Diseased Corneas Research Articles

Aldehyde Dehydrogenases Expression in Corneal Epithelial Cells with Limbal Stem Cell Deficiency.

Purpose: The purpose of the present study is to investigate the expression of aldehyde dehydrogenases (ALDHs) in rabbit corneas with limbal stem cell deficiency (LSCD) and corneas treated with cultured autologous oral mucosa epithelial cell sheet CAOMECS designed to reconstruct the ocular surface with LSCD. Methods: New Zealand white rabbit autologous oral mucosal epithelial cells were isolated from a buccal biopsy and cultured to be grafted back onto corneas of rabbit model of LSCD. Immunofluorescent staining and Western blot analysis were used to compare the expression of ALDH1A1 and ALDH1A3 in healthy, LSCD-diseased, CAOMECS treated corneas. Human oral mucosal and corneal epithelial cells (OMECS and CECs) were cultured and treated with retinoic acid (RA) to further investigate the expression of ALDHs. Results: In healthy corneas, ALDH1A1 and ALDH1A3 were markedly expressed in basal cells of corneal epithelium. In LSCD diseased corneas, ALDH1A1 and ALDH1A3 were markedly expressed in the conjunctivalized apical epithelial cells, the goblet cells, and the stroma. CAOMECS grafted corneas showed a decreased expression of ALDHs as compared to LSCD diseased corneas. Western blot analysis confirmed the up regulation of ALDH1A1 and ALDH1A3 expression in LSCD-diseased corneal epithelial cells. CAOMECS expressed low levels of ALDH1A1 and ALDH1A3, as compared to diseased CECs (D-CEC). When ALDH1A3 was up regulated by retinoic acid treatment in OMECS, Pax-6 expression was down regulated, suggesting a decrease in regenerative capacity when ALDH enzymes are up regulated. Conclusions: These findings report for the first time the up regulation of ALDH1A1 and ALDH1A3 in rabbit corneas with LSCD and document that CAOMECS grafting used to reconstruct corneal epithelium may reduce the expression levels of ALDH enzymes.

Immunohistochemical staining of immunoglobulin G in healthy equine, canine, and feline corneas.

ObjectiveEstablishing an immunohistochemical approach for semi‐quantitative assessment of the presence of immunoglobulin G (IgG) in equine, canine, and feline corneas.ProceduresHealthy corneas of horses, dogs, and cats, euthanized because of a fatal disease or an unrecoverable trauma unrelated to and without a history of ophthalmic disease were formalin‐fixed, paraffin‐embedded, and determined to be pathomorphologically healthy by light microscopy. Automated immunohistochemistry was performed using primary antibodies against IgG, biotin‐conjugated secondary antibodies, and streptavidin‐peroxidase, as well as diaminobenzidine for visualization. After counterstaining with hematoxylin, epithelium, stroma, Descemet´s membrane (DM), and endothelium were semi‐quantitatively scored for the presence of IgG on a 4‐grade scale (0 = no, 1 = faint, 2 = medium, 3 = strong staining) by light microscopy.ResultsCorneal specimens of 20 horses (40 eyes) with a median age of 15.5 years (range 2–31 years), 12 dogs (21 eyes) with a median age of 10.0 years (range 4–16), and 13 cats (24 eyes) with a median age of 10.0 years (range 2–18) were included in the study. Different sexes and breeds were represented. In all corneas (100%), significant medium signal intensity in the stroma was observed. Variable immunosignal was obtained in epithelium, DM, and endothelium.ConclusionThis method reproducibly allows for the detection of IgG in healthy equine, canine, and feline corneas, particularly stroma. Semi‐quantitative results evidence medium presence of IgG in the corneal stroma. Further research is needed to evaluate IgG presence in diseased corneas.

