To identify global gene expression changes in the corneal epithelium of keratoconus (KC) patients compared to non-KC myopic controls.
RNA-sequencing was performed on corneal epithelium samples of five progressive KC and five myopic control patients. Selected results were validated using TaqMan quantitative PCR (qPCR) on 31 additional independent samples, and protein level validation was conducted using western blot analysis on a subset. Immunohistochemistry was performed on tissue microarrays containing cores from over 100 KC and control cases. WNT10A transcript levels in corneal epithelium were correlated with tomographic indicators of KC disease severity in 15 eyes. Additionally, WNT10A was overexpressed in vitro in immortalized corneal epithelial cells.
WNT10A was found to be underexpressed in KC epithelium at the transcript (ratio KC/control = 0.59, P = 0.02 per RNA-sequencing study; ratio = 0.66, P = 0.03 per qPCR) and protein (ratio = 0.07, P = 0.06) levels. Immunohistochemical analysis also indicated WNT10A protein was decreased in Bowman\'s layer of KC patients. In contrast, WNT10A transcript level positively correlated with increased keratometry (Kmax ρ = 0.57, P = 0.02). Finally, WNT10A positively regulated COL1A1 expression in corneal epithelial cells.
A specific Wnt ligand, WNT10A, is reduced at the mRNA and protein level in KC epithelium and Bowman\'s layer. This ligand positively regulates collagen type I expression in corneal epithelial cells. The results suggest that WNT10A expression in the corneal epithelium may play a role in progressive KC.

Most transforming growth factor beta-induced (TGFBI) corneal dystrophies are associated with a characteristic phenotype, clinical course, and a conserved mutation in the TGFBI gene. However, we report a novel TGFBI missense mutation associated with a late-onset, variant Bowman layer dystrophy.
Participants underwent slit-lamp examination and multimodal imaging. Polymerase chain reaction amplification and Sanger sequencing were performed on saliva-derived genomic DNA to screen TGFBI exons 4 and 12 as well as COL17A1 exon 46. PolyPhen-2 and SIFT were used to predict the functional impact of any identified variants.
A 56-year-old Thai woman reported a four-year history of decreased vision and intermittent eye irritation, suggestive of recurrent epithelial erosions, in both eyes. Slit-lamp exam revealed bilateral, irregular, limbal-sparing Bowman layer opacities, which were also noted on anterior segment optical coherence tomography. Phototherapeutic keratectomy was performed in the right eye, improving the best-corrected visual acuity from 20/50 to 20/30. Sequencing of the TGFBI gene revealed a novel heterozygous, missense mutation in exon 12 (c.1571 C > G; p.Ser524Cys), which was present in an affected son and absent in an unaffected son, and was predicted to be damaging by PolyPhen-2 and SIFT. The patient was diagnosed with a variant Bowman layer dystrophy given the late onset of an atypical phenotype and the identification of a novel TGFBI mutation.
A novel TGFBI missense mutation is associated with a late-onset Bowman layer dystrophy. Given the atypical clinical appearance and course, molecular genetic analysis was utilized to establish a definitive diagnosis.

