Identification of Objective Morphometric Markers of Xerostomia in the Oral Mucosa Epithelium with In Vivo Confocal Microscopy.

The purpose of this work was to determine whether the morphology of the oral mucosa epithelium (OME) of patients with xerostomia differ from patients without xerostomia. In total, 34 patients with dry eye disease (DED) with or without xerostomia were examined at The Norwegian Dry Eye Disease Clinic with in vivo confocal microscopy of the lower lip. In addition, age- and gender-matched healthy controls (HC) were included. DED patients with xerostomia had a higher superficial to deep backscatter ratio compared with DED patients without xerostomia (p=0.002) and HC (p=0.001). Regression analysis demonstrated that this ratio was related to xerostomia independently of gender and age (p<0.001). Sensitivity and specificity of detecting xerostomia were 0.78 and 0.85, respectively, when using a superficial to deep backscatter ratio cut-off value of 0.995 (p=0.004). The mean nucleus to cytosol backscatter ratio in the superficial OME was lower in patients with xerostomia than in those without xerostomia (p=0.034). In vivo confocal microscopy is a potential tool for evaluating the oral cavity and to assess changes in the OME associated with xerostomia, objectively and quantitatively. The cause of the increased backscatter in the superficial OME in xerostomia, however, remains to be elucidated.

AI-Based Decision-Support System for Diagnosing Acanthamoeba Keratitis Using In Vivo Confocal Microscopy Images.

Purpose: In vivo confocal microscopy (IVCM) of the cornea is a valuable tool for clinical assessment of the cornea but does not provide stand-alone diagnostic support. The aim of this work was to develop an artificial intelligence (AI)-based decision-support system (DSS) for automated diagnosis of Acanthamoeba keratitis (AK) using IVCM images. Methods: The automated workflow for the AI-based DSS was defined and implemented using deep learning models, image processing techniques, rule-based decisions, and valuable input from domain experts. The models were evaluated with 5-fold-cross validation on a dataset of 85 patients (47,734 IVCM images from healthy, AK, and other disease cases) collected at a single eye clinic in Sweden. The developed DSS was validated on an additional 26 patients (21,236 images). Results: Overall, the DSS uses as input raw unprocessed IVCM image data, successfully separates artefacts from true images (93% accuracy), then classifies the remaining images by their corneal layer (90% accuracy). The DSS subsequently predicts if the cornea is healthy or diseased (95% model accuracy). In disease cases, the DSS detects images with AK signs with 84% accuracy, and further localizes the regions of diagnostic value with 76.5% accuracy. Conclusions: The proposed AI-based DSS can automatically and accurately preprocess IVCM images (separating artefacts and sorting images into corneal layers) which decreases screening time. The accuracy of AK detection using raw IVCM images must be further explored and improved. Translational Relevance: The proposed automated DSS for experienced specialists assists in diagnosing AK using IVCM images.

Early ocular surface and tear film status in congenital aniridia indicates a supportive treatment window.

AIM: To evaluate changes in the ocular surface and tear film with age and mutational status in congenital aniridia. METHODS: 45 participants with congenital aniridia (89 eyes) in a prospective, cross-sectional study. Whole-exome sequencing identified the causative mutation. Examinations included slit-lamp biomicroscopy, in vivo confocal microscopy, Ocular Surface Disease Index (OSDI) score, blink rate, Schirmer I test, Oxford Staining Score (OSS), tear film break-up time (TFBUT) and Ocular Protection Index (OPI). RESULTS: There were age-dependent increases in OSDI (ß=0.34, 95% CI 0.03 to 0.66; p=0.030), blink rate (ß=0.18, 95% CI 0.08 to 0.27; p<0.001) and OSS (ß=0.05, 95% CI 0.03 to 0.07; p<0.001) and age-dependent reductions in tear production (ß=-0.23, 95% CI -0.43 to 0.02; p=0.029) and TFBUT (ß=-0.10, 95% CI -0.17 to -0.04; p<0.001). Perturbed OSDI, OSS, blink rate, tear production and TFBUT were noted after the age of ten and OSDI, OSS, blink rate and TFBUT correlated with deficient corneal nerves and limbal stem cell function. OSDI, blink rate, Schirmer, OSS, TFBUT and OPI were not associated with type of PAX6 mutation, but OSDI, OSS and blink rate associated with grade of aniridia-associated keratopathy. CONCLUSIONS: Ocular surface damage and dry eye signs appear in congenital aniridia regardless of mutation, appearing after 10 years of age and progressing thereafter. An early treatment window may exist for therapies to protect the ocular surface homoeostasis and limbal function, to possibly delay keratopathy development and progression.

