Severe ulcerative keratopathy following implantation of an acellular porcine corneal stromal lenticule in a patient with keratoconus

PURPOSE

To report a case of ulcerative keratopathy following implantation of acellular porcine corneal stroma (APCS) in a patient with keratoconus (KC).

METHODS

A 58 year-old patient initially presented with an ulcerative keratopathy in the left eye. Previously, several corneal procedures (including radial keratotomy, laser-in-situ keratomileusis, crosslinking) were performed for KC. Eight months ago, an APCS lenticule (Xenia corneal implant, Gebauer Medizintechnik GmbH, Neuhausen, Germany) was implanted into a stromal pocket because of progressive keratectasia. Visual acuity was hand movement. Anterior segment optical coherence tomography showed a space between the APCS lenticule and the host stroma. Excimer laser-assisted penetrating keratoplasty (PKP, 8.0/8.1 mm) was performed in the left eye. The corneal explant was investigated by light and transmission electron microscopy.

RESULTS

Best-corrected visual acuity was 20/40 six weeks after PKP. Light microscopy demonstrated a stromal ulceration down to the APCS lenticule. No stromal cells could be found within the APCS lenticule eight months after implantation. The APCS lenticule did not show a green stain of the collagens with Masson-Goldner staining and exhibited a strong Periodic acid-Schiff positive reaction. Electron microscopy of the APCS lenticule revealed cross-linked collagen lamellae without cellular components. Close to the interface, corneal collagen lamellae of the host cornea were disorganized. Few vital keratocytes were present on the surface of the lenticule and appeared to cause mechanical disruption of the host stroma along the lenticule-stroma interface.

CONCLUSION

APCS implantation may lead to severe complications such as ulcerative keratopathy in otherwise uncomplicated KC corneas. In such cases, excimer laser-assisted PKP or Deep Anterior Lamellar Keratoplasty are the methods of choice to restore visual acuity.

Long-Term Follow-Up of Pediatric Excimer Laser-Assisted Penetrating Keratoplasty for Congenital Stromal Corneal Dystrophy

PURPOSE

The purpose of this study was to highlight characteristic clinical and microscopic findings and report the long-term follow-up of pediatric excimer laser-assisted penetrating keratoplasty (excimer-PKP) for congenital stromal corneal dystrophy (CSCD).

METHODS

A 2-year-old Greek child presented with CSCD at our department. Clinical examination showed bilateral flake-like whitish corneal opacities affecting the entire corneal stroma up to the limbus. Genetic testing identified a mutation of the decorin gene (c.962delA). The variant was not present in the parents and represented a de novo mutation. The uncorrected visual acuity was 20/100 in both eyes. Excimer-PKP (8.0/8.1 mm) was performed on the right eye at the age of 2.5 years and on the left eye at the age of 3 years. Postoperatively, alternating occlusion treatment was performed.

RESULTS

The light microscopic examination demonstrated a disorganized extracellular matrix of the corneal stroma characterized by a prominent irregular arrangement of stromal collagen lamellae with large interlamellar clefts containing ground substance, highlighted by periodic acid-Schiff- and Alcian blue-positive reaction detecting acid mucopolysaccharides. Electron microscopy showed disorganization and caliber variation of collagen lamellae and thin filaments within an electron-lucent ground substance. The postoperative course was unremarkable. Both grafts remained completely clear 14 years postoperatively. Corneal tomography showed moderate regular astigmatism with normal corneal thickness. The corrected distance visual acuity was 20/25 in both eyes.

CONCLUSIONS

Excimer-PKP for CSCD might be associated with excellent long-term results and a good prognosis, particularly when the primary surgery is performed at a very young age. However, this requires close postoperative follow-up examinations by an experienced pediatric ophthalmologist to avoid severe amblyopia.

Clinical outcomes of epithelial basement membrane dystrophy after keratorefractive lenticule extraction

PURPOSE

To determine the clinical outcomes of keratorefractive lenticule extraction (KLEx) in eyes with epithelial basement membrane dystrophy (EBMD) that developed after surgery.

SETTING

Onnuri Smile Eye Clinic, Seoul, South Korea.

DESIGN

Retrospective single-center study.

METHODS

This study reviewed the medical records of 26 eyes of 16 patients who exhibited signs of EBMD after KLEx. Postoperatively, corneal findings and visual outcomes were evaluated. Statistical analyses were also performed on eyes without corneal complications after KLEx.

RESULTS

Signs of EBMD were first observed within 1 week postoperatively in 22 eyes (84.6%): 6 eyes (23.1%) showed epithelial defects, 10 eyes (38.5%) showed subepithelial corneal opacity, 5 eyes (19.2%) showed diffuse lamellar keratitis, and 1 eye (3.9%) showed epithelial ingrowth. Symptoms such as pain, while corneal lesions were present, occurred in 21 eyes (80.8%). At 3 months postoperatively, 21 eyes (80.8%) showed no specific findings on slitlamp microscopy after medical treatment, 2 eyes (7.7%) showed subepithelial corneal opacity, 2 eyes (7.7%) showed corneal scar, and 1 eye (3.9%) showed epithelial ingrowth. Uncorrected distance visual acuity was 20/25 or better in 24 eyes (92.3%), and spherical equivalent was within ±1.0 D in 20 eyes (76.9%). The efficacy index of the EBMD group did not significantly differ from the control group, while the safety index was significantly lower.

CONCLUSIONS

Manifestations of EBMD can occur after KLEx and can affect clinical outcomes. Most cases showed favorable results with appropriate nonsurgical treatment; however, some cases had long-term complications such as corneal scarring.

Examination of Subbasal Nerve Plexus and Central Corneal Stromal Microstructure in Subjects With Congenital Aniridia, Using in Vivo Confocal Laser Scanning Microscopy

PURPOSE

During life up to 70% of aniridia subjects develop aniridia-associated keratopathy (AAK). AAK is characterized by limbal stem cell insufficiency, impaired corneal epithelial cell differentiation and abnormal cell adhesion, which leads to centripetal spreading vascularization, conjunctivalization, and thickening of the cornea. Our aim was to examine the subbasal nerve plexus and central corneal stromal microstructure in subjects with congenital aniridia, using in vivo confocal laser scanning microscopy CLSM.

METHODS

31 eyes of 18 patients (55.6% males, mean age: 25.22 ± 16.35 years) with congenital aniridia and 46 eyes of 29 healthy subjects (41.4% males, mean age 30 ± 14.82 years) were examined using the Rostock Cornea Module of Heidelberg Retina Tomograph-III. At the subbasal nerve plexus, corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), corneal total branch density (CTBD), and corneal nerve fiber width (CNFW) were analyzed using ACCMetrics software. Keratocyte density in the anterior, middle and posterior stroma was assessed manually.

RESULTS

The CNFD (2.02 ± 4.08 vs 13.99 ± 6.34/mm2), CNFL (5.78 ± 2.68 vs 10.56 ± 2.82 mm/mm2) and CTBD (15.08 ± 15.62 vs 27.44 ± 15.05/mm2) were significantly lower in congenital aniridia subjects than in controls (p < 0.001 for all). CNFW was significantly higher in aniridia subjects than in controls (0.03 ± 0.004 vs 0.02 ± 0.003 mm/mm2) (p = 0.003). Keratocyte density was significantly lower in all stromal layers of aniridia subjects than in controls (p < 0.001 for all). Stromal alterations included confluent keratocytes, keratocytes with long extensions and hyperreflective dots between keratocytes in aniridia.

CONCLUSIONS

Decrease in CNFD, CNFL, and CTBD, as well as increase in CNFW well refer to the congenital aniridia-associated neuropathy. The decreased keratocyte density and the stromal alterations may be related to an increased cell death in congenital aniridia, nevertheless, stromal changes in different stages of AAK have to be further analyzed in detail.

Diagnostic utility of in vivo confocal microscopy in Acanthamoeba keratitis following corneal crosslinking

Acanthamoeba keratitis (AK) is a rare but potentially sight-threatening complication of corneal collagen crosslinking (CXL) for keratoconus. In this report, we describe an early adolescent male who underwent routine CXL for progressive keratoconus in his left eye. Preprocedural left visual acuity (VA) was 6/9. At day 5 postprocedure, multifocal corneal infiltrates were identified. Corneal scrape, bandage contact lens cultures and herpetic and Acanthamoeba PCR were negative. In vivo, confocal microscopy (IVCM) identified Acanthamoeba cysts within the corneal stroma. Intensive amoebicidal therapy was initiated, but recovery was complicated by significant inflammation, resulting in widespread aggressive corneal vascularisation necessitating topical steroids and steroid-sparing agents. At 10 months, his left VA was 6/24. This report emphasises the importance of maintaining a high index of suspicion for AK in cases of post-CXL microbial keratitis and highlights the diagnostic value of IVCM, particularly in culture-negative and PCR-negative cases.

