Lamellar Corneal Research Articles

Central corneal thickness in full-term Saudi newborns

To establish a standard of normal central corneal thickness (CCT) in normal full-term Saudi newborn. These values could be used as a reference in the early diagnosis and control of the fairly common primary congenital glaucoma in Saudi newborns. The CCT was measured in 100 normal full-term Saudi newborns (200 eyes) during the first 6 days of the postnatal period. All measurements were carried out by one investigator using ultrasonic pachymeter DGH-1000. The mean CCT of 200 eyes (right and left) was 616 ± 61 μm. The mean CCT of the right and left eyes was similar (CCTRE was 617 ± 62 μm, and mean CCTLE was 616 ± 60 μm), with no statistically significant difference (p = 0.417). The mean CCT for males was 631 ± 66 μm and for females 600 ± 50 μm. This difference was statistically significant (p = 0.01). The mean CCT decreases significantly by age [day-1: 626 ± 65 μm, day-2: 601 ± 48 μm and day-3: 574 ± 45 μm (p = 0.049)]. No correlations were found between CCT and gestational age, birth weight, birth length and head circumference. The average CCT in full-term Saudi newborns was found to be 616 ± 61 μm. The mean CCT in males was significantly higher than in females. There was no correlation between CCT and gestational age, birth weight, birth length and head circumference. There were borderline significant differences between CCT in 1-day-, 2-day-, and 3-day-old babies.

Decellularized Bovine Corneal Posterior Lamellae as Carrier Matrix for Cultivated Human Corneal Endothelial Cells

Purpose: To evaluate the potential of decellularized bovine corneas (DBCs) as a carrier matrix for cultivating and transplanting human corneal endothelial cells (HCECs).Methods: Posterior lamellae of ten bovine corneas were decellularized using ethylene diamin tetra-acetic acid (EDTA, 0.1%), aprotinin (10 KIU/mL) and 0.3% sodium dodecyl sulphate (SDS). Hematoxylin-eosin (HE) and 4,6-diamidino-2-phenylindole (DAPI) staining was done to confirm the absence of bovine cells. Quantitative analysis was performed to determine levels of desoxyribonucleic acid (DNA) using a DNA Purification Kit. HCECs were harvested from human donor eyes and seeded on the Descemet’s membrane of the DBCs. Cell morphology was assessed after 6 h of incubation, and at days 1, 4, 7, 10 and 14. Expression of zonula occludens-1 (ZO-1), connexin-43 (CX-43), Na+/K+-adenosine triphosphatase (Na+/K+-ATPase), natrium hydrogen carboanhydrase (Na+/HCO3−), collagen type VIII, collagen type IV and cytokeratin-3 (AE5) were analyzed by immunohistochemistry.Results: HE staining and DAPI staining showed that bovine cells were substantially removed from the stroma and Descemet’s membrane. A significant DNA reduction (mean before decelluraziation 365.3 ± 88.6 ng/mg, mean after decelluarization 23.2 ± 7.9 ng/mg, p < 0.001) was observed. HCECs formed a continuous, viable, predominantly polygonal monolayer with a mean cell density of 2380 ± 179 cells/mm2 on DBCs. Immunohistochemistry analysis demonstrated positive staining for AE5, collagen type VIII, ZO-1, CX-43, Na+/HCO3−, and Na+/K+-ATPase.Conclusions: Phenotypical properties of HCECs on DBCs imply that the HCEC sheets are capable of maintaining an intact barrier and ionic pump function in vitro. DBCs might, therefore, be a promising scaffold for ex vivo expansion of HCECs. This xenogeneic substrate might be used for therapy of isolated corneal endothelial diseases.

