acuity (BSCVA), corneal haze, and complications.

RESULTS

After 6 and 12 months, no eye lost 2 or more lines of BSCVA. After 6 months, the UCVA was 20/20 in 57% of eyes and 20/40 or better in 96%. After 12 months, it was 20/20 in 56% of eyes and 20/40 or better in 96%. No eye developed corneal haze that affected visual acuity. There were no serious or vision-threatening complications.

CONCLUSIONS

Laser-assisted subepithelial keratectomy was safe and effective in treating a wide range of myopia and astigmatism. The potential advantages of LASEK over laser in situ keratomileusis (LASIK) include the elimination of stromal flap complications and greater choice in patient selection. The disadvantages include varying degrees of pain for 2 days and blurry vision for several days postoperatively.

Epithelial defect, diffuse lamellar keratitis, and epithelial ingrowth following post-LASIK epithelial toxicity

This case reports an association between 2 uncommon flap complications in 1 eye related to epithelial toxicity and subsequent epithelial defect secondary to prolonged intraoperative exposure to topical anesthesia. A patient had hyperopic laser in situ keratomileusis (LASIK) for the correction of +2.75 +1.75 x 70 in the left eye. Because of the patient's anxiety and movement, additional topical local anesthesia was used and the flap remained reflected for 5 minutes. Immediately postsurgery, a toxic appearance was noted in the epithelium of the LASIK flap; 24 hours later, a large central epithelial defect was identified. Three days post- LASIK, the epithelial defect had healed but diffuse lamellar keratitis was noted in the interface, particularly underlying the location of the original epithelial defect. Over 6 weeks, a self-limiting epithelial ingrowth developed in the inferior interface. Fourteen months post-LASIK, the uncorrected visual acuity was 6/9 with a residual refraction of +0.50 +0.50 x 90.

Changes of posterior corneal astigmatism and tilt after myopic laser in situ keratomileusis

PURPOSE

The purpose of this study was to assess the changes of posterior corneal astigmatism and tilt after laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness.

METHODS

This prospective nonrandomized (self-controlled) comparative trial included 57 eyes from 14 females and 15 males, whose mean age (+/- standard deviation [SD]) at the time of surgery was 33 +/- 9 years (range, 19-53), with a spherical equivalent (SEQ) of -1.00 to -15.50 (mean, -5.07 +/- 2.81) diopters (D). All LASIK procedures were accomplished with the Keratom II Coherent-Schwind excimer laser and the Moria Model One microkeratome (150-microm head). Subjective refractometry, Orbscan slit-scanning corneal topography analysis, and pachymetry were performed before and 3 months after LASIK for myopia (n= 35; -1.00 to -15.50 D [mean, -4.75 +/- 3.07]) or myopic astigmatism (n= 22; sphere, 0.00 to -9.75 D [mean, -4.75 +/- 2.36]; cylinder, -0.75 to -3.50 D [-1.68 +/- 0.86]). Intended ablation depth ranged from 12 to 108 (mean, 48 +/- 22) microm. Topographic raw data were decomposed into a set of Zernike polynomials as published in detail previously, and parameters for detection of asymmetric mechanical deformation of the cornea were derived. Posterior corneal astigmatism and tilt before and after LASIK were compared, and changes in these variables were correlated with the SEQ change (DeltaSEQ) and the residual corneal bed thickness (RBT).

RESULTS

The RBT after LASIK ranged from 186 to 373 (mean, 280 +/- 42) microm. Overall, astigmatism (0.19 +/- 0.07 D/0.22 +/- 0.13 D; p= 0.80) and tilt (3.58 +/- 0.35 degrees /3.65 +/- 0.48 degrees; p= 0.61) did not change significantly by 3 months after LASIK. In eyes with RBT < or =250 microm, the average change in astigmatism (0.05 +/- 0.11 versus 0.01 +/- 0.13 D; p= 0.46) and tilt (0.21 +/- 0.45 degrees versus 0.04 +/- 0.55 degrees; p= 0.30) was not greater than in eyes with RBT > 250 microm. Change in astigmatism (p= 0.19) and tilt (p= 0.56) did not correlate with the RBT during LASIK.

