In Vivo Confocal Microscopy Findings in Bowman Layer Transplantation.

PURPOSE: To report the in vivo confocal microscopy (IVCM) findings of a case who underwent femtosecond laser-assisted Bowman layer transplantation (BLT). METHODS: This is a case report. RESULTS: In a 25-year-old man with previous diagnosis of keratoconus in whom a BLT was performed using the femtosecond laser-assisted technique, IVCM (Confoscan 4; Fortune Technologies, Vigonza, Italy) was performed 3 months after surgery, obtaining a sequence of 4 digitalized images of the total thickness of the cornea, from the epithelium to the endothelium, and then backward. The images were analyzed with the Navis v. 3.5.0. system (NIDEK, Multi-Instrument Diagnostic System, Japan). In the anterior stroma, before arriving to the graft interphase, activated keratocytes could be observed with higher reflectivity. In this first image of the anterior interphase, a homogenous hyporreflective image could be observed. In the interior of the graft, no keratocytes were found and some hyperreflective particles were present. In addition to the anterior, the posterior interphase presented bright particles. CONCLUSIONS: This is the first report that documents a BLT using IVCM.

Bowman Layer Onlay Graft for Reducing Fluctuation in Visual Acuity After Previous Radial Keratotomy.

PURPOSE: To describe the clinical outcome of a first patient undergoing Bowman layer (BL) transplantation with an onlay graft to reduce fluctuation in visual acuity and refractive error after previous radial keratotomy (RK) surgery. METHODS: In 2018, a 66-year-old woman presented with complaints of long-standing diurnal fluctuation in best-spectacle corrected visual acuity (BSCVA) after RK in 1983. After the removal of host epithelium, a BL graft was positioned onto the host cornea. BSCVA, Scheimpflug-based corneal tomography, and anterior segment optical coherence tomography were evaluated up to 12 months postoperatively. RESULTS: The surgery and postoperative course were uneventful. After surgery, the subjective complaints of visual fluctuation were reduced from 10 to 3 on a scale from 1 to 10. BSCVA (20/40; 0.5) did not change from preoperative to postoperative. Corneal tomography showed an overall central corneal steepening of 5.9 diopters. Biomicroscopy, Scheimpflug imaging, and anterior segment optical coherence tomography showed a completely epithelialized and well-integrated graft, with some minor epithelial remnants located in the preexisting keratotomy incisions. CONCLUSIONS: BL onlay grafting may have the potential to manage patients with subjective complaints of diurnal fluctuation in visual acuity after previous RK.

Bowman layer transplantation using a femtosecond laser.

We describe a variation of the original manual Bowman layer transplantation technique. After the isolation of the graft, a stromal pocket is created using a femtosecond laser. With the use of this technology, which entails preservation of the conjunctiva and the non-use of sutures, we avoid the scleral approach. The femtosecond laser proved to be a feasible surgical support of this technique.

New Surgical Modality for Management of Corneal Perforation Using Bowman Membrane.

PURPOSE: To describe a new surgical modality, "Bowman membrane tuck-in," for management of small to medium sized corneal perforation of a noninfectious etiology. METHODS: Two patients with corneal perforation of a noninfectious etiology and less than 4 mm in size underwent Bowman membrane tuck-in, a new surgical procedure. In this technique, Bowman membrane harvested from the donor cornea was tucked inside the stromal pocket of host tissue, which was prepared by 360-degree anterior stromal lamellar dissection. Patients were followed up for 6 months and were examined for best-corrected visual acuity, epithelialization time, anterior chamber stability, and graft-related complications. RESULTS: During 6-month follow-up, best-corrected visual acuity improved from PL+ (positive) to 20/120 and 20/200 in patient 1 and patient 2, respectively, and epithelialization was completed within a 2-week period in both patients. Surgery was uneventful in both cases; however, anterior chamber re-formation and graft repositioning were performed in patient 1. None of the patients showed signs of rejection or graft failure at 6-month follow-up. CONCLUSIONS: Bowman membrane tuck-in is an effective sutureless and glueless technique for management of corneal perforation of a noninfectious etiology, which may be used in emergency settings for the management of noninfectious corneal perforation of size less than 4 mm.

