Anterior Cornea Research Articles

Evaluation of Femtosecond Laser Clear Corneal Incision: An Experimental Study

To evaluate the changes of corneal topography following femtosecond laser and manual clear corneal incision (CCI). Inflation testing was performed in 14 human eye globes to evaluate the topographic response of the cornea to CCIs. In seven samples (femtosecond laser group), a 2.75-mm three-plane CCI was created using the iFS femtosecond laser (Abbott Medical Optics, Inc., Santa Ana, CA); the remaining seven samples (control group) received a 2.75-mm manual CCI using disposable angled knives. Topographic maps of the anterior and posterior cornea were acquired using a Scheimpflug topographer Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany). Keratometric data were used to analyze the curvature changes of the cornea. The changes of corneal astigmatism were analyzed by vector analysis. After CCI, the mean change of the anterior keratometric power was 0.04 ± 0.39 and 0.05 ± 0.51 diopters (D) (analysis of variance, P > .05) in the femtosecond laser and control groups, respectively. The mean change (P > .05) of the posterior corneal keratometric power was 0.16 ± 0.19 and 0.15 ± 0.18 D, respectively. The average change of the anterior and posterior corneal astigmatism vector magnitude was 0.17 D or less in both groups (P > .05). A slight against-the-rule astigmatic change of the anterior and posterior corneal interfaces was found after both CCI techniques. The 2.75-mm three-plane CCI created with femtosecond laser showed minimal changes of the anterior and posterior corneal topography, comparable with those of single-plane angled manual incision.

In Vivo Confocal Microscopy of Fuchs Endothelial Dystrophy Before and After Endothelial Keratoplasty

This study reveals significant changes of the anterior cornea in Fuchs endothelial dystrophy that probably affect the visual outcomes of endothelial keratoplasty for the disease. To determine whether abnormalities of corneal stromal and subepithelial cells in Fuchs endothelial dystrophy resolve after Descemet stripping endothelial keratoplasty (DSEK). Prospective observational study of 49 corneas of 42 patients with Fuchs dystrophy before DSEK and during 3 years of postoperative follow-up. None of the preoperative corneas were vascularized or had pronounced subepithelial fibrosis on results of slitlamp examination. Corneas were examined using in vivo confocal microscopy to determine stromal cell density and the presence of abnormal subepithelial cells (presumed fibroblasts). The cornea service at Mayo Clinic, Rochester, Minnesota. Forty-nine corneas of 42 patients. Descemet stripping endothelial keratoplasty. Stromal cell density and presence of subepithelial cells. Subnormal cell density in the most anterior 10% of the host stroma in Fuchs dystrophy before DSEK (mean [SD], 22 030 [6479] cells/mm(3) [n = 41]) remained unchanged at 2 (20 433 [4993] cells/mm(3) [n = 35]; P = .36) and 3 years (20 925 [5433] cells/mm(3) [n = 23]; P = .99) after DSEK. Abnormal subepithelial cells, which formed reticular networks deep to the basal epithelial cells, were visible in 33 eyes (67%) and remained present at 3 years after DSEK. Mean preoperative central corneal thicknesses when these subepithelial cells were and were not visible were 652 (45) and 668 (56) μm, respectively (P = .75). The reduced cellularity of the anterior stroma in Fuchs dystrophy does not recover 3 years after restoring endothelial function. Abnormal subepithelial cells, presumably fibroblasts, are present in most corneas with Fuchs dystrophy requiring DSEK, even in cases with mild edema and in the absence of clinically obvious preoperative subepithelial fibrosis. Anterior corneal structural abnormalities might be related to visual outcomes after DSEK.

Analysis of Age-Dependence of the Anterior and Posterior Cornea With Scheimpflug Imaging

