Tel-Aviv Protocol for Postrefractive Surgery Corneal Ectasia: A Case Series

PURPOSE

The aim of this study was to describe the safety and efficacy of the Tel-Aviv Protocol (epithelial photorefractive keratectomy and corneal cross-linking) as a treatment for postrefractive surgery corneal ectasia.

METHODS

This study includes 8 eyes from 7 patients, each diagnosed with postrefractive surgery ectasia years after refractive surgery and treated with the Tel-Aviv Protocol. The procedure included transepithelial PRK using the EX500 excimer laser, a 50-μm laser ablation of the epithelium and anterior stroma, delivered on the visual axis with cyclotorsion correction, treating up to 50% of refractive astigmatism. After the epithelial photorefractive keratectomy, all patients underwent corneal cross-linking.

RESULTS

The mean keratometry (K) and maximal K both decreased [from 43.37 ± 2.23 to 41.84 ± 2.01 ( P = 0.03) and from 44.95 ± 3.08 to 42.78 ± 2.19 ( P = 0.03), respectively]. Astigmatism was significantly reduced (from 3.53 ± 2.36 to 0.88 ± 0.89 diopter; P = 0.02). Uncorrected visual acuity improved significantly in all patients from a mean of 0.56 ± 0.32 to 0.15 ± 0.14 logMAR ( P = 0.01). Best-corrected visual acuity improved from 0.22 ± 0.24 to 0.06 ± 0.06 logMAR ( P = 0.07; 1-tail P = 0.04). All patients maintained visual acuity during the follow-up period, up to 25 months, mean = 329 days. The Tel-Aviv Protocol was found to be safe [mean safety index: 1.63 ± 1.03 (range: 1.00-4)] and effective [mean efficacy index: 1.29 ± 0.66 (range: 0.71-2.1)].

CONCLUSIONS

The Tel-Aviv Protocol, developed initially for keratoconus treatment, is a safe and promising procedure to stop postrefractive surgery ectasia progression while significantly improving vision, thereby avoiding keratoplasty.

Central Toxic Keratopathy After Collagen Cross-Linking: A Case Series

PURPOSE

The aim of this study was to report a case series of central toxic keratopathy (CTK) after collagen cross-linking (CXL) in keratoconus.

METHODS

This is a retrospective case series between January 2020 and September 2021. In this period, CXL was performed for progressive keratoconus in 964 eyes. CXL was performed using the epithelium-off accelerated protocol in all patients with a riboflavin soak time of 20 minutes and a UVA light exposure of 9 mW for 10 minutes using the Avedro KXL (Glaukos Inc, Aliso Viejo, CA) cross-linking system.

RESULTS

Twelve of 964 eyes (1.2%) developed CTK within 1 week of CXL. All patients presented with well-circumscribed, central disciform haze that was broader in the anterior stroma and narrower in the posterior stroma. We noted initial flattening in keratometry up to 3 months post-CXL in these patients, which gradually steepened over 12 months, but did not reach preoperative levels. We also noted exuberant flattening in pachymetry in the first 3 months, which improved over 12 months. There was a statistically significant decrease in pachymetry in patients who developed CTK at 3 and 12 months postoperatively when compared to patients who underwent CXL but did not develop CTK.

CONCLUSIONS

Several reports of CTK postrefractive surgery have been described previously. However, the association of CXL in the development of CTK has not been described previously. Here, we elucidated the clinical features of CTK after CXL and how it differs from corneal scarring or haze that occurs post-CXL.

3D bioprinted photo crosslinkable GelMA/methylcellulose hydrogel mimicking native corneal model with enhanced in vitro cytocompatibility and sustained keratocyte phenotype for stromal regeneration

Corneal transplantation serves as the standard clinical therapy for serious corneal disorders. However, rejection of grafts, significant expenditures, and most crucially, the global donor shortage, may affect the outcome. Recently, 3D bioprinting using biodegradable polymeric materials has become a suitable method for creating tissue replicas with identical architecture. One such most renowned material is GelMA, for its scaffold's three-dimensional structure, biocompatibility, robust mechanics, and favourable optical transmittance. However, GelMA's inadequate viscosity to print at body temperature with better form integrity remains an obstacle. The aim of this work is to create 3D printed GelMA/MC hydrogels for corneal stroma tissue engineering using MC's printability at room temperature and GelMA's irreversible photo cross-linking with UV irradiation. The print speed and pressure conditions for 3D GelMA/MC hydrogels were tuned. Thermal, morphological and physicochemical characteristics were studied for two distinct concentrations of GelMA/MC hydrogels. The hydrogels achieved a transparency of ~78 % (at 700 nm), which was on par with that of the normal cornea (80 %). The in vitro studies conducted using goat corneal stromal cells demonstrated the ability of both hydrogels to promote cell adhesion and proliferation. Expression of Vimentin and keratan sulphate validated the phenotype of keratocytes in the hydrogel. This 3D printed GelMA/MC hydrogel model mimics biophysical characteristics of the native corneal stroma, which may hold promise for clinical corneal stromal tissue engineering.

Thickness of anterior sclera and corneal layers in systemic sclerosis

PURPOSE

To evaluate the thickness of anterior sclera and corneal layers in patients with systemic sclerosis.

METHODS

The present cross-sectional study included 41 patients with systemic sclerosis and 41 age- and gender-matched healthy controls. The study and control groups were compared in terms of the thickness of anterior sclera, corneal epithelium, Bowman's layer, corneal stroma, and Descemet's membrane-endothelium complex. The thickness measurements were obtained using the anterior segment module of spectral-domain optical coherence tomography.

RESULTS

The thickness of anterior sclera, corneal epithelium, Bowman's layer, and Descemet's membrane-endothelium complex were similar in the patients with systemic sclerosis and healthy controls (P > 0.05). Total corneal thickness at the apex was 511.1 ± 33.5 µm in the systemic sclerosis group and 528.4 ± 29.5 µm in the control group (P = 0.015). The corneal stroma was thinner in the systemic sclerosis patients compared to the healthy controls (P = 0.02).

CONCLUSIONS

The corneal stroma was thinner in the patients with systemic sclerosis compared to that of healthy controls, while the thickness of the anterior sclera was similar in both groups.

Corneal epithelial and fibrovascular downgrowth postcataract surgery with intrastromal bleed: a rare case study with multimodal imaging

A woman in her 60s presented with diminution of vision and redness in her right eye (OD) 1.5 months duration, 10 months post cataract surgery. The best-corrected visual acuity (BCVA) on the OD was fingers counting at 0.5 m. The anterior section of the OD demonstrated superior pre-Descemet's intrastromal bleeding, superior dense fibrovascular growth in the corneal mid-stroma and superior fibrovascular downgrowth measuring 5×5 mm in the anterior chamber. Along with topical prednisolone acetate (1%) suspension 4 times per day on a tapering dose, antivascular endothelial growth factor therapy was administered intrastromally and subconjunctivally in the superior bulbar conjunctiva near limbus (0.05 mL of 2.5 mg/0.1 mL at each site). Over the course of a week, the intrastromal bleed had completely stopped. Three months later, at the final follow-up, the BCVA had marginally improved to fingers counting 2 m, with a lingering 4×4 mm nebulomacular scar.

Patterned collagen films loaded with miR-133b@MBG-NH2for potential applications in corneal stromal injury repair

Corneal stromal injury is a common surgical disease. With the development of tissue engineering materials, many artificial corneal scaffolds have been developed to replace allograft corneal transplantation and solve the problem of corneal donor shortage. However, few researchers have paid attention to corneal stromal wound healing. Herein, a nanocomposite of amino modified mesoporous bioactive glass (MBG-NH2) and microRNA-133b (miR-133b) was introduced into the patterned collagen films to achieve corneal stromal injury repair. MBG-NH2nanoparticles as a nano delivery carrier could efficiently load miR-133b and achieve the slow release of miR-133b. The physicochemical properties of collagen films were characterized and found the microgrooved collagen films loaded with miR-133b@MBG-NH2nanoparticles possessed similar swelling properties, optical clarity, and biodegradability to the natural cornea.In vitrocell experiments were also conducted and proved that the patterned collagen films with miR-133b@MBG-NH2possessed good biocompatibility, and miR-133b@MBG-NH2nanoparticles could be significantly uptake by rabbit corneal stromal cells (RCSCs) and have a significant impact on the orientation, proliferation, migration, and gene expression of RCSCs. More importantly, the patterned collagen films with miR-133b@MBG-NH2could effectively promote the migration of RCSCs and accelerate wound healing process, and down-regulate the expression levels ofα-SMA, COL-I, and CTGF genes associated with myofibroblast differentiation of corneal stromal cells, which has a potential application prospect in the repair of corneal stromal injury.

Oxygen-supplemented and topography-guided epithelium-on corneal crosslinking with pulsed irradiation for progressive keratoconus

PURPOSE

To investigate the effects of customized topography-guided epithelium-on crosslinking (epi-on CXL) with oxygen supplementation on procedural efficacy and corrected distance visual acuity (CDVA) in patients with progressive keratoconus (KC) at 1 year.

