Interface fluid associated with diffuse lamellar keratitis and epithelial ingrowth after laser in situ keratomileusis

Interface Corneal Edema Secondary to Steroid-induced Elevation of Intraocular Pressure Simulating Diffuse Lamellar Keratitis

PURPOSE

To describe interface corneal edema secondary to steroid-induced elevation of intraocular pressure (IOP) following LASIK.

METHODS

Retrospective observational case series. Diffuse interface edema secondary to steroid-induced elevation of IOP was observed after LASIK simulating diffuse lamellar keratitis (DLK) in 13 eyes. Mean patient age was 31.4 +/- 5.3 years. Patients were divided into two groups according to provisional misdiagnosis: DLK group (group 1) comprised 11 eyes and infection group (group 2) comprised 2 eyes (microbial keratitis). Mean follow-up was 8.1 +/- 0.5 weeks.

RESULTS

In the DLK group, typical diffuse haze was confined to the interface and extended to the visual axis, impairing vision in all eyes. Provisional diagnosis was late-onset DLK and topical steroids were started. Repeat examination showed elevated IOP as measured at the corneal center and periphery using applanation tonometry (mean 19.1 mmHg and 39.5 mmHg, respectively), causing interface edema with evident interface fluid pockets. Steroids were stopped and topical anti-glaucoma therapy was started. The interface edema decreased and at the end of follow-up the corneal transparency was restored and IOP dropped to normal values. The infection group demonstrated a microbial keratitis-like reaction and underwent flap lifting and interface wound debridement and biopsy with administration of fortified antibiotics and steroids. After elevated IOP was detected, steroids and antibiotics were stopped and topical anti-glaucoma therapy was started, resulting in the resolution of the interface edema.

CONCLUSIONS

Interface fluid syndrome secondary to steroid-induced elevation of IOP might develop in steroid responders after LASIK with a misleading clinical picture simulating DLK or infectious keratitis. Management includes stopping topical steroids and starting topical antiglaucoma therapy.

Imaging interface fluid after laser in situ keratomileusis with corneal optical coherence tomography

A 41-year-old myopic patient who had laser in situ keratomileusis 6 months earlier was treated for a complete retinal detachment (RD) with proliferative vitreoretinopathy. Surgical treatment consisted of an encircling band, pars plana vitrectomy, and silicone oil filling. Postoperatively, the patient developed marked corneal edema with no increase in intraocular pressure (IOP) as measured by applanation tonometry. Interface fluid was confirmed by corneal optical coherence tomography. Quantification of the corneal structures revealed that corneal edema was in the residual posterior stroma predominantly. The epithelial and flap thickness did not change significantly. The case demonstrated that after vitreoretinal surgery for RD repair, transient corneal endothelial cell dysfunction developed, causing marked edema of the posterior corneal stroma and interface fluid accumulation. However, an increase in IOP cannot be excluded.

Lamellar interface fluid accumulation following traumatic corneal perforation and laser in situ keratomileusis

A 41-year-old man with myopic astigmatism had laser in situ keratomileusis (LASIK) in each eye in April 2002. Ten months later, he sustained a central perforating corneal injury to the right eye. One day following repair of the corneal wound, he presented with diffuse corneal epithelial microcystic edema, lamellar interface fluid accumulation, and 20/400 visual acuity. Additional sutures were placed to close a presumed posterior wound gape with complete resolution of the corneal edema and lamellar interface fluid collection. One year later, his best corrected visual acuity measured 20/20+ in the right eye. This case is the first to document lamellar interface fluid accumulation following LASIK owing to traumatic disruption of the corneal endothelium.