The use of in vivo confocal microscopy in fungal keratitis - Progress and challenges.

Fungal keratitis (FK) is a serious and sight-threatening corneal infection with global reach. The need for prompt diagnosis is paramount, as a delay in initiation of treatment could lead to irreversible vision loss. Current "gold standard" diagnostic methods, namely corneal smear and culture, have limitations due to diagnostic insensitivity and their time-consuming nature. PCR is a newer, complementary method used in the diagnosis of fungal keratitis, whose results are also sample-dependent. In vivo confocal microscopy (IVCM) is a promising complementary diagnostic method of increasing importance as it allows non-invasive real-time direct visualization of potential fungal pathogens and manifesting infection directly in the patient's cornea. In numerous articles and case reports, FK diagnosis by IVCM has been evaluated, and different features, approaches, sensitivity/specificity, and limitations have been noted. Here, we provide an up-to-date, comprehensive review of the current literature and present the authors' combined recommendations for fungal identification in IVCM images, while also looking to the future of FK assessment by IVCM using artificial intelligence methods.

Functional and Morphological Evaluation of Meibomian Glands in the Assessment of Meibomian Gland Dysfunction Subtype and Severity.

PURPOSE: To classify subtypes of meibomian gland dysfunction (MGD) and evaluate the dependency of dry eye signs, symptoms, and parameters on MGD subtype. DESIGN: Cross-sectional study. STUDY POPULATION: the right eyes of 447 patients with MGD of various subtypes and 20 healthy volunteers. METHODS: Patients were divided into 4 subtypes of MGD based on meibum expression, meibum quality, and MG loss on meibography images (meibograde of 0-6). Subtypes were patients with high meibum delivery (hypersecretory and nonobvious MGD) and those with low meibum delivery (hyposecretory and obstructive MGD). Additional clinical tests included tear film break-up time (TFBUT), ocular staining, osmolarity, Schirmer I, blink interval timing and the Ocular Surface Disease Index (OSDI) questionnaire. RESULTS: A total of 78 eyes had hypersecretory MGD; 49 eyes had nonobvious MGD; 66 eyes had hyposecretory MGD; and 254 eyes had obstructive MGD. Increased tear film osmolarity and lower TFBUT were found in the low-delivery groups; hyposecretory (P = 0.006, P = 0.016) and obstructive MGD (P = 0.008, P = 0.006) relative to high-delivery MGD (hypersecretory and nonobvious groups, respectively). Worse ocular symptoms and ocular staining were also found in low-delivery MGD groups than the high delivery MGD groups (P < 0.01 and P < 0.006, respectively). CONCLUSIONS: Patients with low-delivery MGD had worse dry eye parameters and ocular symptoms than those with high meibum delivery, indicating the pivotal role of meibum secretion in ocular surface health that should be targeted in MGD therapy. Furthermore, nonobvious MGD cannot be diagnosed using conventional dry eye tests and requires morphologic assessment of meibography images to confirm MG loss.

Diagnostic Test Efficacy of Meibomian Gland Morphology and Function.

Meibomian gland dysfunction (MGD) is the leading cause of dry eye and proposed treatments are based on disease severity. Our purpose was to establish reliable morphologic measurements of meibomian glands for evaluating MGD severity. This retrospective, cross-sectional study included 100 MGD patients and 20 controls. The patients were classified into dry eye severity level (DESL) 1-4 based on symptoms and clinical parameters including tear-film breakup time, ocular staining and Schirmer I. The gland loss, length, thickness, density and distortion were analyzed. We compared the morphology between patients and controls; examined their correlations to meibum expressibility, quality, and DESL. Relative to controls, the gland thickness, density and distortion were elevated in patients (p < 0.001 for all tests). The area under the receiver operating characteristic curve was 0.98 (95% confidence interval [CI], 0.96-1.0) for gland loss, and 0.96 (CI 0.91-1.0) for gland distortion, with a cutoff value of six distorted glands yielding a sensitivity of 93% and specificity of 97% for MGD diagnosis. The gland distortion was negatively correlated to the meibum expressibility (r = -0.53; p < 0.001) and DESL (r = -0.22, p = 0.018). In conclusion, evaluation of meibomian gland loss and distortion are valuable complementary clinical parameters to assess MGD status.