To assess keratometric and higher-order aberrations of the anterior and posterior cornea and their age-related changes. This study investigated one healthy eye of 227 patients (mean age: 55.15 ± 21.2 years; range: 16 to 90 years; 135 right eyes, 92 left eyes). Images were captured from each eye with Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) using automatic mode. Keratometric, astigmatism data, and corneal higher-order aberrations were analyzed. With respect to laterality, no deviance was found in any of the parameters (P > .05). Mean refractive error was 0.52 ± 0.23 diopters. The level of astigmatism decreased significantly with advancing age for both the anterior and posterior corneal surfaces (P < .05). The overall root mean square of the higher-order aberration increased continuously with age (r = 0.517; P < .01), which can be explained by the combined effect of the increased in both the anterior and posterior corneal root mean square higher-order aberrations. Of the higher-order aberrations, the constant increase of the primary and secondary spherical aberration with aging (P < .01) is caused by the spherical aberration growth of the anterior surface. Apart from these, only the vertical coma aberration of the posterior surface and the vertical trefoil aberrations of both the anterior and posterior surfaces showed a significantly positive correlation with aging (P < .05). Corneal astigmatism showed a significant decrease with aging. Of the higher-order aberrations, primary and secondary spherical aberrations, vertical coma, and vertical trefoil significantly increase with age, whereas other higher-order aberrations show no correlation with aging.

The 3895-bp mitochondrial DNA deletion in the human eye: a potential involvement in corneal ageing and macular degeneration

In human skin, the 3895-bp deletion of mitochondrial DNA (mtDNA(3895)) is catalysed by ultraviolet (UV) light through the generation of reactive oxygen species. Given its function in vision, the human eye is exposed to oxidising UV and blue light in its anterior (cornea, iris) and posterior (retina) structures. In this study, we employed a highly sensitive quantitative PCR technique to determine mtDNA(3895) occurrence in human eye. Our analysis shows that the mtDNA(3895) is concentrated in both the cornea and the retina. Within the cornea, the highest mtDNA(3895) level is found in the stroma, the cellular layer conferring transparency and rigidity to the human cornea. Moreover, mtDNA(3895) accumulates with age in the stroma, suggesting a role of this deletion in corneal ageing. Within the retina, mtDNA(3895) is concentrated in the macular region of both the neural retina and the retinal pigment epithelium, supporting the hypothesis that this deletion is implicated in retinal pathologies such as age-related macular degenerescence. Taken together, our results imply that UV and blue light catalyse mtDNA(3895) induction in the human eye.

Corneal Confocal Microscopy Following Conventional, Transepithelial, and Accelerated Corneal Collagen Cross-linking Procedures for Keratoconus

To compare early corneal healing following conventional, transepithelial, and accelerated corneal collagen cross-linking (CXL) protocols. Twenty-four patients with progressive keratoconus were divided into three groups to receive conventional, transepithelial, or accelerated CXL. In vivo corneal confocal microscopy was performed on each patient preoperatively and at 1, 3, and 6 months postoperatively. Closure of the epithelial wound was complete 3 days following conventional and accelerated CXL. The subbasal nerve plexus was essentially obliterated immediately following conventional and accelerated CXL, and virtually no nerve fibers had regenerated by 6 months. The anterior stroma showed significant changes 1 month following conventional CXL; these changes were similar but more pronounced following accelerated CXL. Observed stromal changes included complete obliteration of keratocytes, increased tissue reflectivity, a honeycomb-like appearance, and circular lacunae. Some recovery of keratocyte density was noted after 6 months. These changes were less pronounced in the mid-stroma, and there were no apparent changes to the posterior stroma or endothelium. The cornea appeared to be unaltered following transepithelial CXL. In vivo corneal confocal microscopy analysis of the postoperative impact of CXL on the cornea revealed clear differences among conventional, accelerated, and transepithelial CXL protocols. Accelerated CXL had a greater impact than conventional CXL on the anterior cornea, whereas transepithelial CXL did not appear to alter corneal morphology.

Isolated Frontosphenoidal Synostosis

INTRODUCTION: Unilateral fusion of the coronal (frontoparietal) suture is the most common cause of synostotic frontal plagiocephaly. Frontal flattening can also arise from localized fusion of the frontosphenoidal suture, a rare and often misdiagnosed form of craniosynostosis. We present our institutional experience with this rare clinical entity to highlight the unique and often elusive phenotype. METHODS: A retrospective chart review of our craniofacial database was performed. All patients with isolated synostosis of the frontosphenoidal suture confirmed by computed tomography (CT) were included in our series. Demographic data, clinical and radiographic findings, and clinical course were documented. RESULTS: Three patients demonstrated synostotic frontal plagiocephaly caused by isolated frontosphenoidal synostosis. All patients were female and nonsyndromic. Mean age at presentation was 4.8 months (range, 2.0-9.8). Two patients had fusion of the right side. On initial presentation, patients exhibited normal head circumference with frontal flattening and supraorbital rim recession on the involved side. Additionally, two patients had anterior displacement of the ipsilateral ear. CT imaging was required to confirm the diagnosis in all patients and was done at a mean age of 5.4 months (range, 2.1-10.8). One patient underwent CT imaging at 2.1 months of age and all sutures were patent. Based on this finding, the patient was diagnosed with deformational plagiocephaly and underwent cranial molding helmet therapy with minimal improvement. Repeat CT at 10.7 months of age demonstrated a new fusion of the frontosphenoidal suture. All three patients underwent fronto-orbital correction at mean age of 12.1 months (range, 7.8-16.1). CONCLUSION: Isolated frontosphenoidal synostosis is a rare and oftentimes misdiagnosed cause of frontal plagiocephaly. This rare entity should be considered in any infant with frontal plagiocephaly presenting with orbital rim retrusion falling posterior to the anterior cornea, or that does not improve with growth.