Considerations of Glaucoma in Patients Undergoing Corneal Refractive Surgery

Glaucoma patients present a unique set of challenges to physicians performing corneal refractive surgery. Corneal thickness, which is modified during corneal refractive surgery, plays an important role in monitoring glaucoma patients because of its effect on the measured intraocular pressure. Patients undergo a transient but significant rise in intraocular pressure during the laser-assisted in situ keratomileusis (LASIK) procedure with risk of further optic nerve damage or retinal vein occlusion. Glaucoma patients with filtering blebs are also at risk of damage to the bleb by the suction ring. Steroids, typically used after refractive surgery, can increase intraocular pressure in steroid responders, which is more prevalent among glaucoma patients. Flap interface fluid after LASIK, causing an artificially low pressure reading and masking an elevated pressure has been reported. The refractive surgeon's awareness of these potential complications and challenges will better prepare them for proper management of glaucoma patients who request corneal refractive surgery.

The efficacy of hourly prophylactic steroids in diffuse lamellar keratitis epidemic

PURPOSE

To investigate the inciting agent, clinical features, and the efficacy of hourly steroids in the prophylaxis in a diffuse lamellar keratitis (DLK) epidemic.

METHODS

One hundred and five eyes of 58 patients that had DLK after LASIK were included in the study. To identify the cause of the epidemic, some interventions were made: irrigation solution was changed from BSS to Ringer lactate (week 5), wiping of the interface with a sponge was discontinued (week 6), the air conditioner in the LASIK room was checked (week 6), the routine postoperative topical regimen was changed from fluoromethalone and fluoroquinolones 4 times a day to hourly prednisolone acetate or dexamethasone sodium and fluoroquinolones (week 7), and the trademark of the drape used was changed (week 12).

RESULTS

There was no statistical difference in any of the attack rates associated with variables including BSS versus Ringer lactate (9.9 vs. 14%, p = 0.4), and air conditioner check with wiping versus not wiping the interface with the microsurgical sponge (14.0 vs. 18.2%, p = 0.6). There was a significant decrease in the attack rate from 18.2 to 5.3% with use of the hourly prophylactic topical steroids (p = 0.012). After introduction of a new trademark of the drape, the incidence of DLK was further reduced from 5.3 to 0.7% (p = 0.016).

CONCLUSION

The cause in a particular DLK epidemic should be identified and eliminated adopting a scientific approach. Hourly steroid use for prophylaxis is recommended until the etiologic agent responsible has been identified.

Refractive surgery in glaucoma

PURPOSE OF REVIEW

The purpose of this review is to discuss the topics relevant to the topic of LASIK in glaucoma patients or suspects. The safety of LASIK and the implications of LASIK on glaucoma diagnostic testing are reviewed.

RECENT FINDINGS

Most studies have found no change in the nerve fiber layer thickness or optic disc after LASIK. Several reports of steroid-induced glaucoma after LASIK have been published. Important new syndromes such as the interlamellar stromal cyst have been described. Most investigators, but not all, have found intraocular pressure to be lower after LASIK, most likely an artifact of measurement as a result of reduced central corneal thickness.

SUMMARY

The safety of LASIK in patients with glaucoma has not been proved. However, based on the published literature, LASIK may be a viable option for some glaucoma patients. Although not an absolute contraindication, glaucoma is a relative contraindication, and careful patient education and life-long follow-up is mandatory. The clinician must be ever mindful of the important effects that LASIK may have on diagnostic testing.

Pressure-Induced Interface Keratitis: A Late Complication Following LASIK

PURPOSE

Interface inflammation is a common complication of laser in situ keratomileusis (LASIK). The most well-described presentation is diffuse lamellar keratitis (DLK), which typically develops early after LASIK and responds quickly to topical steroids. In this report, we describe a novel presentation of interface inflammation that resembles DLK in appearance but presents late in the postoperative period, is associated with increased intraocular pressure, and is exacerbated by steroid treatment.

METHODS

A retrospective case series and chart review of all patients treated in our tertiary care private practice for late-onset interface inflammation associated with elevated intraocular pressure.

RESULTS

Ten eyes in 6 patients with late-onset interface inflammation and increased intraocular pressure were identified. At presentation, all patients were presumed to have classic DLK and were treated initially with aggressive topical steroids. Eight of the 10 eyes were receiving topical steroids at the time of presentation. The average time of presentation was 17 days after LASIK (range, 7-34). Elevated intraocular pressure was noted on average 28 days after presentation (range, 8-69). Lamellar inflammation was exacerbated by topical steroids. Resolution of the interface inflammation did not occur until intraocular pressure was controlled.