Cyclosporine Immunomodulation Retards Regeneration of Surgically Transected Corneal Nerves

To determine whether immunomodulation with cyclosporine (CsA) affects reinnervation after surgical transection of stromal nerves. Thy1-YFP+ neurofluorescent mice underwent lamellar corneal surgery and 3 days later, received artificial tears or CsA eye drops for 6 weeks. Serial in vivo wide-field stereofluorescent microscopy was performed to determine changes in nerve fiber density (NFD). Real-time quantitative PCR was performed to determine the expression of neurotrophins and cytokines (IL6 and TNF-α). Compartmental culture of trigeminal ganglion neurons was performed in Campenot devices to determine whether CsA directly affects neurite outgrowth. Yellow fluorescent protein (YFP)-positive cells significantly increased at 3 and 7 days after surgery. The number of YFP-positive cells in the cornea was significantly lower in the CsA group than that in the control group. The percentage increase in NFD between 2 to 6 weeks was greater in the control group (80% ± 10%, P = 0.05) than that in the CsA group (39% ± 21%). The CsA group also exhibited lower expression of IL6 and TNF-α (P = 0.01). In compartmental culture experiments, neurite outgrowth toward side compartments containing CsA was significantly less (2.29 ± 0.4 mm, P = 0.01) than that toward side compartments containing vehicle (3.97 ± 0.71 mm). Immunomodulation with CsA reduces the expression of cytokines (IL6) in the cornea and retards regenerative sprouting from transected corneal stromal nerve trunks. In addition, CsA has a direct growth inhibitory action on neurites as well.

Evaluation of interface quality in organ-cultured lamellar corneal transplants.

BackgroundWith increasing numbers of lamellar keratoplasties, eye banks are challenged to deliver precut lamellar donor tissue. In Europe, the most common technique of corneal storage is organ culture which requires a deswelling process before surgical processing. The aim of this study was to investigate the influence of different deswelling times on the cutting plane quality after microkeratome-assisted lamellar dissection.MethodsEight paired donor corneas (16 specimens) not suitable for transplantation were organ cultured under standard conditions at the Eye Bank of the Ludwig-Maximilians Universität, Munich, Germany. Pairs of corneal buttons were analyzed during the deswelling process in dextrane-containing medium. While one cornea was cut at an early time point during the deswelling process and put back into deswelling medium thereafter, the partner cornea was completely deswollen and dissected after 72 hours. Specimens were then further processed for scanning electron microscopy. Surface quality was assessed both digitally using Scanning Probe Imaging Processing software, and manually by three blinded graders.ResultsThe corneal buttons processed at the beginning of the deswelling process had a smoother surface when compared to the partner cornea that was cut at the end of the deswelling process. In our setting, no relevant difference was detectable between manual and automated microkeratome dissection.ConclusionFor lamellar keratoplasty, organ-cultured corneas should be processed at an early stage during the deswelling process. We interpret the smoother dissection plane during early deswelling as a result of mechanical properties in a highly hydrated cornea.

Use of the Femtosecond Laser for Cataract Surgery with Intraocular Lens Implantation