Acanthoamoeba Keratitis Induced by a Therapeutic, Soft Contact Lens: Diagnosis via Gram Staining

Purpose: We report two cases of <i>Acanthamoeba</i> keratitis diagnosed by Gram staining in patients who had recently worn therapeutic, soft contact lenses and had no history of lens use for visual correction.Case summary: The first patient was initially diagnosed with suspected mixed bacterial or fungal keratitis before a final diagnosis of <i>Acanthamoeba</i> keratitis was confirmed by Gram staining of a corneal smear. The second patient was initially diagnosed with a persistent epithelial defect caused by an earlier lid injury inflicted by a metallic foreign body, and then with a suspected mixed infection combined with herpetic uveitis. The patient was finally diagnosed with <i>Acanthamoeba</i> keratitis by Gram staining of a corneal smear. Both cases were treated with polyhexamethylene biguanide and chlorhexidine.Conclusions: Therapeutic, soft contact lenses are used to enhance corneal, epithelial wound healing in conjunction with antimicrobial prophylaxis. However, application of such a lens to a diseased cornea may predispose to the development of microbial keratitis caused by microorganisms resistant to the usual, prophylactic, antimicrobial eye drops. Therapeutic, soft contact lenses are associated with a risk of <i>Acanthamoeba</i> keratitis; early diagnosis is important. Gram staining of a corneal smear is useful in this context. <i>Acanthamoeba</i> is not eradicated by empirical broad-spectrum antimicrobials.

Osteo-Odonto keratoprosthesis: Tooth for an Eye

Face is the mirror of the mind and the eyes serves as a window to the soul. The sensory system is accountable for providing information to the brain regarding where the body appears in reference to the horizon. Poor vision may lead to loss of balance. Corneal disease is the second most common cause of blindness in the world and occurs in association with a severely damaged corneal and ocular surface. Osteo-Odonto Keratoprosthesis (OOKP) is a surgical procedure to restore vision where the diseased cornea is replaced with an artificial cornea. OOKP consists of autologous tissue derived from tooth and bone that surrounds a central PMMA Optic (Poly Methyl Methacrylate). This review discusses the types, parts, indications, contraindications, surgical techniques and complications of Osteo-Odonto Keratoprosthesis.

Inhibition of Aberrant α(1,2)-Fucosylation at Ocular Surface Ameliorates Dry Eye Disease.

Fucosylation is involved in a wide range of biological processes from cellular adhesion to immune regulation. Although the upregulation of fucosylated glycans was reported in diseased corneas, its implication in ocular surface disorders remains largely unknown. In this study, we analyzed the expression of a fucosylated glycan on the ocular surface in two mouse models of dry eye disease (DED), the NOD.B10.H2b mouse model and the environmental desiccating stress model. We furthermore investigated the effects of aberrant fucosylation inhibition on the ocular surface and DED. Results demonstrated that the level of type 2 H antigen, an α(1,2)-fucosylated glycan, was highly increased in the cornea and conjunctiva both in NOD.B10.H2b mice and in BALB/c mice subjected to desiccating stress. Inhibition of α(1,2)-fucosylation by 2-deoxy-D-galactose (2-D-gal) reduced corneal epithelial defects and increased tear production in both DED models. Moreover, 2-D-gal treatment suppressed the levels of inflammatory cytokines in the ocular surface and the percentages of IFN-γ+CD4+ cells in draining lymph nodes, whereas it did not affect the number of conjunctival goblet cells, the MUC5AC level or the meibomian gland area. Together, the findings indicate that aberrant fucosylation underlies the pathogenesis of DED and may be a novel target for DED therapy.

Morphological characterization of the human corneal epithelium by in vivo confocal laser scanning microscopy.