CONCLUSIONS

This case series describes a clinically distinct form of interface inflammation that presents late and is associated with elevated intraocular pressure. The lamellar inflammation was refractory to topical steroids and only resolved when pressure was controlled. These findings suggest that elevated intraocular pressure can contribute to interface inflammation. Postoperative assessment of intraocular pressure is essential in patients presenting with flap inflammation.

Characteristic clinical findings and visual outcomes

PURPOSE

To describe a potentially serious complication of laser in situ keratomileusis (LASIK) that can masquerade as a persistent epithelial defect.

SETTING

Refractive surgery centers in academic institutions.

METHODS

Charts of 4 eyes in which epithelial-defect-masquerade syndrome was diagnosed were reviewed to determine the time to diagnosis and the presence of associated features that may have contributed to the delay in diagnosis. Clinical findings and outcomes of medical and surgical intervention were recorded.

RESULTS

All eyes developed an epithelial defect involving the edge of the flap during surgery. The diagnosis of epithelial ingrowth was delayed because of the presence of stromal edema (n = 4), diffuse lamellar keratitis (n = 3), and contraction of the flap leading to gutter widening (n = 4). Epithelial ingrowth was diagnosed 5, 7, 15, and 60 days after LASIK. All eyes satisfied the following criteria: convexity of the peripheral epithelium at the edge of the flap associated with light reflections at the end of the flap, fluorescein pooling in the gutter, stromal edema, reduced best spectacle-corrected visual acuity (<20/60 in 3 eyes), and partial healing of the epithelial defect limited to the flap hinge. One eye developed stromal scarring and ulceration that required fortified antibiotics. Surgical repair included epithelial scraping after the flap was lifted and ironing followed by placement of a contact lens after surgery. The epithelial defect healed 5, 7, 21, and 24 days after surgery. The final uncorrected visual acuity ranged from 20/15 to 20/100.

CONCLUSIONS

Epithelial ingrowth following LASIK-associated epithelial defects may masquerade as stromal edema associated with a persistent epithelial defect. A high index of suspicion for epithelial ingrowth is essential to avoid a delayed diagnosis, which can result in irreversible visual loss due to stromal melting and infectious keratitis.

Interface Fluid After Laser in situ Keratomileusis

PURPOSE

To describe a case of interface fluid after laser in situ keratomileusis (LASIK) and review the literature on this rare complication after LASIK.

METHODS

We present a case report and literature review. Articles for this review were chosen from electronic database and manual literature searches. MEDLINE searches were made from 1990 to April 2002, using the key words "interface fluid" and "LASIK."

RESULTS

A 40-year-old man had uneventful LASIK for residual refractive error from previous penetrating keratoplasty in his right eye. Diffuse lamellar keratitis began 1 day postoperatively. Topical corticosteroids were administered. Six weeks after LASIK, a layer of interface fluid developed. Intraocular pressure was 9 mmHg when measured centrally by Goldmann applanation tonometry and 30 mmHg by Tono-pen tonometry. The interface fluid resolved with antiglaucoma agents and corticosteroids combined with cyclosporine.

CONCLUSIONS

This case, along with other reported cases, demonstrate the clinical features of interface fluid after LASIK.

Intraocular pressure-induced interlamellar keratitis after LASIK surgery

PURPOSE

To describe a case of interlamellar stromal keratitis induced by increased intraocular pressure (IOP) after LASIK surgery.

METHODS

Case report and review of the literature.

RESULTS

A 53-year-old white man with a history of treated ocular hypertension underwent uncomplicated LASIK surgery. The postoperative course was complicated by markedly elevated IOP induced by topical corticosteroid drops used to treat what appeared to be diffuse lamellar keratitis. Because IOPs remained uncontrolled despite maximal therapy, topical steroids were discontinued after a total of 9 weeks. The IOP rapidly returned to normal range with complete resolution of the corneal findings. Humphrey visual field analysis, confocal scanning laser imaging of the optic nerve, and stereoscopic disc photographs all demonstrated that significant glaucomatous field loss and optic atrophy developed over this 8-week period.