Evaluation of dynamic corneal response parameters and the biomechanical E-staging after Intacs® SK implantation in keratoconus

PURPOSE

This retrospective longitudinal study evaluated the biomechanical E-staging in KC corneas before and after intracorneal ring segment (ICRS) implantation (Intacs® SK, Addition Technology, Illinois, United States).

METHODS

Biomechanical E-staging for ectatic corneal diseases was applied retrospectively on 49 KC corneas of 41 patients who underwent ICRS implantation. The main outcome parameters included the Corvis Biomechanical Factor (CBiF, the linearized Corvis Biomechanical Index and the biomechanical parameters included), the resulting biomechanical E-staging, the stress-strain index, thinnest corneal thickness (TCT), maximal anterior keratometry (Kmax), and the anterior radius of curvature (ARC). They were evaluated at 1.9 ± 1.1 months preoperatively and postoperatively after 2.8 ± 0.7, 5.8 ± 1.0, and 10.6 ± 2.3 months.

RESULTS

The CBiF decreased (4.9 ± 0.5 | 4.7 ± 0.5, P = 0.0013), and the E-staging increased significantly (2.8 ± 0.8 | 3.1 ± 0.9, P = 0.0012, paired t-test) from preoperatively to the first postoperative follow-up. The difference remained significant after 6 months; however, there was no more difference after 11 months. TCT was stable, whereas Kmax and ARC significantly decreased after ICRS implantation (TCT: 464 ± 49, 470 ± 51, 467 ± 38, 461 ± 48; Kmax: 56.3 ± 4.5, 54.7 ± 4.5, 54.2 ± 4.8, 54.1 ± 4.3; ARC: 51.5 ± 3.4, 48.3 ± 3.8, 48.6 ± 3.0, 48.6 ± 3.2 preoperatively and 3, 6, and 11 months postoperatively, respectively). Besides Kmax and ARC, Ambrósio's relational thickness to the horizontal profile (ARTh) was the only parameter that was significantly lower than preoperatively at any follow-up (P ≤ 0.0024, Wilcoxon matched-pairs test).

CONCLUSION

Intacs® SK implantation results in an increasing biomechanical E-staging in the first postoperative months with stabilization near preoperative values after 1 year. Significantly lower ARTh values at any follow-up document the ICRS effect and contribute to a slightly higher postoperative biomechanical E-staging value.

Corneal Stroma Analysis and Related Ocular Manifestations in Recovered COVID-19 Patients

Purpose

The purpose of this study was to assess the impact of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) on corneal stroma characteristics, ocular manifestations, and post-recovery refractive surgery outcomes after varying recovery durations.

Methods

Fresh corneal lenticules from patients with post-coronavirus disease 2019 (COVID-19; recovered within 135 days) and healthy controls (HCs) after small incision lenticule extraction (SMILE) surgery were obtained for experimental validation of SARS-CoV-2 susceptibility, morphological changes, and immune response of the corneal stroma. Corneal optical density (CD) was measured using the Pentacam HR. Corneal epithelium thickness (ET) and endothelium parameters were evaluated by wide-field optical coherence tomography (OCT) and non-contact specular microscopy (SP-1P), respectively. All the patients were assessed after SMILE surgery until 3 month of follow-up.

Results

The cornea was susceptible to SARS-CoV-2 with the presence of SARS-CoV-2 receptors (CD147 and ACE2) and spike protein remnants (4 out of 58) in post-recovery corneal lenticules. Moreover, SARS-CoV-2 infection triggered immune responses in the corneal stroma, with elevated IL-6 levels observed between 45 and 75 days post-recovery, which were then lower at around day 105. Concurrently, corneal mid-stromal nerve length and branching were initially higher in the 60D to 75D group and returned to control levels by day 135. A similar trend was observed in CD within zones 0 to 2 and 2 to 6 and in the hexagonal cells (HEX) ratio in endothelial cells, whereas ET remained consistent. Notably, these changes did not affect the efficacy, safety, or predictability of post-recovery SMILE surgery.

Conclusions

SARS-CoV-2 induces temporal alterations in corneal stromal morphology and function post-recovery. These findings provided a theoretical basis for corneal health and refractive surgery management in the post-COVID-19 milieu.

Spike sign - To predict the formation of big bubble in deep anterior lamellar keratoplasty in advanced keratoconus

Lamellar surgeries have revolutionized our understanding and practice of keratoplasties. However, the learning curve in deep anterior lamellar keratoplasty (DALK) makes it daunting for novice surgeons. This paper describes a unique intraoperative sign - the radial "spike sign," which heralds the commencement of a big bubble in some cases of advanced keratoconus in eyes that have not undergone any previous surgery. The spike sign was noted during big bubble DALK surgery and was then retrospectively looked for in recorded DALK surgical videos and correlated with the formation of a big bubble. The movement of air after injection was classified into the direct formation of a big bubble, stromal emphysema with no big bubble, and emphysema with the spike sign followed by a big bubble. In total, 104 surgical videos of big bubble attempts were evaluated and classified as such. The spike sign helps reduce the number of unnecessary attempts at big bubble formation during DALK, thus improving surgical outcomes.

Two-phase mechanism in the treatment of corneal stromal fibrosis with topical losartan

Recent studies in rabbits and case reports in humans have demonstrated the efficacy of topical losartan in the treatment of corneal scarring fibrosis after a wide range of injuries, including chemical burns, infections, surgical complications, and some diseases. It is hypothesized that the effect of losartan on the fibrotic corneal stroma occurs through a two-phase process in which losartan first triggers the elimination of myofibroblasts by directing their apoptosis via inhibition of extracellular signal-regulated kinase (ERK)-mediated signal transduction, and possibly through signaling effects on the viability and development of corneal fibroblast and fibrocyte myofibroblast precursor cells. This first step likely occurs within a week or two in most corneas with fibrosis treated with topical losartan, but the medication must be continued for much longer until the epithelial basement membrane (EBM) is fully regenerated or new myofibroblasts will develop from precursor cells. Once the myofibroblasts are eliminated from the fibrotic stroma, corneal fibroblasts can migrate into the fibrotic tissue and reabsorb/reorganize the disordered extracellular matrix (ECM) previously produced by the myofibroblasts. This second stage is longer and more variable in different eyes of rabbits and humans, and accounts for most of the variability in the time it takes for the stromal opacity to be markedly reduced by topical losartan treatment. Eventually, keratocytes reemerge in the previously fibrotic stromal tissue to fine-tune the collagens and other ECM components and maintain the normal structure of the corneal stroma. The efficacy of losartan in the prevention and treatment of corneal fibrosis suggests that it acts as a surrogate for the EBM, by suppressing TGF beta-directed scarring of the wounded corneal stroma, until control over TGF beta action is re-established by a healed EBM, while also supporting regeneration of the EBM by allowing corneal fibroblasts to occupy the subepithelial stroma in the place of myofibroblasts.

Impact of Obesity and Age on Mouse Corneal Innervation at the Epithelial-Stromal Interface

Purpose

The corneal epithelium is the most highly innervated structure in the body. Previously, we reported a novel event whereby stromal axons fuse with basal epithelial cells, limiting nerve penetration into the epithelium. Although corneal-epithelial nerves undergo changes in sensitivity and distribution throughout life and in response to an obesogenic diet, it is unknown if neuronal-epithelial cell fusion is altered. Here, we sought to determine if neuronal-epithelial cell fusion frequency correlates with obesogenic diet consumption and age.

Methods

Corneas were collected from C57BL/6 mice and evaluated for neuronal-epithelial cell fusion frequency using serial block-face scanning electron microscopy. To assess the correlation between diet-induced obesity and fusion frequency, 6-week-old mice were fed either a normal diet or an obesogenic diet for 10 weeks. To assess changes in fusion frequency between young and adult mice under normal dietary conditions, 9- and 24-week-old mice were used.

Results

Mice fed a 10-week obesogenic diet showed 87% of central-cornea stromal nerves engaged in fusion compared with only 54% in age-matched controls (16 weeks old). In 9-week-old normal-diet animals, 48% of central-cornea stromal nerves contained fusing axons and increased to 81% at 24 weeks of age. Corneal sensitivity loss correlated with increased body weight and adiposity regardless of age and diet.

Conclusions

Neuronal-epithelial cell fusion positively correlates with age and obesogenic diet consumption, and corneal nerve sensitivity loss correlates with increased body weight and adiposity, regardless of age and diet. As such, neuronal-epithelial cell fusion may play a role in corneal nerve density and sensitivity regulation.