Evaluation of corneal changes with accommodation in young and presbyopic populations using Pentacam High Resolution Scheimpflug system

To evaluate the changes occurring in the cornea with accommodation in young and presbyopic people. Prospective study. Twenty-three young and 15 presbyopic emmetropic volunteers. The Pentacam High Resolution system was used to obtain data on the anterior eye segments of emmetropic volunteers in unaccommodated (with an accommodation stimulus of 0.0 D) and accommodated (with an accommodation stimulus of 5.0 D for the young volunteers and 1.0 D for the presbyopic) states. Anterior and posterior corneal axial curvature, corneal volume, corneal aberration, anterior chamber depth and anterior chamber volume were evaluated. A significant decline in anterior chamber depth and anterior chamber volume was induced by accommodation in both young and presbyopic volunteers. There was a small but statistically significant change in corneal volume within 3.0, 5.0 and 7.0 mm diameters during accommodation in both groups. The changes in the corneal curvature map were significant with accommodation in both groups, although individual variations were found in anterior and posterior corneal axial curvature. Moreover, the decreased higher order aberrations were found in both anterior and entire cornea. In particular, spherical aberration was changed in the young group with 5.0 D accommodation stimulus. This study showed that accommodation can influence the corneal shape and curvature, and, especially, decreased corneal high-order aberrations. Although the modification in corneal shape was small, it produced variations in higher order aberrations with accommodation that may be beneficial for visual performance in near vision.

Dual versus single Scheimpflug camera for anterior segment analysis: Precision and agreement

To assess the repeatability, reproducibility, and agreement of the Pentacam HR single-camera and Galilei G2 dual-camera Scheimpflug devices in anterior segment analysis. Begitek Clínica Oftalmológica, San Sebastián, Spain. Prospective randomized observational study. Healthy young individuals had 3 consecutive tests by 2 examiners. Analyzed parameters were anterior and posterior cornea simulated keratometry (K), K flat, K steep, astigmatism magnitude and axis, J(0) and J(45) vectors, asphericity, total corneal higher-order wavefront aberrations (root mean square [RMS], coma, trefoil, spherical aberration), central cornea and thinnest-point thicknesses, and anterior chamber depth. Repeatability and reproducibility were evaluated by calculating the within-subject standard deviation (S(w)), some derived coefficients, and the intraclass correlation coefficient. Agreement was assessed with the Bland-Altman method. The single-camera device reproducibility (S(w)) was simulated K, 0.04 diopter (D); J(0), 0.03D; J(45), 0.04 D; total power, 0.04 D; spherical aberration, 0.02 μm; higher-order aberrations (HOAs), 0.02μm; central corneal thickness (CCT), 3.39 μm. The dual-camera device S(w) was simulated K, 0.07 D; J(0), 0.13 D; J(45), 0.04 D; total power, 0.08 D; spherical aberration, 0.02 μm; HOAs, 0.11 μm; CCT, 1.36 μm. Agreement was good for most parameters except total corneal power (mean difference 1.58 D ± 0.22 (SD) and HOA RMS (mean difference 0.48 ± 0.19 μm) (both P<.00). Repeatability and reproducibility were good for all parameters. The single-camera device was more precise for curvature, astigmatism, and corneal wavefront error measurements and the dual-camera device for pachymetry measurements. Agreement was good with some relevant exceptions. Dr. Aramberri is consultant to Costruzione Strumenti Oftalmici, Firenze, Italy. No other author has a financial or proprietary interest in any material or method mentioned.