Direct measurement of anterior corneal curvature changes attributable to epithelial removal in keratoconus.

PURPOSE: To compare the tomography of the corneal epithelium and Bowman layer in eyes with moderate to severe keratoconus before and after epithelial debridement. SETTING: University hospital tertiary referral center. DESIGN: Prospective case series. METHODS: Dual-channel Scheimpflug combined with Placido-disk tomography was used to measure the corneal variables in eyes with keratoconus having corneal crosslinking immediately before and after epithelial debridement. The differences in pachymetry, axial keratometry, astigmatism magnitude, asphericity, total corneal power, and spherical aberrations were computed. RESULTS: The study comprised 30 eyes of 30 patients. After epithelial removal, the central (0.0 to 4.0 mm) and midperipheral (4.0 to 7.0 mm) corneal zones were significantly thinner mean (21 µm ± 14 [SD] and 35 ± 44 µm, respectively). The mean anterior axial flat keratometry (K) (+1.71 diopters [D]), steep K (+2.14 D), maximum K (+2.13 D), corneal astigmatism (+1.11 D), asphericity (-0.31), and total corneal power changes (+2.03 D) were significantly different after epithelial debridement. There were no significant changes in posterior corneal flat K or steep K, posterior corneal astigmatism, or posterior asphericity. There were no significant differences in the mean astigmatic axis (anterior or posterior corneal surface) or spherical aberration after epithelial debridement. CONCLUSIONS: In eyes with moderate to severe keratoconus, the tomography of Bowman layer was significantly steeper than that of the epithelium; thus, epithelial debridement increased the magnitude of anterior corneal keratometry, astigmatism, and prolateness. These data suggest that the corneal epithelium smooths the underlying Bowman layer irregularity in keratoconus.

Technical feasibility of isolated Bowman layer graft preparation by femtosecond laser: a pilot study.

PURPOSE: To evaluate the technical feasibility of isolated Bowman layer (BL) graft preparation by femtosecond laser (FSL) and to compare the ultrastructural morphology to manually dissected grafts. METHODS: Five whole globes were placed in custom-made eye holders and debrided of epithelium. After programming a dissection depth of 20 µm, the FSL was docked into position and 5 isolated BL grafts were created. From 5 additional globes, corneoscleral buttons were procured, mounted in artificial anterior chambers, and stripped of BL via the previously described manual technique. Three specimens from both series were randomly selected and assigned to transmission electron microscopy for ultrastructural evaluation and thickness measurements. RESULTS: All dissections were uneventful and 10 total grafts were produced: 5 by FSL and 5 by manual dissection. Mean graft thickness was 37 (±8.6) µm (n = 3) for the FSL group and 11.7 (±1.6) µm (n = 3) for the manually dissected group. Transmission electron microscopy revealed a thick but relatively smooth posterior cut edge in the FSL group, versus a virtually isolated BL with irregular rests of dispersed stroma in the manually dissected group. CONCLUSIONS: Femtosecond laser may have potential for harvesting intact BL and with a smooth posterior surface, but accompanied by variable amounts of anterior stroma owing to technical limitations.

Corneal Densitometry and Higher Order Aberrations After Bowman Layer Transplantation: 1-Year Results.

PURPOSE: To evaluate corneal densitometry and higher order aberrations (HOAs) up to 1 year after Bowman layer (BL) transplantation. METHODS: This was a retrospective study carried out at a tertiary referral center. Fifteen eyes of 14 patients who underwent BL transplantation for advanced keratoconus and had at least 1 year of follow-up were examined before BL transplantation and postoperatively at 1 day, 1 week, and 1, 3, 6, and 12 months. Corrected distance visual acuity (CDVA) with spectacles and contact lenses, anterior and posterior HOAs, and corneal densitometry were analyzed. RESULTS: One year after surgery, average logarithm of the minimum angle of resolution of spectacle-CDVA changed from 1.35 (±0.46) preoperatively to 0.96 (±0.32, P < 0.001), whereas average logarithm of the minimum angle of resolution of CDVA with contact lens remained stable after surgery (P = 0.126). Anterior and posterior HOA root mean square decreased from 3.08 ± 0.59 to 2.67 ± 0.71 µm and 7.32 ± 2.20 to 6.30 ± 2.18 µm, respectively (P < 0.05). Spherical aberration ((Equation is included in full-text article.)) improved on both anterior and posterior corneal surfaces (P < 0.001). After 1 year, corneal backscattering values showed an increase as compared with preoperative values mostly involving the central and posterior layers of the cornea, with a peak 1 month after surgery (P < 0.005 in zones 2-6 and 6-10 mm). No correlation between HOAs or corneal backscatter and CDVA was found. CONCLUSIONS: Corneal HOAs, especially spherical aberration, decreased for both anterior and posterior corneal surfaces after BL transplantation, whereas corneal backscattering increased, mostly in the central and posterior layers, where the graft has been placed. Changes in HOAs and corneal backscattering did not correlate with CDVA.