Adjunctive bevacizumab therapy in an equine corneal stromal invasive squamous cell carcinoma with a 53-months follow-up

A 17-year-old Appaloosa mare was referred for evaluation of presumed refractory keratitis of the left eye. Gross examination revealed ocular discomfort and corneal neovascularization with a nasal focal opacification affecting approximately 40% of the corneal surface. On ophthalmic examination, extensive subepithelial to mid-stromal vascular branching accompanied by a homogeneous white, dense opacification, which affected up to 80% of the total corneal thickness, were apparent. Signs of concurrent uveitis were absent. Deep-stromal lamellar keratectomy with a conjunctival pedicle graft was performed under general anesthesia. Histopathology confirmed a poorly differentiated corneal stromal invasive squamous cell carcinoma (SI-SCC) with neoplastic cell extension to the surgical margins. Postoperatively, 4 topical mitomycin C 0.04% chemotherapy cycles combined with oral firocoxib therapy were initiated. Seven months after surgery, regrowth of the SI-SCC was clinically suspected. A total volume of 1 ml bevacizumab 2.5% was administered in the standing sedated horse via 3 mid-stromal corneal injections. Four weeks later, intrastromal bevacizumab injections (ISBIs) were repeated, however, this time the solution was injected directly into the main corneal vessel branches.Seven weeks after the second ISBIs, the left eye was comfortable and significant remission of corneal vascularization and opacity was recognized. No recurrence has been noted for a follow-up period of more than 53 months.Equine SI-SCC usually has a very poor prognosis for globe maintenance. To the authors' knowledge this is the first report of well-tolerated intrastromal antivascular endothelial growth factor adjunctive therapy with bevazicumab 2.5% and SI-SCC resolution after a multimodal treatment approach.

Late-onset distal-apical intracorneal ring-segments keratopathy: an analysis of a large sample in a multicenter study

PURPOSE

To review the prevalence and describe the characteristics, of cases with late-onset intracorneal ring segments (ICRS) keratopathy in a multicenter study.

METHODS

A retrospective multicentric case-series study was performed in a specialized keratoconus service, from Buenos Aires, Argentina. An electronic clinical chart from patients with ICRS keratopathy between January 1999 and January 2019 was reviewed. We included cases with late-onset distal-apical ICRS keratopathy, which was defined as a persistent corneal lesion developed 12 months or later after implantation, located over, around, or closer to the ICRS. All the surgeries were performed by a manual corneal tunnel creation technique. Samples were taken to rule out infectious etiology.

RESULTS

From 5217 eyes that underwent ICRS implantation, 13 cases (0.24%) were detected. The keratopathy onset was 72 ± 42.98 months (29-133) after ICRS implantation. Cultures were negative in all cases. An ICRS exchange was made for five cases in stage I and four in stage II. Four cases presented with partial ICRS extrusion in stage III. ICRS exchange was possible in two of them and a penetration keratoplasty was necessary for the rest. All cases remained stable 1 year after surgical procedures.

CONCLUSIONS

A late-onset distal-apical ICRS keratopathy was detected with low prevalence (0.24%) in a large sample. It was classified into three stages according to its severity. Different treatments were selected for each stage, obtaining stable results 1 year after treatment.

Impaired healing in an incision wound in corneal stroma in a lumican-null mouse

PURPOSE

We investigated healing pattern of an incisional wound in corneal stroma of lumican-null (KO) mice.

METHODS

C57BL/6 mice (wild-type, WT) and lumican-null (knockout, KO) mice were used. A linear full-thickness incision was produced in one cornea of each mouse. After intervals of healing, the corneas were processed for the following analyses. Histology was employed to measure the distance between each edge of the disrupted Descemet's membrane at the center of the cornea. Immunohistochemistry and real-time RT-PCR were employed to evaluate the expression of wound healing-related components in the tissue. Cultured ocular fibroblasts were obtained from cornea and sclera of WT and KO postnatal day 1 pups. The cells were subjected to examination for cell proliferation and expression of wound healing-related gene products. In vitro gel contraction assay was used to asses cell contractile activity of WT and KO cells.

RESULTS

At day 5 of incision, the distance between the disrupted Descemet's membrane was larger in a KO mouse as compared with a WT mouse. Myofibroblast appearance in the wound was suppressed by the loss of lumican. The loss of lumican downregulated TGFβ1's effects on mRNA expression of α-smooth muscle actin and collagen Ia1 in cultured ocular fibroblasts. Cell proliferation rate increased in injured stroma, which was further supported by in vitro datum of cell proliferation augmentation by the loss of lumican. Loss of lumican suppressed cell-mediated gel contraction.

CONCLUSION

Loss of lumican perturbs the healing of penetrating incision in mouse corneal stroma in association with suppression of myofibroblast generation.

Glycosaminoglycans: Roles in wound healing, formation of corneal constructs and synthetic corneas

Maintaining the clarity of the cornea is essential for vision, and is achieved through an exquisite array of collagen fibrils and proteoglycans in the corneal stroma. Alterations in the identity and modifications of the glycosaminoglycans (GAGs) are seen both throughout the normal wound healing process and in pathological conditions resulting in corneal opacity. Understanding these changes has been essential for the development of corneal prostheses and corneal reconstruction. The goal of this review article is to summarize and consolidate research in the alterations seen in glycosaminoglycans in injured and hypoxic states, address the role of proteins that can regulate glycosaminoglycans in the corneal wound healing process, and apply these findings to the context of corneal restoration through reconstruction or the insertion of synthetic devices.

Birefringence analysis of collagen supraorganization in cat corneas with tropical keratopathy

OBJECTIVE

To evaluate the birefringent properties of the cornea and examine the supraorganizational aspects of collagen fibers in cats with tropical keratopathy.

PROCEDURE

In this study, 10-micrometer-thick sections of corneal tissue from cats with tropical keratopathy were examined, both in the opaque and transparent areas of the anterior stroma. Control samples were obtained from healthy cat corneas. Polarized light microscopy was employed to evaluate the birefringent properties using two distinct methods. The first method involved measuring the optical retardation associated with corneal birefringence, while the second method assessed the alignment/waviness of the birefringent collagen fibers. Differences were significant when p < .05.

RESULTS

Tropical keratopathy resulted in a significant rise (p < .05) in optical retardation in both opaque and transparent regions of the cat cornea. In the anterior stroma, both the opaque zones and transparent tissue exhibited a higher degree of collagen fiber packing than the control corneas. However, no significant differences (p > .05) in alignment were observed between the transparent tissue of the diseased cornea and the healthy corneas.

CONCLUSION

Supraorganizational changes in collagen fiber packing are not restricted to lesion zones in cat corneas affected by tropical keratopathy. Such alterations also occur in the corneal tissue of the anterior stroma adjoining the lesions. Therefore, it is plausible that the transparent tissue of the anterior stroma in corneas affected by the disease may have functional abnormalities, despite its macroscopic healthy appearance. Additional investigations are required to clarify the implications of these potential defects and their conceivable contribution to tropical keratopathy.

Collagen crosslinking impacts stromal wound healing and haze formation in a rabbit phototherapeutic keratectomy model

Purpose

The purpose of this study was to evaluate the elastic modulus, keratocyte-fibroblast-myocyte transformation, and haze formation of the corneal stroma following combined phototherapeutic keratectomy (PTK) and epithelium-off UV-A/riboflavin corneal collagen crosslinking (CXL) using an in vivo rabbit model.

Methods

Rabbits underwent PTK and CXL, PTK only, or CXL 35 days before PTK. Rebound tonometry, Fourier-domain optical coherence tomography, and ultrasound pachymetry were performed on days 7, 14, 21, 42, 70, and 90 post-operatively. Atomic force microscopy, histologic inflammation, and immunohistochemistry for α-smooth muscle actin (α-SMA) were assessed post-mortem.

Results

Stromal haze formation following simultaneous PTK and CXL was significantly greater than in corneas that received PTK only and persisted for more than 90 days. No significant difference in stromal haze was noted between groups receiving simultaneous CXL and PTK and those receiving CXL before PTK. Stromal inflammation did not differ between groups at any time point, although the intensity of α-SMA over the number of nuclei was significantly greater at day 21 between groups receiving simultaneous CXL and PTK and those receiving CXL before PTK. The elastic modulus was significantly greater in corneas receiving simultaneous CXL and PTK compared with those receiving PTK alone.

Conclusions

We showed that stromal haze formation and stromal stiffness is significantly increased following CXL, regardless of whether it is performed at or before the time of PTK. Further knowledge of the biophysical cues involved in determining corneal wound healing duration and outcomes will be important for understanding scarring following CXL and for the development of improved therapeutic options.

An Efficient Technique for the Long-term Preservation of SMILE Lenticules Using Desiccation

PURPOSE

To evaluate a desiccation protocol for the long-term preservation of human small incision lenticule extraction (SMILE) lenticules and to study their integration in an in vivo rabbit model.