Meibomian Gland Morphology Is a Sensitive Early Indicator of Meibomian Gland Dysfunction.

PURPOSE: To investigate the relationship between meibomian gland (MG) morphology and clinical dry eye tests in patients with meibomian gland dysfunction (MGD). DESIGN: Cross-sectional study. SUBJECTS: Total 538 MGD patients and 21 healthy controls. METHODS: MG loss on meibography images of upper (UL) and lower lids (LL) was graded on a scale of 0 (lowest degree of MG loss) to 3. MG length, thickness, and interglandular space in the UL were measured. Clinical tests included meibum expression and quality, tear film break-up time, ocular staining, osmolarity, Schirmer I, blink interval timing, and Ocular Surface Disease Index (OSDI) questionnaire. RESULTS: Mean UL and LL meibogrades were significantly higher in MGD patients compared to controls (P < .001 for UL and LL). The sensitivity and specificity of the meibograde as a diagnostic parameter for MGD was 96.7% and 85%, respectively. Schirmer I was significantly increased in MGD patients with meibograde 1 compared to patients with meibograde 0, 2, and 3 in the UL (P < .05). MG thickness increased with higher meibograde (P < .001). MG morphology correlated significantly but weakly with several clinical parameters (P < .05). OSDI did not correlate with any MG morphologic parameter. CONCLUSIONS: Grading of MG loss using meibograde effectively diagnoses MGD. Compensatory mechanisms such as increased aqueous tear production and dilation of MGs make early detection of MGD difficult by standard clinical measures of dry eye, whereas morphologic analysis of MGs reveals an early stage of MGD, and therefore represents a complementary clinical parameter with diagnostic potential.

PEG-stabilized carbodiimide crosslinked collagen-chitosan hydrogels for corneal tissue engineering.

Implantable biomaterials that mimic the extracellular matrix (ECM) in key physical and physiological functions require components and microarchitectures that are carefully designed to maintain the correct balance between biofunctional and physical properties. Our goal was to develop hybrid polymer networks (HPN) that combine the bioactive features of natural materials and physical characteristics of synthetic ones to achieve synergy between the desirable mechanical properties of some components with the biological compatibility and physiological relevance of others. In this study, we developed collagen-chitosan composite hydrogels as corneal implants stabilized by either a simple carbodiimide cross-linker or a hybrid cross-linking system comprised of a long-range bi-functional cross-linker (e.g. poly(ethylene glycol) dibutyraldehyde (PEG-DBA)), and short-range amide-type cross-linkers (e.g. 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and N-hydroxysuccinimide (NHS)). Optimum hybrid hydrogel demonstrated significantly enhanced mechanical strength and elasticity by 100 and 20%, respectively, compared to its non-hybrid counterpart. It demonstrated excellent optical properties, optimum mechanical properties and suturability, and good permeability to glucose and albumin. It had excellent biocompatibility and when implanted into pig corneas for 12 months, allowed seamless host-graft integration with successful regeneration of host corneal epithelium, stroma, and nerves.

Dendritic cell maturation in the corneal epithelium with onset of type 2 diabetes is associated with tumor necrosis factor receptor superfamily member 9.

Type 2 diabetes mellitus is characterized by a low-grade inflammation; however, mechanisms leading to this inflammation in specific tissues are not well understood. The eye can be affected by diabetes; thus, we hypothesized that inflammatory changes in the eye may parallel the inflammation that develops with diabetes. Here, we developed a non-invasive means to monitor the status of inflammatory dendritic cell (DC) subsets in the corneal epithelium as a potential biomarker for the onset of inflammation in type 2 diabetes. In an age-matched cohort of 81 individuals with normal and impaired glucose tolerance and type 2 diabetes, DCs were quantified from wide-area maps of the corneal epithelial sub-basal plexus, obtained using clinical in vivo confocal microscopy (IVCM). With the onset of diabetes, the proportion of mature, antigen-presenting DCs increased and became organized in clusters. Out of 92 plasma proteins analysed in the cohort, tumor necrosis factor receptor super family member 9 (TNFRSF9) was associated with the observed maturation of DCs from an immature to mature antigen-presenting phenotype. A low-grade ocular surface inflammation observed in this study, where resident immature dendritic cells are transformed into mature antigen-presenting cells in the corneal epithelium, is a process putatively associated with TNFRSF9 signalling and may occur early in the development of type 2 diabetes. IVCM enables this process to be monitored non-invasively in the eye.