Gelatinous drop-like corneal dystrophy is a very rare autosomal recessive disease classified as an epithelial and subepithelial corneal dystrophy. Patients typically present under the age of 20 with drop-like corneal lesions showing high corneal fluorescein uptake. Their disease course is typically protracted and prone to frequent relapses. The condition is caused by a dysfunction of the epithelial barrier, leading to protein deposits most likely originating from tear fluid. Histology typically shows subepithelial amyloid deposits with corresponding defects of Bowman\'s layer and epithelial atrophy. Where topical lubricating and anti-inflammatory therapy proves insufficient, penetrating allogenic limbokeratoplasty can be considered in a curative approach. In this report, we present disease courses of 2 unrelated patients. Current findings on pathogenesis are discussed.
Die gelatinöse Hornhautdystrophie ist eine sehr seltene, autosomal-rezessiv vererbte Erkrankung aus dem Formenkreis der epithelialen und subepithelialen Dystrophien. Die Patienten präsentieren sich typischerweise im 1. – 2. Lebensjahrzehnt mit tröpfchenförmigen, gelatinösen Hornhautauflagerungen mit hoher kornealer Fluoresceinaufnahme. Typisch sind schwere Verläufe mit ausgeprägter Rezidivneigung. Zugrunde liegt eine gestörte epitheliale Barrierefunktion, die vermutlich zu Einlagerungen von Proteinen aus dem Tränenfilm führt. Histologisch zeigen sich tropfenförmige subepitheliale Amyloideinlagerungen mit korrespondierenden Defekten der Bowman-Schicht sowie einer Epithelatrophie. Neben topischer befeuchtender und antiinflammatorischer Therapie kann in kurativem Ansatz eine allogene perforierende Limbokeratoplastik durchgeführt werden. In dieser Kasuistik werden die Krankheitsverläufe zweier nicht verwandter Patientinnen präsentiert. Aktuelle Erkenntnisse zur Pathogenese werden diskutiert.

OBJECTIVE: Keratoconus can be surgically challenging, especially in advanced cases. Classic corneal transplantation techniques, may often be associated with complications. New alternative procedures like isolated Bowman layer transplantation (as a corneal stromal inlay or as a corneal onlay) and corneal allogenic intrastromal ring segments (CAIRS) have recently shown promising results. The aim of this review is to describe the main new surgical developments for treating keratoconus.
RESULTS: Intrastromal Bowman layer transplantation has recently shown to be effective in halting keratoconus progression and maintaining visual acuity with contact lenses, at least up to 5-7 years postoperatively. Because intrastromal dissection can be challenging, we have recently developed a technique that allows using Bowman layer grafts as an onlay, that is positioned onto the patient\'s anatomical Bowman layer or anterior stroma, achieving comparable results as with Bowman layer inlay transplantation. CAIRS may also be an effective treatment, improving visual acuity, corneal surface parameters and keratoconus progression.
CONCLUSIONS: There are currently some new alternative treatments such as isolated Bowman layer inlay or onlay transplantation and CAIRS, both of which seem effective at treating keratoconus and which may offer a less invasive surgical approach.

OBJECTIVE: To describe the clinical outcome of a first patient undergoing Bowman layer (BL) transplantation with an onlay graft to reduce fluctuation in visual acuity and refractive error after previous radial keratotomy (RK) surgery.
METHODS: In 2018, a 66-year-old woman presented with complaints of long-standing diurnal fluctuation in best-spectacle corrected visual acuity (BSCVA) after RK in 1983. After the removal of host epithelium, a BL graft was positioned onto the host cornea. BSCVA, Scheimpflug-based corneal tomography, and anterior segment optical coherence tomography were evaluated up to 12 months postoperatively.
RESULTS: The surgery and postoperative course were uneventful. After surgery, the subjective complaints of visual fluctuation were reduced from 10 to 3 on a scale from 1 to 10. BSCVA (20/40; 0.5) did not change from preoperative to postoperative. Corneal tomography showed an overall central corneal steepening of 5.9 diopters. Biomicroscopy, Scheimpflug imaging, and anterior segment optical coherence tomography showed a completely epithelialized and well-integrated graft, with some minor epithelial remnants located in the preexisting keratotomy incisions.
CONCLUSIONS: BL onlay grafting may have the potential to manage patients with subjective complaints of diurnal fluctuation in visual acuity after previous RK.