SETTING

Private eye clinic, Brisbane, Australia.

DESIGN

Retrospective, single-center, nonrandomized case series.

METHODS

Topography-guided epi-on CXL using the Mosaic system was performed on patients with progressive KC. Oxygen goggles; transepithelial riboflavin; and pulsed, high UV-A irradiance (1 second on, 1 second off; 30 mW/cm2) were applied to enhance oxygen kinetics and bioavailabilities of riboflavin and UV-A. Guided by baseline topography, a higher UV-A dose (15 J/cm2) was applied to the area of steepest anterior curvature with decreasing fluence (as low as 7.2 J/cm2) toward the outer 9 mm. Postoperative CDVA and maximum keratometry (Kmax) were evaluated.

RESULTS

102 eyes (80 patients) were followed for 11.5 ± 4.8 months. At the latest follow-up, mean CDVA (logMAR), mean K, and Kmax (diopters [D]) improved from 0.18 ± 0.28, 46.2 ± 3.8, and 53.0 ± 5.67 at baseline to 0.07 ± 0.18, 45.8 ± 3.7, and 51.9 ± 5.56, respectively (P < .001). 3 eyes (3%) lost more than 1 CDVA line, and another 3 eyes (3%) had increased Kmax greater than 2 D. 43 eyes were followed for at least 12 months (n = 43): mean CDVA, mean K, and Kmax improved from 0.19 ± 0.33 logMAR, 46.5 ± 3.5 D, and 53.6 ± 5.67 D to 0.07 ± 0.17 logMAR, 46.0 ± 3.5 D, and 52.33 ± 5.49 D, respectively (P ≤ .002). No complications were observed.

CONCLUSIONS

Tailoring oxygen-supplemented epi-on CXL with differential UV-A energy distributions, guided by baseline topography, in patients with KC seems to be safe and effective. At 1 year, study reports sustained improved CDVA and corneal stabilization.

Real-world socioeconomic determinants of corneal crosslinking in a national cohort

PURPOSE

To characterize recent socioeconomic trends in patients with keratoconus/corneal ectasias undergoing corneal crosslinking (CXL).

SETTING

A deidentified administrative medical claims database comprised commercial and Medicare Advantage health claims from across the United States.

DESIGN

Population-based retrospective cohort study.

METHODS

This study identified 552 patients with keratoconus/corneal ectasia who underwent CXL and 2723 matched controls who did not undergo CXL based on Current Procedural Terminology coding from a U.S. national insurance claims database from 2016 to 2020. For each patient, characteristics, including sex, race, age, household net worth, education level, insurance plan type, and geographic region, were extracted. Multivariate logistic regression was conducted to determine the odds of undergoing crosslinking.

RESULTS

Age 30 years or older (odds ratio [OR], 0.34, P < .001) was associated with decreased likelihood of undergoing CXL. Sex, race, education, and patient income were not associated with odds of undergoing CXL. Patients with health maintenance organization insurance had lower odds of undergoing CXL (OR, 0.64, P = .047). Geographically, patients on the east coast (OR, 0.37, P < .001) and Lower Midwest (OR, 0.31, P < .001) had statistically lower odds of undergoing crosslinking.

CONCLUSIONS

This is the first study to identify socioeconomic determinants of CXL, and it highlights that geographic location and insurance type may limit accessibility to patients.

Analysis of the effect of calcium ions on promoting the penetrability of riboflavin into the corneal stroma by iontophoresis

PURPOSE

To investigate the effect of calcium ions on promoting the penetrability of riboflavin into the corneal stroma by iontophoresis and to analyse the possible mechanism.

METHODS

Forty rabbits were divided into five groups randomly: 0.1% riboflavin-balanced salt solution (BSS) by iontophoresis group, 0.1% riboflavin-saline solution by iontophoresis group, 0.1% riboflavin-zinc gluconate solution by iontophoresis group, 0.1% riboflavin-calcium gluconate solution by iontophoresis group and classical riboflavin instillation after corneal de-epithelialization as the control group. The riboflavin concentrations in corneal stroma were determined and compared by high-performance liquid chromatography (HPLC) after removing epithelium and endothelium.

RESULTS

Iontophoretic delivery of a 0.1% riboflavin-calcium gluconate solution was the closest to the effect of classical de-epithelialization. The other solvents were unsufficient at enhancing the permeability of the riboflavin.

CONCLUSION

Calcium ions can promote the penetrability of riboflavin into the corneal stroma by iontophoresis.

Glycosaminoglycans and collagen fibril distribution at various depths of the corneal stroma of normal and CXL treated rats

Corneal collagen cross-linking (CXL) is widely used to treat keratoconus and ecstatic corneal disorders. The present studies were carried out to investigate the distribution of glycosaminoglycans (GAGs) and collagen fibril (CF) at different depths of the normal and CXL treated corneal stroma of four week old rats 7 days after standard CXL application. Ten Wistar rats' corneas were used for the study. The epithelium of the cornea from the left eye of each rat was removed and treated with standard CXL application using riboflavin and Ultraviolet-A (UVA) (3 mW/cm2 for 30 min). The cornea from the right eye was used as the control cornea. The cornea was removed from the eye and processed for transmission electron microscopy. A bottom mounted Quemesa camera was used to capture digital images and these images were analysed using iTEM software. In the control cornea, the GAGs area size was not significantly different in the anterior, middle, and posterior stroma. In the CXL treated rats the GAGs area size gradually increased from the anterior to the posterior stroma whereas the spacing between the GAGs gradually decreased. There were very large GAGs present in the posterior stroma of the CXL treated rats. When comparing the control and CXL cornea, the GAGs area in the CXL cornea was significantly higher and inter-GAGs-spacing was smaller than in the control cornea. In the control cornea, the collagen fibrils diameter was higher in the anterior stroma and lowest in the posterior stroma. In the CXL treated cornea, the CF diameter and the interfibrillar spacing gradually decreased from the anterior to the posterior stroma. On comparison between the control and the CXL treated cornea, the interfibrillar spacing was significantly smaller in the CXL treated cornea than the control cornea in the anterior, middle, and posterior stroma but there was no difference in the diameter. The CXL treatment significantly increased the GAGs area and decreased the inter-GAGs-spacing, and inter-CF-spacing. This could be due to the gradual decline in the availability of riboflavin, UVA, and oxygen in the middle and posterior stroma. Further studies are required to investigate the role of keratan sulphate and chondroitin sulphate by using monoclonal antibodies with immunogold technique.

Case of Progressive Keratoconus With Newly Diagnosed Pellucid Marginal Degeneration After Corneal Cross-Linking

PURPOSE

The purpose of this study was to document, to our knowledge, the first reported case of keratoconus progression accompanied with newly diagnosed pellucid marginal degeneration after corneal cross-linking (CXL).

METHODS

A novel case of further keratoconus progression plus development of pellucid marginal degeneration in the same eye after CXL was documented with supporting evidence from Scheimpflug and optical coherence tomography imaging.

RESULTS

A male patient was diagnosed with progressive keratoconus in the left eye and treated with CXL when aged 25 years. Although strongly cautioned not to rub his eyes, he admitted that he continued eye rubbing in association with atopic disease. At a follow-up examination 3.5 years after CXL, progressive keratoconus was detected and pellucid marginal degeneration was newly diagnosed in the left eye. The eye was retreated with CXL.

CONCLUSIONS

This case illustrates that progressive keratoconus and pellucid marginal degeneration can occur in the same eye after CXL and demonstrates the deleterious effects that can develop with continued eye rubbing.

Study on the biological properties of SMILE-derived corneal stromal lenticules after long-term cryopreservation in nutrient capsules

PURPOSE

To investigate the long-term preservation effects of nutrient capsules on the physiological activity, collagen fiber structure and transmittance of corneal stromal lenticules derived from small incision lenticule extraction (SMILE).

METHODS

A new nutrient capsule was constructed for long-term preservation of SMILE-derived corneal stromal lenticules. The lenticules were randomly divided into 99% anhydrous glycerol, and hydrogel nutrient capsules. After preserving for 1 year at -80 °C, lenticules were compared with fresh lenticules. The optical transmittance, tissue morphology, ultrastructure, cells activity and immunogenicity of the lenticules was detected and compared between different groups.

RESULTS

The rate of apoptotic cells was significantly higher in the glycerol group compared with the nutrient capsule group (P < 0.0001). More viable cells were present in the lenticules after nutrient capsule preservation compared to the glycerol group (P = 0.0003). The mean transmittance of the lenticules in the glycerol group (50 ± 18%) was significantly lower (P = 0.0008) compared to the control group (75 ± 11%), and the lenticules transmittance of the nutrient capsule group (64 ± 15%) after long-term preservation was not significantly different (P = 0.23) compared to the control group. The structure of HE staining showed that the collagen fibers in the nutrient capsule group were arranged in parallel and neatly, and a few cavitation vesicles were visible inside the tissue. There was no significant difference in the number of lenticular collagen fibers in the nutritional capsule group compared to the fresh lenticule group (P = 0.06). HLA-DR, HLA-ABC, CD45, CD25 and CD69 expression was low in all groups of lenticules after preservation.