Development of the continuous curvilinear lenticulerrhexis technique for small incision lenticule extraction.

PURPOSE: To develop and evaluate the new continuous curvilinear lenticulerrhexis (CCL) technique for small incision lenticule extraction. METHODS: Thirty-one eyes of 20 patients with myopia were included in the study. The CCL technique for lenticule extraction was developed and used in 16 eyes of 10 patients (CCL group). The traditional technique of lenticule extraction was used in 15 eyes of 10 patients (traditional group). Uncorrected and corrected distance visual acuity, manifest refraction, lenticule quality, the duration of the extraction procedure, microdistorsions in Bowman's layer under optical coherence tomography (Optovue OCT; Optovue, Inc., Fremont, CA), and adverse events were evaluated at 1 day and 1 month postoperatively. RESULTS: At the first postoperative month, all eyes in both groups had an uncorrected distance visual acuity of 1.0 or better. The safety indices were 1.12 and 1.09 for the CCL and traditional groups, respectively. The efficacy indices were 1.06 and 1.09 for the CCL and traditional groups, respectively. All lenticules in the CCL group had intact, round margins, whereas one lenticule in the traditional group had a microdefect margin. There was no statistically significant difference in duration of lenticule extraction or microdistorsions in Bowman's layer. No eyes in the CCL group developed diffuse lamellar keratitis, as compared to one eye in the traditional group. CONCLUSIONS: The CCL technique exhibited excellent safety and efficacy for myopia correction, suggesting CCL is a promising technique that merits further development and study.

Midstromal isolated Bowman layer graft for reduction of advanced keratoconus: a technique to postpone penetrating or deep anterior lamellar keratoplasty.

Midstromal implant of an isolated Bowman layer graft is a new approach to reduce ectasia in eyes with advanced keratoconus. The procedure should postpone penetrating or deep anterior lamellar keratoplasty. Ten eyes of 9 patients with progressive, advanced keratoconus and contact lens intolerance underwent the procedure with no intraoperative adverse events. Throughout the study period, we observed no complications related to stromal dissection and/or the Bowman layer graft. Maximum corneal power decreased from a mean (SD) of 74.5 (7.1) diopters (D) before to 68.3 (5.6) D after surgery (P = .002). Hence, implant of an isolated Bowman layer graft may offer a safe and effective new technique to reduce ectasia in eyes with advanced keratoconus, potentially allowing continued long-term contact lens wear. The low risk of complications may render the procedure suitable as a treatment to postpone penetrating or deep anterior lamellar keratoplasty in cases with impending contact lens intolerance and/or corneal scarring (clinicaltrials.gov Identifier: NCT01686906).

Anterior segment optical coherence tomography-guided big-bubble technique.

