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Pterygia are common conjunctival degenerations with well-documented risk factors but an unclear pathogenesis. Better understanding of the pathogenesis of pterygium could lead to improved surgical outcomes and decreased postoperative recurrence. Currently, pterygium excision with conjunctival autograft remains the preferred surgical technique to decrease pterygium recurrence. Many adjuvant therapies have been used in pterygium surgery to varying degrees of success. Topical cyclosporine, an immunosuppressive medication, in conjunction with conjunctival autograft was found to be most successful in decreasing pterygium recurrence according to a recent meta-analysis. Other adjuvant therapies such as mitomycin-C (MMC), 5-fluorouracil (5-FU), and beta-irradiation have also been used, though usage of these may cause multiple adverse effects. Recent research indicates that interactions between mouse double minute 2 (MDM2) and p53 could play a role in the occurrence of pterygium. Nutlin, an MDM2 antagonist, was found to have significantly less toxicity in conjunctival cells when compared with MMC on laboratory analysis of pterygium samples.

PurposeTo determine the expressions of SARS-CoV-2 receptor angiotensin-converting enzyme 2 (ACE2) and type II transmembrane serine protease (TMPRSS2) genes in human and mouse ocular cells and comparison to other tissue cells.MethodsHuman conjunctiva and primary pterygium tissues were collected from pterygium patients who underwent surgery. The expression of ACE2 and TMPRSS2 genes was determined in human primary conjunctival and pterygium cells, human ocular and other tissue cell lines, mesenchymal stem cells as well as mouse ocular and other tissues by reverse transcription-polymerase chain reaction (RT-PCR) and SYBR green PCR.ResultsRT-PCR analysis showed consistent expression by 2 ACE2 gene primers in 2 out of 3 human conjunctival cells and pterygium cell lines. Expression by 2 TMPRSS2 gene primers could only be found in 1 out of 3 pterygium cell lines, but not in any conjunctival cells. Compared with the lung A549 cells, similar expression was noted in conjunctival and pterygium cells. In addition, mouse cornea had comparable expression of Tmprss2 gene and lower but prominent Ace2 gene expression compared with the lung tissue.ConclusionConsidering the necessity of both ACE2 and TMPRSS2 for SARS-CoV-2 infection, our results suggest that conjunctiva would be less likely to be infected by SARS-CoV-2, whereas pterygium possesses some possibility of SARS-CoV-2 infection. With high and consistent expression of Ace2 and Tmprss2 in cornea, cornea rather than conjunctiva has higher potential to be infected by SARS-CoV-2. Precaution is necessary to prevent possible SARS-CoV-2 infection through ocular surface in clinical practice.

The precorneal tear film is maintained by blinking and exhibits different phases in the tear cycle. The tear film serves as the most anterior surface of the eye and plays an important role as a first refractive component of the eye. Alterations in tear film dynamics may cause both vision-related and ocular surface-related symptoms. Although the optical quality associated with the tear film dynamics previously received little attention, objective measurements of optical quality using wavefront sensors have enabled us to quantify optical aberrations induced by the tear film. This has provided an objective method for assessing reduced optical quality in dry eye; thus, visual disturbances were included in the definition of dry eye disease in the 2007 Dry Eye Workshop report. In addition, sequential measurements of wavefront aberrations have provided us with valuable insights into the dynamic optical changes associated with tear film dynamics. This review will focus on the current knowledge of the mechanisms of wavefront variations that are caused by different aspects of tear film dynamics: specifically, quality, quantity and properties of the tear film, demonstrating the respective effects of dry eye, epiphora and instillation of eye drops on the quality of vision.

The study highlights the importance of considering these factors for studying microbiomes of sparsely colonized sites such as the ocular surface for better reliability of data and provides potential sources of bias in analyzing microbial composition of low abundance on the ocular surface. By exploring the mechanism of early perforation and thinning of cornea with P. aeruginosa infection after PM10 exposure, they report that PM10 exposure worsens the defense mechanism by oxidative stress, inflammation, and susceptibility to infection, and SKQ1 protects by reversing the adverse effects of PM10 via mitochondria-targeted antioxidant effects. Alenezi et al. demonstrate differential expression of genes in corneal infections in their study to understand the pathogenic mechanism of microbial keratitis, particularly the overreactive immune response to infection that causes corneal scarring and vision loss. Conflict of interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Dry eye disease encompasses a broad range of etiologies and disease subtypes which have similar clinical manifestations. Medications can cause dry eye disease or symptoms of dryness as a side effect by either interfering with the lacrimal gland or meibomian gland function, or both, and by other mechanisms that affect the ocular surface homeostasis. This is important to know and recognize as eliminating the offending medication can reverse the symptoms and, in many cases, prevent further deterioration of the ocular surface inflammation. This review focuses on drugs like systemic isotretinoin and taxanes, which cause meibomian gland dysfunction; immune checkpoint inhibitors that cause lacrimal gland dysfunction; gliptins and topical antiglaucoma medications that cause cicatrizing conjunctivitis; and epidermal growth factor receptor inhibitors, fibroblast growth factor receptor inhibitors, and belantamab mafodotin, which cause mucosal epitheliopathy. Many of these medications, particularly the newer anticancer agents, have only recently been introduced for clinical use, and knowledge and awareness of their ocular side effects are still evolving. This review aims to update ophthalmologists on the drug-induced causes of dry eye disease or symptoms of dryness, which is avoidable by discontinuation of the incriminating agent or can be mitigated by reducing the dose or frequency of usage.