CONCLUSIONS

Nutrient capsules can preserve lenticules for a long time and maintain the transmission structure and cells activity of lenticules.

Clinical, Anatomical, and Densitometric Changes following Dresden vs. Accelerated Corneal Cross-Linking in Progressive Keratoconus

BACKGROUND

To compare clinical, anatomical, and densitometric changes following Dresden (DCXL) vs. accelerated (ACXL) corneal UVA cross-linking (CXL; Avedro KXL, Geuder, Heidelberg, Germany) in progressive keratoconus (KC).

METHODS AND MATERIAL

In this retrospective study, we analyzed 20 patients following DCXL (3 mW/cm², 30 min, 5.4 J/cm²) and 44 patients following ACXL (9 mW/cm², 10 min, 5.4 J/cm²) between January 2016 and February 2020. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), central corneal thickness (CCT), steepest keratometry (Kmax), keratoconus index (KI), thinnest pachymetry (Pthin), and corneal densitometry (CD) were measured before and 3, 6, 12, and 24 months after CXL.

RESULTS

During the follow-up period, no changes in UCVA, BSCVA, Kmax, KI, or Pthin occurred. CCT significantly decreased 3 months after DCXL (p = 0.032) and ACXL (p = 0.006). At the 12- and 24-month follow-up, CCT remained decreased in the DCXL (p = 0.035, 0.036, respectively) but not in the ACXL group. At the 12-month follow-up, the reduction in CCT was significantly greater in DCXL compared to ACXL (p = 0.012). At the 3-, 6-, 12-, and 24-month follow-ups, we found a significant increase in the anterior stroma CD following DCXL (p = 0.019, 0.026, 0.049, 0.047, respectively) but not ACXL. The CD changes were localized in the central concentric zones (0.0 to 6.0 mm). No intra- or postoperative complications occurred.

CONCLUSION

ACXL and DCXL effectively halted KC progression. ACXL proved to be a safe time-saving alternative to conventional DCXL. DCXL led to a reduction in CCT and an increment in the CD of the central anterior stroma during 24 months of follow-up.

Biomimetic Corneal Stroma for Scarless Corneal Wound Healing via Structural Restoration and Microenvironment Modulation

Corneal injury-induced stromal scarring causes the most common subtype of corneal blindness, and there is an unmet need to promote scarless corneal wound healing. Herein, a biomimetic corneal stroma with immunomodulatory properties is bioengineered for scarless corneal defect repair. First, a fully defined serum-free system is established to derive stromal keratocytes (hAESC-SKs) from a current Good Manufacturing Practice (cGMP)-grade human amniotic epithelial stem cells (hAESCs), and RNA-seq is used to validate the phenotypic transition. Moreover, hAESC-SKs are shown to possess robust immunomodulatory properties in addition to the keratocyte phenotype. Inspired by the corneal stromal extracellular matrix (ECM), a photocurable gelatin-based hydrogel is fabricated to serve as a scaffold for hAESC-SKs for bioengineering of a biomimetic corneal stroma. The rabbit corneal defect model is used to confirm that this biomimetic corneal stroma rapidly restores the corneal structure, and effectively reshapes the tissue microenvironment via proteoglycan secretion to promote transparency and inhibition of the inflammatory cascade to alleviate fibrosis, which synergistically reduces scar formation by ≈75% in addition to promoting wound healing. Overall, the strategy proposed here provides a promising solution for scarless corneal defect repair.

Clinical and Morphological in Vivo Confocal Microscopy Findings following a Modified Biphasic Higher Fluence Transepithelial Corneal Crosslinking

Purpose: To compare the refractive efficacy and morphological changes in the cornea following a novel biphasic higher fluence transepithelial corneal crosslinking (BI-TE-CXL) and transepithelial corneal crosslinking (TE-CXL) in adults keratoconus.Methods: Patients with progressive keratoconus who required corneal crosslinking were assigned to the BI-TE-CXL group (32 eyes, phase 1: 7.2 J/cm2 for 5 min and 20 s of pulsed-light exposure, KXL, Glaukos-Avedro; phase 2: 3.6 J/cm2 for 6 min and 40 s of continuous light exposure at the front curvature apex with a 6 mm diameter light spot, UVX-2000, IROC) or the TE-CXL group (32 eyes, uniform 7.2 J/cm2 for 5 min and 20 s of pulsed-light exposure, KXL, Glaukos-Avedro). Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), corneal fluorescein staining (CFS), corneal topography, anterior segment optical coherence tomography (AS-OCT), and in vivo corneal confocal microscopy (IVCM) were performed 3, 6, 12 and 24 months after surgery.Results: The CFS scores in the BI-TE-CXL group were significantly higher than those in the TE-CXL group on the first two days after surgery (p < 0.001). The Kmax (at 12 and 24 months) and CDVA (logMAR) were significantly lower in the BI-TE-CXL group than those in the TE-CXL group (p < 0.05). The corneal demarcation line under AS-OCT was visible in 81.3% of patients in the BI-TE-CXL group and 15.6% in the TE-CXL group. The depth of the demarcation line under IVCM was significantly deeper in the BI-TE-CXL group (248.3 ± 25.0 μm) than that of the TE-CXL group (136.5 ± 15.6 μm) in the central cornea (p < 0.001). The cross-linked collagen structures in the central cornea were still present after 12 months in the BI-TE-CXL group. No significant difference in sub-basal nerve density between the two groups (p > 0.05).Conclusions: Following BI-TE-CXL, CDVA was significantly improved, accompanied by deeper demarcation line depth and persistent crosslinked structures in the central corneal stroma.

Current Advances in Corneal Stromal Stem Cell Biology and Therapeutic Applications

Corneal stromal stem cells (CSSCs) are of particular interest in regenerative ophthalmology, offering a new therapeutic target for corneal injuries and diseases. This review provides a comprehensive examination of CSSCs, exploring their anatomy, functions, and role in maintaining corneal integrity. Molecular markers, wound healing mechanisms, and potential therapeutic applications are discussed. Global corneal blindness, especially in more resource-limited regions, underscores the need for innovative solutions. Challenges posed by corneal defects, emphasizing the urgent need for advanced therapeutic interventions, are discussed. The review places a spotlight on exosome therapy as a potential therapy. CSSC-derived exosomes exhibit significant potential for modulating inflammation, promoting tissue repair, and addressing corneal transparency. Additionally, the rejuvenation potential of CSSCs through epigenetic reprogramming adds to the evolving regenerative landscape. The imperative for clinical trials and human studies to seamlessly integrate these strategies into practice is emphasized. This points towards a future where CSSC-based therapies, particularly leveraging exosomes, play a central role in diversifying ophthalmic regenerative medicine.

Refractive surgical correction and treatment of keratoconus

Keratoconus is an ectatic corneal disorder that causes severe vision loss. Surgical options allow us to correct, partially or totally, the induced refractive error. Intracorneal ring segments (ICRS) implantation represents a minimally invasive surgical option that improves visual acuity, with a high success rate and a low overall complication rate. Corneal allogenic ICRS consists of ring segments derived from allogenic eye bank-processed donor corneas. Selective topography-guided transepithelial photorefractive or phototherapeutic keratectomy combined with CXL is another way in selected cases to improve spectacles corrected distance visual acuity. The microphotoablative remodeling of the central corneal profile is generally planned by optimizing the optical zones and minimizing tissue consumption. Phakic intraocular lens (PIOL) implant is considered in patients with stable disease and acceptable anatomical requirements. The two types of pIOLs, depending on their implantation inside the eye, are anterior chamber-pIOLs, which fixate to the anterior surface of the iris by using a polymethomethacrolate claw at the two haptics, and posterior chamber-pIOLs. In patients with both cataracts and keratoconus, the correct IOL power is difficult to obtain due to the irregular corneal shape and K values. Toric IOL is recommended, but carefully judging the topography and the possible need of subsequent keratoplasties.

Incidental finding of a retained intracorneal wooden foreign body

We present a case of an intracorneal wooden foreign body that remained undetected for 15 years following an ocular injury sustained during gardening. The patient presented with stable visual acuity despite the long-standing presence of a wooden splinter embedded in the cornea. Interestingly, Pentacam corneal tomography did not show any abnormalities despite the foreign body piercing through the corneal stroma and endothelium. This case may serve as an opportunity to re-examine the approach to managing chronic and stable intracorneal wooden foreign bodies and explore the implications of continued observation rather than surgical management.