Regarding the growing interest and importance of understanding the cellular changes of the cornea in diseases, a quantitative cellular characterization of the epithelium is becoming increasingly important. Towards this, the latest research offers considerable improvements in imaging of the cornea by confocal laser scanning microscopy (CLSM). This study presents a pipeline to generate normative morphological data of epithelial cell layers of healthy human corneas. 3D in vivo CLSM was performed on the eyes of volunteers (n=25) with a Heidelberg Retina Tomograph II equipped with an in-house modified version of the Rostock Cornea Module implementing two dedicated piezo actuators and a concave contact cap. Image data were acquired with nearly isotropic voxel resolution. After image registration, stacks of en-face sections were used to generate full-thickness volume data sets of the epithelium. Beyond that, an image analysis algorithm quantified en-face sections of epithelial cells regarding the depth-dependent mean of cell density, area, diameter, aggregation (Clark and Evans index of aggregation), neighbor count and polygonality. Imaging and cell segmentation were successfully performed in all subjects. Thereby intermediated cells were efficiently recognized by the segmentation algorithm while efficiency for superficial and basal cells was reduced. Morphological parameters showed an increased mean cell density, decreased mean cell area and mean diameter from anterior to posterior (5,197.02 to 8,190.39 cells/mm2; 160.51 to 90.29 µm2; 15.9 to 12.3 µm respectively). Aggregation gradually increased from anterior to posterior ranging from 1.45 to 1.53. Average neighbor count increased from 5.50 to a maximum of 5.66 followed by a gradual decrease to 5.45 within the normalized depth from anterior to posterior. Polygonality gradually decreased ranging from 4.93 to 4.64 sides of cells. The neighbor count and polygonality parameters exhibited profound depth-dependent changes. This in vivo study demonstrates the successful implementation of a CLSM-based imaging pipeline for cellular characterization of the human corneal epithelium. The dedicated hardware in combination with an adapted image registration method to correct the remaining motion-induced image distortions followed by a dedicated algorithm to calculate characteristic quantities of different epithelial cell layers enabled the generation of normative data. Further significant effort is necessary to improve the algorithm for superficial and basal cell segmentation.

Identification of presumed corneal neuromas and microneuromas using laser-scanning in vivo confocal microscopy: a systematic review

Background/aimsThis systematic review critically evaluated peer-reviewed publications describing morphological features consistent with, or using terms related to, a ‘neuroma’ or ‘microneuroma’ in the human cornea using laser-scanning in vivo confocal...

A clinical study on indications and demography for penetrating keratoplasty in northwest Rajasthan

Background: Penetrating keratoplasty (PK) is a surgical procedure where a diseased cornea is replaced by donated corneal tissue which has been removed from a recently deceased individual having no known diseases. Objectives: The objectives of the study were to assess the indications and demographic profile of patients undergoing PK. Materials and Methods: In this retrospective cross-sectional non-interventional hospital-based clinical analysis study, hospital records of patients who had undergone for PK surgery at PBM Eye Hospital, S.P. Medical College, Bikaner, Rajasthan, from 1991 to 2020 were reviewed for demographic data (age, sex, age at presentation, etc.), indications for PK, treatment history and comorbid conditions. A total of 387 patients were included in this study. Results: The most common age group for PK was 61–70 years (22.23%) followed by 51–60 years (21.05%) and 41–50 years (15.48%). About 65.96% patients were male, 30.87% patients were female, and 3.17% patients were children (

Corneal Distortion and Corneal Morphological Parameters in Naïve Eyes Analyzed with a Scheimpflug Camera

