Corneal Lenticule Research Articles

Cryopreservation of extracted corneal lenticules after small incision lenticule extraction for potential use in human subjects.

Purpose:To describe the technique of cryopreservation of corneal lenticules extracted after small incision refractive lenticule extraction (ReLEx SMILE) and initial results of femtosecond laser intrastromal lenticular implantation for hyperopia.Methods:Lenticules were collected from patients undergoing ReLEx SMILE for the correction of myopia and subjected to a tissue processing technique and cryopreservation. These lenticules were subsequently used to treat 8 hyperopic eyes and 1 aphakic eye. A femtosecond laser was used to create a pocket into each patient's cornea, followed by implantation of a cryopreserved lenticule. The patients were monitored through follow-up examinations for a mean 155.4 days (38–310 days).Results:The mean interval from storage of lenticules to removal from liquid nitrogen was 96 days (range, 19–178 days). Mean spherical equivalent of hyperopic eyes treated was +4.50 ± 1.1 diopter (D). Mean keratometry and pachymetry changed from preoperative 43.9 D and 531.6 μm to 47.4 D and 605.2 μm, respectively, postoperatively. Mean residual spherical equivalent for hyperopic eyes was +0.6 D and +4.1 D for the aphakic eye. None of the eyes showed evidence of rejection or loss of best-corrected visual acuity at the end of the follow-up period.Conclusions:The cryopreservation technique seems to be a safe method of long-term storage of refractive lenticules extracted after ReLEx SMILE for use in allogeneic human subjects. It may potentially be a safe and effective alternative to excimer laser ablation for hyperopia because of the low risks of regression, haze, flap-related complications, postoperative dry eye, and higher-order aberrations.Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: CTRI/2014/01/004331.

Changes in corneal deformation parameters after lenticule creation and extraction during small incision lenticule extraction (SMILE) procedure.

PurposeTo investigate the effects of lenticule creation and subsequent corneal lenticule extraction on corneal deformation parameters during small incision lenticule extraction (SMILE) procedure.Materials and MethodsIn this prospective study, 18 eyes of 10 patients (27.90±7.11 years, −5.64±2.45 diopters) scheduled for SMILE procedure were enrolled. Changes in the corneal deformation parameters, including deformation amplitude (DA), applanation time(AT1 and AT2), applanation length(AL1 and AL2), corneal velocity(CV1 and CV2), peak distance(P.Dist.), radius and intraocular pressure values were measured preoperatively, immediately after lenticule creation and subsequent to corneal lenticule extraction in all eyes with the Corvis Scheimpflug Technology (Corvis ST, OCULUS, Wetzlar, Germany). Repeated measures analysis of variance (ANOVA) with bonferroni-adjusted post hoc comparisons was performed to investigate changes following each step of the procedure.ResultsAll surgical procedures were uneventful. A significant difference was detected among the three time points (pre-operation, post-lenticule creation and post lenticule extraction) for AT1 (P<0.001), AT2 (P = 0.001), DA(P<0.001), and IOP(P = 0.002). Bonferroni-adjusted post hoc comparisons indicated that there was no significant change in AT1, AT2, DA, or IOP after lenticule creation (post hoc P>0.05), but there was a significant change in these parameters following subsequent corneal lenticule extraction (post hoc P<0.01), when compared to values obtained pre-operatively. The scheimpflug camera of the Corvis ST demonstrated the intralamellar small gas bubbles formed from the vaporisation of tissue after lenticule creation and a gray zone was observed between the cap and the residual stromal bed after lenticule extraction.ConclusionsThere is a significant change in corneal deformation parameters following SMILE procedure. The changes may be caused predominantly by stromal lenticule extraction, while lenticule creation with femtosecond laser may not have an obvious effect on corneal deformation properties.

Morphological analysis of corneal refractive lenticules--is there a correlation with refractive results?