Correspondence to Dr Vishal Jhanji; vishaljhanji@gmail.com When corneal endotheliitis was first reported by Khodadoust and Attarzadeh in 1982, it was thought to be caused by an autoimmune process.1 The clinical presentation was similar to corneal allograft rejection due to the presence of linear corneal keratic precipitates (KPs). CMV infection has also been reported in patients with corneal endothelial rejection after penetrating keratoplasty in Southeast Asia.4 Hsiao et al detected CMV DNA in 10% of aqueous samples, 26.7% of recipient corneas and 20% of donor corneas obtained during keratoplasty.4 All patients in Hsiao et al’s study with CMV-positive aqueous developed CMV endotheliitis postoperatively and experienced graft failure eventually. [...]analysis confirmed that a history of glaucoma and anterior uveitis significantly increased the development of CMV endotheliitis in the postoperative period.

Background/AimsWe aimed to investigate the refractive changes in the posterior corneal surface in keratoconus (KC) associated with wearing spherical corneal rigid gas-permeable contact lenses (corneal GPs) with apical touch or three-point touch fitting and the effect of spherical corneal GPs on corneal biomechanics.MethodsPatients with KC wearing corneal GPs every day without facing complications were enrolled as a single group. Corneal tomographic data were obtained using a three-dimensional anterior segment optical coherence tomography from the same eye with and without corneal GPs. Dioptric data from the central 3-mm zone of the posterior corneal surface were decomposed into spherical, regular astigmatism, asymmetry and higher-order irregularity components using Fourier harmonic analysis. The corneal biomechanical indices were deformation amplitude ratio within 2 mm, integrated radius, stiffness parameter at first applanation and linear Corvis Biomechanical Index. Correlations between the difference in Fourier indices with and without corneal GPs and the corneal biomechanical parameters were analysed.ResultsThirty-two eyes of 32 patients with KC were enrolled. Spherical, regular astigmatism and asymmetry components were significantly smaller with corneal GP wear than without the wear (all p<0.001). All biomechanical indices were significantly correlated with the difference in the spherical components with and without corneal GPs.ConclusionCorneal biomechanical properties of KC were correlated with posterior corneal surface flattening induced by wearing corneal GPs on the spherical components. This effect is greater in biomechanically weaker corneas.

Background To assess the corneal stress-strain index (SSI), which is a marker for material stiffness and corneal biomechanical parameters, in myopic eyes. Methods A total of 1054 myopic patients were included in this study. Corneal visualisation Scheimpflug technology was used to measure the SSI. Corneal biomechanics were assessed using the first and second applanation times (A1-and A2-times); maximum deflection amplitude (DefAmax); deflection area (HCDefArea); the highest concavity peak distance (HC-PD), time (HC-time), and deflection amplitude (HC-DefA); integrated radius (IR); whole eye movement (WEM); stiffness parameter (SP-A1;, biomechanically corrected intraocular pressure (BIOP); and Corvis biomechanical index (CBI). Scheimpflug tomography was used to obtain the mean keratometery (Km) and central corneal thickness (CCT). According to the spherical equivalent (SE) (low myopia: SE ≥ − 3.00D and high myopia: SE ≤ − 6.00D.), the suitable patients were divided into two groups. Results The mean SSI value was 0.854 ± 0.004. The SSI had a positive correlation with A1-time (( r  = 0.272), HC-time ( r  = 0.218), WEM ( r  = 0.288), SP-A1 ( r  = 0.316), CBI ( r  = 0.199), CCT ( r  = 0.125), bIOP ( r  = 0.230), and SE ( r  = 0.313) (all p -values<0.01). The SSI had a negative correlation with HCDefA ( r  = − 0.721), HCDefArea ( r  = − 0.665), HC-PD( r  = − 0.597), IR ( r  = − 0.555), DefAmax ( r  = − 0.564), and Km ( r  = − 0.103) (all p-values<0.01). There were significant differences in SSI (t = 8.960, p<0.01) and IR (t = − 3.509, p<0.01) between the low and high myopia groups. Conclusions In different grades of myopia, the SSI values were lower in eyes with higher SEs. It indicates that the mechanical strength of the cornea may be compromised in high myopia. The SSI was positively correlated with the spherical equivalent, and it may provide a new way to study the mechanism of myopia.

Corneal opacification is the fourth most common cause of blindness globally behind cataracts, glaucoma, and age-related macular degeneration. The standard treatment of serious corneal scarring is corneal transplantation. Though it is effective for restoring vision, the treatment outcome is not optimal, due to limitations such as long-term graft survival, lifelong use of immunosuppressants, and a loss of corneal strength. Regulation of corneal stromal wound healing, along with inhibition or downregulation of corneal scarring is a promising approach to prevent corneal opacification. Pharmacological approaches have been suggested, however these are fraught with side effects. Tissue healing is an intricate process that involves cell death, proliferation, differentiation, and remodeling of the extracellular matrix. Current research on stromal wound healing is focused on corneal characteristics such as the immune response, angiogenesis, and cell signaling. Indeed, promising new technologies with the potential to modulate wound healing are under development. In this review, we provide an overview of cell-free strategies and some approaches under development that have the potential to control stromal fibrosis and scarring, especially in the context of early intervention.

The corneal endothelium is the posterior monolayer of cells that are responsible for maintaining overall transparency of the avascular corneal tissue via pump function. These cells are non-regenerative in vivo and therefore, approximately 40% of corneal transplants undertaken worldwide are a result of damage or dysfunction of endothelial cells. The number of available corneal donor tissues is limited worldwide, hence, cultivation of human corneal endothelial cells (hCECs) in vitro has been attempted in order to produce tissue engineered corneal endothelial grafts. Researchers have attempted to recreate the current gold standard treatment of replacing the endothelial layer with accompanying Descemet’s membrane or a small portion of stroma as support with tissue engineering strategies using various substrates of both biologically derived and synthetic origin. Here we review the potential biomaterials that are currently in development to support the transplantation of a cultured monolayer of hCECs.