Background: The study of the corneal biomechanical properties (CBP) is gaining always more interest, thanks to the applications to refractive surgery and to the overall management of several corneal diseases.
 Purpose: To analyze the eventual relationships between corneal distortion and morphologic features in healthy subjects.
 Methods: one eye of one hundred and fifty-two healthy participants, 87 women and 65 men, aging from 23 to 65 years old, were evaluated in this study. Every eye underwent a complete clinical examination, that included also a tomographic scan using Pentacam HR (Oculus, Wetzlar, Germany) and a biomechanical evaluation using Corvis ST (Oculus, Wetzlar, Germany). Linear regressions among refractive defect, corneal volume (CV), anterior corneal curvature and central corneal thickness (CCT) vs corneal biomechanical features provided by Corvis ST have been ran using SPSS software version 18.0.
 Results: Corneal distortion factors showed a low correlation both with corneal morphological parameters and with refractive defect. No significant correlations (p> 0.01) were found among morphologic and biomechanical features evaluated.
 Discussion: results observed in this study could help in recognize the healthy range of values of CBP parameters provided by CST. This information could be very useful in many ophthalmology topics such as the accurate IOP measurement, the early diagnosis of corneal degenerations, such as keratoconous, and the screening of subject undergoing refractive surgery.
 Conclusions: even if data of this study need to be confirmed in further ones with larger populations, results here observed suggest that Corvis ST is a device providing an evaluation of corneal distortion not influenced by morphological corneal factors. This information could help in better screening and managing the diseased corneas.

A study on outcome of penetrating keratoplasty in various types of corneal pathologies

Introduction: Penetrating keratoplasty involves surgical removal of diseased or damaged cornea from the host and replacement with a full thickness donor cornea. The major goals of penetrating keratoplasty are to improve visual acuity, to maintain the integrity of the eye and to treat various infection or neoplastic conditions. Depending on the location of the corneal abnormality, it may be sufficient to replace the anterior corneal layers (anterior lamellar keratoplasty) or the posterior corneal stroma and endothelium (posterior lamellar keratoplasty or descements stripping endothelial keratoplasty or descements stripping endothelial keratoplasty). Materials and Methods: This study has been done in department of Ophthalmology, Pt. J.N.M. Medical College, Raipur (C.G) from July 2009 to October 2010 and consists of group of patients attending eye OPD and admitted in department of ophthalmology. All patients included in the study were enquired about their history of diminution of vision, previous surgery, duration and any other associated symptoms. The patients underwent a detailed preoperative examination including visual acuity measurement with snellen’s chart, retinoscopy and subjective correction and slit lamp biomicroscopy. Observations: Among 40 patients 23 were male and 17 were female maximum patients were above 40 years of age. Out of 40 cases (100%), 23 cases (57.5%) were therapeutic and 17 cases (42.5%) were optical purpose. The mean age of the donor cornea was (61-80 years) age group which is used in 65% (26) cases. Maximum cases (40%) had corneal ulcer followed by corneal opacity (35%) and adherent leucoma (17%). Out of 40 cases in 32 cases of PKP shows complications. Improvement in visual acuity was seen in majority of cases. Conclusion: In this study we concluded that penetrating keratoplasty is most useful to save vision and structural integrity in case of corneal blindness. Keywords: Corneal pathologies, Penetrating keratoplasty, Visual acuity.

Precision, agreement and utility of a contemporary non‐contact corneal aesthesiometer

BackgroundThe measurement of corneal sensitivity threshold is important for several ocular surface diseases. The current study assesses the precision, agreement and utility of corneal sensitivity threshold measurement using a new, purpose‐built non‐contact corneal aesthesiometer.MethodsA new instrument and an established non‐contact corneal aesthesiometer device was used to measure the corneal sensitivity threshold on the right eye of 40 healthy human participants. Exclusion criteria included: corneal pathology, previous ocular surgery, ocular trauma, contact lens wear, diabetes or peripheral neuropathy. A forced‐response, double‐staircase method was used to obtain corneal sensitivity threshold from the mean of three readings per participant, for each non‐contact corneal aesthesiometer. Screen demarcations relative to the corneal limbus facilitated alignment with the new device. Repeatability of the new instrument was tested three consecutive times on the same day. Intra‐observer and inter‐observer reproducibility and agreement were determined using one‐way analysis of variance or analysis of variance and Bland–Altman analysis, respectively.ResultsForty eyes of 40 participants were assessed (15:25 M:F, 30.5 ± 11.4-years). The new instrument demonstrated good repeatability (p = 0.47). There was no difference in the mean corneal sensitivity threshold between the new (0.60 ± 0.36-mbar) and established (0.60 ± 0.34-mbar) aesthesiometers (p = 0.92). Utilising the new instrument, inter‐observer reproducibility (on a different subset of 10 participants) yielded thresholds of 0.41 ± 0.16-mbar and 0.42 ± 0.13-mbar (p = 0.88) for the two observers. Bland–Altman analysis confirmed good intra and inter‐observer agreement. Screen demarcations relative to the limbus, enabled easier corneal alignment.ConclusionThe new non‐contact corneal aesthesiometer confirmed very good repeatability and reproducibility, as well as good agreement with the long‐established instrument. Overall, this contemporary approach enables accurate and precise assessment of corneal sensitivity and thus, corneal nerve function, in normal and diseased cornea.