Femtosecond laser technology offers a promising approach to minimally invasive corneal surgery. Recently, femtosecond laser-assisted cataract surgery has been approved by the FDA. Femtosecond laser systems can create more precise and reproducible surgical incisions under computer control than with the conventional manual technique. Femtosecond laser-assisted cataract surgery may become a standard procedure for cataract surgery with intraocular lens implantation. *Corresponding author: Tatsuya Mimura, MD, Ph.D, Department of Ophthalmology, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655 Japan, Tel: +81 35800-5108; Fax: +81 33817-0798; E-mail: mimurat-tky@umin.ac.jp Received October 10, 2012; Accepted October 12, 2012; Published October 15, 2012 Citation: Mimura T, Yamazaki K (2012) Use of the Femtosecond Laser for Cataract Surgery with Intraocular Lens Implantation. J Transplant Technol Res 2:e116. doi:10.4172/2161-0991.1000e116 Copyright: © 2012 Mimura T, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Cataract is one of the major causes of preventable blindness in both developing and industrialized countries. Today most cataracts can be treated safely by modern surgical techniques involving phacoemulsification of the lens and intraocular lens (IOL) implantation. The management of cataract has changed considerably over the last few years with various improvements in surgical techniques, especially adoption of the femtosecond laser. This laser was first introduced for flap creation during laser in-situ keratomileusis (LASIK) [1-6]. Since then, the femtosecond laser has been used in a variety of procedures for corneal surgery, including predissection of corneal grafts for penetrating keratoplasty [7], anterior and posterior lamellar keratoplasty [8-12], and Descemet’s stripping automated endothelial keratoplasty. It has also been used for refractive surgery [13], including LASIK, limbal relaxing incisions, intrastromal ring segment implantation [14], and correction of presbyopia. Most recently, use of the femtosecond laser has been expanded to include cataract surgery [15]. The name femtosecond laser indicates the short duration of its laser pulses (1 femtosecond (fs) = 1 × 10−15 seconds). Other lasers used for ocular surgery, such as the argon (photocoagulation), excimer (photo ablation), and ND: YAG (photo disruption) lasers have a longer pulse time of 10-9 seconds. Several companies have developed femtosecond laser units for cataract surgery. These include the LenSx (Alcon, Fort Worth, TX), Optimedica Catalyst (Optimedica Corporation, Sant Clara, CA, USA), Technolas Workstation and IntraCor (Technolas Perfect Vision GmbH, Munich, Germany), and LensAR Laser System (LensAR Inc., Winter Park, FL). The femtosecond laser first received FDA approval for use in lamellar corneal surgery and additional approval for femtosecond laser-assisted cataract surgery was granted in 2010. Femtosecond laser systems can create precise and reproducible surgical incisions under computer control. The chief benefit of using a femtosecond laser for cataract surgery is that it replaces manual incision with a dedicated knife or forceps for creation of the initial corneal incisions, capsulotomy, and initial lens fragmentation. Successful intraocular use of the femtosecond laser for lens fiber disruption [16], treatment of presbyopia [17], and accommodation surgery [18] has been achieved in animal models. The first surgeon to report the performance of femtosecond laser-assisted cataract surgery in humans was Nagy in 2009 [19]. Since this initial report, many further reports and reviews of femtosecond laser-assisted cataract surgery have been published [20-41]. The first advantage of femtosecond-assisted cataract surgery is more precise capsulorrhexis and phacoemulsification at a lower power than with the conventional manual technique [19,41]. For accurate centration and fixation of advanced IOLs, including toric, multifocal, and accommodating IOLs, use of the femtosecond laser to achieve accurate capsulorhexis may be an effective option. A second advantage is that the femtosecond laser creates precise corneal incisions. Three-dimensional computer control of the corneal incision using a femtosecond laser may reduce the risk of endophthalmitis associated with manual self-sealing clear corneal incisions. The third advantage is that the femtosecond laser allows precise placement of limbal relaxing incisions, which are effective for reducing astigmatism after cataract surgery. The fourth advantage is that femtosecond laser light is not absorbed by the surrounding tissues, including the cornea, resulting in no risk of corneal damage. Despite all these positive aspects, the laser units are still relatively large and under development. Additionally, femtosecond laser machines equipped with a rotating Scheimpflug camera or optical coherence tomography incur additional costs for spare parts and annual maintenance, and are considerably more expensive compared with the current standard method of cataract surgery. Further investigation of postoperative complications such as endophthalmitis is also necessary. If these issues can be solved, femtosecond laser-assisted cataract surgery may become a standard procedure for treating cataract in the near future. Development of a femtosecond laser combined with a phacoemulsification unit is also expected.

Corneal Physiology and Responses to Cross-Linking and Intracorneal Rings in Keratoconus

ABSTRACT Keratoconus is a noninflammatory, usually, bilateral progressive disease. It is a pathology characterized by a progressive thinning and ectasia of the stroma that results in cone-shaped cornea. In advanced keratoconus with corneal opacities, keratoplasty, can be the only surgical alternative for a long time. Recently, new treatment alternatives were developed in keratoconus treatment, such as intracorneal ring segments and corneal cross- linking. Intracorneal ring segment acts as spacer elements between the bundles of corneal lamellae producing a shortening of the central arc length. Corneal cross-linking treatment increases the stiffness of the cornea. Several studies reported that collagen cross-linking can delay or stop keratoconus progression and produce better quality of vision. How to cite this article Kiliç A. Corneal Physiology and Responses to Cross-Linking and Intracorneal Rings in Keratoconus. Int J Keratoco Ectatic Corneal Dis 2012;1(1):1-6.