PURPOSE: To evaluate the feasibility of intraoperative anterior segment (AS) optical coherence tomography (OCT) for quantification of the corneal depth reached with the dissecting cannula used for deep anterior lamellar keratoplasty, as well as its correlation with the success rate of big-bubble formation. DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: One hundred consecutive keratoconus patients. INTERVENTION: Deep anterior lamellar keratoplasty was performed using the big-bubble technique. During surgery, the cannula used for pneumatic dissection was inserted into the peripheral stroma and advanced as deep and far toward the center as believed adequate by the surgeon. Then, after retracting the cannula, AS OCT was performed. The cannula was placed back in position and creation of the big bubble was attempted. MAIN OUTCOME MEASURES: Stromal depth reached with the cannula tip, success rate in achieving big-bubble formation, and complication rate. RESULTS: Bubble formation was obtained in 70 of 100 eyes (70%). In all remaining eyes, the procedure was completed by manual deep lamellar dissection. The average depth reached by the cannula tip was 104.3±34.1 µm from the internal corneal surface; the mean value recorded in cases of successful big-bubble formation (90.4±27.7 µm) was statistically lower than that measured in failed procedures (136.7±24.2 µm). In 1 case, corneal perforation occurred during the insertion of the cannula and required conversion to penetrating keratoplasty (PK). In 8 eyes, small microperforations occurred during stromal excision but could be managed conservatively, avoiding conversion to PK. In 2 advanced cones, an incomplete bubble formation was obtained, necessitating manual peripheral stromal removal. CONCLUSIONS: Successful big-bubble formation can be anticipated if pneumatic dissection is attempted at a sufficiently deep level. Although an ideal depth could not be defined, AS OCT allows objective evaluation of the depth reached by the cannula tip used for pneumatic dissection. The AS OCT findings may confirm the decision to proceed with air injection. It is possible that cannula repositioning based on the AS OCT depth may improve the success rate for big-bubble formation.

Femtosecond sub-bowman keratomileusis: a prospective, long-term, intereye comparison of safety and outcomes of 90- versus 100-µm flaps.

PURPOSE: To analyze the long-term safety profile, visual and refractive results, and incidence of complications between sub-Bowman keratomileusis with 90- and 100-µm flaps. DESIGN: Prospective, randomized, comparative clinical study. METHOD: A total of 385 candidates (770 eyes) underwent bilateral, single-sitting, sub-Bowman keratomileusis, with flap creation (90 or 100 µm) on IntraLase 60-kHz (Abott Medical Optics) and ablation on Technolas 217z100 (Technolas PV) . Right and left eyes were randomized to undergo 90- or 100-µm flap procedures. Preoperative and postoperative assessment included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, and topographic analysis. All cases were followed up until 12 months after surgery. After excluding cases lost to follow-up, a final analysis of 368 patients was carried out (368 eyes in each of the 2 groups). The main outcome measures were BSCVA, UCVA, complication rates, and residual spherical equivalent refractive error. RESULTS: The mean preoperative values were: spherical equivalent, -6.08 ± 2.7 diopters (D; 90-µm group) and -5.99 ± 2.8 D (100-µm group; P = .7); and logarithm of the minimal angle of resolution BSCVA, 0.01 ± 0.03 (90-µm group) and 0.01 ± 0.04 (100-µm group: P = .8). Postoperative 12-month values were: spherical equivalent, -0.02 ± 0.4 D (90-µm group) and -0.01 ± 0.4 D (100-µm group; P = .8); logarithm of the minimal angle of resolution BSCVA, -0.05 ± 0.07 (90-µm group) and -0.04 ± 0.07 (100-µm group; P = .8); and logarithm of the minimal angle of resolution UCVA, 0.012 ± 0.01 (90-µm group) and 0.017 ± 0.02 (100-µm group; P = .2). No loss of BSCVA was seen in any case. The efficacy indices were 1.039 ± 0.21 (90-µm group) and 1.014 ± 0.24 (100-µm group; P = .2); safety indices were 1.163 ± 0.21 (90-µm group) and 1.158 ± 0.22 (100-µm group; P = .6); and vision difference indices were 0.09 ± 0.14 (90-µm group) and 0.10 ± 0.15 (100-µm group; P = .1). Both groups had a low but comparable incidence of diffuse lamellar keratitis and microstriae. However, the incidence of microstriae (although visually asymptomatic) was significantly higher in ablation with spherical equivalent of -9 D or more compared with lesser ablations (6.7% vs 0.8%; P < .001). CONCLUSIONS: The 1-year follow-up of femtosecond sub-Bowman keratomileusis with 90- and 100-µm flaps suggests that both the flap options have comparable outcomes.