CONCLUSIONS

Zernike decomposition of topographic height data discloses that no significant asymmetric mechanical deformation of the posterior corneal curvature occurs after myopic LASIK. Further studies with long-term follow-up are needed to clarify whether this symmetry of the posterior corneal surface can indeed be preserved over time after LASIK if the RBT is < 250 microm.

Laser in situ keratomileusis intraoperative complications using one type of microkeratome

OBJECTIVE

To identify the incidence and refractive outcome of intraoperative laser in situ keratomileusis (LASIK) complications using one type of microkeratome.

DESIGN

Retrospective noncomparative case series.

PARTICIPANTS

Three hundred thirty-four consecutive myopic LASIK patients (September 1997 to November 1998) operated on by one surgeon.

INTERVENTION

Myopic LASIK surgeries were performed with the Mediate Mel 60 Aesculap Meditec Laser system.

MAIN OUTCOME MEASURES

Preoperative and 1-year postoperative spherical equivalent, best spectacle-corrected visual acuity (BSVA), and corneal anatomic features (as obtained from videokeratography) were recorded, as was the incidence of intraoperative complications.

RESULTS

Forty-eight (14%) eyes had keratome-related complications. Thirty-seven (77%) eyes were immediately treated; the remaining eyes were treated on a later date. One year after treatment, 13% of the immediately treated complicated eyes maintained the preoperative BSVA; 24% had a 1-line loss; 2.7% had a greater loss of BSVA.

CONCLUSIONS

Microkeratome-related complications may result in loss of BSVA. The complication of an irregular flap had the poorest refractive outcome in this series of eyes. We did not find any statistically significant relationship between corneal anatomic factors and keratome-related complications in this series.

Laser in situ keratomileusis for myopia and astigmatism: safety and efficacy: a report by the American Academy of Ophthalmology

OBJECTIVE

This document describes laser in situ keratomileusis (LASIK) for myopia and astigmatism and examines the evidence to answer key questions about the efficacy and safety of the procedure.

METHODS

A literature search conducted for the years 1968 to 2000 retrieved 486 citations and an update search conducted in June 2001 yielded an additional 243 articles. The panel members reviewed 160 of these articles and selected 47 for the panel methodologist to review and rate according to the strength of evidence. A Level I rating is assigned to properly conducted, well-designed, randomized clinical trials; a Level II rating is assigned to well-designed cohort and case-control studies; and a Level III rating is assigned to case series and poorly designed prospective and retrospective studies, including case-control studies.

RESULTS

The assessment describes randomized controlled trials published in 1997 or later (Level I evidence) and more recent comparative and noncomparative case series (Level II and Level III evidence), focusing on results for safety and effectiveness. It is difficult to extrapolate results from these studies that are comparable to current practices with the most recent generation lasers because of the rapid evolution of LASIK technology and techniques. It is also difficult to compare studies because of variations in the range of preoperative myopia, follow-up periods, lasers, nomograms, microkeratomes and techniques, the time frame of the study, and the investigators' experience.

CONCLUSIONS

For low to moderate myopia, results from studies in the literature have shown that LASIK is effective and predictable in terms of obtaining very good to excellent uncorrected visual acuity and that it is safe in terms of minimal loss of visual acuity. For moderate to high myopia (>6.0 D), the results are more variable, given the wide range of preoperative myopia. The results are similar for treated eyes with mild to moderate degrees of astigmatism (<2.0 D). Serious adverse complications leading to significant permanent visual loss such as infections and corneal ectasia probably occur rarely in LASIK procedures; however, side effects such as dry eyes, night time starbursts, and reduced contrast sensitivity occur relatively frequently. There were insufficient data in prospective, comparative trials to describe the relative advantages and disadvantages of different lasers or nomograms.