Biocompatible of human acellular cornea matrix

AbstractPurpose The aim of this study was to construct a rabbit anterior cornea replacement with an acellular human cornea matrix (AHCM) as a scaffoldMethods Cornea was taken from the enucleated eye from patient with melanoma of choroidea. Before the decellularization process, human corneas were washed 3 times in sterile phosphate buffered saline. To remove the hereditary materials, the cornea discs were immersed in a Triton X 100 solution and Ammonium Hydroxide with a solvent/tissue mass ratio of 20:1 (vol./wt.). AHCMs were transplanted into the right corneas of 9 Chinchilla rabbits. The superficial corneas of the right eye of the rabbits were excised with a 6‐mm punch. AHCM lamellas (150 mm, 6 mm diameter) were made using a microkeratome. AHCM were transplanted and fixed with 10‐0 nylon into rabbit corneas. All rabbits received topical levofloxacin eye. The non‐operated, contralateral eye was used as a positive control. Follow‐up clinical examinations included slit‐lamp examination to assess corneal optical clarity, neo‐vascularization and degradation of grafts. After post‐operative 8 weeks, rabbits were euthanized respectively and the corneal specimens were examined by H&amp;E stainingResults After lamellar implantation of the AHCM, all animals survived without infections or other complications during the follow‐up period. The transplanted AHCM could be recognized in the rabbit corneas at 8 weeks after operation, with no neo‐vascularization and inflammation or any other rejection signs in or around the transplanted disks, as demonstrated by H&amp;E staining. H&amp;E staining showed that the implants were well integrated within the host corneas, with cells infiltrating the transplanted disks.Conclusion Acellular human cornea matrix has a good biocompatible properties after lamellar keratoplasty

Effect of Age on Components of Peripheral Ocular Aberrations

To investigate the effect of age on the contributions of the anterior cornea and internal components to ocular aberrations in the peripheral visual field. Ocular aberrations were measured in 10 young emmetropes and 7 older emmetropes using a modified commercial Hartmann-Shack aberrometer across 42° × 32° of central visual field. Anterior corneal aberrations were estimated from anterior corneal topography using theoretical ray-tracing. Internal aberrations were calculated by subtracting anterior corneal aberrations from ocular aberrations. Anterior corneal aberrations of young subjects were reasonably compensated by the internal aberrations, except for astigmatism for which the internal contribution was small out to the 21° field limit. The internal coma and spherical aberration of the older subjects were considerably smaller in magnitude than those of the young subjects such that the compensation for anterior corneal aberrations was poorer. This can be explained by age-related changes in the lens shape and refractive index distribution. Loss of balance between anterior cornea and internal components of higher order aberrations with increasing age, found previously for on-axis vision, applies also to the peripheral visual field.

Corneal Haze Determined by Confocal Microscopy 2 Years After Descemet Stripping With Endothelial Keratoplasty for Fuchs Corneal Dystrophy

To quantify corneal light scatter and its relationship to vision after Descemet stripping with endothelial keratoplasty (DSEK). Eyes with Fuchs corneal dystrophy were examined before and 1, 3, 6, 12, and 24 months after DSEK. Outcome measures were high- and low-contrast visual acuity, contrast sensitivity, and forward light scatter. Corneal reflectivity (backscatter), expressed in scatter units (SU), was quantified using in vivo confocal microscopy. Comparing 49 study eyes with 35 normal eyes, the mean (SD) corneal subepithelial layer was more reflective than normal before (2325 [613] vs 1208 [287] SU, P<.001) and through 24 months after DSEK (1760 [432] SU, P<.001). Interface reflectivity remained higher than in normal stroma through 24 months (1228 [287] vs 827 [188] SU, P<.001). At 1 year, forward light scatter correlated with subepithelial reflectivity (r=0.28, P=.01) but not interface reflectivity. Recipient age was correlated with improvement in subepithelial reflectivity at 12 months (r=–0.41, P=.01, 34 eyes) and 24 months (r=–0.36, P=.02, 26 eyes) after DSEK, and the improvement of subepithelial haze in eyes of participants aged 62 years or younger was correlated with improvement in forward light scatter at 12 months (r=0.52, P=.008) and 24 months (r=0.62, P=.004). In Fuchs corneal dystrophy, the corneal subepithelial region is a more important source of forward light scatter than the DSEK interface. Subepithelial haze improves more in younger patients and is associated with improvement in forward light scatter. Visual function after DSEK is affected by residual haze in the anterior host cornea more so than the surgical interface. Haze, which likely is experienced as glare disability, improves after surgical intervention but improves more in younger patients.