METHODS

Lenticules were retrieved after SMILE procedures in patients, then desiccated according to a novel protocol. Histologic and electron microscopic analyses were performed. Six rabbit eyes received grafts with an inlay technique, which consisted of inserting a desiccated lenticule into a stromal pocket. Rabbits were killed at different times between 6 and 24 weeks. Rabbit corneas were analyzed using optical coherence tomography, histology, and DAPI staining.

RESULTS

Microscopic analysis of desiccated lenticules showed a preserved stromal architecture after rehydration. A decellularization of the lenticules after desiccation was observed without any chemical treatment. All rabbit corneas remained clear after grafting human lenticules and no rejection occurred. Optical coherence tomography showed regular lenticular implantation and no decrease in lenticule thickness. Histologic analysis showed no inflammatory infiltration around lenticules and no nuclear material inside lenticules after 6 months.

CONCLUSIONS

A favorable integration of desiccated human SMILE lenticules in rabbit corneas was observed. The refractive issue of lenticular implantation must be investigated next. Clinical trials are needed to evaluate the use of desiccated SMILE lenticules to treat hyperopia or keratoconus in humans. [J Refract Surg. 2023;39(7):491-498.].

Genipin increases extracellular matrix synthesis preventing corneal perforation

PURPOSE

Corneal melting and perforation are feared sight-threatening complications of infections, autoimmune disease, and severe burns. Assess the use of genipin in treating stromal melt.

METHODS

A model for corneal wound healing was created through epithelial debridement and mechanical burring to injure the corneal stromal matrix in adult mice. Murine corneas were then treated with varying concentrations of genipin, a natural occurring crosslinking agent, to investigate the effects that matrix crosslinking using genipin has in wound healing and scar formation. Genipin was used in patients with active corneal melting.

RESULTS

Corneas treated with higher concentrations of genipin were found to develop denser stromal scarring in a mouse model. In human corneas, genipin promoted stromal synthesis and prevention of continuous melt. Genipin mechanisms of action create a favorable environment for upregulation of matrix synthesis and corneal scarring.

CONCLUSION

Our data suggest that genipin increases matrix synthesis and inhibits the activation of latent transforming growth factor-β. These findings are translated to patients with severe corneal melting.

Fresh Human Myopic Lenticule Intrastromal Implantation for Keratoconus Using SMILE Surgery in a Long-term Follow-up Study: Ultrastructural Analysis by Transmission Electron Microscopy

PURPOSE

To investigate new intrastromal histological structures that develop after myopic human lenticular implantation in keratoconus with femtosecond laser-assisted small incision lenticule extraction (SMILE) surgery using transmission electron microscopy.

METHODS

Sixty eyes with advanced keratoconus indicated for corneal transplantation were included in this study. Fresh myopic lenticular implants were placed in all eyes through SMILE surgery. Lenticular implants were extracted from patients with myopic refractive errors of the cornea, untreated keratoconus, and treated keratoconus following 1, 2, and 3 years of surgery. These five lenticular samples were examined under the electron microscope and compared.

RESULTS

Disorganized and thinned collagen fibers were observed in the stroma with degenerative stromal cells (telocyte-like cells and keratocytes) in the keratoconic cornea. Apoptotic bodies and cell debris were easily observed near the disorganized fibers. In contrast, the myopic refractive error of the control and treatment groups demonstrated well-organized parallel lamellar structures. Healthy keratocytes and telocyte-like cells were observed in samples obtained 1, 2, and 3 years after lenticular implantation. Thus, telocyte-like cells may be activated by appropriate stimuli, such as stem cells, and be involved in stromal regeneration.

CONCLUSIONS

Fresh myopic intrastromal lenticular implantation is a safe, economical, and reliable technique that leads to increased corneal thickness, improved visual acuity, and the regeneration of healthy keratocytes and telocyte-like cells that are involved in stromal regeneration. [J Refract Surg. 2022;38(8):520-528.].

Late onset of a persistent, deep stromal and endothelial scarring after corneal collagen crosslinking for keratoconus: A case report

INTRODUCTION

To report a late onset, deep stromal and endothelial corneal scar in a keratoconus patient after corneal collagen cross-linking (CXL).

CASE DESCRIPTION

Observational case report. A 29-year-old man with bilateral keratoconus received an accelerated (A-CXL 10*9) epithelium-off CXL procedure in the left eye.6-months postoperatively, a 2.2 × 1.2 mm inferocentral corneal scar was detected, which was located in the posterior stroma ranging from approximately 350 µm until the endothelium, therefore was situated below the demarcation line. A topical corticosteroid treatment did not influence the magnitude or configuration of the scar. Visual acuity was never affected, which includes the examination 12 months postoperatively.

CONCLUSIONS

We report a case of a late onset deep stromal and endothelial corneal scar 6 months after accelerated CXL as postoperative complication without affecting visual acuity.

Deep blue dot corneal degeneration: a rare corneal degeneration

A female patient in the age group 55-60 years presented to us with blurring of vision in both eyes. On slit-lamp examination, numerous circular to oval fleck-like discrete blue opacities at the level of deep corneal stroma and Descemet's membrane was observed. These lesions were predominantly seen in the central two-thirds of the cornea. Considering the age of presentation and the clinical features, the probable diagnosis of 'deep blue dot corneal degeneration' was made.

Chlorhexidine in the treatment of microsporidial stromal keratitis and the effect of host immunity: A case series and literature review

Microsporidial stromal keratitis is an increasingly well-known vision-threatening disease. A large proportion of cases are initially misdiagnosed as herpes simplex keratitis and treated with topical steroids. In most of such cases, medical treatment failed, and corneal transplantation was required. This study reported the results of 0.02% topical chlorhexidine used to treat three cases of microsporidial stromal keratitis and reviewed the literature on the outcomes of microsporidial stromal keratitis treatment. In the first case, histopathology of a specimen from penetrating keratoplasty (PK) revealed severe chronic inflammation involving the entire stromal layer but no microorganism activity after the application of topical chlorhexidine for 10 months. The second case exhibited complete resolution of keratitis after topical chlorhexidine. The patient in the third case did not respond to medical treatment, and therapeutic PK was performed. Histopathological examination revealed numerous microsporidial spores that had colonized in the mid and deep stroma, where few inflammatory cells were observed. These findings explain the variable microsporidial susceptibility to chlorhexidine, suggesting the crucial role of host immunity. In cases of host immunity, topical chlorhexidine may represent a promising option for the treatment of microsporidial stromal keratitis.

The Aotearoa Research Into Keratoconus Study: Geographic Distribution, Demographics, and Clinical Characteristics of Keratoconus in New Zealand

PURPOSE

To investigate the epidemiologic, demographic, and basic clinical characteristics of individuals with keratoconus managed by optometrists in New Zealand (NZ)/Aotearoa.

METHODS

A prospective, longitudinal, nationwide, survey protocol was completed for every patient with keratoconus who underwent a consultation with participating optometrists in a 2-year period. Data for each patient included date of birth, sex, self-reported ethnicity, new or previous diagnosis, uncorrected (UCVA) and best-corrected visual acuity (BCVA), type of refractive correction required to obtain BCVA and keratometric readings obtained using keratometry or computerized topography.

RESULTS

One thousand eight hundred sixty-nine cases were identified, with a mean age of 41.0 ± 15.7 years, 56.4% being men, and 87.3% with previous diagnosis. The distribution of cases was skewed toward Auckland (41.6%), Waikato (21.3%), Wellington (16.8%), and Bay of Plenty (13.3%). Self-reported ethnicities were predominantly NZ European (54.4%), Māori (24.7%), and Pacific Peoples (15.5%), disproportionate to the general population profile (74.0%, 14.9%, and 7.4% respectively). Most eyes (64.3%) were managed with rigid contact lenses (corneal lens in 34.2%). The mean K-mean was 49.0 ± 5.7 D. The mean UCVA was 6/42 and BCVA was 6/9. Māori and Pacific Peoples had both the highest K-mean and proportions of eyes graded stage IV on the Amsler-Krumeich scale.

CONCLUSIONS

The results indicate that keratoconus is relatively common in NZ with at least 1869 patients managed by optometrists in 2 years. Most eyes had mild to moderate disease; however, Māori and Pacific Peoples seem to have greater disease severity. An ethnic predilection is apparent, with Māori and Pacific Peoples overrepresented relative to their population proportions, reinforcing a long-held clinical suspicion.

[Mineral dysmetabolism in corneal diseases]

Functional status and biological properties of connective tissues significantly depend on the mineral elements involved in their metabolism. Connective tissue portion of the corneal stroma makes up most of its thickness; pathological changes in collagen fibers and the stroma can cause a range of corneal diseases, some of which are specifically associated with disorders of mineral metabolism. The article considers impairments of mineral metabolism as possible pathophysiological mechanisms in certain diseases and disorders of the cornea, and describes in detail the abnormalities associated with mineral dysmetabolism observed in patients with keratoconus.