LASIK complications: etiology, management, and prevention

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

Keratolysis Following Excimer Laser Phototherapeutic Keratectomy in a Patient With Keratoconus

PURPOSE

We report a case of keratolysis following phototherapeutic keratectomy (PTK) for a subepithelial nodule in a patient with keratoconus.

METHODS

A 29-year-old male with keratoconus who became contact lens intolerant because of a raised subepithelial nodule was treated with excimer laser phototherapeutic keratectomy (PTK).

RESULTS

The epithelium failed to heal postoperatively, and progressive keratolysis led to a central descemetocele by the eighth postoperative day. The patient was managed with a penetrating keratoplasty.

CONCLUSIONS

Excimer laser phototherapeutic keratectomy has been shown to be an effective treatment for subepithelial nodules in patients with keratoconus. Rapidly progressive keratolysis is a potential complication of this procedure.

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

PURPOSE

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

METHODS

Review of literature and the experience of the authors.

RESULTS

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

CONCLUSION

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

Posterior corneal curvature changes after myopic laser in situ keratomileusis

OBJECTIVE

To assess the posterior corneal power and asphericity changes after myopic laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness.

DESIGN

Prospective nonrandomized (self-controlled) comparative study.

PARTICIPANTS

Fifty-seven eyes of 14 women and 15 men, mean age at the time of surgery 33 +/- 9 (range, 19-53) years with a spherical equivalent (SEQ) of -1.00 to -15.50 (mean, -5.07 +/- 2.81) diopters (DI).

INTERVENTION

All procedures were performed with the Keratom II Coherent-Schwind excimer laser and and the Moria Model One microkeratome (150-microm head). Subjective refractometry, Orbscan slit scanning corneal topography analysis and pachymetry were performed before and 3 months after LASIK for myopia (n=35, -1.00 to -15.50 D, mean -4.75 +/- -3.07 D) or myopic astigmatism (n=22, sphere 0.00 to -9.75 D, mean -4.75 +/- 2.36 D; cylinder -0.75 to -3.50 D, mean -1.68 +/- 0.86 D). Intended ablation depth ranged from 12 to 108 (mean, 48 +/- 22) microm. Topographic raw data were decomposed into a set of Zernike polynomials as published in detail previously, and parameters potentially indicative for detection of a "mild keratectasia" were derived.

MAIN OUTCOME MEASURES

Posterior central corneal power and asphericity before and after LASIK were compared, and changes of these variables were correlated with the SEQ change (deltaSEQ)and the residual corneal bed thickness RBT).

RESULTS

The mean RBT after LASIK was 280 +/- 42 microm. Overall, change of posterior power (-6.28 +/- 0.22 D/ -6.39 +/- 0.23 D, P=0.02) was statistically significant and change of asphericity (0.98 +/-0.07/1.14 +/- -.20, P<0.0001) was highly significant. In eyes with RBT < or =250 microm, the average change of posterior central power (-0.20 +/- 0.10 D vs. -0.08 +/- 0.18 D) was significantly greater than in eyes with RBT >250 microm (P=0.003). The change of posterior corneal power correlated significantly with deltaSEQ (P=0.004) and the RBT (P=0.002).

CONCLUSIONS

Increased negative keratometric diopters and oblate asphericity of the posterior corneal curvature suggest that mild "keratectesia" of the cornea may be common early after LASIK. Further stuudies with longer follow-up are required to clarify whether this biomechanical deformation is progressive and whether a residual bed thickness of >250 microm can completely prevent it.

Central Necrotic Lamellar Inflammation After Laser in situ Keratomileusis

PURPOSE

To report four cases of corneal interface complications that occurred after excimer laser in situ keratomileusis (LASIK).

METHODS

Four eyes of three patients underwent technically uneventful LASIK.