Development of a Fully Synthetic Corneal Stromal Construct via Supramolecular Hydrogel Engineering

Recent advances in the field of ophthalmology show great potential in the design of bioengineered constructs to mimic the corneal stroma. Hydrogels based on synthetic supramolecular polymers, are attractive synthetic mimics of the natural highly hydrated corneal stroma. Here, a fully synthetic corneal stromal construct is developed via engineering of an injectable supramolecular hydrogel based on ureido-pyrimidinone (UPy) moieties. The hydrogel displays a dynamic and tunable behavior, which allows for control of biochemical and mechanical cues. Two hydrogels are developed, a fully synthetic hydrogel functionalized with a bioactive cyclic arginine-glycine-aspartate UPy (UPy-cRGD) additive, and a hybrid hydrogel based on UPy-moieties mixed with collagen type I fibers. Both hydrogels supported cell encapsulation and associated cellular deposition of extracellular matrix (ECM) proteins after 21 days. Excitingly, the hydrogels support the activation of isolated primary keratocytes into stromal fibroblasts as well as the differentiation toward more quiescent corneal stromal keratocytes, demonstrated by their characteristic long dendritic protrusions and a substantially diminished cytokine secretion. Furthermore, cells survive shear stresses during an injectability test. Together, these findings highlight the development of an injectable supramolecular hydrogel as a synthetic corneal stromal microenvironment able to host primary keratocytes.

Parameters of a basic ophthalmic examination that can ensure proper timing of corneal crosslinking in patients with keratoconus

BACKGROUND

By the time patients with keratoconus are referred to specialists for treatment, the disease-related thinning of their corneas has already made them ineligible (< 400 μm) for corneal crosslinking (CXL).

PURPOSE

To find basic ophthalmic examination parameters that can ensure proper timing of referral for CXL.

METHODS

We reviewed cases referred to Toyama University Hospital for the treatment of keratoconus from August 2011 to May 2021 to identify the frequency of contraindication due to minimal corneal thickness (MCT) < 400 μm at first visit. We performed a receiver operator characteristic (ROC) analysis of basic exam parameters (uncorrected distance visual acuity, corrected distance visual acuity, corrected distance visual acuity with hard contact lens, sphericity, cylindricity, and/or corneal astigmatism) potentially predicting eligibility for CXL. For those with an area under the curve (AUC) > 0.8, we determined cut-off values and calculated sensitivity and specificity.

RESULTS

Analyses included 66 eyes of 38 Japanese patients aged 25.0 ± 7.1 yrs (range 12-38 yrs) (56 male eyes and 10 female eyes). Thirty percent of the patients had an MCT < 400 μm. The AUC for uncorrected distance visual acuity (UCDVA) was 0.85. A cut-off value of 1.22 (converted to decimal visual acuity: ≥ 0.06) yielded 87% sensitivity and 75% specificity. The AUC for corrected distance visual acuity (CDVA) was 0.90. A cut-off of 0.52 (converted to decimal visual acuity: ≥ 0.3) yielded 89% sensitivity and 75% specificity.

CONCLUSIONS

It is advisable to refer patients with keratoconus to a specialized facility for CXL when either of the following conditions is present: (i) UCDVA (decimal visual acuity) ≥ 0.06 or (ii) CDVA (decimal visual acuity) ≥ 0.3.

Comparisons of the protein expressions between high myopia and moderate myopia on the anterior corneal stroma in human

PURPOSE

To investigate the differentially expressed proteins (DEP) between high myopia and moderate myopia on the anterior corneal stroma.

METHODS

Tandem mass tag (TMT) quantitative proteomics was utilized to reveal proteins. DEPs were screened by the multiple change of more than 1.2 times or less than 0.83 and the P value < 0.05. The DEPs were functional annotated by Gene Ontology (GO) terms. Proteins and protein interaction (PPI) networks were conducted with String online tool. Parallel reaction monitoring (PRM) data processing was used to verify the TMT proteomics results.

RESULTS

There are 36 DEPs between high myopia and moderate myopia on the anterior corneal stroma, of which 11 proteins are upregulated, 25 proteins are downregulated. The GO analysis demonstrated keratinocyte migration and structural constituent of cytoskeleton that are significantly changed with most of the proteins decreased in high myopic corneas. Keratin 16 (KRT16) and erythrocyte membrane protein band 4.1-like protein 4B are the only two proteins involved in both functions. The PPI analysis showed keratin type II cytoskeletal 6A (KRT6A) and KRT16 that have strong connections. Immunoglobulin lambda variable 8-61(IGLV8-61) and nicotinamide phosphoribosyl transferase (NAMPT) have consistent results with the TMT.

CONCLUSIONS

The high myopic corneas have 36 DEPs compared to the moderate myopic corneas on the anterior corneal stroma. Keratinocyte migrations and structural constituent of cytoskeleton are weakened in high myopic corneas, which may partly account for the lower corneal biomechanics in high myopic eyes. The lower expressed KRT16 plays important roles in high myopic corneas.

First European results of a new refractive lenticular extraction procedure-SmartSight by SCHWIND eye-tech-solutions

BACKGROUND

To evaluate vision 3 months after SmartSight lenticule extraction treatments.

DESIGN

Case series.

METHODS

This case series of patients were treated at Specialty Eye Hospital Svjetlost in Zagreb, Croatia. Sixty eyes of 31 patients consecutively treated with SmartSight lenticule extraction were assessed. The mean age of the patients was 33 ± 6 years (range 23-45 years) at the time of treatment with a mean spherical equivalent refraction of -5.10 ± 1.35 D and mean astigmatism of 0.46 ± 0.36 D. Monocular corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA) were assessed pre- and post-operatively. Ocular and corneal wavefront aberrations have been postoperatively compared to the preoperative baseline values. Changes in ocular wavefront refraction, as well as changes in keratometric readings are reported.

RESULTS

At 3 months post-operatively, mean UDVA was 20/20 ± 2. Spherical equivalent showed a low myopic residual refraction of -0.37 ± 0.58 D with refractive astigmatism of 0.46 ± 0.26 D postoperatively. There was a slight improvement of 0.1 Snellen lines at 3-months follow-up. Compared to the preoperative status, ocular aberrations (at 6 mm diameter) did not change at 3 months follow-up; whereas corneal aberrations increased (+0.22 ± 0.21 µm for coma; +0.17 ± 0.19 µm for spherical aberration; and +0.32 ± 0.26 µm for HOA-RMS). The same correction was determined using changes in ocular wavefront refraction, as well as changes in keratometric readings.

CONCLUSION

Lenticule extraction after SmartSight is safe and efficacious in the first 3 months postoperatively. The post-operative outcomes indicate improvements in vision.

New dawn for keratoconus treatment: potential strategies for corneal stromal regeneration

Keratoconus is a progressive, ectatic and blinding disorder of the cornea, characterized by thinning of corneal stroma. As a highly prevalent among adolescents, keratoconus has been a leading indication for corneal transplantation worldwide. However, the severe shortage of donor corneas is a global issue, and the traditional corneal transplantation surgeries may superinduce multiple complications, necessitating efforts to develop more effective strategies for keratoconus treatment. In this review, we summarized several strategies to promote corneal stromal regeneration or improve corneal stromal thickness, including cell-based therapies, biosynthetic alternatives for inducing corneal regeneration, minimally invasive intrastromal implantation and bioengineered tissues for implantation. These strategies provided more accessible but safer alternatives from various perspectives for keratoconus treatment, paving the way for arresting the keratoconus progression in its earlier stage. For the treatments of corneal ectatic diseases beyond keratoconus, these approaches will provide important references and widen the therapy options in a donor tissue-independent manner.

Biaxial hyperelastic and anisotropic behaviors of the corneal anterior central stroma along the preferential fibril orientations. Part I: Measurement and calibration of personalized stress-strain curves

Lacking specimens is the biggest limitation of studying the mechanical behaviors of human corneal. Extracting stress-strain curves is the crucial step in investigating hyperelastic and anisotropic properties of human cornea. 15 human corneal specimens extracted from the small incision lenticule extraction (SMILE) surgery were applied in this study. To accurately measure the personalized true stress-strain curve using corneal lenticules, the digital image correlation (DIC) method and finite element method were used to calibrate the stress and the strain of the biaxial extension test. The hyperelastic load-displacement curves obtained from the biaxial extension test were performed in preferential fibril orientations, which are arranged along the nasal-temporal (NT) and the superior-inferior (SI) directions within the anterior central stroma. The displacement and strain fields were accurately calibrated and calculated using the digital image correlation (DIC) method. A conversion equation was given to convert the effective engineering strain to the true strain. The stress field distribution, which was simulated using the finite element method, was verified. Based on this, the effective nominal stress with personalized characteristics was calibrated. The personalized stress-strain curves containing individual characteristic, like diopter and anterior surface curvature, was accurately measured in this study. These results provide an experimental method using biaxial tensile test with corneal lenticules. It is the foundation for investigating the hyperelasticity and anisotropy of the central anterior stroma of human cornea.