Microsporidial Stromal Keratitis: Epidemiological Features, Slit-Lamp Biomicroscopic Characteristics, and Therapy

PURPOSE

Microsporidial stromal keratitis is a rare form of infectious keratitis, with only 7 cases reported in the United States to date. This study was performed to evaluate risk factors, clinical features, and response to therapy.

METHODS

A retrospective review of the medical records of all patients diagnosed with microsporidial stromal keratitis seen in the practices of the authors between 1999 and 2020 was performed. Diagnosis was determined by cytology or histopathology in corneal specimens. Risk factors, presence or absence of distinctive clinical features, and response to medical and surgical therapies were recorded.

RESULTS

Nine patients-7M:2F, aged 7 to 99 years-with microsporidial stromal keratitis were identified. Exposures to recreational water and hymenopteran insect bites, both epidemiologically linked risk factors for systemic microsporidial infection, were identified in our patients. Presence of stromal edema with features of disciform keratitis and a distinctive granular keratitis were observed in 6 of 9 and 5 of 9 patients, respectively. Poor response to medical therapy was noted. Penetrating keratoplasty was effective in curing the infection. Final visual acuity was 20/40 or better in 6 of 9 patients.

CONCLUSIONS

In patients with slowly progressive keratitis, history of exposure to recreational water or hymenopteran insects should be sought. In patients with corneal edema consistent with disciform keratitis, with evolution to a granular keratitis, microsporidia should be considered in the differential diagnosis. In cases of established microsporidial stromal keratitis, penetrating keratoplasty should be considered if prompt response to medical therapy is not noted.

Precision and refractive predictability of a new nomogram for femtosecond laser-assisted corneal arcuate incisions

PURPOSE

Validating a new nomogram for low to moderate astigmatism (0.75 D to 2.5 D) correction with epithelium- and Bowman-penetrating femtosecond laser-assisted arcuate incisions.

METHODOLOGY

Prospective, interventional case series at the Augen- und Laserklinik, Castrop-Rauxel, Germany. Cataract patients with low to moderate corneal astigmatism were treated with femtosecond laser-assisted arcuate incisions. Patients with previous refractive corneal treatment were excluded. Outcome assessment was based on manifest refraction, astigmatic vector analysis and visual acuity.

RESULTS

The study analysed 43 eyes of 33 patients after three months and 35 eyes of 27 patients after 12 months. After 12 months, 100% of all eyes treated had ≤1.0 D and 97% ≤0.5 D of subjective residual astigmatism. Mean residual astigmatism was 0.27 D. 90% of all eyes were within one line of difference between UDVA and CDVA. SEQ Mean Absolute Error was 0.26 D and SEQ. Mean error was -0.08 ± 0.32 D. CI was 0.98 ± 0.2 D, and Index of Success, 0.20 ± 0.18 D.

CONCLUSION

The Castrop nomogram showed results that are comparable to or better than results presented in the literature for existing nomograms. Our results for astigmatic reduction are comparable to published results for TIOL implantation. It seems to be a predictable and safe measure to reduce manifest astigmatism.

The role of bone morphogenetic protein 4 in corneal injury repair

PURPOSE

Corneal injury may cause neovascularization and lymphangiogenesis in cornea which have a detrimental effect to vision and even lead to blindness. Bone morphogenetic protein 4 (BMP4) regulates a variety of biological processes, which is closely relevant to the regulation of corneal epithelium and angiogenesis. Herein, we aimed to evaluate the effect of BMP4 on corneal neovascularization (CNV), corneal lymphangiogenesis (CL), corneal epithelial repair, and the role of BMP4/Smad pathway in these processes.

METHODS

We used MTT assay to determine the optimal concentration of BMP4. The suture method was performed to induce rat CNV and CL. We used ink perfusion and HE staining to visualize the morphological change of CNV, and utilized RT-qPCR and ELISA to investigate the expression of angiogenic factors and lymphangiogenic factors. The effects of BMP4 and anti-VEGF antibody on migration, proliferation and adhesion of corneal epithelium were determined by scratch test, MTT assay and cell adhesion test.

RESULTS

BMP4 significantly inhibited CNV and possibly CL. Topical BMP4 resulted in increased expression of endogenous BMP4, and decreased expression of angiogenic factors and lymphangiogenic factors. Compared with anti-VEGF antibody, BMP4 enhanced corneal epithelium migration, proliferation and adhesion, which facilitated corneal epithelial injury repair. Simultaneously, these processes could be regulated by BMP4/Smad pathway.

CONCLUSIONS

Our results demonstrated unreported effects of BMP4 on CNV, CL, and corneal epithelial repair, suggesting that BMP4 may represent a potential therapeutic target in corneal injury repair.

Late Corneal Stromal Deposits After COVID-19

ABSTRACT

We present 2 cases of striking stromal corneal infiltrates months after COVID-19 infection. While we cannot prove that these infiltrates are caused by or directly related to COVID-19, we did not find any other plausible cause that could explain these ophthalmic signs. In these cases, the ongoing process was detected in relatively early stages due to scheduled visits with patients and responded positively to prednisolone acetate 1% ophthalmic suspension. However, we do not know the response to treatment in more advanced cases.

In Vivo Confocal Microscopy of Stromal Lenticule Addition Keratoplasty for Advanced Keratoconus

PURPOSE

To investigate the in vivo corneal microscopic changes after femtosecond laser-assisted stromal lenticule addition keratoplasty in keratoconus by means of in vivo confocal microscopy.

METHODS

Patients affected by advanced keratoconus were included in the study. Negative meniscus-shaped stromal lenticules, produced with a femtosecond laser (VisuMax; Carl Zeiss Meditec) from eye bank corneas were transplanted into a stromal pocket dissected in the recipient cornea at a depth of 120 µm. In vivo confocal microscopy was performed during the 12-month follow-up to investigate changes of the corneal and lenticule structure.

RESULTS

Ten patients were enrolled in the study. No changes of the dendritic cell population were documented during the follow-up period. Mild edema and stromal keratocyte activation gradually decreased during the first month. Subbasal nerve density returned to preoperative values after 6 months. Donor-recipient interfaces appeared hyperreflective but gradually improved over time with significantly reduced reflectivity after 3 months. No evidence of stromal inflammatory cell migration or matrix opacification was observed. Endothelial and keratocyte density remained stable over time. A variable degree of stromal radially distributed folds, not visible on biomicroscopy, was observed in the lenticule and in the posterior recipient stroma.

CONCLUSIONS

Stromal lenticule addition keratoplasty produces transitory nerve plexus density reduction and minor inflammatory reaction that rapidly decreases during the first month. Donor-recipient interface reflectivity is comparable to a femtosecond laser refractive procedure with no sign of stromal opacification or stromal rejection in 1 year of follow-up. [J Refract Surg. 2020;36(8):544-550.].

Canonical NF-κB signaling maintains corneal epithelial integrity and prevents corneal aging via retinoic acid

Disorders of the transparent cornea affect millions of people worldwide. However, how to maintain and/or regenerate this organ remains unclear. Here, we show that Rela (encoding a canonical NF-κB subunit) ablation in K14+ corneal epithelial stem cells not only disrupts corneal regeneration but also results in age-dependent epithelial deterioration, which triggers aberrant wound-healing processes including stromal remodeling, neovascularization, epithelial metaplasia, and plaque formation at the central cornea. These anomalies are largely recapitulated in normal mice that age naturally. Mechanistically, Rela deletion suppresses expression of Aldh1a1, an enzyme required for retinoic acid synthesis from vitamin A. Retinoic acid administration blocks development of ocular anomalies in Krt14-Cre; Relaf/f mice and naturally aged mice. Moreover, epithelial metaplasia and plaque formation are preventable by inhibition of angiogenesis. This study thus uncovers the major mechanisms governing corneal maintenance, regeneration, and aging and identifies the NF-κB-retinoic acid pathway as a therapeutic target for corneal disorders.

Individualized Corneal Cross-linking With Riboflavin and UV-A in Ultrathin Corneas: The Sub400 Protocol

PURPOSE

To determine whether corneal cross-linking (CXL) with individualized fluence ("sub400 protocol") is able to stop keratoconus (KC) progression in ultrathin corneas with 12-month follow-up.

DESIGN

Retrospective, interventional case series.

METHODS

Thirty-nine eyes with progressive KC and corneal stromal thicknesses from 214 to 398 μm at the time of ultraviolet irradiation were enrolled. After epithelium removal, ultraviolet irradiation was performed at 3 mW/cm² with irradiation times individually adapted to stromal thickness. Pre- and postoperative examinations included corrected distance visual acuity (CDVA), refraction, Scheimpflug, and anterior segment optical coherence tomography imaging up to 12 months after CXL. Outcome measures were arrest of KC progression at 12 months postoperatively and stromal demarcation line (DL) depth.