Wedge Resection and Lamellar Dissection for Pellucid Marginal Degeneration

To describe the use of crescentic corneal lamellar wedge resection and autolamellar dissection for the correction of pellucid marginal degeneration (PMD), and to assess its effectiveness in improving uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), astigmatism, corneal topography, and contact lens or spectacle tolerability. The setting was a specialist referral corneal surgery center, United Kingdom. A retrospective review was performed of all patients who underwent a corneal wedge resection for PMD at our institutions. All patients had progressive deterioration of BCVA, increased astigmatism, and intolerance to contact lens wear. The irregular corneal shape with ectasia was detected clinically and confirmed by Orbscan tomography. A crescentic wedge of ectatic corneal tissue was excised in each case, the extent of which was judged both clinically and by Orbscan. Complete host deep lamellar dissection (limbus to limbus) was performed in 3 cases and partial host lamellar dissection in 3 cases to enable closure by mobilizing the host anterior lamellar cornea. Mersilene 10-0 (Ethicon, Somerville, NJ) sutures were used and adjusted to achieve a 90-degree shift in the axis of astigmatism. Seven eyes of 6 patients had wedge resections performed by 1 surgeon (S.M.D.). The patients were followed for a mean of 10.7 months (SD, 9.2; range, 1-25 months). The eyes of patients with >1 month of follow-up had improved UCVA and BCVA. Four of 5 eyes of patients with >2 months of follow-up had a BCVA of 6/12 or better. Four patients were able to manage with improved visual acuity in spectacles, and 1 patient chose to wear contact lenses to achieve 6/7.5. One patient with only 6 months of follow-up had a UCVA of 6/7.5. The average reduction in keratometric cylinder for cases with >2 months of follow-up was 9.1 diopters (SD, 5.3; range, 3.1-16.3 diopters). Corneal wedge resection with and without lamellar dissection is an effective surgical intervention for corneal ectasia in PMD and avoids allogeneic transplantation by way of a large penetrating or lamellar keratoplasty. The technique has a low intraoperative complication rate and gives improved UCVA, BCVA, keratometric cylinder, and spectacle or contact lens tolerance.

Anti-Spoofing Method for Iris Recognition by Combining the Optical and Textural Features of Human Eye

In this paper, we propose a fake iris detection method that combines the optical and textural features of the human eye. To extract the optical features, we used dual Purkinje images that were generated on the anterior cornea and the posterior lens surfaces based on an analytic model of the human eye’s optical structure. To extract the textural features, we measured the amount of change in a given iris pattern (based on wavelet decomposition) with regard to the direction of illumination. This method performs the following two procedures over previous researches. First, in order to obtain the optical and textural features simultaneously, we used five illuminators. Second, in order to improve fake iris detection performance, we used a SVM (Support Vector Machine) to combine the optical and textural features. Through combining the features, problems of single feature based previous works could be solved. Experimental results showed that the EER (Equal Error Rate) was 0.133%.

Tomographic Corneal Profile Analysis of Central Toxic Keratopathy After LASIK

To describe a case of bilateral central toxic keratopathy (CTK) in a post-laser in situ keratomileusis-treated patient using tomographic methods for more than a 1-year follow-up. Case report and literature review. Tomographic analysis of a patient with bilateral CTK revealed flattening of the anterior cornea curvature and thinning at the level of anterior stromal bed, with minimal changes of the posterior curvature. A thin central flap was also noted on optical coherence tomography (OCT). Over the course of a year, the patient's hyperopic shift resolved with steepening of the anterior curvature and concomitant thickening of the flap and stromal bed. Using Scheimpflug imaging and Visante OCT, we demonstrated that the hyperopia that accompanies CTK is related to anterior corneal curvature changes. We also found that the majority of corneal tissue loss occurs at the anterior stromal bed mainly in the first postoperative week and is followed by a regeneration of tissue. A thin central flap was noted, and it is not clear whether this was created intraoperatively or resulted from the presence of CTK, requiring further study.