Endothelial Cell Density Before and After the Preparation of Corneal Lamellae for Descemet Membrane Endothelial Keratoplasty With a Stromal Rim

To assess the endothelial cell density before and after the preparation of precut posterior corneal lamellae for Descemet membrane (DM) endothelial keratoplasty with a stromal rim with the aim of standardizing this new technique and establishing the parameters of corneas intended for manual preparation under the conditions of an ocular tissue bank. Two groups of corneoscleral buttons were used to prepare lamellae consisting of a central zone of endothelium-DM surrounded by a supporting peripheral stromal rim. Group 1 contained 12 corneas with a live endothelial cell density (LECD) of 2500 cells per square millimeter or more. Group 2 contained 10 corneas with a density of 2500 cells per square millimeter or less. The preparation was performed manually using an artificial anterior chamber. The endothelial cell density (ECD) and the percentage of dead cells were assessed before and immediately after preparation and after 48 hours of organ culture storage at 31°C. Immediately after preparation, on average, 4.9% and 5.2% of dead cells were found in group 1 and group 2, respectively. After 48 hours of storage, the percentage decreased significantly in both the groups. There was no significant decrease in the ECD 48 hours after preparation in group 1; however, there was a significant decrease in group 2. The amount of tissue wasted during preparation was 24%. The decrease in ECD is dependent on the initial values: the cell loss is less in corneas with higher original densities. We suggest that the minimal acceptable LECD of lamellae should be 2500 cells per square millimeter.

Application of femtosecond laser in lenticular and therapeutic corneal surgery

Femtosecond laser represents the frontier technique in the field of refractive surgery,and its novel scanning mode is under investigation.It has transformed from simple refractive correction to multifield therapy for the advantages in accuracy and safety.Such technique has been employed in the treatment of keratoconus,penetrating and lamellar corneal transplantation,the completion of channel for intrastromal corneal ring segments implantation and achievement of collagen cross-linking.Femtosecond laser can achieve better outcomes in keratolimbal allograft and corneal biopsy for ocular surface reconstruction and histopathologic diagnosis.Also,femtosecond laser has been applied in the treatment of presbyopia and cataract.With improvement in related technique,femtosecond laser might be utilized more frequently in clinical practice.This paper focus on its novel application in therapeutic corneal surgeiries. Key words: Femtosecond laser; Cornea; Lens

A Prospective Study Comparing EndoGlide and Busin Glide Insertion Techniques in Descemet Stripping Endothelial Keratoplasty

To compare a new insertion method using an EndoGlide (Angiotech/Network Medical Products) with the standard Busin glide (Moria USA) assisted insertion of the posterior lamellar corneal graft in Descemet stripping endothelial keratoplasty (DSEK). Prospective, consecutive, comparative, nonrandomized study. Surgery was performed between October 2008 and October 2010 in 52 eyes of 52 consecutive patients with endothelial dysfunction suitable for DSEK. Twenty-two consecutive eyes underwent the new EndoGlide-assisted insertion of donor lenticule and 30 eyes underwent the surgery using the Busin glide. Six-month follow-up data are available for all patients. Clinical details, best-corrected visual acuity, manifest refraction, intraoperative and postoperative complications, and corneal endothelial cell loss were assessed at 6 months after DSEK. At 6 months after surgery, the best-corrected visual acuity was similar in both groups (0.13 logarithm of the minimal angle of resolution in the EndoGlide eyes as compared with 0.15 logarithm of the minimal angle of resolution in the Busin group; P = .34). Mean spherical equivalent was 0.65 diopter (D) and 0.51 D, and mean refractory cylinder was 1.39 D and 1.08 D, respectively (P = .40). The endothelial cell loss was much lower in the EndoGlide group (25.76%) as compared with the Busin group (47.46%; P < .0001). In conclusion, the new EndoGlide results in significantly less endothelial cell loss than Busin glide donor insertion in DSEK. The visual outcomes and refractive changes were similar in both groups.