RESULTS

Thirty-five eyes (90%) showed tomographical stability at 12 months after surgery. No eyes showed signs of endothelial decompensation. A significant correlation was found between DL depth and irradiation time (r = +0.448, P = .004) but not between DL depth and change in K_max (r = -0.215, P = .189). On average, there was a significant change (P < .05) in thinnest stromal thickness (-14.5 ± 21.7 μm), K_max (-2.06 ± 3.66 D) and densitometry (+2.00 ± 2.07 GSU). No significant changes were found in CDVA (P = .611), sphere (P = .077), or cylinder (P = .915).

CONCLUSIONS

The "sub400" individualized fluence CXL protocol standardizes the treatment in ultrathin corneas and halted KC progression with a success rate of 90% at 12 months. The sub400 protocol allows for the treatment of corneas as thin as 214 μm of corneal stroma, markedly extending the treatment range. The DL depth did not predict treatment outcome. Hence, the depth is unlikely related to the extent of CXL-induced corneal stiffening but rather to the extent of CXL-induced microstructural changes and wound healing.

Customized Ablation Area PTK as a Technique for Salzmann's Degeneration and Other Focal Stromal Pathologies

PURPOSE

To introduce a customized ablation area photo-therapeutic keratectomy (PTK) technique that uses a preoperatively generated laser ablation profile to accurately match and ablate the area of the pathology.

METHODS

A case of mid-peripheral Salzmann's nodular degeneration causing recurrent epithelial erosion is described. The white-to-white distance, on a slit-lamp image of the patient's eye, was measured by a Placido and dual-Scheimpflug analyzer and used as a scale on a Java-based image processing program to extrapolate the focal corneal pathology's vertical and horizontal dimensions on the corneal plane. The lesion's depth was measured by corneal optical coherence tomography (OCT). Customized ablation area transepithelial PTK, tailored to the exact dimensions of the pathology was then performed in one pass, regionally ablating the area of the pathology only.

RESULTS

Complete epithelial healing was observed by the next day with unaltered visual acuity of 20/20. Corneal OCT performed at 1 and 3 months postoperatively showed near-complete resolution of the lesion. The patient was followed up for a total of 6 months with no reported symptoms of corneal erosions.

CONCLUSIONS

The application of a customized laser ablation area in the treatment of Salzmann's nodular degeneration and other focal stromal pathologies avoids unnecessary epithelial and stromal ablation. This contributes to faster visual recovery and less refractive impact, especially for peripheral lesions. [J Refract Surg. 2020;36(5):340-344.].

Effect of penetration enhancer with novel corneal cross-linking using recombinant human decoron in porcine eyes

The aim of the study was to investigate the effectiveness of exogenous recombinant human decoron and an accompanying penetration-enhancing solution in stiffening ex-vivo porcine corneas both transepithelially and after de-epithelialization. Eight porcine paired eyes were treated transepithelially: one eye with a pre-treatment solution (Pre-Tx), penetration enhancing solution (PE), and decoron while the fellow eye was treated by the same protocol but without decoron. A second group included 4 de-epithelialized pairs treated identically. The final group included 4 de-epithelialized pairs with one eye treated with Pre-Tx, PE, and decoron while the fellow eye was treated without PE. Uniaxial tensile testing was used to compare the corneal stiffness between the different treatment conditions. Residual tissue underwent immunohistochemistry analysis to evaluate the depth of penetration of decoron into the corneal stroma. There was no stiffening effect exhibited among corneas treated transepithelially with decoron compared to control (P > 0.05) and poor stromal penetration was exhibited on tissue analysis. Among de-epithelialized corneas, there was a significant stiffening effect seen in those treated with decoron at 3%, 4%, 5%, & 6% strain (P < 0.05) compared to control. Among de-epithelialized corneas there was also a significant stiffening effect seen in those treated with the PE and decoron at 4%, 5%, & 6% strain (P < 0.05) with improved stromal penetration confirmed by immunohistochemistry, versus without PE. De-epithelialization is necessary for effective stromal penetration of decoron. Depth of penetration and subsequent corneal stiffening may be improved with a penetration enhancing solution. Compared to riboflavin, decoron requires shorter treatment time and spares UV light exposure.

Oxygen Kinetics During Corneal Cross-linking With and Without Supplementary Oxygen

PURPOSE

To measure and simulate oxygen kinetics during corneal cross-linking at different irradiances with and without supplementary oxygen.

DESIGN

Experimental, laboratory study.

METHODS

In de-epithelialized porcine eyes, a femtosecond-laser-generated tunnel was used to place a fiber probe in corneal depths of 100, 200, and 300 μm to measure the local oxygen concentration. After riboflavin imbibition, the corneas were irradiated at 3, 9, 18, and 30 mW/cm² while the oxygen concentration was measured. All experiments were performed under normoxic (21%) and hyperoxic (>95%) conditions. The obtained data were used to identify parameters of a numerical model for oxygen consumption and diffusion.

RESULTS

The equilibrium stromal oxygen concentration under atmospheric oxygen at 3 mW/cm² was 2.3% in 100 μm decreasing to <1% in 300 μm. With 9, 18, and 30 mW/cm², no oxygen was available in 200 μm, respectively, 100 μm or deeper. Using a hyperoxic environment, the concentration was 50% using 3 mW/cm² in 100 μm, decreasing to 40% in 300 μm. At 9 mW/cm², the concentrations were 5%, 3%, and 1% in 100, 200 and 300 μm, respectively. Using 18 and 30 mW/cm², all oxygen was depleted at 100 μm; however, oxygen half-lives were longer at 18 mW/cm² than at 30 mW/cm². The oxygen model was able to reproduce the experiments and indicated an exponential decay with increasing distance to the anterior surface.

CONCLUSION

Supplementary oxygen increases the oxygen availability during corneal cross-linking. At higher irradiances, supplementary oxygen is beneficial and eliminates the bottleneck of oxygen allowing a potentially more efficient cross-linking. The calibrated numerical model can quantify the spatial oxygen concentration related to different scenarios such as irradiance or environmental oxygen concentration.

Comparison of the Distribution of Lenticule Decentration Following SMILE by Pupil Center or Tear Film Mark Centration

PURPOSE

To investigate lenticule decentration following small incision lenticule extraction (SMILE) via the pupil center or tear film mark centration method and compare induction of corneal higher order aberrations (HOAs) between the two methods.

METHODS

This study analyzed decentration values obtained from tangential topography difference maps of 100 eyes (100 patients) undergoing SMILE with the pupil center (n = 50) or tear film mark (n = 50) centration method. Total HOAs and component aberrations were measured preoperatively and 6 months postoperatively. Relationships between the magnitudes of decentration and induced corneal HOAs were assessed.

RESULTS

Both vertical and total decentered displacement were significantly different (P < .001) between the two centration groups. A significant relationship between the preoperative pupillary offset and decentration was noted in the pupil center group (P < .001), but not in the tear film mark group (P = .530). Significantly greater induction of total HOAs, coma, and vertical coma (all P < .001), as well as horizontal coma (P = .001) and spherical aberration (P = .023), were observed in the pupil center group. Association between the total decentered displacement and induced total HOAs (P < .001), as well as all other significantly increased phenomena, was also significant in the pupil center group. Differences in decentered displacement and induced corneal HOAs were significant for preoperative pupillary offset (angle kappa) greater than 200 µm, but not for angle kappa less than 200 µm.

CONCLUSIONS

SMILE with tear film mark centration can yield improved treatment centration and less induction of total HOAs, coma, and spherical aberrations. [J Refract Surg. 2020;36(4):239-246.].

Association Between Keratoconus and Thyroid Gland Dysfunction: A Cross-Sectional Case-Control Study

PURPOSE

To examine the clinical association between thyroid gland dysfunction and keratoconus.

METHODS

This was a cross-sectional case-control study conducted between May 2018 and July 2019. After performing Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) examination, flat, steep, and maximum simulated keratometric readings were recorded for each patient. Serum concentrations of free triiodothyronine, free thyroxine, and thyroid-stimulating hormone were measured. Further examinations by an endocrinologist were indicated for patients with positive laboratory results to confirm thyroid gland dysfunction.

RESULTS

One hundred eighty-seven patients with bilateral keratoconus and 187 sex- and age-matched healthy controls without keratoconus were analyzed. Mean age was 26.4 ± 8.2 years for the patients with keratoconus and 27.1 ± 9.4 years for the control patients, with no significant difference. The results showed that thyroid gland dysfunction prevalence was 10 of 187 patients with keratoconus (5.3%) and 2 of 187 control patients (1.1%), and the difference was statistically significant (P = .036). For the patients with keratoconus and thyroid gland dysfunction, 8 were women and 2 were men. Additionally, 6 patients (2 men and 4 women) had hyperthyrosis and 4 women had hypothyrosis. For controls, the two patients had hypothyrosis.