ReLEx®flex is a corneal refractive procedure performed by removing corneal lenticules with a femtosecond (fs) laser system. Using electron microscopy, tissue parameters of extracted lenticules were analysed for potential correlations to the refractive results. Furthermore, the effect of previous contact lens (CL) wear on refractive stability (regression) was tested. 19 lenticules from 11 patients (age 24-56 years, 8 f, 3 m) were prepared for EM. The central areas of the samples were photographed and the distance between the collagen fibres and their diameters were digitally measured. ANOVA analysis was used to correlate postoperative refractional stability with time of preoperative CL use, fibre diameter and the coefficient of variation (CV) of fibre distance. 14 of 19 lenticules were from patients who had worn CL preoperatively. The cumulative duration of CL wear averaged around 31.2 ± 35.5 thousand hours. Preoperative CL use significantly influenced the postoperative regression: the longer time patients had worn CL, the greater was the regression towards myopia (p = 0.01). Additionally, the morphological parameters collagen fibre diameter (p = 0.09) and CV of fibre distance (p = 0.07) had an impact on regression. Prolonged CL use and alterations in ultrastructural patterns affected the refractive stability after ReLExflex. Although the pathophysiological relationships between CL use, corneal morphological parameters, and refractive stability are still poorly understood, these findings could potentially be used as prognostic markers for postoperative refraction after ReLExflex.

Lamellar corneal lenticule graft to treat keratolysis after AlphaCor keratoprosthesis implantation.

Clinical assessment of AlphaCor keratoprosthesis and evaluation of surgical method to treat keratolysis in case of stromal necrosis occurrence. This is a noncomparative, retrospective, interventional case series. The medical records of 12 eyes of 12 patients who underwent consecutive AlphaCor keratoprosthesis implantations were reviewed. Patients with severe bilateral corneal pathology unsuitable for a conventional corneal graft, a best-corrected visual acuity (BCVA) from light perception (LP) to 20/200, with no active ocular surface inflammation, controlled intraocular pressure prior to the surgery, and an unstimulated Schirmer test of &gt;2.5 mm at 5 minutes were included. Postoperative medications included topical dexamethasone, ciprofloxacin, and 2% cyclosporine A. Main outcome measures included BCVA and complications occurrence. After a mean follow-up of 25 ± 12.3 months (range 2-38 months), 8 (66.7%) AlphaCor devices were retained. Postoperative BCVA ranged from LP to 20/63 (mean gain of 2.5 ± 3.1 lines). Seven cases of stromal melt (58.3%) occurred. Three were reversed to penetrating keratoplasty and 3 had a donor corneal layer fixated over the AlphaCor with satisfactory results (mean follow-up 23 ± 1.6 months). There were no instances of endophthalmitis, retinal detachment, or glaucoma exacerbation. AlphaCor showed a low incidence of the classic keratoprosthesis complications but a high occurrence of recipient cornea necrosis. Corneal melts were successfully managed in 3 cases by lamellar corneal lenticule graft, thereby increasing the retention of AlphaCor and maintaining BCVA.

Preparing Uniform-Thickness Corneal Endothelial Grafts from Donor Tissues Using a Non-Amplified Femtosecond Laser

Corneal grafts for Descemet’s Stripping Automated Endothelial Keratoplasty are commonly prepared using mechanical microkeratomes. However, the cuts produced in such way render corneal lenticules that are thinner centrally than peripherally, thus inducing a hyperopic shift. Here we describe a novel device for preparing donor corneal grafts, in which a single low-energy femtosecond laser system is used as both a light source for optical coherence tomography and for cutting the graft illuminating from the endothelial side. The same laser is first utilized to obtain three-dimensional optical coherence tomography images of the donor tissue for guiding the dissection and obtaining grafts of uniform thickness with no applanation or contact. This device allows an optimal procedure for preparing consistently thin posterior grafts for transplantation.

Descemet-stripping automated endothelial keratoplasty donor tissue preparation using the double-pass microkeratome technique

To compare human donor corneal lenticule thickness, endothelial cell viability, area of cell damage, and cell counts between corneal tissue prepared with a double-pass microkeratome cut versus the standard single-pass microkeratome cut. University of Colorado Teaching Hospital, Aurora, Colorado, USA. Experimental study. Eleven matched pairs of human donor corneas unfit for transplantation were used for analysis. Tissue was prepared using a Moria CB microkeratome and artificial anterior chamber. One cornea was prepared using the standard single-pass cut; the second cornea was prepared with a double-pass technique. Visante optical coherence tomography images were obtained from each cornea, and central and peripheral thickness measurements were made. The tissue was also stained with trypan blue and alizarin red to assess tissue damage from preparation. The mean central thickness measurement was 92 μm ± 20 (SD) for the double-pass technique and 126 ± 34 μm for the single-pass technique. The area of cell damage after preparation was not significantly different between the 2 methods; however, there was a statistically significant increase in the ratio of nonviable to viable cells for the double-pass technique. The double-pass microkeratome technique for donor preparation resulted in a thinner lenticule than a single-pass technique and an increase in endothelial cell damage.