Efficacy of Pig-to-Rhesus Lamellar Corneal Xenotransplantation

PURPOSE. To solve the shortage of donor corneas, a decellularizing method based on hypertonic saline treatment was introduced, and a favorable outcome was observed in pig-to-rabbit lamellar corneal transplantation. This study was an investigation of the efficacy of pig-to-nonhuman primate lamellar corneal transplantation, using both decellularized and fresh porcine corneas to assess feasibility as a substitute for human corneas. METHODS. Nine Chinese rhesus macaques underwent lamellar corneal transplantation using both decellularized (n = 5) and fresh (n = 4) porcine corneas. Clinically acceptable graft size (7.5 mm in diameter) and minimal immunosuppression based on topical and systemic corticosteroids were applied. Rejection signs, histology of porcine grafts, and serial changes in recipients' blood profile, including memory T-cell subset, anti-α-Gal and donor pig-specific antibodies, and complement were evaluated. Changes in aqueous complement concentration were also assessed at 4 weeks after transplantation. RESULTS. Of the decellularized porcine lamellar grafts, 80% remained transparent for more than 6 months, whereas half of the fresh porcine lamellar grafts developed chronic rejection. Rejected grafts showed extensive cellular infiltration, predominantly CD8(+) T lymphocytes and macrophages. Immunologic profiles of the recipients with rejected grafts showed a significant increase in the concentration of aqueous complement, an enhancement of memory T cells, and an abrupt increase in donor pig-specific antibodies. CONCLUSIONS. The findings suggested that decellularized porcine cornea could be a promising substitute for human corneal allograft. Fresh porcine cornea may be a feasible option for a substitute if combined with more potent immunosuppression or if obtained from transgenic pigs with complement-regulatory proteins.

Histopathological changes after deep anterior lamellar keratoplasty using the ‘big‐bubble technique’

During deep anterior lamellar keratoplasty (DALK), endothelium and Descemet's membrane are separated from the corneal stroma by intrastromal air injection ('big-bubble technique'). The aim of our study is to analyse histopathological changes in host corneal tissue caused by air insufflation in patients with keratoconus, their variability in 10 patients and their possible clinical implication. The excised anterior corneal lamellae of 10 patients with keratoconus having undergone DALK using the 'big-bubble technique' were analysed by light and transmission electron microscopy as well as immunohistochemistry. In addition, intrastromal air accumulations were quantified morphometrically. Intrastromal air was detected in all examined excised lamellae (8% of stromal volume), but with large variability (SD 8.8). It was detected preferentially in the inner layer of the corneal stroma and represented there up to 39% of the stromal volume. In addition, the air was predominantly located at one periphery of the excised lamellae. Intrastromal air bubbles were larger in the inner than in the superficial stromal layer and characterized by round shape and a CD68-negative collagenous 'pseudocapsule'. We detected no air-injection-induced alterations in Bowman's layer and epithelium. Our results show that 'big-bubble DALK' causes significant intrastromal air accumulations in the cornea. Pathologists should be conscious of this phenomenon and the high topographic variability. Intrastromal air in the recipient rim may be accompanied by a decrease in mechanical stability and could contribute to postoperative suture loosening.

Treatment of fungal keratitis by corneal iameilar resection combined with amniotic membrane tranplantion and conjunctival flap covering

Objective To evaluate the effect of corneal lamellar resection plus amiotic membrane (AM) transplantation combind with conjunctival flap covering for fungal keratitis. Methods The corneal lamella of focus was resected and covered with preserved or fresh amniotic membrane which was immersed in Fluconazole injection solution for half an hour and conjunctival flap. The AM and conjunctival flap were fixed up by suture. The conjunctival pedicle was snipped under surface anaesthesia and removed the suture after one motth. Results Keratitis of 19 eyes was controled, AM was totally or partly absorbed. Conjunctiva and cornea healed up when suture was removed. Following-up 6 months to 3 years, visual acuities of 8 eyes were CF ～ 0.1,11 eyes were 0.2 ～ 0.5. All of conjunctival flaps were translucent in healing up. Blood vessels were atrophic, and most hollows of corneal surface became shallow. Conclusions This measure is one of efficient ways for treatment of fungal keratitis. Key words: fungal keratitis; corneal lamellar resection; counjunctiva; anmiotic membrane; surgery