Use of Nanoindentation in Determination of Regional Biomechanical Properties of Rabbit Cornea After UVA Cross-Linking

Purpose

To evaluate the regional effects of different corneal cross-linking (CXL) protocols on corneal biomechanical properties.

Methods

The study involved both eyes of 50 rabbits, and the left eyes were randomized to the five intervention groups, which included the standard CXL group (SCXL), which was exposed to 3-mW/cm2 irradiation, and three accelerated CXL groups (ACXL1-3), which were exposed to ultraviolet-A at irradiations of 9 mW/cm2, 18 mW/cm2, and 30 mW/cm2, respectively, but with the same total dose (5.4 J/cm2). A control (CO) group was not exposed to ultraviolet-A. No surgery was done on the contralateral eyes. The corneas of each group were evaluated by the effective elastic modulus (Eeff) and the hydraulic conductivity (K) within a 7.5-mm radius using nanoindentation measurements.

Results

Compared with the CO group, Eeff (in regions with radii of 0-1.5 mm, 1.5-3.0 mm, and 3.0-4.5 mm) significantly increased by 309%, 276%, and 226%, respectively, with SCXL; by 222%, 209%, and 173%, respectively, with ACXL1; by 111%, 109%, and 94%, respectively, with ACXL2; and by 59%, 41%, and 37%, respectively, with ACXL3 (all P < 0.05). K was also significantly reduced by 84%, 81%, and 78%, respectively, with SCXL; by 75%, 74%, and 70%, respectively, with ACXL1; by 64%, 62%, and 61%, respectively, with ACXL2; and by 33%, 36%, and 32%, respectively, with ACXL3 (all P < 0.05). For the other regions(with radii between 4.5 and 7.5 mm), the SCXL and ACXL1 groups (but not the ACXL2 and ACXL3 groups) still showed significant changes in Eeff and K.

Conclusions

CXL had a significant effect on corneal biomechanics in both standard and accelerated procedures that may go beyond the irradiated area. The effect of CXL in stiffening the tissue and reducing permeability consistently decreased with reducing the irradiance duration.

A review of the epithelial and stromal effects of corneal collagen crosslinking

Induced corneal collagen crosslinking and mechanical stiffening via ultraviolet-A photoactivation of riboflavin (UVA CXL) is now a common treatment for corneal ectasia and Keratoconus. Some effects of the procedure such as induced mechanical stiffening, corneal flattening, and cellular toxicity are well-known, but others remain more controversial. Authors report a variety of contradictory effects, and provide evidence based on individual results and observations. A full understanding of the effects of and mechanisms behind this procedure are essential to predicting its outcome. A growing interest in modifications to the standard UVA CXL protocol, such as transepithelial or accelerated UVA CXL, makes analyzing the literature as a whole more urgent. This review presents an analysis of both the agreed-upon and contradictory results reported and the various methods used to obtain them.

Corneal crosslinking with riboflavin using sunlight

PURPOSE

To assess whether sunlight might be used to induce a biomechanical stiffening effect in riboflavin-soaked corneas similar to the effect observed in corneal crosslinking (CXL) using riboflavin and UV-A light.

SETTING

Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland.

DESIGN

Experimental study.

METHODS

52 porcine eyes were assayed. The concentration of riboflavin in the corneal stroma was estimated using UV-A transmission in a preliminary experiment. Then, the duration of sunlight exposure to achieve a fluence of 7.2/cm 2 was calculated. Finally, de-epithelialized corneas were divided equally into 3 groups and soaked with riboflavin 0.1% (control group and Group 1) or 0.5% (Group 2). Eyes from Groups 1 and 2 were then exposed to sunlight. The elastic modulus was calculated as an indicator of stiffness.

RESULTS

Riboflavin concentration in Group B was higher by a factor of 2.8 than Group A. According to live illuminance measurements and stromal riboflavin concentration, the sunlight exposure duration varied between 16 minutes and 45 minutes. Groups 1 and 2 had higher elastic modulus than controls ( P < .0001) but did not differ between them ( P = .194). The stiffening effect was 84% and 55%, respectively.

CONCLUSIONS

Sunlight exposure of ex vivo corneas soaked in both riboflavin 0.1% and 0.5% resulted in increased corneal stiffness. Specifically, riboflavin 0.1% with longer UV-A exposure showed a trend for a greater stiffening effect, which might open new alleys for the use of oral riboflavin and fractioned sunlight exposure as less invasive CXL techniques.

Dexpanthenol/sodium hyaluronate eye drops for corneal epithelial healing following corneal cross-linking in patients with keratoconus

PURPOSE

To evaluate the effect of dexpanthenol 2%/sodium hyaluronate 0.15% eye drops on corneal epithelial healing and corneal microstructural changes following corneal cross-linking (CXL) in patients with keratoconus.

METHODS

The study included 42 eyes of 21 patients with keratoconus who underwent CXL on both eyes. One eye of each patient was instilled dexpanthenol 2%/sodium hyaluronate 0.15% eye drops (DP/SH group) and the fellow eye was instilled unpreserved sodium hyaluronate 0.15% eye drops (SH group). The epithelial healing process was assessed every day until complete reepithelialization was achieved. The in vivo confocal microscopy (IVCM) findings were also recorded.

RESULTS

The mean epithelial defect size 48.6 ± 6.7 mm2 for the DP/SH group and 48.2 ± 5.3 mm2 for the SH group. Complete reepithelialization was seen after 2.24 ± 0.44 days (range 2-4 days) in the DP/SH group and 3.43 ± 0.60 days (3 to 5 days) in the SH group. Posterior keratocyte density and endothelial cell density were similar in both groups. The mean subbasal nerve plexus density was significantly higher in the DP/SH group (postoperative 1 month: 1.13 ± 1.51, 3 months: 3.53 ± 2.55, 6 months: 7.07 ± 1.42) compared to the SH group (postoperative 1 month: 0.87 ± 1.43, 3 months: 2.89 ± 2.62, 6 months 6.33 ± 1.29). The DP/SH group revealed faster subbasal nerve regeneration and less edema compared to the SH group.

CONCLUSION

Dexpanthenol 2%/sodium hyaluronate 0.15% eye drops were effective and safe for corneal epithelial healing, and promoted faster corneal reepithelialization, nerve regeneration, and keratocyte repopulation with reduced corneal edema compared to sodium hyaluronate eye drops.

Long-Term Outcomes After Corneal Cross-linking for Progressive Keratoconus and Corneal Ectasia: A 10-Year Follow-Up of the Pivotal Study

OBJECTIVES

To report on the topographic and visual outcomes 10 years after corneal cross-linking in patients with progressive keratoconus and corneal ectasia after refractive surgery.

METHODS

Cross-sectional cohort study of an original, prospective, randomized, clinical trial. Patients treated in a single center cornea and refractive surgery practice as part of the U.S. pivotal trials, which led to the Food and Drug Administration approval of corneal cross-linking, were recruited for a 10-year follow-up examination. LogMar lines (LL) of uncorrected visual acuity (UCVA) and best spectacle--corrected visual acuity (BSCVA), maximum keratometry, and thinnest pachymetry were evaluated. In addition, the Belin ABCD progression display was used to determine progression (95% confidence interval) of the anterior curvature, posterior curvature, and corneal thickness of each individual eye included.

RESULTS

Nineteen eyes of 13 patients treated with standard cross-linking returned for a 10-year follow-up examination. Mean maximum keratometry changed from 58.2±12.0 diopters (D) to 58.3±10.1 D, thinnest pachymetry changed from 440.6±51.6 µm to 442.3±54.4 μm, UCVA changed from 0.79±0.42 LL to 0.86±0.46 LL, and BSCVA changed from 0.38±0.26 LL to 0.33±0.34 LL, 10 years after cross-linking. Individually, 68.5% of the entire cohort, 81.8% of keratoconus eyes, and 50% of eyes with corneal ectasia remained topographically stable 10 years after standard cross-linking.

CONCLUSIONS

In the entire cohort, visual acuity and topography remained stable 10 years after cross-linking. Over the long-term, eyes with keratoconus seem to be more stable than those with corneal ectasia.

Corneal Collagen Cross-Linking for Late Onset Progressive Keratoconus in Iridocorneal Endothelial Syndrome

PURPOSE

The aim of this study was to report the first case of successful use of corneal collagen cross-linking (CXL) to halt the progression of keratoconus in a patient with concurrent iridocorneal endothelial (ICE) syndrome.

METHODS

A 30-year-old White man was referred to our subspecialty corneal clinic for further investigation of right corectopia. The patient was asymptomatic and was otherwise fit. Slit-lamp examination revealed a right oval-shaped pupil decentered superiorly, a transillumination defect at the 5-o'clock position, minimal gutta-like changes in the corneal endothelium, and few inferior peripheral anterior synechiae. Dilated fundoscopy was normal in both eyes, with healthy optic discs, maculae, and peripheral retinae. Specular microscopy and slit-lamp findings suggested ICE syndrome. Subsequent investigation with corneal tomography showed progressive signs of inferior corneal ectasia with steepening, and thinning in the right eye, consistent with keratoconus. The left eye was unremarkable.