Effects of a Novel Push-through Technique Using the Implantable Collamer Lens Injector System for Graft Delivery during Endothelial Keratoplasty

PurposeTo investigate effects of a new push-through insertion method for donor lenticules using an injector system on endothelial viability ex vivo and in a clinical case series of endothelial keratoplasty.MethodsAn ex vivo delivery model was used with porcine corneoscleral rims. We compared the endothelial viability in a new push-through insertion method using the Visian Implantable Collamer Lens (ICL) injector versus that of standard forceps-assisted insertion for lenticule delivery. Twenty porcine corneal lenticules were divided into four groups by insertion method and wound size. Vital dye staining was performed and devitalized areas were semi-quantitatively assessed by digital imaging. In the clinical case series, Descemet's stripping endothelial keratoplasty (DSEK) using the push-through method was performed in seven patients and endothelial outcome was determined six months postoperatively.ResultsMean devitalized areas for the push-through method were significantly lower than for forceps-assisted insertion through 3.2 mm incision (23.99 ± 2.17% vs. 50.48 ± 5.07%, p = 0.009) in the ex vivo model. Average endothelial cell counts of donor tissues of patients who underwent DSEK were 26.4% lower six months postoperatively.ConclusionsPush-through delivery of donor lenticules using the Visian ICL injector system appears to be less harmful to endothelial cells than conventional forceps-assisted delivery.

Surface Quality of Femtosecond Dissected Posterior Human Corneal Stroma Investigated With Atomic Force Microscopy

To investigate and compare the surface roughness and morphology of posterior stromal lenticules created with a femtosecond laser using various pulse energies to that obtained with a mechanical microkeratome. A 150 kHz femtosecond laser platform (IntraLase iFS; Abbott Medical Optics) was programmed to create an 8.5-mm-diameter posterior stromal lenticule in 12 human corneal tissues. Specimens were dissected using different pulse energies (1.00, 0.75, 0.65, and 0.50) and fixed 2 μm spot separations. Three additional posterior corneal lenticules were prepared using a mechanical microkeratome (Moria Evolution 3; Moria). After the procedure, each corneal tissue was examined by atomic force microscopy (Autoprobe CP; Veeco). Femtosecond laser-treated tissues revealed similar morphological features, however, with significant differences in surface roughness in relation to the energy pulse used for lamellar dissection (P<0.001). The most regular stromal surface was achieved when using 0.50 μJ pulse energy; on the contrary, the roughest specimens were those dissected using 1.00 μJ pulse energy. No differences in surface roughness were measured between mechanically resected tissues and those treated using 0.50 μJ pulse energy (P>0.05). Atomic force microscopy submicron analysis of femtosecond-dissected donor tissues provided quantitative demonstration of the relation between pulse energy and stromal surface roughness. Surface quality of posterior corneal lenticules, comparable with that provided by mechanical microkeratome, is significantly improved when setting pulse energy for lamellar dissection of 0.50-μJ and 2-μm spot separations.