A porous collagen-based hydrogel and implantation method for corneal stromal regeneration and sustained local drug delivery

Biomaterials designed to replace the diseased cornea could be used to treat corneal blindness where human donor tissue is in short supply, but challenges are the integration of biomaterials with host tissue and cells, avoiding a rapid material degradation and maintaining corneal transparency. Additionally, implantation surgery often triggers an aggressive wound healing response that can lead to corneal thinning and opacity. Here, we report a collagen-based hydrogel with transparency and mechanical properties suitable for replacing a substantial portion of a damaged or diseased corneal stroma. The porous hydrogel permitted migration and population by host cells while maintaining transparency and thickness six months after surgical implantation in an in vivo model of human corneal surgery. With a novel hybrid surgical implantation technique inspired by LASIK refractive surgery, rapid wound healing occurred around implants to maintain biomaterial integrity, transparency and function. Host stromal cell repopulation and regeneration of host epithelium and nerves were observed, as necessary steps towards corneal regeneration. Finally, as a proof-of-principle, the hydrogel loaded with a neuroregenerative drug achieved sustained slow-release drug delivery in vitro. The proposed hydrogel and novel implantation technique together represent a therapeutic approach with translational potential for replacing and regenerating diseased corneal stromal tissue.

Correlation between Corneal Topographic Patterns and Refractive Status of the Eye in an Adult Iranian Population: Tehran Study.

Purpose:To evaluate the corneal topographic patterns in an adult Iranian population and investigate its correlation with the refractive status of the eye.Methods:In a cross-sectional study named “Tehran Study,” 1023 samples were selected by the cluster sampling method from the downtown area of Tehran. Eight hundred and forty-nine adults aged over 15 years participated. All selected participants were refracted and underwent topography imaging.Results:The patients' ages ranged from 15 to 91 years with a mean of 40.33 ± 16 years. The most frequent topographic patterns were symmetric bowtie (SB) (34%), SB with inferior steepening (SB-IS) (14.1%), and round (10.5%). The orders changed in categorization by refractive status: The most frequent pattern in all subgroups (emmetropia, myopia, and hyperopia) was SB with frequencies 32.7%, 35.8%, and 22.5%, respectively. Although the second order was asymmetric bowtie (AB) with AB-IS in the emmetropic and myopic subgroups, in the hyperopic subgroup, round pattern had the second place. The third place was different in all groups. The rarest patterns in the whole were SB with skewed radial axis (SRAX) and AB with SRAX. The first prevalent topographic pattern was SB in all age groups and in both genders. The prevalence of round pattern, irregular pattern, and SRAX significantly increased in older ages, and the prevalence of SB decreased in older ages. The first observed prevalent pattern was SB in both sexes, but the second most prevalent pattern was AB-IS and round in females and males, respectively.Conclusions:Corneal topographic pattern might be related to the refractive status of the eye. The information about normal topographic patterns provides a reference for comparison with diseased corneas.