Background: X-linked Alport syndrome results from the effect of COL4A5 mutations on basement membranes in the kidney, ear and eye. This study investigated individuals with X-linked Alport syndrome for corneal abnormalities.Patients and Methods: Six men and four women from 8 families with genetically-diagnosed X-linked Alport syndrome underwent ophthalmological examination including slit lamp examination and corneal endothelial specular microscopy. Results for corneal microscopy for men and women with X-linked disease were compared separately with the mean values for age- matched normals using the student\'s t test.Results: Five of the 6 men had end-stage kidney failure, all 6 had a hearing loss, three had lenticonus, and three had a central fleck retinopathy. Two men had a history of recurrent corneal erosions but no evidence of posterior polymorphous corneal dystrophy. None of the four women had kidney failure, but two had a hearing loss, and two had a central fleck retinopathy. One woman, whose son had recurrent corneal erosions, also had erosions, but no features of a posterior polymorphous corneal dystrophy.Corneal specular microscopy demonstrated abnormalities in affected men and women, with larger endothelial cells (p = .0001 in men, p = .004 in women) fewer 6-sided cells (p = .0001, p = .001 respectively) and reduced cell density (p = .03, p = .02 respectively) than normal.Conclusions: Recurrent corneal erosions are common in men and women with X-linked Alport syndrome, but posterior polymorphous corneal dystrophy is rare. The abnormal corneal endothelial cells in affected men and women are consistent with an abnormal Descemet membrane, and the reduced cell density resembles the reduced podocyte numbers found in the Alport glomerulus.

As the outermost layer of the eye, the cornea is vulnerable to physical and chemical trauma, which can result in loss of transparency and lead to corneal blindness. Given the global corneal donor shortage, there is an unmet need for biocompatible corneal substitutes that have high transparency, mechanical integrity and regenerative potentials. Herein we engineered a dual-layered collagen vitrigel containing biomimetic synthetic Bowman\'s membrane (sBM) and stromal layer (sSL). The sBM supported rapid epithelial cell migration, maturation and multilayer formation, and the sSL containing tissue-derived extracellular matrix (ECM) microparticles presented a biomimetic lamellar ultrastructure mimicking the native corneal stroma. The incorporation of tissue-derived microparticles in sSL layer significantly enhanced the mechanical properties and suturability of the implant without compromising the transparency after vitrification. In vivo performance of the vitrigel in a rabbit anterior lamellar keratoplasty model showed full re-epithelialization within 14 days and integration of the vitrigel with the host tissue stroma by day 30. The migrated epithelial cells formed functional multilayer with limbal stem cell marker p63 K14 expressed in the lower layer, epithelial marker K3 and K12 expressed through the layers and tight junction protein ZO-1 expressed by the multilayers. Corneal fibroblasts migrated into the implants to facilitate host/implant integration and corneal stromal regeneration. In summary, these results suggest that the multi-functional layers of this novel collagen vitrigel exhibited significantly improved biological performance as corneal substitute by harnessing a fast re-epithelialization and stromal regeneration potential.

Purpose: To characterize the three-dimensional (3D) thickness profile and age-related changes of Bowman\'s layer (BL), and endothelium/Descemet\'s membrane (En/DM) complex among healthy individuals using Corneal Microlayer Tomography (CML-T), and to describe its repeatability and accuracy.Methods: Sixty-six eyes of 41 healthy volunteers; 27 eyes (< 40 years old), and 39 eyes (>40 years old) were imaged using HD-OCT. Automatic and manual segmentation of the corneal layers was performed, and 3D thickness maps were generated, using custom-built CML-T software. A regional analysis of mean thickness parameters between the 2 age groups was performed. A regression analysis was used to assess the correlation between age, and thickness maps. Intraclass Correlation Coefficients (ICC), Coefficients of Variation (COV), and Bland-Altman plots were used to assess the reliability of the repeated measurements in 198 locations.Results: CML-T successfully mapped the BL and En/DM in all included eyes. Thickness maps showed a significant increase in corneal thickness (CT), BL thickness (BMT), and En/DM complex thickness (DMT) toward the periphery with a mean difference 28 µm (p < .001), 1.1 µm (p < .001), and 1.4 µm (p < .001), respectively. There was a strong correlation between age and central DMT (r = 0.61; p < .001), while there was no correlation between age and both CT, and BMT. ICC values ranged from 0.9 (BMT) to 0.997 (DMT), and from 0.808 (BMT) to 0.979 (CT) for intraoperator repeatability of manual measurements, and the accuracy of auto matic measurements, respectively. COV values were lower than 7.5% in all cases.Conclusion: CML-T is a novel tool that can generate 3D-thickness maps of both BL and En/DM. CT, BMT, and DMT increase toward the periphery in healthy corneas. DMT increases with aging, while BMT does not. We also report excellent repeatability, accuracy and good agreement between automatic and manual measurements.