Femtosecond Laser Lenticule Transplantation in Rabbit Cornea: Experimental Study

To evaluate the feasibility of femtosecond laser-induced lenticule transplantation in the rabbit cornea and to observe the relative histologic characteristics of corneal tissue and nerve repair after transplantation. Eight healthy, purebred, New Zealand white rabbits underwent femtosecond laser small-incision lenticule extraction (SMILE) surgery in the right eye. Lenticules were inserted into a femtosecond laser-created corneal stromal pocket in the left eye, which was defined as femtosecond laser corneal lenticule transplantation. Postoperative observation and examination were completed to evaluate the surgery. In the early postoperative period, inflammation of the cornea was noted, tissue around the lenticule was edematous, and cells were activated. Tissue edema remained at postoperative day 10. By 1 month, edema had resolved, activated cells gradually became quiescent, and nerve fiber regeneration was observed. By 3 months, the lenticule integrated into the recipient cornea, extracellular matrix gradually cleared, and thicker nerve fibers were noted. By 6 months postoperative, morphology and distribution of the corneal stromal fibers were close to normal, and the number of nerve fibers was reduced. Femtosecond laser corneal lenticule transplantation in rabbits is feasible, as the lenticule was shown to thrive and integrate with the recipient stroma. Nerve regeneration begins after 1 month.

L’intervention combinée greffe-cataracte

Corneal pathologies leading to keratoplasty are often associated with cataract and combined surgery is therefore mandatory. Triple procedure with penetrating keratoplasty and concurrent cataract extraction followed by intra ocular lens (IOL) implantation is usually the preferential choice because visual rehabilitation is theoretically more rapid. Surgeons have to be aware of surgical conditions during open-sky surgery because vitreous pressure is not counterbalanced by anterior chamber pressure. Today, many surgeons prefer non-simultaneous procedures with cataract surgery performed months after grafting because of the improvement in spherical refractive error. More recently, new triple procedures, Descemet's stripping automated keratoplasty and concurrent cataract surgery have gained popularity, especially in patients with Fuchs dystrophy associated with cataract. Surgery starts with phacoemulsification, followed by endothelium exchange through a 3 to 5 mm incision. Advantages against classic triple procedure are quick visual rehabilitation, fewer induced refractive errors, minimal postoperative discomfort and corneal integrity. Surgeons have to consider an eventual postoperative hyperopic shift secondary to corneal lenticule shape when choosing adequate intraocular lens.

Comparison of decellularization methods for human corneal lenticules

AbstractPurpose Human or animal thin corneal lenticules (L) have been used as biological carrier to experimentally reconstitute tissue‐engineered grafts. Decellularization of the stroma proved to reduce immune rejection after allografts in animals. Aim: to assess different decellularization methods of human corneal L.Methods Stromal L were prepared with a Moria microkeratome on human organ cultured corneas mounted on an artificial anterior chamber. After desepithelialization, an anterior L was obtained with a 90 μm head and a posterior one with a 110 μm head. Four physical methods (sonification at 37 kHz for 45 minutes (min), 3 freeze/thaw cycles in liquid nitrogen, heating at 50°C for 60 min, and hypoxia) and four chemical methods (75% ethanol for 2x10 min, 0,1% sodium Dodecyl sulphate for 24 hours (h), 4M urea for 4h, and 29% NaCl for 24h) were tested. Efficiency and safety were assessed by determining: 1/mortality of the keratocytes using the Hoechst‐Ethidium‐Calcein triple labelling (Pipparelli, IOVS2011;52:6018), 2/alteration of the stroma using transparency measurement (analysis of modulation and contrast transfer functions), and collagen fibres analysis by transmitted electron microscopy (TEM), and 3/elimination of the cell debris using a staining of cell cytoplasm (Dioc 6) and TEM.Results 75% ethanol and hypoxia triggered complete keratocytes mortality with minimal alterations of the stroma. None of the methods eliminated dead cells debris. Combination with the sonification helped fragmenting cellsConclusion Two simple and rapid methods allow complete decellularization of human corneal L. The ability of these Lt to promote endothelial cells adhesion and proliferation is under investigation.

The Use of Precut, γ-Irradiated Corneal Lenticules in Boston Type 1 Keratoprosthesis Implantation

To report the use of a sterile, γ-irradiated corneal tissue without viable endothelium (VisionGraft Sterile Cornea; Tissue Banks International) in lieu of fresh donor cornea in Boston type 1 keratoprosthesis (KPro) implantation. Retrospective, interventional small case series. Eleven eyes of 11 patients underwent Boston type 1 keratoprosthesis implantation using VisionGraft Sterile Cornea between April 2009 and October 2010. Precut donut-shaped corneal lenticules, using femtosecond laser, measuring 8.5 mm in diameter with a 3-mm central hole were used. Surgical procedures were uneventful. Complete corneal re-epithelization was noted within 10 days in all cases. No complications related to the donor cornea (eg, stromal necrosis, wound leak, or device extrusion) occurred over an average follow-up of 16.5 months. VisionGraft Sterile Cornea eliminates the need for use of fresh donor corneal tissue for Boston type 1 keratoprosthesis procedures, which makes this procedure a viable sight-restoring option when donor corneal tissues are not readily available.