DISCUSSION

The IOP should be immediately evaluated in patients who present with interlamellar stromal keratitis more than 1 week after LASIK. If the IOP is elevated, corticosteroid drops should be discontinued to prevent permanent visual loss. Furthermore, if a glaucoma specialist examines a patient with a history of LASIK and unexplained visual field loss, the medical record should be reviewed to determine if the postoperative course was complicated by this diffuse lamellar keratitis-like phenomenon.

Mismatch between flap and stromal areas after laser in situ keratomileusis as source of flap striae

PURPOSE

To calculate theoretically the magnitude of the excess area between the lower surface of the flap and the underlying ablated stroma.

METHODS

On the initial assumptions of a nonextensible flap and a spherical cornea, flap and ablated stromal areas were determined as a function of myopic correction in the range of 0 to -12 diopters (D) for typical values of corneal radius (7.8 mm) and flap thickness (160 microm), together with a range of ablation zone diameters (4.0 mm, 6.0 mm, 8.0 mm, and 10.0 mm).

RESULTS

Excess flap area increases with the magnitude of the refractive correction and the diameter of the ablated zone. For a -6.0 D correction and an 8.0 mm ablation zone, the excess area is nominally about 1.0 mm(2), giving a potential overlap of the flap at the edge opposite the hinge of about 100 microm. CONCLUSIONS; Excess flap area may cause striae because of wrinkling. Although a nonextensible flap is assumed in the model, any stretching or contraction due to cutting the flap will be independent of the refractive correction. Hence, a mismatch in areas must still occur. This geometric effect may have clinical consequences in optical aberration, refractive regression, or impaired wound healing.

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.

Interface fungal infection after laser in situ keratomileusis presenting as diffuse lamellar keratitis. A clinicopathological report

PURPOSE

To report clinicopathological analyses of 3 cases of interface fungal infection following laser in situ keratomileusis (LASIK) and diffuse lamellar keratitis (DLK).

SETTING

Center for Research on Ocular Therapeutics and Biodevices and Arthur and Holly Magill Research Center for Vision Correction, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

Clinicopathological analysis of 5 eyes of 3 patients who developed culture-proven interface fungal infection after LASIK was performed. Detailed pathological analysis of the amputated flap from 1 case included light, scanning, and transmission electron microscopy.

RESULTS

Culture and pathological analysis revealed Candida albicans in all 3 cases. Common links among the cases were early onset of DLK following intensive corticosteroid and antibiotic treatment and later onset of interface fungal infection. All cases resolved, and good visual acuity was restored after medical treatment with antifungal agents.

CONCLUSIONS

Interface fungal infection after LASIK can be sight-threatening. Early lifting of the flap, fungal culture, and aggressive antifungal treatment are required to treat this complication and avoid deleterious sequelae.

Some possible longer-term ocular changes following excimer laser refractive surgery

While the short- and medium-term refractive and acuity results of excimer laser refractive surgery may now be generally satisfactory, the relatively brief history of the procedures involved (around 10 years or less) means that those concerned with eye care must remain vigilant to the possibility of longer-term problems. This paper reviews some relevant studies of potential post-surgical effects, including imperfect corneal healing and recovery of innervation, reduced corneal sensitivity and dry eye problems, changes in corneal rigidity leading to slow refractive change, possibly misleading reductions in measured intraocular pressure, and retinal and vitreous pathology.

Steroid-induced glaucoma after laser in situ keratomileusis associated with interface fluid

PURPOSE

To report the ocular manifestations and clinical course of eyes developing interface fluid after laser in situ keratomileusis (LASIK) surgery from a steroid-induced rise in intraocular pressure.

DESIGN

Retrospective, noncomparative interventional case series.