RESULTS

Epithelium-off accelerated corneal CXL was performed in the affected eye. Early post-CXL follow-up (1 week) was unremarkable, and further follow-ups were arranged at 3, 6, 12, and 24 months, respectively. In subsequent reviews, the patient's vision and corneal tomography findings were stable.

CONCLUSIONS

We describe the first case of corneal CXL for progressive keratoconus with ICE syndrome. co-existing keratoconus and ICE syndrome can occur, and corneal cross-linking was used successfully in this case to halt keratoconus progression. However, further studies will need to establish the impact of epithelium-off corneal cross-linking, especially in more severely affected eyes.

Novel Correlation between TGF-β1/-β3 and Hormone Receptors in the Human Corneal Stroma

This study investigated the interplay between transforming growth factor beta (TGF-β1/T1 and TGF-β3/T3), and sex hormone receptors using our 3D in vitro cornea stroma model. Primary human corneal fibroblasts (HCFs) from healthy donors were plated in transwells at 106 cells/well and cultured for four weeks. HCFs were supplemented with stable vitamin C (VitC) and stimulated with T1 or T3. 3D construct proteins were analyzed for the androgen receptor (AR), progesterone receptor (PR), estrogen receptor alpha (ERα) and beta (ERβ), luteinizing hormone receptor (LHR), follicle-stimulating hormone receptor (FSHR), gonadotropin-releasing hormone receptor (GnRHR), KiSS1-derived peptide receptor (KiSS1R/GPR54), and follicle-stimulating hormone subunit beta (FSH-B). In female constructs, T1 significantly upregulated AR, PR, ERα, FSHR, GnRHR, and KiSS1R. In male constructs, T1 significantly downregulated FSHR and FSH-B and significantly upregulated ERα, ERβ, and GnRHR. T3 caused significant upregulation in expressions PR, ERα, ERβ, LHR, FSHR, and GNRHR in female constructs, and significant downregulation of AR, ERα, and FSHR in male constructs. Semi-quantitative Western blot findings present the interplay between sex hormone receptors and TGF-β isoforms in the corneal stroma, which is influenced by sex as a biological variable (SABV). Additional studies are warranted to fully delineate their interactions and signaling mechanisms.

Unusual presentation of infectious crystalline keratopathy: A case report with literature review

INTRODUCTION

Infectious crystalline keratopathy (ICK) is a rare corneal disease. ICK has been recognised in patients with immunocompromised cornea or post penetrating keratoplasty. Here we report a case of ICK in an apparently healthy cornea.

CASE DESCRIPTION

A 25-years old Chinese female, with no history of systemic or ocular disease, presented to the eye clinic with one-month history of right eye (RE) blurring of vision with foreign body sensation. On examination, there were dense white crystalline needle-like projections over inferior paracentral corneal stroma with intact epithelium. There was also presence of lower eyelid epiblepharon with lashes rubbing against the diseased area. Corneal scraping cultures were suggestive of bacterial infection. Patient responded well with corneal epithelium debridement, intensive topical antibiotics and epiblepharon correction to prevent further microtrauma.

CONCLUSIONS

The only contributing factor for ICK in our patient was trichiasis from epiblepharon. Repetitive microtrauma caused by the eyelashes lead to direct penetration and inoculation of normal ocular flora into the corneal stroma. Clinicians need to be vigilant in ruling out other possible causes such as lid abnormalities when managing an ICK patient without apparent risk factors.

[Clinical analysis of corneal interface infection]

Objective: To analyze the clinical features of corneal interface infection. Methods: A retrospective case series study was conducted to explore the clinical features of interstitial corneal infection. The data of eight patients (eight eyes) who were diagnosed with interstitial corneal infection after undergoing corneal transplant or corneal refractive surgery and visited Beijing Tongren Eye Center from January to December 2018 were collected, including two male and six female patients aged between 18 and 55 years (median age, 27 years). The patients' general information, surgical type, onset time, and clinical manifestations were recorded. The lesions were examined by in vivo corneal laser confocal microscopy (IVCM), and microbial cultures and drug sensitivity tests were performed. Results: Among the 8 patients, 4 had undergone small-incision lenticule extraction (SMILE), 2 had undergone lamellar keratoplasty, and 2 had undergone endothelial keratoplasty. The onset of infection occurred between 2 and 30 days after surgery, with a mean of 9.8 days. Among the 3 patients who had undergone SMILE, the treatment outcome was corneal haze or opacity, while the remaining 5 cases required corneal transplantation for interstitial infections. The pathogens of the 4 cases of interstitial infection after corneal transplantation were all Candida species. Under the IVCM, patients with corneal interstitial bacterial infections showed a large amount of necrotic tissue with no normal tissue structure in the corneal stroma, with infiltration of inflammatory cells and local aggregation of inflammatory cells, but no typical pathogen was observed. Patients with fungal infections showed fungal hyphae under the corneal cap (filamentous fungal infection) or dense, punctate, high-reflection structures in the corneal interstitial space (yeast-like fungal infection). Conclusions: Corneal interlayer infection is difficult to diagnose early and has a poor prognosis. IVCM can assist in early diagnosis. The pathogen spectrum of corneal interlayer infection may differ from that of corneal infection caused by trauma.

P49-A103 Allogeneic limbo-DALK: a novel surgical technique for patients with corneal stromal disease and limbal stem cell deficiency

PURPOSE

To describe a novel corneal surgical technique combining Deep Anterior Lamellar Keratoplasty (DALK) with grafting of allogeneic limbal stem cells (limbo-DALK) as treatment for eyes with corneal stromal pathology and limbal stem cell deficiency (LSCD).

METHODS

This is a series of six Limbo-DALKs in five eyes of five patients. One patient received a second limbo-DALK after graft failure following the first procedure. Two of the donor corneae were HLA matched. Clinical records of included patients were reviewed retrospectively. All patients had been diagnosed with LSCD due to various pathologies. Analysed data included demographic data, diagnoses and clinical history, graft visualization and thickness measurements by anterior segment OCT, visual acuity and epithelial status. Follow-up visits were 6 weeks and 3, 6, 9, 12 and 18 months postoperatively with final suture removal at 18 months and further follow-up examinations twice yearly thereafter.

RESULTS

Two grafts showed total epithelial closure after 2 days, two after 14 days. In one eye, full closure of corneal epithelium did not occur after the first limbo-DALK, but could be achieved one month after second limbo-DALK. No endothelial graft rejection was seen.

CONCLUSION

Based on data from this pilot series, limbo-DALK seems to be a novel viable surgical approach for eyes with severe LSCD and stromal corneal pathology.

Ultrastructural Examination of the Corneal Interface after Predescemetic Deep Anterior Lamellar Keratoplasty (DALK) - A Case Report with Light and Transmission Electron Microscopy

PURPOSE

To examine corneal buttons with light and transmission electron microscopy (TEM) to visualize the interface area and highlight the ultrastructural corneal changes after deep anterior lamellar keratoplasty (DALK).

METHODS

Two patients underwent excimer laser-assisted penetrating repeat keratoplasty after predescemetic DALK. The corneal buttons were examined by light microscopy and TEM.

RESULTS

The light microscopic examination of the corneal buttons revealed fragments of a second Descemet's membrane in the central and midperipheral areas (Case 1). In both cases, visualization of the interface area was not possible by light microscopy. The donor and host stroma were tightly attached without dehiscence. TEM identified the interface area by irregularities in the collagen distribution between the donor and host stroma. The thickness of the remaining recipient corneal stroma measured approximately 30 µm (Case 1) and 100 µm (Case 2), respectively. In the host stroma, TEM revealed the absence or degeneration of keratocytes, accumulation of amorphous material between the collagen lamellae, and vacuolar inclusions dispersed in the stroma, forming a band-like zone anterior to Descemet's membrane.

CONCLUSION

The interface area after DALK has been mainly investigated by in vivo confocal microscopy. Light microscopy and TEM findings indicate remodeling processes after DALK that are associated with increased keratocyte degeneration and structural alterations of the extracellular matrix in the host stroma. The choice of surgical method may influence the postoperative morphological and functional outcome since these findings were primarily apparent in the remaining host stroma. Therefore, complete exposure of Descemet's membrane is an important prognostic factor for the postoperative visual outcome.

Analysis of Biomechanical Response After Corneal Crosslinking with Different Fluence Levels in Porcine Corneas

PURPOSE

To evaluate corneal stiffening of porcine corneas induced by corneal crosslinking (CXL) with constant irradiance as a function of total fluence.