Clinical indications of penetrating keratoplasty in a tertiary care centre of North India

Background: Corneal diseases are one of the major causes of blindness and visual impairment in developing countries. Penetrating keratoplasty is a surgical procedure where a damaged or diseased cornea is replaced by donor corneal tissue. Aim was to determine the indications of penetrating keratoplasty (PK) in a tertiary health care centre of North India.Methods: A retrospective analysis of the records of 288 patients, who underwent penetrating keratoplasty (PK) from January 2016 to December 2018 at Regional Institute of Ophthalmology, PGIMS Rohtak were included in this study. All patients who underwent PK during this time period were included in our study except those who underwent regrafting.Results: A total of 288 patients who underwent penetrating keratoplasty (PK) surgery were included in our study. Out of 288, 184 (63.88%) were males and 104 (36.11%) were females. In our study, 162 (56.25%) patients underwent optical PK, 76 (26.38%) had tectonic PK and 50 (17.36%) underwent therapeutic PK. Most common indication for optical PK was bullous keratopathy followed by corneal opacity. Most common reason for tectonic PK was found to be corneal perforation while for therapeutic PK was sloughing corneal ulcer followed by recalcitrant fungal keratitis.Conclusions: Though bullous keratopathy (BK) was the most common indication for penetrating keratoplasty in North India, but in our study 27% patients had tectonic PK and 17% patients underwent therapeutic PK which is significantly higher than documented data from South India and developed countries. It can be because of low literacy level, lack of awareness and late presentation to ophthalmologist in North India.

Analysis of Age, Gender, and Refractive Error-Related Changes of the Anterior Corneal Surface Parameters Using Oculus Keratograph Topography.

Purpose:To assess refractive error, gender, and age-related differences in corneal topography of a normal population with Oculus Keratograph 4.Methods:This cross-sectional study included a total of 500 normal eyes of 500 individuals with ages ranging from 10 to 70 years. All participants underwent detailed ocular examinations, including visual acuity measurement, slit-lamp examination, and refractive error evaluation. Slit-lamp examination was performed for all individuals to rule out apparent corneal diseases. Corneal topography parameters were assessed using Oculus Keratograph. The data were analyzed based on gender, refractive error, and age groups using independent sample t-test and one-way analysis of variance.Results:Of a total of 500 participants (age: 29.51 ± 11.53 years) recruited for the present study, 66.4% were female, and 33.6% were male. The mean spherical equivalent of refraction was − 0.98 ± 1.65 diopters. Significant differences were noted in steep keratometry (P = 0.035) and corneal astigmatism (P = 0.014) between genders. Assessment of the data based on refractive error revealed significant differences in an index of vertical asymmetry (P < 0.001), index of height asymmetry (P = 0.003), and index of height decentration (P = 0.011). Considering age groups, significant differences were observed in flat keratometry readings (P < 0.001), mean corneal astigmatism (P = 0.02), minimum radius of curvature (P = 0.037), and apex power (P < 0.001).Conclusions:There was a prominent variation in some topographic parameters based on gender, age, and refractive error. The information on corneal parameters obtained with Oculus Keratograph from normal eyes provides a reference for comparison with diseased corneas.

Alterations in corneal biomechanics underlie early stages of autoimmune-mediated dry eye disease