Evaluation of Corneal Epithelial Healing Under Contact Lens with Spectral-Domain Anterior Segment Optical Coherence Tomography (SDOCT)

Purpose:To describe a novel technique of using Spectral-domain (SD) anterior segment optical coherence tomography (SD-OCT) in the evaluation of corneal epithelial healing under a therapeutic contact lens (TCL) after lamellar keratoplasty and Epi-LASIK procedures.Design:Prospective, non-comparative, observational case series.Methods:Ten eyes of eight patients undergoing lamellar corneal transplantation and Epi-LASIK procedures at the Singapore National Eye Centre were included in the study. Ultra-high resolution SD-OCT scans of the cornea with a TCL in-situ were performed sequentially on the first, third and fifth day after procedure, with the RTVue (Optovue, Inc, Fremont, CA, USA), and the image findings were correlated with the clinical picture. Complete epithelial healing was verified with removal of TCL and fluorescein staining. Results:5 eyes underwent Descemet’s stripping automated endothelial keratoplasty (DSAEK), 1 eye underwent deep anterior lamellar keratoplasty (DALK) and 4 eyes underwent Epi-LASIK. All eyes had complete epithelial healing with TCL in-situ by the third post-operative day. SD-OCT images were able to demonstrate the epithelial layer distinctly under the TCL in all cases.Conclusions:SD-OCT is a valuable imaging tool for monitoring the progression of epithelial healing with TCL in situ in patients following corneal surgical procedures.

Effect of αGal on corneal xenotransplantation in a mouse model

It has been reported that hyperacute rejection (HAR) does not occur after pig-to-nonhuman corneal xenotransplantation. However, considering that immune privilege is already disrupted in most human corneal recipients, and the expression of αGal can be gradually reduced after pig-to-rat corneal transplantation, the long-term survival of corneal grafts from wild-type pigs cannot be guaranteed. Accordingly, we aimed to investigate the effect of αGal on the change in anti-Gal antibodies, using sensitized α1,3-galactosyltransferase gene-knockout (GTKO) mice recipients. C57BL/6 (B6) and GTKO mice were divided into 5 groups and underwent orthotopically full thickness cormeal transplantation as follows (n=4 for each group): (1) group 1: B6 to B6; (2) group 2: fresh porcine posterior corneal lamella to B6; (3) fresh porcine posterior corneal lamella to GTKO; (4) group 4: decellularized porcine posterior corneal lamella to GTKO, and (5) group 5: B6 to GTKO. Before transplantation, all GTKO recipients were sensitized using intraperitoneal injections of rabbit blood cells. Median survival times (MST) for the corneal grafts of the different groups were compared and plasma concentrations of IgG/IgM anti-Gal antibodies were evaluated at 1 week, 2 weeks and 3 weeks post-transplantation. There were no differences in MSTs between groups. Although there was no HAR of fresh porcine posterior corneal grafts even in sensitized GTKO recipients, αGal expression was induced in the transplanted fresh porcine corneal grafts and plasma concentration of IgG anti-Gal antibody was gradually increased in fresh porcine cornea-grafted GTKO recipients. On the contrary, αGal expression did not increase in the grafts and plasma concentration of anti-Gal antibodies did not change after transplantation using decellularized porcine corneas. Our findings suggest that αGal may affect the long-term survival of porcine corneal xenografts via antibody-mediated rejection, although αGal does not have an effect on acute rejection and decellularized porcine corneas may enable the long-term survival of porcine corneal xenografts.