RESULTS

One day after LASIK, patients presented with severe pain, blurred vision, conjunctival infection, and diffuse opacity at the interface. Two days after LASIK, significant features were central opacity, striae in the flap, loss of uncorrected and best spectacle-corrected visual acuity, and corneal sensitivity. The findings did not improve by using drugs or by lifting the flap and irrigating the bed. The central opacity partially resolved over 8 to 12 months, leaving a hyperopic shift (one patient), striae (one patient), and loss of two or more lines of best spectacle-corrected visual acuity (three patients).

CONCLUSION

This severe central inflammation after LASIK could be an extreme manifestation of diffuse lamellar keratitis.

Laser in situ keratomileusis after penetrating keratoplasty

PURPOSE

To assess the outcomes of laser in situ keratomileusis (LASIK) after penetrating keratoplasty (PKP).

SETTING

Hospital de Clínicas de Porto Alegre, Department of Ophthalmology, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.

METHODS

Fourteen eyes of 13 patients who had LASIK after PKP were retrospectively reviewed. The interval between LASIK and PKP was at least 1 year, and the follow-up after LASIK was also at least 1 year. All patients had a stable refractive error for a minimum of 6 months after all sutures were removed, regular and symmetric topographic astigmatism, and a minimal ultrasonic central corneal pachymetry of 500 microm. The Chiron Automatic Corneal Shaper and the Meditec Aesculap MEL 60 excimer laser were used.

RESULTS

At 12 months, mean myopia decreased from -5.33 diopters (D) +/- 4.22 (SD) to 0.19 +/- 1.71 D, mean hyperopia decreased from +5.04 +/- 3.32 D to + 0.42 +/- 0.46 D, and mean astigmatism decreased from 5.37 +/- 2.12 D to 2.82 +/- 2.42 D (47.5% of mean percentage reduction). Retreatment was necessary in 42.9% of eyes because of cylindrical undercorrection. Uncorrected visual acuity improved in 11 eyes (78.6%). Best spectacle-corrected visual acuity improved in 6 eyes (42.8%) and was maintained in 4 eyes (28.6%); 5 eyes (35.7%) lost 1 Snellen line. Intraoperative complications included 1 buttonhole flap. Postoperative complications included interface epithelial ingrowth at the periphery (2 eyes) and pseudophakic retinal detachment 2 years after LASIK (1 eye).

CONCLUSION

Laser in situ keratomileusis after PKP safely and predictably corrected the spherical component of the refraction. However, the predictability of LASIK in correcting post-PKP astigmatism was poor.

In vivo and in vitro demonstration of epithelial cell-induced myofibroblast differentiation of keratocytes and an inhibitory effect by amniotic membrane

PURPOSE

To examine the role of epithelial cells in inducing the differentiation of keratocytes into myofibroblasts and to determine whether this effect may be inhibited by amniotic membrane matrix.

METHODS

In vivo, a 9-mm diameter, partial-thickness corneal flap was created in 12 rabbit eyes (6 rabbits), which were equally subdivided into three groups. The first group was implanted with one layer of a 6-mm diameter human amniotic membrane, from which the epithelium had been removed by dispase. The second group received an implantation of dispase-treated amniotic membrane with cultured rabbit corneal epithelial cells. The third group received the same implantation as the second group except that the cultured corneal epithelial cells were sandwiched between two layers of membrane. All corneas were removed 2 weeks later and were subjected to Masson trichrome staining and immunofluorescence staining with monoclonal antibodies to alpha-smooth muscle (alpha-SM) actin for myofibroblasts and cytokeratins for epithelial cells. In vitro collagen gels impregnated with different types of human ocular surface fibroblasts were seeded with or without rabbit corneal epithelial cells before testing for gel contraction.

RESULTS

Positive staining of alpha-SM actin was noted only in keratocytes adjacent to corneal epithelial cells at the incision site and those grown on the basement membrane side of the amniotic membrane. Negative staining was noted when epithelial cells were removed by dispase or when cultured corneal epithelial cells were sandwiched between two layers of membrane. Gel contraction by fibroblasts was significantly promoted when epithelial cells were seeded on the gel. In the latter situation, positive staining of alpha-SM actin was noted in fibroblasts subjacent to epithelial cells but not in those impregnated in the gel.