The role of Bowman's layer in corneal regeneration after phototherapeutic keratectomy: a prospective study using in vivo confocal microscopy.

PURPOSE: To examine the role of Bowman's layer (BL) on the nature of anterior corneal regeneration after excimer laser phototherapeutic keratectomy (PTK). METHODS: A cohort of 13 patients underwent PTK to remove either 7 mum of BL for treatment of primary recurrent corneal erosions (RCE; six patients) or complete BL removal (15-mum ablation) to treat RCE or poor vision secondary to map-dot-fingerprint (MDF) dystrophy (seven patients). Clinical examinations and laser-scanning in vivo confocal microscopy (IVCM) were conducted before surgery and at a mean of 4 and 8 months after surgery. RESULTS: Total BL removal resulted in a significant decline in subbasal nerve density at 4 months (P = 0.007) that barely recovered to preoperative levels at 8 months (P = 0.055). With BL partially present, subbasal nerve density did not significantly change from preoperative levels. Superficial, wing, and basal epithelial cell density recovered to preoperative levels within 4 months after PTK, regardless of the presence of BL. Subepithelial keratocytes, however, were more densely distributed in corneas without BL relative to those with a partial BL present (P = 0.005), and increased anterior keratocyte reflectivity was noted in all eyes without BL and in no eye with a partial BL present. CONCLUSIONS: Subbasal nerve regeneration is delayed and subepithelial keratocyte density and reflectivity remain elevated up to 10 months after total BL removal by PTK. The results provide initial evidence for a possible role of BL in facilitating rapid stromal wound healing and an associated recovery of anterior corneal transparency and the restoration of epithelial innervation after epithelial trauma.

Predictive factors of femtosecond laser flap thickness measured by online optical coherence pachymetry subtraction in sub-Bowman keratomileusis.

PURPOSE: To evaluate possible factors responsible for the difference between predicted and measured parameters during 100 microm flap creation with a femtosecond laser (IntraLase FS30) using online optical coherence pachymetry (OCP). SETTING: AugenVersorgungsZentrum, Weilheim, and the Technical University of Munich, Munich, Germany. METHODS: In this nonrandomized prospective interventional case study, 287 eyes of 146 consecutive patients were monitored by online OCP before and after flap creation with the femtosecond laser. The laser-specific settings were held constant during the study to attempt a 100 microm flap in all eyes. A multiple linear regression model with backward variable selection procedure was applied to evaluate possible multivariable explanatory powers of several covariates. In addition, very thin and very thick flaps (ie, lower and upper quartiles of flap thickness distribution) were analyzed separately in a logistic regression model. RESULTS: Central flap thickness measured with online OCP subtraction varied according to a Gaussian distribution from 57 to 138 microm, with a mean of 100.4 microm +/- 13.6 (SD). Regression analysis between predicted and measured flap thickness showed no predictive power of 11 variables including the keratometry value of the cornea, preoperative corneal thickness, and patient age. CONCLUSION: The plano applanation interface of the IntraLase FS30 femtosecond laser produced ultrathin flaps for sub-Bowman keratomileusis that were independent of some preoperative and surgical factors known to affect outcomes with mechanical microkeratomes.

Cauterización de la membrana de Bowman y el injerto de membrana amniótica en la queratopatía bullosa dolorosa poscirugía de catarata / Cauterization of Bowman´s membrana and amniotic membrane graft in painful bullous keratopathy after cataract surgery