CONCLUSIONS

This study showed that there is a possible association between keratoconus and thyroid gland dysfunction, but more studies are needed to build upon these results. [J Refract Surg. 2020;36(4):253-257.].

Incidence and Reasons for Intrastromal Corneal Ring Segment Explantation

PURPOSE

To determine the main causes of intrastromal corneal ring segment (ICRS) explantation and define the incidence rate.

DESIGN

Multicenter, observational consecutive case series.

METHODS

Consecutive cases of ICRSs explanted in the last 10 years were reviewed. Clinical data included age of the patients at explantation, reasons for implantation and explantation, date of implantation and explantation, tunnel creation technique, and ICRS type. Main outcomes measures were the reasons for ICRS removal and the incidence rate.

RESULTS

During the study period, 121 ICRSs (119 patients) were explanted, with an explantation rate of 5.60%. Functional failure (74 eyes, 61.16%) represents the main cause for ICRS removal: of them, 48 (39.67%) ICRSs were removed for refractive failure and 26 (21.49%) in the setting of a keratoplasty related to poor visual performance of the implanted eye. In addition, 47 eyes (38.84%) had ICRS removal for anatomic failure: among them, 36 (29.75%) were explanted for spontaneous extrusion (overall extrusion rate: 1.58%), 7 (5.79%) for suspected infectious keratitis, 3 (2.48%) for corneal melting, and 1 (0.83%) for corneal perforation. Mild cases of keratoconus were more prone to be explanted because of a loss of the initial improved visual acuity, whereas spontaneous extrusion happened often in advanced cases of keratoconus.

CONCLUSIONS

We report the largest series of ICRS explantation as of this writing. The main cause of explantation was functional refractive failure followed by spontaneous extrusion of the ICRS, that is, correlated to an anatomic failure at the site of implantation in an advanced disease.

TGFβ1 and TGFβ2 proteins in corneas with and without stromal fibrosis: Delayed regeneration of apical epithelial growth factor barrier and the epithelial basement membrane in corneas with stromal fibrosis

The purpose of this study was to investigate the expression and localization of transforming growth factor (TGF) β1 and TGFβ2 in rabbit corneas that healed with and without stromal fibrosis, and to further study defective perlecan incorporation in the epithelial basement membrane (EBM) in corneas with scarring fibrosis. A total of 120 female rabbits had no surgery, -4.5D PRK, or -9D PRK. Immunohistochemistry (IHC) was performed at time points from unwounded to eight weeks after surgery, with four corneas at each time point in each group. Multiplex IHC was performed for TGFβ1 or TGFβ2, with Image-J quantitation, and keratocan, vimentin, alpha-smooth muscle actin (SMA), perlecan, laminin-alpha 5, nidogen-1 or CD11b. Corneas at the four-week peak for myofibroblast and fibrosis development were evaluated using Imaris 3D analysis. Delayed regeneration of both an apical epithelial growth factor barrier and EBM barrier function, including defective EBM perlecan incorporation, was greater in high injury -9D PRK corneas compared to -4.5D PRK corneas without fibrosis. Defective apical epithelial growth factor barrier and EBM allowed epithelial and tear TGFβ1 and tear TGFβ2 to enter the corneal stroma to drive myofibroblast generation in the anterior stroma from vimentin-positive corneal fibroblasts, and likely fibrocytes. Vimentin-positive cells and unidentified vimentin-negative, CD11b-negative cells also produce TGFβ1 and/or TGFβ2 in the stroma in some corneas. TGFβ1 and TGFβ2 were at higher levels in the anterior stroma in the weeks preceding myofibroblast development in the -9D group. All -9D corneas (beginning two to three weeks after surgery), and four -4.5D PRK corneas developed significant SMA + myofibroblasts and stromal fibrosis. Both the apical epithelial growth factor barrier and/or EBM barrier functions tended to regenerate weeks earlier in -4.5D PRK corneas without fibrosis, compared to -4.5D or -9D PRK corneas with fibrosis. SMA-positive myofibroblasts were markedly reduced in most corneas by eight weeks after surgery. The apical epithelial growth factor barrier and EBM barrier limit TGFβ1 and TGFβ2 entry into the corneal stroma to modulate corneal fibroblast and myofibroblast development associated with scarring stromal fibrosis. Delayed regeneration of these barriers in corneas with more severe injuries promotes myofibroblast development, prolongs myofibroblast viability and triggers stromal scarring fibrosis.

Repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography in myopic and postphotorefractive keratectomy eyes

PURPOSE

To investigate repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography (OCT) in myopic and postphotorefractive keratectomy (PRK) eyes.

SETTING

Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran.

DESIGN

Prospective observational study.

METHODS

Total corneal, epithelial, and stromal thicknesses were measured using RTVue-XR OCT with Pachymetry + Cpwr (6.0 mm algorithm) and PachymetryWide (9.0 mm algorithm) scan patterns. The repeatability of 25 zones of 9.0 mm map and 17 zones of 6.0 mm map and the agreement between measurements of these 2 algorithms were calculated.

RESULTS

Ninety-five myopic and 117 post-PRK patients were evaluated. By the 9.0 mm algorithm, coefficient of variation (CoV) for total cornea was 2.33% or lesser and 2.49% or lesser and for epithelium was 5.14% or lesser and 5.18% or lesser; and by the 6.0 mm algorithm, CoV for total cornea was 1.80% or lesser and 2.59% or lesser and for epithelial thickness was 3.08% or lesser and 4.80% or lesser in myopic and post-PRK eyes, respectively. Bland-Altman mean difference for epithelial thickness was 0.69 or lesser and 1.16 or lesser and 95% limits of agreement for epithelial thickness was 6.81 or lesser and 8.56 or lesser in myopic and post-PRK eyes, respectively.

CONCLUSIONS

Good repeatability was seen in measurements of total corneal, stromal, and epithelial thicknesses by both algorithms. Agreement of the 2 algorithms in central zone was also good. However, large range of variation in paracentral thickness measurements did not allow us to consider these algorithms as interchangeable.

Corneal Stroma Regeneration: New Approach for the Treatment of Cornea Disease

Corneal grafting is one of the most common forms of human tissue transplantation. The corneal stroma is responsible for many characteristics of the cornea. For these reasons, an important volume of research has been made to replicate the corneal stroma in the laboratory to find an alternative to classical corneal transplantation techniques.There is an increasing interest today in cell therapy of the corneal stroma using induced pluripotent stem cells or mesenchymal stem cells since these cells have shown to be capable of producing new collagen within the host stroma and even to improve its transparency.The first clinical experiment on corneal stroma regeneration in advanced keratoconus cases has been reported and included. Fourteen patients were randomized and enrolled into 3 experimental groups: (1) patients underwent implantation of autologous adipose-derived adult stem cells alone, (2) patients received decellularized donor corneal stroma laminas, and (3) patients received implantation of recellularized donor laminas with adipose-derived adult stem cells. Clinical improvement was detected with all cases in their visual, pachymetric, and topographic parameters of the operated corneas.Other recent studies have used allogenic SMILE implantation lenticule corneal inlays, showing also an improvement in different visual, topographic, and keratometric parameters.In the present report, we try to summarize the available preclinical and clinical evidence about the emerging topic of corneal stroma regeneration.

In Vivo Corneal Confocal Microscopy and Histopathology of Keratitis Fugax Hereditaria From a Pathogenic Variant in NLRP3

PURPOSE

To apply in vivo corneal confocal microscopy (IVCM) to study the pathogenesis of keratitis (keratoendotheliitis) fugax hereditaria, an autosomal dominant cryopyrin-associated periodic keratitis, associated with the c.61G>C pathogenic variant in the NLRP3 gene, in its acute and chronic phase, and to report histopathologic findings after penetrating keratoplasty.

DESIGN

This was an observational case series.

METHODS

The study population included 6 patients during an acute attack, 18 patients in the chronic phase, and 1 patient who underwent penetrating keratoplasty. Interventions included Sanger sequencing for the NLRP3 variant c.61C>G, a clinical examination, corneal photography, IVCM, light microscopy, and immunohistochemistry. Our primary outcome measures included IVCM and histopathologic findings.

RESULTS

During the acute attack, hyperreflective cellular structures consistent with inflammatory cells transiently occupied the anterior to middle layers of the corneal stroma. Other corneal layers were unremarkable. With recurring attacks, central oval stromal opacities accumulated. IVCM revealed that they contained long, hyperreflective, needle-shaped structures in the extracellular matrix. Using light microscopy, the anterior half of the stroma displayed thin and finely vacuolated lamellae, and keratocytes throughout the stroma were immunopositive for syndecan.