CONCLUSION

Epithelial cells are capable of inducing the differentiation of adjacent fibroblasts into myofibroblasts; such an induction requires a close epithelial-mesenchymal contact. Amniotic membrane alone does not induce this effect and can help block such induction by epithelial cells.

An optometrist's personal perspective of aspects of refractive surgery

The latter part of the last century has seen significant evolution in the area of refractive surgery, such that is has become a viable alternative to contact lenses, or spectacles, for an increasing number of patients. The developments of the principal techniques, in this ever-expanding field, are reviewed, and the increasing rôle of the optometrist in the pre-, intra- and post-operative management of the refractive surgery patient is described, based upon the author's personal experience within a non-profit, refractive surgery setting. In addition to highlighting pertinent features of the objective evaluation of patients, the importance of subjective assessment, pre- and postoperatively, is discussed, in terms of maximising post-surgery patient satisfaction. The scope for future research in this dynamic area is also considered.

Treatment of Progressive or Recurrent Epithelial Ingrowth With Ethanol Following Laser in situ Keratomileusis

PURPOSE

To evaluate the use of ethanol in the treatment of progressive or recurrent epithelial ingrowth following laser in situ keratomileusis (LASIK).

METHODS

Four eyes of four patients with aggressive epithelial ingrowth following LASIK underwent epithelial ingrowth removal with 50% ethanol. Aggressive epithelial ingrowth was defined as, 1) progressive enlargement on serial examination with an area of ingrowth involving at least 30% of the flap surface area, 2) epithelial ingrowth associated with stromal melting as evidence on clinical or topographic examination, or 3) recurrent epithelial ingrowth in the same area following previous removal.

RESULTS

Epithelial ingrowth was removed successfully in all eyes. No eye lost best spectacle-corrected visual acuity. One eye with multiple risk factors for failure experienced nonprogressive recurrence. No eyes required reoperation for recurrent epithelial ingrowth. No eyes experienced progression of stromal melt. Regularization of corneal topography was observed in an eye with preoperative stromal melting. The only complication was a tendency for the development of diffuse lamellar keratitis. Two eyes (50%) experienced diffuse lamellar keratitis following epithelial ingrowth removal with ethanol, which resolved completely with topical corticosteroids.

CONCLUSION

Ethanol may be a useful adjunct in the treatment of aggressive or recurrent epithelial ingrowth following LASIK. Cautious use with the lowest concentration of ethanol may prove useful in these difficult epithelial ingrowth cases. Randomized and prospective studies are recommended to evaluate our experience.

Late Onset Diffuse Lamellar Keratitis Associated With an Epithelial Defect in Six Eyes

PURPOSE

To report six cases of late onset diffuse lamellar keratitis associated with epithelial defects 2 to 12 months following uncomplicated laser in situ keratomileusis (LASIK).

METHODS

Retrospective case series.

RESULTS

The interface inflammation and epithelial defects were treated aggressively with topical corticosteroids and topical antibiotics with complete resolution over 1 to 2 weeks. There were no complications or loss of best spectacle-corrected visual acuity. These cases illustrate new understanding in the etiology of diffuse lamellar keratitis following lamellar surgery.

CONCLUSION

Late onset diffuse lamellar keratitis in association with epithelial defects may occur following LASIK. Treatment with topical antibiotics and topical corticosteroids may result in uncomplicated, complete resolution.

Diffuse Lamellar Keratitis Induced by Trauma 6 Months After Laser in situ Keratomileusis

This case report illustrates an unusual presentation of diffuse lamellar keratitis triggered by a foreign body striking the eye 6 months after laser in situ keratomileusis (LASIK). The etiology of diffuse lamellar keratitis is unclear. The infiltrate within the plane of the flap after removal of the foreign body supports the theory that diffuse lamellar keratitis is an inflammatory reaction.