Introducción: La queratectomía con cauterización de la membrana de Bowman y el injerto de membrana amniótica son algunos de los tratamientos paliativos en pacientes con queratopatía bullosa dolorosa sin criterio de trasplante corneal. Describir los resultados de cada una de estas técnicas fue nuestro objetivo fundamental en este estudio. Métodos: Se realizó un estudio descriptivo con 34 pacientes con queratopatía bullosa dolorosa poscirugía de catarata. Se distribuyeron en dos grupos: queratectomía con cauterización de la membrana de Bowman y queratectomía con injerto de membrana amniótica con seguimiento por seis meses. Resultados: A los seis meses se mantenían sin bulas 64,7 y 41,2 por ciento de los casos con cauterización de la membrana de Bowman e injerto de membrana amniótica respectivamente. El incremento de la vascularización corneal fue mínimo para ambas técnicas quirúrgicas. Se logró el alivio de los síntomas en la primera semana de la cirugía para 82,4 por ciento en la cauterización de la membrana de Bowman y 94,1 por ciento en el injerto de membrana amniótica. A los seis meses de la cirugía se mantenían asintomáticos 88,2 y 70,6 por ciento de los casos con cauterización de la membrana de Bowman e injerto de membrana amniótica, respectivamente. La epitelización corneal se produjo antes de los 14 días en el 100 por ciento de los pacientes tratados con injerto de membrana amniótica y en el 94,1 por ciento de los pacientes con cauterización de la membrana de Bowman. Conclusiones: Ambas técnicas quirúrgicas fueron eficaces en el tratamiento a corto plazo de la queratopatía bullosa dolorosa poscirugía de catarata.

Introduction: Keratectomy with cauterization of Bowman´s membrane and the amniotic membrane graft are some of the palliative therapies to be applied in patients with painful bullous keratopathy without any criterion of corneal transplant. To describe the results of each technique was our fundamental objective in this study. Methods: A descriptive study of 34 patients with painful bullous keratopathy after cataract surgery was carried out. They were divided into two groups: one undergoing keratectomy with cauterization of Bowman´s membrane and the other amniotic membrane graft followed-up for six months. Results: After six months, 64.7 percent of cases with cauterization of Bowman´s membrane and 41.2 percent of those with amniotic membrane graft had no blebs. Increase of corneal vascularization as minimal for both techniques. The symptom relief in the first week of surgery was observed in 82.4 percent and 94.1 percent of cases respectively. After six months, the patients kept asymptomatic in 88.2 percent of cases with cauterized Bowman´s membrane and 70.6 percent of amniotic membrane grafts. Corneal epithelization occurred before 14 days of surgery in 100 percent of patients treated with graft and in 94.1 percent of cauterized cases. Conclusions: Both surgical techniques are effective in short-term treatment of painful bullous keratopathy after a cataract surgery.

Wavefront-guided excimer laser ablation using photorefractive keratectomy and sub-Bowman's keratomileusis: a contralateral eye study.

PURPOSE: To explain the basic science and clinical evidence that has led to the development of a new technique in corneal refractive surgery--sub-Bowman's keratomileusis (SBK). METHODS: A comprehensive review of the literature and report of a contralateral eye study of 50 patients (100 eyes) enrolled at 2 sites (25 patients per site) and randomized according to the dominant eye was conducted. All eyes underwent a wavefront-guided refractive correction using the Alcon LADARVision4000 System. In one eye, an 8.5-mm, ETOH-assisted photorefractive keratectomy (PRK) was performed. In the second eye, an 8.5-mm, 100-microm flap was attempted using a 60 kHz IntraLase FS femtosecond laser. Pre- and postoperative tests included best spectacle-corrected visual acuity, uncorrected visual acuity, corneal topography, wavefront aberrometry, retinal image quality, contrast sensitivity, and biomechanical response of the cornea. Patients completed subjective questionnaires at each follow-up. RESULTS: Clinical results demonstrate that SBK provides quicker visual recovery, although the data suggest that the 3- and 6-months results are similar in terms of visual outcomes. Reichert Ocular Response Analyzer results demonstrate that its impact on the cornea is similar to PRK. CONCLUSIONS: This study indicates that SBK provides the visual recovery of a LASIK procedure with the Optical Response Analyzer results similar to PRK.

Biomechanical and wound healing characteristics of corneas after excimer laser keratorefractive surgery: is there a difference between advanced surface ablation and sub-Bowman's keratomileusis?