Autoimmune-mediated dry eye disease is a pathological feature of multiple disorders including Sjögren's syndrome, lupus and rheumatoid arthritis that has a life-long, detrimental impact on vision and overall quality of life. Although late stage disease outcomes such as epithelial barrier dysfunction, reduced corneal innervation and chronic inflammation have been well characterized in both human patients and mouse models, there is little to no understanding of early pathological processes. Moreover, the mechanisms underlying the loss of cornea homeostasis and disease progression are unknown. Here, we utilize the autoimmune regulatory (Aire)-deficient mouse model of autoimmune-mediated dry eye disease in combination with genome wide transcriptomics, high-resolution imaging and atomic force microscopy to reveal a potential extracellular matrix (ECM)-biomechanical-based mechanism driving cellular and morphological changes at early disease onset. Early disease in the Aire-deficient mouse model is associated with a mild reduction in tear production and moderate immune cell infiltration, allowing for interrogation of cellular, molecular and biomechanical changes largely independent of chronic inflammation. Using these tools, we demonstrate for the first time that the emergence of autoimmune-mediated dry eye disease is associated with an alteration in the biomechanical properties of the cornea. We reveal a dramatic disruption of the synthesis and organization of the extracellular matrix as well as degradation of the epithelial basement membrane during early disease. Notably, we provide evidence that the nerve supply to the cornea is severely reduced at early disease stages and that this is independent of basement membrane destruction or significant immune cell infiltration. Furthermore, diseased corneas display spatial heterogeneity in mechanical, structural and compositional changes, with the limbal compartment often exhibiting the opposite response compared to the central cornea. Despite these differences, however, epithelial hyperplasia is apparent in both compartments, possibly driven by increased activation of IL-1R1 and YAP signaling pathways. Thus, we reveal novel perturbations in corneal biomechanics, matrix organization and cell behavior during the early phase of dry eye that may underlie disease development and progression, presenting new potential targets for therapeutic intervention.

Artificial corneas versus donor corneas for repeat corneal transplants.

Individuals who have failed one or more full thickness penetrating keratoplasties may be offered repeat corneal surgery using an artificial or donor cornea. An artificial or prosthetic cornea is known as a keratoprosthesis. Both donor and artificial corneal transplantations involve removal of the diseased and opaque recipient cornea (or the previously failed cornea) and replacement with another donor or prosthetic cornea. To assess the effectiveness of artificial versus donor corneas in individuals who have had one or more failed donor corneal transplantations. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2019, Issue 11); Ovid MEDLINE; Ovid Embase; LILACS (Latin American and Caribbean Health Sciences Literature database); ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 4 November 2019. Two review authors independently assessed reports from the electronic searches to identify randomized controlled trials or controlled clinical trials. Any discrepancies were resolved by discussion or consultation. We used standard methodological procedures expected by Cochrane. For discussion purposes, we summarized findings from relevant comparative case series. We performed no data synthesis. We did not identify any randomized controlled trials or controlled clinical trials comparing artificial corneas with donor corneas for repeat corneal transplantations. The optimal management for those individuals who have failed a conventional corneal transplantation is unknown. Currently, in some centers, artificial corneal devices are routinely recommended after just one graft failure, while in other centers, they are not recommended until after multiple graft failures, or not at all. To date, there have been no controlled trials comparing the visual outcomes and complications of artificial corneal devices (particularly the Boston type 1 keratoprosthesis, which is the most commonly implanted artificial corneal device) with repeat donor corneal transplantation, in order to guide surgeons and their patients. Such a trial is needed and would offer significant benefit to an ever-increasing pool of people with visual disability due to corneal opacification, most of whom are still in productive stages of their lives.

The effect of sodium fluorescein on anterior eye surface measurements

PurposeDuring image acquisition, certain topographers require the addition of sodium fluorescein (NaFl) dye to the tear film. This study investigates the effect of NaFl dye on corneal topography and tear surface quality. MethodThe E300 corneal topographer (Medmont International Pty Ltd., Victoria, Australia) was used to measure ocular surface topography and quality of 57 eyes of 57 healthy individuals without dry eye symptoms, age 35.1 ± 15.2 years (mean ± standard deviation) ranging between 19 and 65 years. The mean of three simulated keratometry values, a variety of corneal shape descriptors, and Tear Film Surface Quality (TFSQ) were measured under three different conditions; without NaFl (baseline), with the addition of a single dose NaFl, and using a double dose of NaFl. ResultsCompared to baseline, the Inferior-Superior (IS) index decreased significantly after a single dose (P = 0.034) or double dose of NaFl (P = 0.030). The corneal surface was significantly more regular without NaFl (P = 0.003) or one insertion of NaFl (P = 0.024) when compared to two doses of NaFl. There was no association with age, or dry eye signs or symptoms on the variance observed in any of the indices between baseline, intervention I, and intervention II (P > 0.05). Agreement between corneal surface indices reduced following the addition of NaFl. ConclusionIn comparison to measurements taken without an ocular dye, one dose of NaFl resulted in increased reliability and consistency in corneal topography measurements using the E300 topographer, but 2 doses decreased reliability and consistency. Practitioners ought to be aware that tear film surface regularity and inferior-superior corneal power changed significantly following the addition of NaFl in those with healthy corneas. Its effect in diseased corneas is unknown.