Wide-field corneal subbasal nerve plexus mosaics in age-controlled healthy and type 2 diabetes populations.

A dense nerve plexus in the clear outer window of the eye, the cornea, can be imaged in vivo to enable non-invasive monitoring of peripheral nerve degeneration in diabetes. However, a limited field of view of corneal nerves, operator-dependent image quality, and subjective image sampling methods have led to difficulty in establishing robust diagnostic measures relating to the progression of diabetes and its complications. Here, we use machine-based algorithms to provide wide-area mosaics of the cornea's subbasal nerve plexus (SBP) also accounting for depth (axial) fluctuation of the plexus. Degradation of the SBP with age has been mitigated as a confounding factor by providing a dataset comprising healthy and type 2 diabetes subjects of the same age. To maximize reuse, the dataset includes bilateral eye data, associated clinical parameters, and machine-generated SBP nerve density values obtained through automatic segmentation and nerve tracing algorithms. The dataset can be used to examine nerve degradation patterns to develop tools to non-invasively monitor diabetes progression while avoiding narrow-field imaging and image selection biases.

Innervation of tissue-engineered corneal implants in a porcine model: a 1-year in vivo confocal microscopy study.

PURPOSE: To examine the pattern of nerve regeneration within tissue-engineered corneal substitutes grafted into host porcine corneas over a 1-year postoperative period. METHODS: Biodegradable corneal substitutes from cross-linked collagen were implanted into the left eyes of 12 pigs by deep lamellar keratoplasty. Regeneration of severed nerves into the central implant region was investigated with in vivo confocal microscopy. Both implant-recipient and control (right) eyes were examined before surgery and 2, 6, 10, and 12 months after surgery, to quantify the number, density, diameter, and branching of nerve fiber bundles at various corneal depths. Transmission electron microscopy was used to confirm the presence of nerve bundles. RESULTS: Two months after surgery, corneal nerve ingrowth was observed within the deep anterior stroma, with a number and density of regenerated nerves significantly higher than in nonsurgical control eyes (P < 0.01). Nerves within the superficial anterior stroma regenerated by 6 to 10 months after surgery, and the first subbasal epithelial nerves were seen 10 months after surgery. After 1 year, subbasal nerve density recovered to preoperative levels. Nerve fibers in the deep anterior stroma remained significantly thinner relative to control eyes after 1 year (P < 0.001), where both superficial anterior and subbasal nerve diameter did not change relative to control eyes. CONCLUSIONS: The pattern of reinnervation within tissue-engineered corneal substitutes has been quantified in vivo. Innervation proceeded rapidly in the deep anterior stroma, followed by repopulation of more superficial regions. One year after surgery, nerve density within the tissue-engineered cornea increased or remained unchanged relative to controls in all corneal regions examined.

Spectroscopic whole-blood indicators of end-stage renal disease and the hemodialysis treatment.

The diffuse reflection spectrum in the 500-1670 nm region for whole blood taken from healthy subjects and end-stage renal disease (ESRD) patients was measured to test the feasibility of optically monitoring ESRD and its treatment by hemodialysis. Spectral regions where optical absorption significantly differed between healthy subjects and ESRD patients were used to form a multiple linear discriminant classification model. With this model a total of 41 whole-blood samples were classified into healthy, pretreatment and posttreatment ESRD classes. 96.7% of original and cross-validated cases and 100% of independent validation cases were correctly classified, indicating ESRD and its treatment exhibit characteristic spectral features in whole blood. Upon comparison of the discriminant model variables with a few key clinical blood parameters, model variables were found to significantly correlate with hematocrit and plasma levels of urea and potassium (P<0.05). The results of this study suggest that the optical signature of whole blood conveys basic clinical status information, and provides a path for investigating improved indices of hemodialysis toxicity, adequacy and patient outcome.

Reduced Corneal Nerve Fiber Density in Type 2 Diabetes by Wide-Area Mosaic Analysis.