Femtosecond Laser–Assisted Superficial Lamellar Keratectomy for the Treatment of Superficial Corneal Leukomas

To determine if superficial lamellar corneal excision with femtosecond laser followed by phototherapeutic keratectomy (PTK) using a masking substance improves visual acuity and optical quality of patients with severe corneal opacities. Twelve eyes with corneal haze or scarring underwent confocal microscopy to estimate the opacities' thickness and calculate the excision depth. Femtosecond laser was then used to create a superficial corneal flap. PTK and smoothening with masking substance (0.25% sodium hyaluronate) were done to improve corneal regularity and decrease corneal scarring. Follow-up was performed at 1, 6, and 12 months. Mean logarithm of the minimum angle of resolution of best spectacle-corrected visual acuity improved from 0.62 (mean decimal 0.26) to 0.30 (mean decimal 0.58) at 1 year (P = 0.035). Haze grades improved significantly. Coma-like aberration decreased postoperatively. Results showed that superficial corneal excision with femtosecond laser augmented with PTK laser smoothening assisted with 0.25% sodium hyaluronate improved visual acuity and could be considered as an alternative to more invasive procedures in patients with severe corneal opacities.

Advances in keratoconus treatment

Keratoconus is a noninflammatory, usually bilateral, progressive disease. It is a pathology characterized by a progressive thinning and ectasia of the stroma that results in a cone-shaped cornea. In advanced keratoconus with corneal opacities, keratoplasty was regarded as the only surgical alternative. Recently, new treatment alternatives were developed in keratoconus treatment, such as intracorneal ring segments and corneal crosslinking. Intracorneal ring segments act as spacer elements between the bundles of corneal lamellae, producing a shortening of the central arc length. Corneal crosslinking treatment increases the stiffness of the cornea. Several studies reported that collagen crosslinking can delay or stop keratoconus progression and produce a better quality of vision. A combination of crosslinking and intracorneal ring segments shows a positive, synergistic effect. Keratoconus is a disease of the corneal stroma and that usually presents itself in patients at an early age, thus the endothelial cell layer in eyes with keratoconus is young and almost healthy. Full-thickness penetrating keratoplasty has been a well-accepted surgical treatment for advanced keratoconus. Recently, great advances have been seen and new techniques of keratoplasty have been introduced in the treatment of keratoconus. These are mainly the lamellar keratoplasty techniques and the advanced shaped side-cut techniques, particularly with the use of femtosecond lasers.

Corneal Morphological Changes After Myopic Excimer Laser Refractive Surgery

To evaluate the changes in central corneal thickness (CCT) and corneal volume (CV) in eyes that have undergone myopic photorefractive keratectomy (PRK). CCT and CV obtained with an Oculus Pentacam before 1, 3, and 6 months after PRK were analyzed in 84 eyes with a mean preoperative refraction of -4.93 ± 2.23 diopter. The changes were compared with the amount of refractive treatment. The differences were evaluated with the Student t test and the correlations with the Pearson index. One month after PRK, CCT and CV mean differences were 73.2 ± 31.5 μm (P < 0.001) and 2.2 ± 1.7 mm (P < 0.001), respectively. Three months after PRK, CCT and CV mean differences were 66.6 ± 26.7 μm (P < 0.001) and 1.4 ± 1.3 mm (P < 0.001), respectively. Six months after PRK, CCT and CV mean differences were 65.3 ± 25.7 μm (P < 0.001) and 1.4 ± 1.3 mm (P < 0.001), respectively. The effective treatment at each follow-up point was correlated with CCT changes (R = 0.62, 0.71, and 0.73, respectively), but not with CV changes (R = 0.04, 0.04, and 0.01, respectively). Our findings support the hypothesis that after myopic PRK, when a series of corneal lamellae are severed centrally, the remaining peripheral segments relax. The squeezing force on the matrix is reduced, and the distance between the lamellae expands.

Comparison of immunogenicity and porcine-to-rhesus lamellar corneal xenografts survival between fresh preserved and dehydrated porcine corneas