Refractive, Tomographic and Biomechanical Outcomes after Implantation of Ferrara ICRS in Keratoconus Patients

ABSTRACT Background Nowadays, ICRS are a step in the treatment of keratoconus. The purpose of this study was to evaluate the refractive effect and the tomographic and biomechanical parameters in keratoconus patients implanted with Ferrara ICRS, and their stability after 18 months. Materials and methods Twenty eyes of 20 keratoconus patients implanted with ICRS were evaluated. The average follow-up was 18 months. UDVA, CDVA, biomicroscopy, tomography (Pentacam) and biomechanics (ORA) of the cornea were evaluated before and after surgery. For the comparison of groups, the Wilcoxon test was used. Results The mean UDVA improved from 1.00 to 0.30 and the mean CDVA improved from 0.51 to 0.12; both were statistically significant (p = 0.0001). The average keratometry decreased from 50.7D to 47.5D (p = 0.0003), and the average astigmatism decreased from 5.5D to 3.5D (p = 0.0058). The mean CCT did not change significantly after surgery, but the mean TPP increased from 441.2 to 455.2 µm (p = 0.004). There was a significant reduction in the anterior cornea elevation, both the central (from 16.2-8.8; p = 0.0066) and the minimum (from–43.2 to −57.1; p = 0.0228). No significant change was found for posterior corneal elevation and for biomechanical parameters (hysteresis or CRF). Discussion There was a significant improvement of UDVA and CDVA after ICRS implantation, in keratoconic eyes. There was a significant and stable corneal flattening, and a decrease of the astigmatism. Corneal biomechanic parameters did not change. How to cite this article Salgado-Borges JM, Costa-Ferreira C, Monteiro M, Guilherme-Monteiro J, Torquetti L, Ferrara P, Ambrósio R Jr. Refractive, Tomographic and Biomechanical Outcomes after Implantation of Ferrara ICRS in Keratoconus Patients. Int J Keratoco Ectatic Corneal Dis 2012;1(1):16-21.

New Bi-Sign Aspheric IOL and Its Application

To present a bi-sign aspheric intraocular lens (IOL) and make theoretical comparisons with spherical and one-sign aspheric IOLs for retinal image quality in mesopic conditions and intermediate image capability in photopic conditions. Using ray-tracing in pseudophakic eye models, retinal image quality in terms of modulation transfer function was analyzed between the bi-sign aspheric and three types of one-sign aspheric IOLs and the spherical IOL for the range of corneal asphericities and different lens misalignments at 5 mm pupil diameter; comparison is made with the spherical IOL at defocus conditions characterized by negative refractive errors at 3 mm pupil diameter. Retinal image quality of the bi-sign aspheric lens was equal to or exceeded the one-sign aspheric and spherical IOLs in the majority of anterior cornea asphericities and lens misalignments within the spatial frequencies of 6 to 15 c/deg. Intermediate image capability of the bi-sign aspheric exceeded the spherical IOL. A new bi-sign aspheric lens produces regions of opposite spherical aberrations in the eye model with pupil diameters above 3 mm to balance out aberrations within the lens itself in addition to compensating corneal aberration as with a one-sign aspheric lens. This allows reduction in the variability of the retinal image quality at different anterior cornea asphericities and lens misalignments, when compared with a one-sign aspheric and spherical lens. The bi-sign aspheric produces positive longitudinal spherical aberration in the eye model within 3 mm pupil diameter that improves intermediate image capability when compared with the spherical IOL.

Decellularized Human Cornea for Reconstructing the Corneal Epithelium and Anterior Stroma

In this project, we strived to develop a decellularized human cornea to use as a scaffold for reconstructing the corneal epithelium and anterior stroma. Human cadaver corneas were decellularized by five different methods, including detergent- and nondetergent-based approaches. The success of each method on the removal of cells from the cornea was investigated. The structural integrity of decellularized corneas was compared with the native cornea by electron microscopy. The integrity of the basement membrane of the epithelium was analyzed by histology and by the expression of collagen type IV, laminin, and fibronectin. Finally, the ability of the decellularized corneas to support the growth of human corneal epithelial cells and fibroblasts was assessed in vitro. Corneas processed using Triton X-100, liquid nitrogen, and poly(ethylene glycol) resulted in incomplete removal of cellular material. Corneas processed with the use of sodium dodecyl sulfate (SDS) or with sodium chloride (NaCl) plus nucleases successfully removed all cellular material; however, only the NaCl plus nuclease treatment kept the epithelial basement membrane completely intact. Corneas processed with NaCl plus nuclease supported both fibroblast and epithelial cell growth in vitro, while corneas treated with SDS supported the growth of only fibroblasts and not epithelial cells. Decellularized human corneas provide a scaffold that can support the growth of corneal epithelial cells and stromal fibroblasts. This approach may be useful for reconstructing the anterior cornea and limbus using autologous cells.