PURPOSE: To describe the biomechanical and wound healing characteristics of corneas after excimer laser keratorefractive surgery. METHODS: Histologic, ultrastructural, and cohesive tensile strength evaluations were performed on 25 normal human corneal specimens, 206 uncomplicated LASIK specimens, 17 uncomplicated sub-Bowman's keratomileusis (SBK) specimens, 4 uncomplicated photorefractive keratectomy (PRK) specimens, 2 uncomplicated advanced surface ablation (ASA) specimens, 5 keratoconus specimens, 12 postoperative LASIK ectasia specimens, and 1 postoperative PRK ectasia specimen and compared to previously published studies. RESULTS: Histologic and ultrastructural studies of normal corneas showed significant differences in the direction of collagen fibrils and/or the degree of lamellar interweaving in Bowman's layer, the anterior third of the corneal stroma, the posterior two-thirds of the corneal stroma, and Descemet's membrane. Cohesive tensile strength testing directly supported these morphologic findings as the stronger, more rigid regions of the cornea were located anteriorly and peripherally. This suggests that PRK and ASA, and secondarily SBK, should be biomechanically safer than conventional LASIK with regard to risk for causing keratectasia after surgery. Because adult human corneal stromal wounds heal slowly and incompletely, all excimer laser keratorefractive surgical techniques still have some distinct disadvantages due to inadequate reparative wound healing. Despite reducing some of the risk for corneal haze compared to conventional PRK, ASA cases still can develop corneal haze or breakthrough haze from the hypercellular fibrotic stromal scarring. In contrast, similar to conventional LASIK, SBK still has the short- and long-term potential for interface wound complications from the hypocellular primitive stromal scar. CONCLUSIONS: Ophthalmic pathology and basic science research show that SBK and ASA are improvements in excimer laser keratorefractive surgery compared to conventional LASIK or PRK, particularly with regard to maintaining corneal biomechanics and perhaps moderately reducing the risk of corneal haze. However, most of the disadvantages caused by wound healing issues remain.

Complications of sub-Bowman's keratomileusis with a femtosecond laser in 3009 eyes.

PURPOSE: To assess the safety and complication rate of sub-Bowman's keratomileusis (SBK) in 3009 eyes. METHODS: The flaps were created using the IntraLase femtosecond laser, and excimer ablation was performed with the Bausch & Lomb H.Eye.Tech laser system. The complications of SBK were evaluated retrospectively. The types of complications were grouped into intra- and postoperative flap related. RESULTS: In 3009 SBK procedures, the total complication rate was 0.63%. Intra- and postoperative flap-related complication rates were 0.33% and 0.30%, respectively. Only 1 (0.033%) eye lost one line of best spectacle-corrected visual acuity from diffuse lamellar keratitis (DLK). Intraoperative complications included flap tear, free cap, bubble escape, and flap folds. Postoperative complications included DLK and epithelial ingrowth. Other flap-related complications such as uneven bed, buttonhole, short flap, flap striae, or wrinkles did not occur in this series. All intraoperative complications were managed within the same day. CONCLUSIONS: The complication rate of SBK is low. Vision loss is also rare.

Epi-LASIK using the Amadeus II microkeratome: evaluation of cut quality using light and electron microscopy.

PURPOSE: To investigate the cut quality and surface characteristics of the epithelial flap and underlying Bowman's membrane created by the Amadeus II (AMO) microkeratome on human corneas using light and electron microscopy. SETTING: Center for Refractive Therapy, Department of Ophthalmology, Ludwig-Maximilians University, Munich, Germany. METHODS: Using a 9.0 mm type II suction ring and settings, as recommended by the manufacturer, epithelial laser in situ keratomileusis (epi-LASIK) was performed in 2 fresh human eyes of 1 donor. Ocular pathology and previous ocular surgery were ruled out. Tissues for light microscopy were examined using hematoxylin-eosin and periodic acid-Schiff reaction staining. Further tissue samples were examined using scanning electron microscopy and transmission electron microscopy. RESULTS: Light microscopy showed a thoroughly separated epithelial sheet with no evident anatomical abnormalities. Stratification of the separated epithelium layer and cell shape was conserved. The cleavage plane was located at Bowman's membrane. Scanning electron microscopy showed a consistent transition from adherent epithelium to the denuded area. Bowman's layer showed a very smooth surface without remains of basal lamina. Transmission electron microscopy examination showed interruptions of the basement membrane at high magnification. CONCLUSIONS: This in vitro study found a high cut quality using the epi-LASIK separator of the Amadeus II microkeratome. The resulting cleavage plane at Bowman's membrane was well suited for the subsequent laser ablation.