A Foldable Nonpenetrating Keratoprosthesis: Medium to Long-Term Clinical Results in Patients with Corneal Blindness due to Noninflammatory Anterior Cornea Disease.

PURPOSE:To report the medium to long-term safety and performance outcomes of the KeraKlear nonpenetrating artificial cornea (KeraKlear) as the primary procedure in patients with corneal blindness due to noninflammatory anterior cornea disease.METHODS:Fifteen patients with corneal blindness (preoperative visual acuity [VA] of ≥20/200) due to a non-inflammatory anterior corneal condition were included in this prospective, single-center study. Preoperative diagnoses included corneal scars, keratoconus, and corneal dystrophies. Diseased corneas were implanted with the KeraKlear (KeraMed Inc., Irvine, California, USA) by a single surgeon (JMV) using a femtosecond laser to create all incisions. Participants were followed up with for as long as 64 months. Uncorrected Snellen VA and postoperative complications were recorded.RESULTS:The average age at the time of surgery was 49.6 years old and 67% of patients were female. The patients experienced an average improvement in uncorrected Snellen VA of 7.6 lines (−1.17 logMAR). Average uncorrected vision at the last visit was 20/100 (0.73 logMAR), and median uncorrected vision at the last visit was 20/70 (0.54 logMAR). One patient experienced extrusion of the KeraKlear due to infection. There were no cases of glaucoma, retroprosthetic membrane, or endophthalmitis, the three most common complications of penetrating keratoprostheses (KPro).CONCLUSIONS:Medium and long-term outcomes of the KeraKlear indicate that this device is a viable alternative to corneal transplantation as a primary procedure in patients with non-inflammatory causes of corneal blindness, especially when corneal tissue is not available. The KeraKlear does not penetrate into the anterior chamber, and therefore, is less susceptible to the most common complications of penetrating KPro including endophthalmitis, glaucoma, and retroprosthetic membrane. The KeraKlear also has a comparable or improved adverse event rate compared to penetrating keratoplasty.

Collagen fibrils and proteoglycans of peripheral and central stroma of the keratoconus cornea - Ultrastructure and 3D transmission electron tomography

Keratoconus (KC) is a progressive corneal disorder in which vision gradually deteriorates as a result of continuous conical protrusion and the consequent altered corneal curvature. While the majority of the literature focus on assessing the center of this diseased cornea, there is growing evidence of peripheral involvement in the disease process. Thus, we investigated the organization of collagen fibrils (CFs) and proteoglycans (PGs) in the periphery and center of KC corneal stroma. Three-dimensional transmission electron tomography on four KC corneas showed the degeneration of microfibrils within the CFs and disturbance in the attachment of the PGs. Within the KC corneas, the mean CF diameter of the central-anterior stroma was significantly (p ˂ 0.001) larger than the peripheral-anterior stroma. The interfibrillar distance of CF was significantly (p ˂ 0.001) smaller in the central stroma than in the peripheral stroma. PGs area and the density in the central KC stroma were larger than those in the peripheral stroma. Results of the current study revealed that in the pre- Descemet’s membrane stroma of the periphery, the degenerated CFs and PGs constitute biomechanically weak lamellae which are prone to disorganization and this suggests that the peripheral stroma plays an important role in the pathogenicity of the KC cornea.