BACKGROUND: This study compares the clinical outcomes of femtosecond laser small-incision lenticule extraction (SMILE) for the correction of myopia and myopic astigmatism greater than - 10 D, and - 10 D or less respectively.
METHODS: 60 eyes/patients were equally selected into group 1 (myopia and myopic astigmatism of - 10 D or less) and group 2 (myopia and myopic astigmatism of over - 10 D), both of which were treated with SMILE. Visual and refractive outcomes, corneal higher-order aberrations, and Bowman\'s layer micro-distortions were evaluated preoperatively, 3 months, and 6 months postoperatively.
RESULTS: LogMAR corrected distance visual acuity (CDVA) of group 1 and group 2 was - 0.069 ± 0.047 and - 0.053 ± 0.073 6 months postoperatively (P = 0.48). 100% eyes in group 1 and 97% in group 2 were within 1 D of targeted correction (P = 0.45). Meanwhile, 100% eyes in group 1 and 97% in group 2 had an uncorrected distance visual acuity of 20/25 or better (P = 0.20). Changes in corneal higher-order aberrations root mean square, coma, and trefoil were similar between the two groups but spherical aberration was higher in group 2 (P < 0.01). Micro-distortions were observed in 53% in group 1 and 77% in group 2. More micro-distortions were observed in group 2 (3.40 ± 2.66) than in group 1 (2.07 ± 2.29) (P = 0.041). The total number of micro-distortions was not correlated with postoperative CDVA (P = 0.77).
CONCLUSIONS: Visual outcomes showed similar results of SMILE for myopic correction of > - 10 D and ≤ - 10 D. Refractive outcomes showed slightly under-correction in higher myopic eyes. Higher myopic treatment tends to induce more spherical aberrations. Micro-distortions had no impact in visual and refractive outcomes.

To assess differences between epithelium thickness (ET) and Bowman\'s layer thickness (BLT) maps in keratoconic eyes and healthy eyes.
Cross-sectional study.
Setting: institutional.
47 patients (1 eye) with keratoconus (KC) and 20 healthy subjects (1 eye).
epithelium and Bowman\'s layer measurements were performed by using custom-designed polarization-sensitive optical coherence tomography (PS-OCT) with a conical scanning optics design. En face corneal ET and BLT maps with a diameter of 11 mm were computed. Main outcome measurements were mean ET and BLT of 25 sectors; the thinnest (minET, minBLT) and thickest sectors (maxET, maxBLT) were assessed. Ratios between thinnest/thickest sectors (R1) and between mean ET and BLT of the inferior temporal quadrant/superior nasal quadrant (R2) were calculated (R1ET, R1BLT; R2ET, R2BLT). Receiver operator characteristic (ROC) curve analysis was used to assess the diagnostic power of statistically different parameters.
In healthy eyes, smooth ET maps were observed. KC eyes showed a \"doughnut pattern.\" The BLT maps of healthy eyes had a smooth appearance, but highly irregular \"moth\"-like damage pattern could be observed in keratoconic eyes. Highest area under the curve values were found for the thinnest sector of the BLT map, the R1ET, and the thinnest sector of the ET map.
PS-OCT imaging enables the visualization of significant differences of the corneal epithelium and the Bowman\'s layer in en face maps covering almost the entire cornea. ET and BLT profiles could clearly show their diagnostic importance for the distinguishing of keratoconic eyes and healthy eyes.