PARTICIPANTS/INTERVENTION

We examined six eyes of four patients who had diffuse lamellar keratitis develop after uneventful myopic LASIK surgery and were treated with topical corticosteroids. PRINCIPAL OUTCOME MEASURE: Slit-lamp findings, intraocular pressure measurements, and visual field loss.

RESULTS

All eyes had a pocket of fluid develop in the lamellar interface between the flap and the stromal bed associated with a corticosteroid-induced rise in intraocular pressure. However, because of the interface fluid, intraocular pressure was normal or low by central corneal Goldmann applanation tonometry in all eyes. The elevated intraocular pressure was diagnosed by peripheral measurement in several cases after months of elevated pressure. All six eyes had visual field defects develop. Three eyes of two patients had severe glaucomatous optic neuropathy and decreased visual acuity develop as a result of undiagnosed steroid-induced elevated intraocular pressure.

CONCLUSIONS

A steroid-induced rise in intraocular pressure after LASIK can cause transudation of aqueous fluid across the endothelium that collects in the flap interface. The interface fluid leads to inaccurately low central applanation tonometry measurements that obscure the diagnosis of steroid-induced glaucoma. Serious visual loss may result.

Treatment of interface keratitis with oral corticosteroids

PURPOSE

To describe the results of treating interface keratitis using a combination of intensive topical and oral corticosteroids.

SETTING

Casey Eye Institute, Portland, Oregon, USA.

METHODS

Thirteen eyes treated for grade 2 to 3 interface keratitis using an oral corticosteroid (prednisone 60 to 80 mg) as well as an hourly topical corticosteroid were retrospectively reviewed. The best corrected visual acuity (BCVA) was used as an objective guide of whether to treat with intense topical and oral corticosteroids, flap irrigation, or both. Predisposing factors such as intraoperative epithelial defects or a history of severe allergies or atopy were also looked for.

RESULTS

All 13 eyes responded favorably to the combination of intensive topical and oral corticosteroids and had a BCVA of 20/20 after the keratitis resolved. In 6 eyes (46%), the patients had a history of severe seasonal allergies. One day postoperatively, 3 eyes (23%) had an epithelial defect and 2 eyes (15%), lint particles or debris embedded in the interface. With oral corticosteroid use, 3 patients (23%) noted mild stomach irritation and 2 (15%) noted nervousness. All 5 side effects resolved without sequelae. No patient developed a serious side effect.

CONCLUSIONS

A short, intense course of an oral corticosteroid was an effective treatment in patients with grade 2 or higher interface keratitis when combined with a topical corticosteroid administered hourly. The BCVA is a helpful objective measure of the severity of interface keratitis and can be used to guide the clinician in the therapeutic strategy.

Role of instrument cleaning and maintenance in the development of diffuse lamellar keratitis

OBJECTIVE

To determine if instrument cleaning techniques affect the rate of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK).

DESIGN

Retrospective case series.

PARTICIPANTS

Two hundred ten eyes of 109 patients.

METHODS

A record review was performed of all patients who underwent LASIK at the Jules Stein Eye Institute from April 1 through June 24, 1999. During the first 6 weeks, the instruments used in LASIK surgery were cleaned according to our conventional protocol. At the end of this 6-week period, the cleaning protocol was modified and used for a subsequent 6-week period. For each eye during the two periods, the status of DLK on the first postoperative day was recorded.

MAIN OUTCOME MEASURES

Presence of DLK.

RESULTS

During the first 6-week period, 118 eyes of 60 patients underwent LASIK surgery. In the subsequent 6 weeks, 92 eyes of 49 patients underwent LASIK surgery. The two groups included patients with similar demographic background: gender, age, and target correction. Diffuse lamellar keratitis was present in 13 of 118 eyes (11%) using our conventional protocol. In only 2 of 92 eyes (2%) did DLK develop after the protocol was modified. Using the chi-square test, the difference between the two groups was statistically significant (P = 0.01).

CONCLUSIONS

Diffuse lamellar keratitis is a fairly uncommon phenomenon after LASIK surgery. Although the cause remains to be elucidated, these results demonstrated a reduced incidence of DLK associated with alteration of cleaning procedures and a decrease in stagnant instrument cleaning fluids. The authors recommend that refractive centers avoid the use of stagnant fluids in their instrument cleaning and sterilizing protocols to minimize the occurrence of DLK outbreaks.