Femtosecond Laser Photodisruptive Effects on the Posterior Human Corneal Stroma Investigated with Atomic Force Microscopy

To analyze the effects of femtosecond laser pulses on the posterior human corneal stroma with atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM). A femtosecond laser (IntraLase iFS, Abbott, USA) was programmed to create a full posterior lamellar dissection in 9 human corneal tissues, using 3 different pulse energies (1.00 µJ, 0.75 µJ, and 0.50 µJ). Three corneal tissues were prepared in a similar fashion using a mechanical microkeratome (Moria Evolution 3, Moria, France). Six corneal tissues received an 8.00-mm diameter full cylindrical resection using either the femtosecond laser or the Barron trephine (Katena Products Inc., USA). The posterior corneal lenticules were first examined at AFM (Autoprobe CP, Veeco, USA). Both the posterior lenticules and the trephined corneal samples were scanned by ESEM (FEI Quanta 400, USA). Granules and crater-like features were observed on the stromal interface of all the laser dissected tissues, likely due to a secondary thermal effect of femtosecond laser dissection. Collagen fibers were seen only on samples treated with the 0.50 µJ pulse energy. Images of an even stromal surface were observed on the posterior stroma of mechanically dissected corneal samples. Mechanical and thermal effects, induced by femtosecond laser pulses on the human corneal stroma, were seen with AFM. Surface regularity of the photodisrupted stroma was inversely and non-linearly related to the pulse energy. The femtosecond laser provided high surface quality for lamellar resection of the posterior stroma comparable to those provided by mechanical devices.

Spontaneous Corneal Clearing after Descemet's Stripping without Endothelial Replacement

To report spontaneous corneal clearing with improved visual acuity and central endothelial cell repopulation after Descemet's stripping without endothelial replacement. Interventional case report. A 34-year-old woman with bilateral decreased vision secondary to corneal edema from endothelial dysfunction underwent Descemet's stripping endothelial keratoplasty (DSEK) in the right eye and Descemet's stripping only in the left eye. Histopathologic evaluation confirmed a dual diagnosis of Fuchs' endothelial dystrophy and posterior polymorphous membrane dystrophy from Descemet's membrane specimens removed from each eye. After primary graft failure with regraft in the right eye, the second posterior corneal lenticule detached and was removed and not replaced. The cornea cleared, and central endothelial cell repopulation was documented by confocal microscopy. Therefore, Descemet's stripping without endothelial replacement was performed in the left eye. The left cornea also cleared with central endothelial cell repopulation. Postoperative visual acuity and central endothelial cell repopulation. Endothelial migration after Descemet's stripping alone in the left eye, with probable host endothelial cell repopulation in the right eye. Endothelial cell migration after Descemet's stripping procedure without insertion of endothelial graft can occur, resulting from host endothelial cell repopulation with corneal clearing and improved visual acuity.

Simultaneous Descemet Stripping Automated Endothelial Keratoplasty and Aphakic Iris-Fixated Intraocular Lens Implantation: A Case Series

To report 3 cases of simultaneous Descemet stripping automated endothelial keratoplasty (DSAEK) and aphakic iris-fixated intraocular lens (IOL) implantation in patients with aphakia and bullous keratopathy. We retrospectively documented the clinical characteristics of patients before and after simultaneous DSAEK and aphakic iris-fixated IOL implantation undergoing operation between November 2008 and September 2009. None of the cases showed any intraoperative complications. During the postoperative period, the corneal lenticule was clear and well-attached, and the iris-fixated IOL was well-positioned. Simultaneous DSAEK and aphakic iris-fixated IOL implantation can be used successfully and simultaneously in patients with aphakia and bullous keratopathy.