Effect of preoperative duration of stromal edema in bullous keratopathy on early visual acuity after endothelial keratoplasty

To clarify the relationship between visual acuity after Descemet-stripping automated endothelial keratoplasty (DSAEK) and the preoperative duration of stromal edema. Yamaguchi University Hospital, Yamaguchi, Japan. Comparative case series. Patients who had DSAEK were divided into 2 groups based on whether the preoperative duration of stromal edema was less than 12 months (Group A) or more than 12 months (Group B). No patient had postoperative conditions that might have affected postoperative visual outcomes. Postoperatively, the corrected distance visual acuity (CDVA) was measured and the morphology of the anterior cornea evaluated by in vivo laser confocal microscopy. The postoperative CDVA in Group A ranged from 20/50 to 20/16 at 3 months and from 20/66 to 20/16 at 6 months; the maximum CDVA was 20/40 to 20/13. The postoperative CDVA in Group B ranged from 20/66 to 20/40 at 3 months and 6 months; the maximum CDVA was 20/66 to 20/33. The structure of the anterior cornea was normal in patients in Group A but was abnormal with fibroblastic cells in the anterior stroma in patients in Group B. Patients with a preoperative duration of stromal edema of more than 12 months had pathologic changes in the corneal stroma that may have adversely affected visual acuity after DSAEK. Given that stromal edema, including that associated with bullous keratopathy, has been proposed to be a progressive condition, DSAEK may be most effective when performed early after the onset of edema, before the occurrence of pathologic changes in the stroma.

Nonlinear Optical Macroscopic Assessment of 3-D Corneal Collagen Organization and Axial Biomechanics

To characterize and quantify the collagen fiber (lamellar) organization of human corneas in three dimensions by using nonlinear optical high-resolution macroscopy (NLO-HRMac) and to correlate these findings with mechanical data obtained by indentation testing of corneal flaps. Twelve corneas from 10 donors were studied. Vibratome sections, 200 μm thick, from five donor eyes were cut along the vertical meridian from limbus to limbus (arc length, 12 mm). Backscattered second harmonic-generated (SHG) NLO signals from these sections were collected as a series of overlapping 3-D images, which were concatenated to form a single 3-D mosaic (pixel resolution: 0.44 μm lateral, 2 μm axial). Collagen fiber intertwining was quantified by determining branching point density as a function of stromal depth. Mechanical testing was performed on corneal flaps from seven additional eyes. Corneas were cut into three layers (anterior, middle, and posterior) using a femtosecond surgical laser system and underwent indentation testing to determine the elastic modulus for each layer. The 3-D reconstructions revealed complex collagen fiber branching patterns in the anterior cornea, with fibers extending from the anterior limiting lamina (ALL, Bowman's layer), intertwining with deeper fibers and reinserting back to the ALL, forming bow spring-like structures. Measured branching-point density was four times higher in the anterior third of the cornea than in the posterior third and decreased logarithmically with increasing distance from the ALL. Indentation testing showed an eightfold increase in elastic modulus in the anterior stroma. The axial gradient in lamellar intertwining appears to be associated with an axial gradient in the effective elastic modulus of the cornea, suggesting that collagen fiber intertwining and formation of bow spring-like structures provide structural support similar to cross-beams in bridges and large-scale structures. Future studies are necessary to determine the role of radial and axial structural-mechanical heterogeneity in controlling corneal shape and in the development of keratoconus, astigmatism, and other refractive errors.

Hornhauttrübungen bei einer Kontaktlinsenträgerin mit hämodialysepflichtiger Niereninsuffizienz

A 53-year-old contact lens wearer on renal dialysis developed visual impairment due to corneal opacity. The opacity was of a crystalline type and diffusely scattered in the anterior cornea. As oxalosis was suspected ascorbic acid was immediately omitted from the dialysis treatment schedule. Within a few weeks the visual acuity recovered and the corneas became nearly clear. The cornea is an uncommon manifestation site for oxalosis. Nevertheless, one should be aware of this possible sign for oxalosis, which can be a life-threatening complication of treatment with high dose ascorbic acid.