Purpose: To determine if corneal subbasal nerve plexus (SBP) parameters derived from wide-area depth-corrected mosaic images are associated with type 2 diabetes. Methods: One hundred sixty-three mosaics were produced from eyes of 82 subjects by laser-scanning in vivo confocal microscopy (IVCM). Subjects were of the same age, without (43 subjects) or with type 2 diabetes (39 subjects). Mosaic corneal nerve fiber length density (mCNFL) and apical whorl corneal nerve fiber length density (wCNFL) were quantified and related to the presence and duration of diabetes (short duration < 10 years and long duration ≥ 10 years). Results: In mosaics with a mean size of 6 mm2 in subjects aged 69.1 ± 1.2 years, mCNFL in type 2 diabetes was reduced relative to nondiabetic subjects (13.1 ± 4.2 vs. 15.0 ± 3.2 mm/mm2, P = 0.018). Also reduced relative to nondiabetic subjects was mCNFL in both short-duration (14.0 ± 4.0 mm/mm2, 3.2 ± 3.9 years since diagnosis) and long-duration diabetes (12.7 ± 4.2 mm/mm2, 15.4 ± 4.2 years since diagnosis; ANOVA P = 0.023). Lower mCNFL was associated with presence of diabetes (P = 0.032) and increased hemoglobin A1c (HbA1c) levels (P = 0.047). By contrast, wCNFL was unaffected by diabetes or HbA1c (P > 0.05). Global SBP patterns revealed marked degeneration of secondary nerve fiber branches outside the whorl region in long-duration diabetes. Conclusions: Wide-area mosaic images provide reference values for mCNFL and wCNFL and reveal a progressive degeneration of the SBP with increasing duration of type 2 diabetes.

Dry Eye Disease Patients with Xerostomia Report Higher Symptom Load and Have Poorer Meibum Expressibility.

The purpose of the study was to investigate if xerostomia (dry mouth) is associated with symptoms and signs of dry eye disease (DED). At the Norwegian Dry Eye Clinic, patients with symptomatic DED with different etiologies were consecutively included in the study. The patients underwent a comprehensive ophthalmological work-up and completed self-questionnaires on symptoms of ocular dryness (Ocular Surface Disease Index [OSDI] and McMonnies Dry Eye Questionnaire) and the Sjögren's syndrome (SS) questionnaire (SSQ). Three hundred and eighteen patients (52% women and 48% men) with DED were included. Patient demographics were: 0 to 19 years (1%), 20 to 39 (25%), 40 to 59 (34%), 60 to 79 (35%) and 80 to 99 (5%). Xerostomia, defined as "daily symptoms of dry mouth the last three months" (as presented in SSQ) was reported by 23% of the patients. Female sex was more common among patients with xerostomia (81%) than among non-xerostomia patients (44%; P<0.001). Patients with xerostomia (60 ± 15 years) were older than those without xerostomia (51 ± 17; P<0.001). The use of prescription drugs was more prevalent among xerostomia patients (65%) than among non-xerostomia patients (35%; P<0.021; adjusted for age and sex). Patients with xerostomia had a higher OSDI score (19.0 ± 10.0) than those without xerostomia (12.9 ± 8.0; P<0.001). Moreover, xerostomia patients had more pathological meibum expressibility (0.9 ± 0.7) than those without xerostomia (0.7 ± 0.8; P = 0.046). Comparisons of OSDI and ocular signs were performed after controlling for the effects of sex, age and the number of systemic prescription drugs used. In conclusion, xerostomia patients demonstrated a higher DED symptom load and had poorer meibum expressibility than non-xerostomia patients.

Stable corneal regeneration four years after implantation of a cell-free recombinant human collagen scaffold.

We developed cell-free implants, comprising carbodiimide crosslinked recombinant human collagen (RHC), to enable corneal regeneration by endogenous cell recruitment, to address the worldwide shortage of donor corneas. Patients were grafted with RHC implants. Over four years, the regenerated neo-corneas were stably integrated without rejection, without the long immunosuppression regime needed by donor cornea patients. There was no recruitment of inflammatory dendritic cells into the implant area, whereas, even with immunosuppression, donor cornea recipients showed dendritic cell migration into the central cornea and a rejection episode was observed. Regeneration as evidenced by continued nerve and stromal cell repopulation occurred over the four years to approximate the micro-architecture of healthy corneas. Histopathology of a regenerated, clear cornea from a regrafted patient showed normal corneal architecture. Donor human cornea grafted eyes had abnormally tortuous nerves and stromal cell death was found. Implanted patients had a 4-year average corrected visual acuity of 20/54 and gained more than 5 Snellen lines of vision on an eye chart. The visual acuity can be improved with more robust materials for better shape retention. Nevertheless, these RHC implants can achieve stable regeneration and therefore, represent a potentially safe alternative to donor organ transplantation.