Surface quality of human corneal lenticules after femtosecond laser surgery for myopia comparing different laser parameters

To determine the surface characteristics of human corneal lenticules after femtosecond laser surgery for myopia. The Carl Zeiss Meditec AG VisuMax® femtosecond laser system was used for refractive correction called Femtosecond Lenticule Extraction on 24 myopic eyes. The surface regularity on the refractive corneal lenticules recovered was evaluated by assessing scanning electron microscopy images using an established scoring system. Three different energy levels 150, 180, and 195 nJ were compared (n = 8 in each group). Surface irregularities were caused by tissue bridges, cavitation bubbles, or scratches. The surface regularity index (R(2) = 0.74) decreased as pulse energy increased. The average surface regularity score obtained was 7.5 for 150 nJ, 7.25 for 180 nJ, and 6.25 for 195 nJ. The human corneal lenticules created with the VisuMax® femtosecond laser system are of predictable, good-quality surface. This study shows the influence of pulse energy on surface regularity in human eyes. Further studies should focus on optimization of laser parameters as well as surgical technique to improve the regularity of the corneal stromal bed and so make the advantages of the femtosecond laser technology over conventional techniques clearer in the future.

Surface Quality of Porcine Corneal Lenticules after Femtosecond Lenticule Extraction

Purpose: To determine the surface characteristics of porcine corneal lenticules after Femtosecond Lenticule Extraction. Methods: The Carl Zeiss Meditec AG VisuMax® femtosecond laser system was used to create refractive corneal lenticules on 10 freshly isolated porcine eyes. The surface regularity on the corneal lenticules recovered was evaluated by assessing scanning electron microscopy images using an established scoring system. Results: All specimens yielded comparable score results of 5–7 points (SD = 0.59) per lenticule (score range minimum 4 to maximum 11 points). Surface irregularities were caused by tissue bridges, cavitation bubbles or scratches. Conclusion: The Femtosecond Lenticule Extraction procedure is capable of creating corneal lenticules of predictable surface quality. However, future studies should focus on the optimization of laser parameters as well as surgical technique to improve the regularity of the corneal stromal bed.

Candida Keratitis After Descemet Stripping and Automated Endothelial Keratoplasty

To report the donor-to-host transmission of Candida albicans after Descemet stripping and automated endothelial keratoplasty (DSAEK). An 80-year-old woman with pseudophakic bullous keratopathy developed an infiltrate in the donor corneal lenticule after DSAEK. Donor corneoscleral rim cultures grew C. albicans. Gram stain of the removed corneal lenticule demonstrated budding yeast and pseudohyphae, and cultures yielded C. albicans. Despite topical and systemic antifungal therapy and therapeutic penetrating keratoplasty, the patient developed a blind painful eye and underwent enucleation. This case report indicates that fungal keratitis may occur from donor-to-host transmission after DSAEK. The location of the infected tissue poses diagnostic and therapeutic challenges for the surgeon.

Changes in donor corneal lenticule thickness after Descemet’s stripping automated endothelial keratoplasty (DSAEK) with organ-cultured corneas

Aims:The aim of the study was to quantify changes in donor and host corneal tissue after Descemet’s stripping automated endothelial keratoplasty (DSAEK) using organ-cultured corneas and to correlate these findings...

Flipping the Inverted Donor Disk in Descemet Stripping Automated Endothelial Keratoplasty

We describe a technique we used to flip the donor corneal lenticule during Descemet stripping automated endothelial keratoplasty. In this case, in which we performed standard phacoemulsification and intraocular lens implantation as a combined procedure with Descemet stripping automated endothelial keratoplasty, the donor lenticule unfolded upside down in the anterior chamber (AC). To flip the donor to a stromal side up position with minimum manipulation, we first passed in a needle and fixed it on the edge of the lenticule. This needle was used to push the edge of the lenticule upward while we filled up the AC with balanced salt solution, directing the fluid to push the distal edge down and away. Having flipped the lenticule halfway, the procedure was continued by placing the needle on the midperipheral stroma of the donor lenticule and sliding it toward the recipient cornea. Then, the AC was filled with air to allow adhesion of the donor, and at the end of surgery, the air was replaced with balanced salt solution. The cornea cleared over a period of 10 days after surgery. At the end of the fourth postoperative week, the final best-corrected visual acuity was 20/50.