CONCLUSIONS

The acute attacks and chronic stromal deposits mainly involve the anterior to middle layers of the corneal stroma, and the disease is primarily a keratitis rather than a keratoendotheliitis. IVCM shows that inflammatory cells invade only the stroma during an acute attack. IVCM and light microscopic findings suggest that the central corneal opacities represent gradual deposition of extracellular lipids. The disease could make a good in vivo model to study activation of the NLRP3 inflammasome in cryopyrin-associated periodic syndromes.

Comparison of FDA-Reported Visual and Refractive Outcomes of the Toric ICL Lens, SMILE, and Topography-Guided LASIK for the Correction of Myopia and Myopic Astigmatism

PURPOSE

To compare U.S. Food and Drug Administration (FDA)-reported visual and refractive outcomes following surgical correction of myopia and myopic astigmatism using the Visian Toric Implantable Collamer Lens (STAAR Surgical, Monrovia, CA) (Toric ICL), small incision lenticule extraction (SMILE), and topography-guided laser in situ keratomileusis (TG-LASIK).

METHODS

FDA summary of safety and effectiveness data (SSED) were analyzed for each of the three platforms. Primary outcomes measured were efficacy, safety, stability, and accuracy of refractive correction. Stratified mean refractive spherical equivalent (MRSE) data were assessed.

RESULTS

One hundred twenty-four Toric ICL patients (210 eyes), 357 SMILE patients (357 eyes), and 212 TG-LASIK patients (249 eyes) were included. SMILE eyes had a significant improvement in postoperative uncorrected distance visual acuity with respect to preoperative corrected distance visual acuity from 3 to 12 months (P < .001), whereas TG-LASIK had no further improvement from 3 to 12 months (P = .79). For preoperative MRSE greater than 10.00 diopters (D), there was a significant difference in the percentage of eyes achieving postoperative MSRE within ±0.50 D between Toric ICL (66%) and SMILE (100%) (P < .001). SMILE was consistently more accurate than Toric ICL for cylinder within ±0.25 D (P < .001), ±0.50 D (P < .001), and ±1.00 D (P = .0014).

CONCLUSIONS

All three platforms analyzed in this study had excellent efficacy, safety, stability, and accuracy. Stratified analysis revealed that SMILE may be comparable to Toric ICL for patients with high myopia or myopic astigmatism, and SMILE may have a longer visual recovery compared to TG-LASIK than previously indicated. [J Refract Surg. 2019;35(11):699-706.].

The Efficacy of Topical HGF on Corneal Fibrosis and Epithelial Healing after Scar-Producing PRK Injury in Rabbits

Purpose

To determine the effect of topical hepatocyte growth factor (HGF) on myofibroblast development and corneal opacity after fibrosis-producing photorefractive keratectomy (PRK).

Methods

Twelve New Zealand rabbits had transepithelial PRK. Six rabbits received topical recombinant human HGF (rhHGF) (50 µL of 0.1 mg/mL) 3 times a day for 1 week beginning 6 hours prior surgery and until full closure of the epithelium, and 6 control rabbits received vehicle by the same schedule. Slit lamp photos were taken immediately and at 43 to 45 hours after surgery to determine the rate of epithelial healing. Slit lamp photographs and immunohistochemistry for α-smooth muscle actin were analyzed at 1 month in masked fashion.

Results

The rhHGF group tended to have slower re-epithelization when compared with the controls, but no statistically significant difference was noted (P = 0.62). There was no significant difference in the density of myofibroblasts in the central stroma (P = 0.49) or corneal opacity (P = 0.84) between the HGF and control groups at 1 month after PRK.

Conclusions

Topical rhHGF applied three times a day during the early postoperative period prior to epithelial closure did not significantly change the corneal epithelial healing rate, myofibroblast density, or opacity compared with vehicle after transepithelial -9.0 D PRK injury of the central cornea in rabbits.

Translational Relevance

HGF has been reported to decrease myofibroblast generation and fibrosis in many organs, but topical HGF applied to the cornea until epithelial healing had no effect on scarring fibrosis in rabbit corneas.

Incidence and Risk Factors of Opaque Bubble Layer Formation According to Flap Thickness During 500-kHz FS-LASIK

PURPOSE

To present the incidence, risk factors, and effect of opaque bubble layer (OBL) formation during flap creation in laser-assisted in situ keratomileusis (LASIK) with a 500-kHz femtosecond laser on visual performance.

METHODS

In this retrospective study, preoperative characteristics (age, sex, keratometric value, spherical equivalent, and central corneal thickness) and intraoperative surgical factors (used energy, docking type, and flap thickness) were compared between eyes with and without OBL formation during flap creation. Possible risk factors for specific types of OBLs were analyzed.

RESULTS

One hundred thirty-five eyes of 71 patients underwent LASIK, and OBL developed in 98 eyes (72.59%). In the univariate analysis, the greater than 80-µm flap group was associated with a lower OBL occurrence than the 80-µm flap group (P = .0424, odds ratio [OR] = 0.481) and hard docking was associated with increased OBL formation (P = .0001, OR = 6.859). In the multivariate analysis, hard docking was a risk factor for OBL development (P = .0003, OR = 6.329). In the subgroup analysis, hard docking had a marginal effect on OBL occurrence in the 80-µm flap group (P = .086, OR = 3.564), but it had a strong effect in the greater than 80-µm flap group (P = .0018, OR = 10.210).

CONCLUSIONS

Hard docking is a risk factor for OBL development. However, hard docking had a small effect on OBL occurrence in the 80-µm flap group during LASIK. OBL formation did not affect visual performance. [J Refract Surg. 2019;35(9):583-589.].

Risk factors for early flap misalignment following microkeratome-assisted laser in situ keratomileusis: A retrospective large database analysis

PURPOSE

To determine factors associated with early flap misalignment following microkeratome-assisted laser in situ keratomileusis.

MATERIALS AND METHODS

This retrospective study included the right eyes of consecutive patients who underwent laser in situ keratomileusis procedure between 2005 and 2016 at Care-Vision Laser Centers, Tel-Aviv, Israel. Patients were divided into two groups according to whether or not they subsequently developed early flap misalignment.

RESULTS

A total of 14,582 eyes (mean age of patients: 32.4 ± 10.3 years) were included. Post-laser in situ keratomileusis early flap misalignment developed in 158 eyes (1.1%). Misalignment was more frequent during the spring (32.3% vs 22.8%, p = 0.003) and in a higher operating room temperature (23.34 ± 1.06 vs 22.98 ± 1.26, p < 0.001). In addition, in the misalignment group, there was a higher rate with the of use of the a Moria M2 microkeratome (rather than sub-Bowman's keratomileusis microkeratome) head (55.2% vs 40.5%, respectively, p < 0.001). In a multivariable analysis adjusted for surgeon and year of surgery, high operating room temperature (odds ratio = 1.22, p = 0.006), treatment zone of 9.0 mm (as opposed to smaller treatment zones, odds ratio = 1.54, p = 0.04), and springtime (odds ratio = 1.58, p = 0.02) were associated with flap misalignment. There was a significant difference in misalignment rates between surgeons (p = 0.02).

CONCLUSION

This study found that larger treatment zones, higher operating room temperature, operating during the spring, and the use of Moria M2 microkeratome were associated with increased flap misalignment rates. The association with operating room temperature and seasonal variation is of interest and merits further research.

Stromal Rejection After SMILE for the Correction of Astigmatism After Graft

PURPOSE

To describe a case of stromal rejection in a 46-year-old man after small incision lenticule extraction (SMILE) for the correction of residual astigmatism following deep anterior lamellar keratoplasty (DALK).

METHODS

Case report.

RESULTS

Nine years after an uneventful DALK in the left eye, the patient (uncorrected distance visual acuity [UDVA] = 20/200, corrected distance visual acuity [CDVA] = 20/32, and refraction = -3.25 -4.25 × 165°) underwent SMILE using the VisuMax femtosecond laser platform (Carl Zeiss Meditec, Jena, Germany). The next day, the UDVA, CDVA, and refraction were 20/40, 20/32, and -1.25 -0.50 × 15°, respectively. One week later, the patient presented complaining of pain, photophobia, and blurred vision; at this time, there was a reduction in UDVA to 20/400 and CDVA to 20/63. With a diagnosis of stromal rejection, the patient was treated with corticosteroids (sub-Tenon injection and oral). Five months later, UDVA was 20/40, CDVA was 20/25, and refraction was -1.25 -0.75 × 90°. The graft had completely cleared.

CONCLUSIONS

SMILE can be an effective alternative for the correction of astigmatism after DALK, but the risks of inflammatory responses and graft rejection call for caution. [J Refract Surg. 2019;35(11):737-739.].