Progression to end-stage glaucoma after laser in situ keratomileusis

We describe 2 patients, one a glaucoma suspect because of family history and the other with juvenile glaucoma. Both patients developed complications after laser in situ keratomileusis that required frequent topical steroids, leading to steroid-induced glaucoma. In both cases, corneal edema from the acute rise in intraocular pressure (IOP) caused inaccurate IOP measurement by standard methods. The inability to recognize glaucoma early may have resulted in significant irreversible vision loss.

Delayed diffuse lamellar keratitis after laser in situ keratomileusis

Two cases are reported of delayed diffuse lamellar keratitis after uneventful laser in situ keratomileusis. The first patient presented with an epithelial defect 6 weeks after laser in situ keratomileusis. Three days later the defect was healed but diffuse lamellar keratitis was noted. This was treated with topical dexamethasone and ketorolac with complete resolution of the diffuse lamellar keratitis over 3 weeks. The second patient presented with an epithelial defect and gross diffuse lamellar keratitis 10 weeks after laser in situ keratomileusis. Treatment was with topical dexamethasone and ciprofloxacin with gradual resolution of the diffuse lamellar keratitis. Common to both patients was a background of rosacea, implanted debris with no initial reaction, and epithelial defects leading to diffuse lamellar keratitis. It is suggested that these two cases represent epithelial defect associated corneal infiltration, which resembles classical diffuse lamellar keratitis with the spread of inflammatory cells through a path of least resistance.

Interface fluid after laser in situ keratomileusis

We report a case in which raised intraocular pressure (IOP) was associated with interface fluid after uneventful bilateral laser in situ keratomileusis (LASIK). The patient presented with diffuse lamellar keratitis in both eyes 3 weeks postoperatively that was treated aggressively with topical corticosteroids. A steroid-induced rise in IOP resulted in interface fluid accumulation and microcystic edema. Measurements with the Goldmann tonometer revealed an IOP of 3.0 mm Hg in both eyes. However, Schiotz tonometry recorded a pressure of 54.7 mm Hg in both eyes. Reduction in the dosage of topical corticosteroid and medical treatment of the raised IOP resulted in resolution of the microcystic edema and interface fluid accumulation. This case highlights the inaccuracies of IOP measurement after LASIK and the resulting complications.

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.

Ultrastructure of the lamellar corneal wound after laser in situ keratomileusis in human eye

A 30-year-old patient with keratoconus, a stable refraction, and normal central corneal thickness had laser in situ keratomileusis (LASIK). Six months later, she had uneventful penetrating keratoplasty for keratectasia. The lamellar LASIK interface could not be clearly identified by light microscopy. The corneal wound site did not stain for methyl metalloproteinase 1 or 2. Both the corneal flap undersurface and the stromal bed were devoid of interconnections and cells. Throughout the lamellar incision, including the laser-ablated zone, the surface was smooth on scanning electron microscopy. The collagen fibrils on both sides of the incision remained well aligned with one another, indicating good flap apposition. Under higher magnification transmission electron microscopy, some collagen fragments were found in the interface, especially adjacent to the hinge. The diameter of the collagen fibrils along the lamellar wound were identical to those farther from the incision. The absence of bridging collagen fibrils and cells between the flap undersurface and the stromal bed confirms the clinically known lack of wound repair at the interface and explains the easy separation of the flap from the stromal bed months after LASIK and the possible formation of an interface fluid pocket.

Diffuse lamellar keratitis: isolation of endotoxin and demonstration of the inflammatory potential in a rabbit laser in situ keratomileusis model

PURPOSE

To systematically examine sources of endotoxin contamination in eye centers as a potential cause of diffuse lamellar keratitis (DLK) and to demonstrate the inflammatory potential of endotoxin in a rabbit model of laser in situ keratomileusis (LASIK) surgery.

SETTING

University of Calgary, Calgary, Alberta, Canada.