METHODS

Ninety corneas from freshly enucleated porcine eyes were divided into five groups of 18 eyes. Groups 1-4 underwent epi-off CXL using a dextran-based riboflavin solution and an irradiance of 18 mW/cm2, group 5 served as the control group. Groups 1 to 4 were treated with a total fluence of 20, 15, 10.8, and 5.4 J/cm2, respectively. Thereafter, biomechanical measurements were performed on 5 mm wide and 6 mm long strips using an uniaxial material tester. Pachymetry measurements were performed on each cornea.

RESULTS

At 10% strain, the stress was 76, 56, 52, and 31% higher in groups 1-4, respectively compared to the control group. The Young's modulus was 2.85 MPa for group 1, 2.53 MPa for group 2, 2.46 MPa for group 3, 2.12 MPa for group 4, and 1.62 MPa for the control group. The difference between groups 1 to 4 and the control group 5 were statistically significant (p = <0.001; p = <0.001; p = <0.001; p = 0.021). In addition, group 1 showed significantly more stiffening than group 4 (p = <0.001), no other significant differences were found. Pachymetry measurements revealed no statistically significant differences among the five groups.

CONCLUSION

Additional mechanical stiffening can be achieved by increasing the fluence of the CXL. There was no threshold detected up to 20 J/cm2. A higher fluence could compensate the weaker effect of accelerated or epi-on CXL procedures.

ECM-Like Adhesive Hydrogel for the Regeneration of Large Corneal Stromal Defects

The repair of large-diameter corneal stroma defects is a major clinical problem. Although some studies have attempted to use hydrogels to repair corneal damage, most of these hydrogels can only be used for focal stromal defects that are ≤3.5 mm in diameter due to poor hydrogel adhesion. Here, a photocurable adhesive hydrogel that mimics the extracellular matrix (ECM) with regard to composition for repairing 6 mm-diameter corneal stromal defects in rabbits is investigated. This ECM-like adhesive can be rapidly cured after light exposure, with high light transmittance and good mechanical properties. More importantly, this hydrogel maintains the viability and adhesion of cornea-derived cells and promotes their migration in vitro in 2D and 3D culture environments. Proteomics analysis confirms that the hydrogel promotes cell proliferation and ECM synthesis. Furthermore, in rabbit corneal stromal defect repair experiments, it is proven by histological and proteomic analysis that this hydrogel can effectively promote corneal stroma repair, reduce scar formation, and increase corneal stromal-neural regeneration at the six months follow-up. This work demonstrates the great application of ECM-like adhesive hydrogels for the regeneration of large-diameter corneal defects.

P05-A152 Human platelet lysate for cornea organ culture

PURPOSE

Comprehensible concerns have been raised regarding the safety of FBS-based culture media. In this talk we discuss the benefits of using human platelet lysate (HPL) for the xeno-free culture of human donor corneas, isolated corneal stromal keratocytes (CSK) and stromal fibroblasts (SF).

METHODS

32 human corneas unsuitable for transplantation from 16 human donors were cultured for 25-days in either 2%FBS or 2%HPL medium and compared by phase contrast microscopy (ECD and morphology), and next generation sequencing (NGS). Effects of 0.5%FBS, 5%FBS, 0.5%HPL, 2%HPL and 10%hPL on cultured human CSK and SF were evaluated.

RESULTS

Differential cornea culture showed lower endothelial cell loss in the 2%HPL vs. 2%FBS group (ECL hPL=-0.7% vs. FBS=-3.8%; p=0.01). 2%HPL led to the upregulation of cytoprotective, anti-inflammatory and anti-fibrotic genes (e.g. HMOX1, SERPINE1, ANGPTL4, LEFTY2) and the downregulation of pro-inflammatory/apoptotic genes (e.g. CXCL14, SIK1B, PLK5, PPP2R3B). CSK/SF cell viability remained high in all groups (98-100%). Cell numbers and proliferation rates increased (p=0.024-0.001), CSK marker expression decreased with higher fractions of HPL and FBS (p<0.001). SMA1 increased with higher amounts of FBS (p=0.003) but decreased with incremental HPL substitution in both cell types (p=0.014). HPL contained more TGF-β1 (100%hPL 1.861±0.231ng/ml vs. 100%FBS 0.015±0.010ng/ml, p<0.001). bFGF and HGF were only detectable in 100% hPL (bFGF 0.067±0.017ng/ml, HGF 1.074±0.050ng/ml).

CONCLUSION

2%HPL is a suitable xeno-free substitution for 2%FBS in human cornea organ culture, inducing less ECL and potentially beneficial alterations in gene expression. CSK and SF can be cultured with xeno-free hPL. To maintain CSK characteristics substitution must remain minimal (0.5% hPL/FBS). hPL contains the antifibrotic HGF und bFGF, suppressing myofibroblast conversion.

Expanding indications for corneal cross-linking

PURPOSE OF REVIEW

The aim of this study was to summarize the recent developments in corneal cross-linking (CXL) and its indications, including corneal ectasias, refractive surgery and infectious keratitis.

RECENT FINDINGS

Advances in CXL technology, such as the use of higher-intensity LED ultraviolet (UV) light sources and a better understanding of the UV-riboflavin photochemical reaction, have enabled safer and more effective methods of cross-linking thin and ultra-thin corneas, and more effective accelerated transepithelial/'epi-on' CXL procedures that are beginning to supplant the Dresden protocol as the 'gold standard' CXL method. CXL is also being used in combination with laser surgery, not only to expand the patient base who can receive refractive surgery, but also to help rehabilitate vision in patients with ectasia. CXL, and CXL combined with photorefractive keratectomy (PRK), can result in corneal flattening of 1-2 D, and corneal regularization of 4-5 D, respectively. Finally, photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) has been shown to be an effective therapy for infectious keratitis, both alone, and in combination with antimicrobial drugs.

SUMMARY

CXL has evolved from a single technique to treat a single corneal ectasia, keratoconus, to several techniques with several indications, spanning a spectrum of corneal ectasias, as well as visual rehabilitation, refractive procedures and infectious keratitis treatment.

Transforming growth factor beta receptor 2 (Tgfbr2) deficiency in keratocytes results in corneal ectasia

PURPOSE

We hypothesized that Transforming growth factor beta receptor 2 (Tgfbr2) deletion in keratocyte (Tgfbr2kera-cko), the corneal stroma cell, can result in corneal thinning and generate a potential model for Cornea Ectasia (CE).

METHODS

Corneal thickness of Tgfbr2kera-cko and Tgfbr2Ctrl was examined with Optical Coherence Tomography (OCT) at post-natal (P) days 42 and 70, respectively. Histological H&E staining, transmission electron micrograph (TEM), and immunofluorescence staining (IFS) were harnessed to examine corneal cell morphology, proliferation, differentiation, and collagen fibrils.

RESULTS

Slit-Lamp revealed that corneas were transparent in both Tgfbr2kera-cko and Tgfbr2Ctrl, however, Tgfbr2kera-cko cornea was 33.5% and 42.9% thinner as compared with those of Tgfbr2Ctrl at P42 and P70, respectively. H&E and semithin section staining with toluidine blue-O confirmed that Tgfbr2kera-cko cornea has a thinner stroma. In contrast, the epithelium in Tgfbr2kera-cko was substantially thicker. The cell proliferation marker Ki67 expression level increased ∼9% in Tgfbr2kera-cko corneal epithelium as compared with that in Tgfbr2Ctrl, however, the Krt14 and Krt12 expression pattern was not obviously changed in Tgfbr2kera-cko corneal epithelium. It was noticed that Col1a1 expression was substantially reduced in Tgfbr2kera-cko as compared with that in Tgfbr2Ctrl. TEM showed that keratocytes were unhealthy and stromal collagen fibril density was significantly reduced in Tgfbr2kera-cko as compared with that in Tgfbr2Ctrl cornea. Moreover, mechanical eye-rubbing on Tgfbr2kera-cko resulted in corneal hydrops and edema.

CONCLUSION

Tgfbr2 in keratocytes is indispensable for the corneal stroma at postnatal homeostasis. The cornea phenotype manifested in these Tgfbr2kera-cko mice resembles corneal ectasia disease in humans.

The corneal fibroblast: The Dr. Jekyll underappreciated overseer of the responses to stromal injury

PURPOSE

To review the functions of corneal fibroblasts in wound healing.

METHODS

Literature review.

RESULTS

Corneal fibroblasts arise in the corneal stroma after anterior, posterior or limbal injuries and are derived from keratocytes. Transforming growth factor (TGF) β1 and TGFβ2, along with platelet-derived growth factor (PDGF), are the major modulators of the keratocyte to corneal fibroblast transition, while fibroblast growth factor (FGF)-2, TGFβ3, and retinoic acid are thought to regulate the transition of corneal fibroblasts back to keratocytes. Adequate and sustained levels of TGFβ1 and/or TGFβ2, primarily from epithelium, tears, aqueous humor, and corneal endothelium, drive the development of corneal fibroblasts into myofibroblasts. Myofibroblasts have been shown in vitro to transition back to corneal fibroblasts, although apoptosis of myofibroblasts has been documented as a major contributor to the resolution of fibrosis in several in situ corneal injury models. Corneal fibroblasts, aside from their role as a major progenitor to myofibroblasts, also perform many critical functions in the injured cornea, including the production of critical basement membrane (BM) components during regeneration of the epithelial BM and Descemet's membrane, production of non-basement membrane-associated stromal collagen type IV to control and downregulate TGFβ effects on stromal cells, release of chemotactic chemokines that attract bone marrow-derived cells to the injured stroma, production of growth factors that modulate regeneration and maturation of the overlying epithelium, and production of collagens and other ECM components that contribute to stromal integrity after injury.