An accurate method to determine Bowman's layer thickness in vivo in the human cornea.

PURPOSE: To determine an accurate value for Bowman's layer (BL) thickness in vivo in humans. METHODS: Seventeen corneal transplant patients were examined preoperatively by laser-scanning in vivo confocal microscopy (IVCM), and corneal buttons were removed postoperatively and sectioned for light microscopy (LM). Nine corneas with uniformly thick BL by LM were used for thickness measurement. In the uniformly thick samples, probable overestimation of BL thickness in vivo by a first in vivo method (Method 1) led to the development of a revised in vivo method (Method 2). Method 2 was used to measure BL thickness in 20 healthy volunteers. RESULTS: In nine patients, mean BL thickness prior to transplantation was 13.7 ± 1.6 µm by IVCM (Method 1) while BL thickness of the removed corneal button was 9.7 ± 1.7 µm by LM (P < 0.001). The correlation of BL thickness between IVCM (Method 1) and LM was poor (P = 0.226). In 20 right eyes of 20 normal corneas, both in vivo methods were used to determine BL thickness. Mean BL thickness by Method 1 was 13.2 ± 1.6 µm and by Method 2 was 9.1 ± 1.4 µm (P < 0.001). BL thickness measurements by both in vivo methods were highly correlated (P < 0.001). CONCLUSION: BL thickness by a revised in vivo method was close to LM values in this study and to values reported in fixed tissue in other studies. The authors believe this revised method provides the most accurate estimates of BL thickness in vivo to date.

A biosynthetic alternative to human donor tissue for inducing corneal regeneration: 24-month follow-up of a phase 1 clinical study.

Corneas from human donors are used to replace damaged tissue and treat corneal blindness, but there is a severe worldwide shortage of donor corneas. We conducted a phase 1 clinical study in which biosynthetic mimics of corneal extracellular matrix were implanted to replace the pathologic anterior cornea of 10 patients who had significant vision loss, with the aim of facilitating endogenous tissue regeneration without the use of human donor tissue. The biosynthetic implants remained stably integrated and avascular for 24 months after surgery, without the need for long-term use of the steroid immunosuppression that is required for traditional allotransplantation. Corneal reepithelialization occurred in all patients, although a delay in epithelial closure as a result of the overlying retaining sutures led to early, localized implant thinning and fibrosis in some patients. The tear film was restored, and stromal cells were recruited into the implant in all patients. Nerve regeneration was also observed and touch sensitivity was restored, both to an equal or to a greater degree than is seen with human donor tissue. Vision at 24 months improved from preoperative values in six patients. With further optimization, biosynthetic corneal implants could offer a safe and effective alternative to the implantation of human tissue to help address the current donor cornea shortage.

Collagen-phosphorylcholine interpenetrating network hydrogels as corneal substitutes.

A biointeractive collagen-phospholipid corneal substitute was fabricated from interpenetrating polymeric networks comprising 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide and N-hydroxysuccinimide crosslinked porcine atelocollagen, and poly(ethylene glycol) diacrylate crosslinked 2-methacryloyloxyethyl phosphorylcholine (MPC). The resulting hydrogels showed an overall increase in mechanical strength beyond that of either original component and enhanced stability against enzymatic digestion (by collagenase) or UV degradation. More strikingly, these hydrogels retained the full biointeractive, cell friendly properties of collagen in promoting corneal cell and nerve in-growth and regeneration (despite MPC's known anti-adhesive properties). Measurements of refractive indices, white light transmission and backscatter showed the optical properties of collagen-MPC are comparable or superior to those of the human cornea. In addition, the glucose and albumin permeability were comparable to those of human corneas. Twelve-month post-implantation results of collagen-MPC hydrogels into mini-pigs showed regeneration of corneal tissue (epithelium, stroma) as well as the tear film and sensory nerves. We also show that porcine collagen can be substituted with recombinant human collagen, resulting in a fully-synthetic implant that is free from the potential risks of disease transmission (e.g. prions) present in animal source materials.