METHODS

In this prospective study, all water sources that routinely come in contact with LASIK instruments, including sterilizer reservoirs, eyedrops, microkeratome blades, and cleaning solutions, were examined for endotoxins at 5 eye centers. Bacterial cultures were performed on water samples from 5 sterilizer reservoirs. A LASIK flap was created in 8 rabbit eyes using an Automated Corneal Shaper microkeratome (Bausch & Lomb). The flaps were reflected, and a dose of endotoxin at various concentrations was placed on the interface. After 1 minute, the flap was irrigated and repositioned. The rabbit eyes were examined daily with a slitlamp biomicroscope for 3 days for the development of DLK, which was classified on a scale from grade 1 to 4 (mild to severe). The rabbits were killed at the conclusion of the study, and the interfaces were stained to rule out infectious etiologies.

RESULTS

Endotoxin was detected in significant concentrations in tap water, filtered and distilled water, instrument washbasins, and sterilizer reservoirs at all 5 centers. The cultures of the water samples taken from the sterilizer reservoirs ranged from no growth to the presence of >100 colony-forming units of Flavobacterium and Pseudomonas aeruginosa. Endotoxins caused DLK-like interface inflammation in all eyes tested. Examination of stained scrapings showed no microorganisms in the interface of the rabbit eyes.

CONCLUSION

Endotoxin contamination was detected in water sources that routinely come in contact with LASIK instruments. Endotoxins were capable of inducing interface inflammation in a rabbit model and may therefore be a significant factor in epidemic DLK.

Interface Fluid and Diffuse Corneal Edema After Laser in situ Keratomileusis

PURPOSE

To report a new complication of interface fluid accumulation and corneal edema in an uneventful laser in situ keratomileusis (LASIK) procedure.

METHODS

Uncomplicated bilateral LASIK for myopia using the Hansatome microkeratome was performed. One day postoperatively, the patient noted decreased visual acuity. The topical corticosteroid was changed from dexamethasone to prednisolone acetate 1% every 2 hours. Two weeks later the patient reported worsening visual acuity in both eyes. Uncorrected visual acuity was 20/200 in the right eye and 20/100 in the left. Slit-lamp biomicroscopy indicated significant fluid build-up in the interface. Intraocular pressure (IOP) by Goldmann applanation tonometry was 15 mmHg in the right eye and 14 mmHg in the left.

RESULTS

After 4 weeks, intraocular pressure by bidigital pressure was increased and high. The corticosteroid was discontinued and antiglaucoma medication lowered the intraocular pressure, which resulted in corneal clearing and disappearence of interface fluid in both eyes.

CONCLUSIONS

Early recognition of this new complication of LASIK is necessary. The falsely low reading of IOP in the setting of interface fluid was the result of easy compressibility of the fluid-filled space and reflects the pressure of the interface fluid. This apparently low IOP reading can be an additional sign of the existence of interface fluid. The corticosteroid should be discontinued and antiglaucoma medication instituted. This should lead to a lowering of intraocular pressure and result in corneal clearing and disappearence of the interface fluid with improvement in visual acuity.

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.

Paradoxical hypotony after laser in situ keratomileusis

We present a case of paradoxically low (0 to 2 mm Hg) intraocular pressure (IOP) measured by Goldmann applanation and Tono-Pen tonometry in an eye with corticosteroid-induced high IOP after laser in situ keratomileusis. The patient complained of blurred vision and ocular pain in both eyes. The eyes were firm by palpation, and the IOP measured by Schiotz indentation tonometry was 38 mm Hg. An interface fluid pocket was identified by slitlamp examination, and the corneal surface became steeper. These findings resolved after flap relifting, interface irrigation, and addition of antiglaucoma medications. We postulate that the paradoxically low reading by applanation tonometry was due to fluid accumulation within the flap-bed interface. The applanation tonometry reflected the interface fluid pocket pressure rather than the real high IOP. An exceedingly low IOP should be verified by palpation or by Shiotz indentation tonometry, and interface fluid should be identified.

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.