To compare the immunogenicity of fresh preserved and dehydrated lamellar porcine corneas in porcine-to-mouse heterotopic transplantation and to investigate the survival of preserved porcine corneas as xenografts in porcine-to-rhesus lamellar corneal transplantation. Dehydrated and fresh preserved, endothelium deprived, porcine corneas were cut into fragments and grafted beneath the kidney capsule of BALB/c mice. Porcine-specific delayed type hypersensitivity (DTH) and antibody (IgM, IgG) immune responses of the recipient mice were assessed. In addition, fresh preserved and dehydrated porcine corneas were used in porcine-to-rhesus lamellar corneal xenotransplantation. The rhesus recipients were divided into three groups. Dehydrated corneas were applied to Group 1 and 3, and fresh preserved corneas were applied to Group 2. Only Group 3 received subconjunctival injections with triamcinolone acetonide for 1 month. All xenografts were evaluated by slit-lamp microscopy for 6 months. Two recipients in each group were examined by in vivo confocal microscopy and then killed for corneal histopathological staining 3 months after surgery. Neither fresh preserved nor dehydrated corneal fragments evoked any measurable change in mice recipient humoral immune status, but both could induce porcine-specific DTH at 1, 2, and 4 week after being grafted. However, the intensity of the DTH responses evoked by dehydrated corneas was lower than that evoked by fresh preserved corneas. In porcine-to-rhesus lamellar keratoplasty, with the exception one graft in Group 2 that developed characteristics of rejection, all the xenografts remained transparent or translucent up to 6 month after surgery. Histopathological examination of Group 1 showed that the infratemporal xenografts were much thicker and displayed some inflammatory cell infiltration in the peripheral portion of the graft and bed interface. However, in Group 3, which was treated with triamcinolone acetonide, there was an easily identified scar at the lamellar interface with no inflammatory cells present. In the rejected graft in Group 2, infiltrating cells included a few eosinophils and massive lymphocytes. Confocal microscopy examination showed that activated keratocytes localized in the anterior stroma and highly reflective tissue at the interface of the graft and bed. Porcine corneas might be an ideal source for clinical lamellar corneal xenotransplantation. In cases of tectonic lamellar transplantation, the possibility to use dehydrated pig material may become an option in the future.

UVA-light and Riboflavin-mediated Corneal Collagen Cross-linking

Keratoconus and other corneal conditions associated with progressive stromal thinning including keratectasia after laser-assisted in situ keratomileusis (LASIK) and pellucid marginal degeneration represent therapeutic challenges. Until recently, available therapies including contact lenses, epikeratoplasty, intrastromal corneal rings, and corneal transplantation targeted, in principle, the abnormal shape of the cornea by mechanical means. The underlying molecular pathogenic mechanisms of corneal ectasia were not addressed with any of these therapies until the introduction of corneal collagen cross-linking to clinical practice in 1999.1 This breakthrough clinical application was the result of multiple laboratory observations and discoveries made over preceding decades. Early experiments of Cannon and Foster2 showed that degraded normal collagen or synthesis of abnormal collagen might play a role in the pathogenesis of keratoconus. This concept was later confirmed by subsequent clinical and experimental studies. Keratoconus was characterized by progressive stromal thinning and ectasia3 as a result of increased expression of lysosomal and proteolytic enzymes4–7 and decreased concentration of protease inhibitors,5,8 which result in corneal thinning and altered configuration of corneal collagen lamellae.9,10

Simultaneous phacoemulsification, lens implantation and endothelial keratoplasty: Triple procedure

Simultaneous Descemet stripping endothelial keratoplasty, phacoemulsification, and intraocular lens implantation are indicated in Fuchs' dystrophy with associated cataract. Compared to the standard method of the triple procedure which includes penetrating keratoplasty, this new method has the advantages of sutureless surgery, small limbal incision, faster recovery, less surface problems, less astigmatism, stronger tensile strength and more predictable calculation of the intraocular lens power. This is the first report of such a combination of procedures in our literature. A 76-year-old woman suffered from a gradual bilateral visual loss. The best corrected visual acuity was 20/60 (right eye) and finger counting at 1m (left eye). Corneal thickness was 590 microm and 603 microm, respectively. A marked cornea guttata and nuclear cataract were present in both eyes. Phacoemulsification, lens implantation, and Descemet stripping were done in the left eye. The posterior lamellar corneal graft, 8.0 mm in diameter and about 150 microm thick, was bent and inserted through the limbal incision. The air was injected into the anterior chamber to attach the graft to the recipient stroma. The cornea remained clear, and the transplant was attached during a two-year follow-up. Visual acuity was 20/40 after two months, and 20/25 after one year. CONCLUSION. The new technique proved itself as a good choice for the treatment of a mild Fuchs' dystrophy associated with cataract.