CONCLUSIONS

Corneal fibroblasts are major contributors to and overseers of the corneal response to injuries.

The role of KS GAGs in the microstructure of CXL-treated corneal stroma; a transmission electron microscopy study

The mechanical and physical properties of the cornea originate from the microstructure and composition of its extracellular matrix. It is known that collagen fibrils, with a relatively uniform diameter, are organized in a pseudo-hexagonal array. It has been suggested that proteoglycans and the interaction of their glycosaminoglycan (GAG) side chains with themselves and collagen fibrils are important for collagen fibril organization inside the cornea. There are several diseases such as keratoconus in which the regular collagen fibrillar packing becomes distorted causing corneal optical and mechanical properties to be compromised. The primary purpose of the present work was to investigate the role of GAGs on the microstructure of corneal extracellular matrix before and after corneal crosslinking (CXL) treatment. For this purpose, keratan sulphates (KS) were removed from corneal samples using the keratanase enzyme and the CXL procedure was used to crosslink the specimens. The transmission electron microscopy was then used to characterize the diameter of collagen fibrils and their interfibrillar spacing. It was found that KS GAG depletion increased the collagen interfibrillar spacing while the CXL treatment significantly decreased the interfibrillar spacing. The enzyme and CXL treatments had an insignificant effect on the diameter of collagen fibrils. The underlying mechanisms responsible for these observations were discussed in terms of the assumption that GAG chains form duplexes that behave as tiny ropes holding collagen fibrils in place.

Predicting corneal cross-linking treatment efficacy with real-time assessment of corneal riboflavin concentration

PURPOSE

To assess predictability of tissue biomechanical stiffening induced by UV-A light-mediated real-time assessment of riboflavin concentration during corneal crosslinking (CXL) of human donor tissues.

SETTING

Studio Italiano di Oftalmologia, Rome, Italy.

DESIGN

Laboratory study.

METHODS

20 sclerocorneal tissues were randomly stratified to undergo CXL with either the epithelium intact (n = 12) or removed (n = 8). Samples underwent corneal soaking with 0.22% riboflavin formulation (RitSight) with dosing time of t = 10 minutes and t = 20 minutes in epithelium-off and epithelium-on protocols, respectively. All tissues underwent 9-minute UV-A irradiance at 10 mW/cm 2 using theranostic device (C4V CHROMO4VIS). The device used controlled UV-A light irradiation to induce both imaging and treatment of the cornea, providing a real-time measure of corneal riboflavin concentration and treatment efficacy (ie, theranostic score) during surgery. Tissue biomechanics were assessed with an air-puff device (Corvis), which was performed before and after treatment. A 3-element viscoelastic model was developed to fit the corneal deformation response to air-puff excitation and to calculate the mean corneal stiffness parameter (k c ).

RESULTS

Significant corneal tissue stiffening ( P < .05) was induced by the theranostic UV-A device in either CXL treatment protocol. Significant correlation was found between the theranostic score and the increase in k c ( R = 0.75; P = .003). The score showed high accuracy (94%) and precision (94%) to predict correctly samples that had improved tissue biomechanical strengthening.

CONCLUSIONS

Real-time assessment of corneal riboflavin concentration provided a predictive and precise approach for significant improvement of tissue strength on individual corneas, regardless of CXL treatment protocol.

Corneal epithelial basement membrane assembly is mediated by epithelial cells in coordination with corneal fibroblasts during wound healing

Purpose

To understand which cell types, either alone or in combination, contribute to the assembly of the epithelial basement membrane (BM) during corneal wound healing.

Methods

A 3D corneal organotypic model and an in situ rabbit photorefractive keratectomy (PRK) model were used in this study. The 3D corneal organotypic model was established by culturing the rabbit corneal epithelial cells with either corneal fibroblasts or myofibroblasts embedded in collagen type I for 18 days. Corneal fibroblasts were isolated from fresh rabbit corneas, and the myofibroblasts were derived either directly from bone marrow or differentiated from corneal fibroblasts. Immunocytochemistry for alpha-smooth muscle actin (SMA), vimentin, desmin, and vinculin markers confirmed well-differentiated myofibroblasts. Immunohistochemistry was performed in cryofixed sections for BM markers, including laminin alpha-5, laminin beta-3, perlecan, nidogen-1, and collagen type IV. Specimens were also examined with transmission electron microscopy (TEM). Corneas were collected from rabbits after -3 diopter (D) PRK at different time points after surgery, with four corneas at each time point in each group. Cryofixed corneal sections were stained for vimentin, alpha-SMA, and nidogen-1.

Results

The formation of an epithelial BM with expression of laminin alpha-5, laminin beta-3, perlecan, nidogen-1, and collagen IV was observed at the interface between the corneal epithelial cells and corneal fibroblasts. TEM images further confirmed the presence of epithelial BM in organotypic cultures of epithelial cells and corneal fibroblasts. No epithelial BM was observed in cultures of corneal epithelial cells and myofibroblasts (cornea or bone marrow derived), corneal epithelial cells alone, or corneal fibroblasts alone. In rabbit corneas after -3D PRK, a strong association was observed between the regenerating epithelial BM and the presence of corneal fibroblasts at the site of epithelial BM generation.

Conclusions

The corneal epithelial BM assembly is mediated by epithelial cells in coordination with corneal fibroblasts during wound healing.

Enhanced immune responses to vaccine antigens in the corneal stroma

To examine the widely accepted dogma that the eye is an immune-privileged organ that can suppress antigen immunogenicity, we explored systemic immune responses to a model vaccine antigen (tetanus toxoid) delivered to six compartments of the rodent eye (ocular surface, corneal stroma, anterior chamber, subconjunctival space, suprachoroidal space, vitreous body). We discovered that antigens delivered to corneal stroma induced enhanced, rather than suppressed, antigen-specific immune responses, which were 18- to 30-fold greater than conventional intramuscular injection and comparable to intramuscular vaccination with alum adjuvant. Systemic immune responses to antigen delivered to the other ocular compartments were much weaker. The enhanced systemic immune responses after intrastromal injection were related to a sequence of events involving the formation of an antigen "depot" in the avascular stroma, infiltration of antigen-presenting cells, up-regulation of MHC class II and costimulatory molecules CD80/CD86, and induction of lymphangiogenesis in the corneal stroma facilitating sustained presentation of antigen to the lymphatic system. These enhanced immune responses in corneal stroma suggest new approaches to medical interventions for ocular immune diseases and vaccination methods.

Comparison of Continuous versus Pulsed Mode in Accelerated Corneal Collagen Cross-linking for Keratoconus

PURPOSE

To compare efficacy and safety between the two modes of energy delivery-pulsed and continuous, in accelerated corneal collagen cross-linking (KXL) to stop the keratoconus advancement through topographical, visual, and refractive endpoints.

METHODS

It was a prospective, comparative, randomized, interventional trial. Patients with bilateral progressive keratoconus were subjected to pulsed mode KXL (P-KXL) in the right and continuous mode KXL (C-KXL) treatment in the left eye. In both methods, additional supplemental oxygen was delivered to corneal surface using a nasal cannula connected to an oxygen supply. Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity, posttreatment manifest spherical equivalent and astigmatism, and corneal topography were studied. The deformation amplitude index (DAI) was measured by Corvis-ST. Postoperative follow-up was done.

RESULTS

One hundred eyes of 50 patients underwent P-KXL in the right eye and C-KXL in the left eye. The average follow-up was 12.1 ± 1.2 months. At 1 year posttreatment, the UDVA had a mean change of 0.11 ± 0.14 logMAR in P-KXL and 0.18 ± 0.14 logMAR in C-KXL groups. The line of demarcation was observed at 251.13 ± 18.28 μ and 245.28 ± 28.26 μ deep, respectively, in P-KXL- and C-KXL-treated eyes at 6 months' follow-up. The DAI as measured by Corvis-ST showed a significant decrease from pretreatment values of 1.12 ± 0.13 mm to 0.84 ± 0.14 mm (P < 0.01) in P-KXL eyes and from 1.04 ± 0.14 mm to 0.85 ± 0.15 mm (P = 0.03) in C-KXL eyes. Both the groups did not show any statistically significant endothelial cell loss posttreatment.

CONCLUSION

C-KXL can give similar functional outcomes as P-KXL with the help of supplemental oxygen delivery with the added advantage of a shortened procedure time in comparison to pulsed mode.