China
Africa
Explore chapters and articles related to this topic
Ocular Irritation Testing
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
George P. Daston, F. E. Freeberg
The corneal epithelium is a stratified columnar epithelium, typically 5 to 6 cells thick in the rabbit, 7 to 10 in the human. Bowman’s membrane is thick in the human (8 to 12 μm), but much thinner (approximately 2 μm) in rabbits.5 The endothelium is a single layer of low cuboidal cells. Both epithelia form a coherent barrier to diffusion. The corneal stroma, which is by far the thickest part of the cornea, is composed of collagen fibrils which are arranged in a highly regular pattern in order to achieve transparency. The fluid content of the stroma is higher than that of the adjacent sclera,26 and this probably also contributes to its transparency.
Models of Toxicity Screening Using Cultured Cells
Published in John J. Lemasters, Constance Oliver, Cell Biology of Trauma, 2020
Roberta L. Grant, Daniel Acosta
The epithelial layer is composed of four to seven layers of cells and is classified as a tight epithelium. Unlike the skin, the corneal epithelium does not have a keratinized layer of cells that can act as a protective barrier. The tear film keeps the epithelial cells moist, provides growth factors, washes away substances that come into contact with the eye, and contains proteolytic enzymes that help protect against ocular infections.
Ophthalmology
Published in Stephan Strobel, Lewis Spitz, Stephen D. Marks, Great Ormond Street Handbook of Paediatrics, 2019
This is common in some underdeveloped countries and is due to a deficiency of dietary vitamin A intake. It is characterised by a thickening of the corneal epithelium, keratinisation of the epithelium and a diffuse corneal opacity. Secondary pannus and corneal vascularisation can occur. In addition to corneal pathology, white foamy lesions (Bitit’s spots) of the temporal conjunctiva occur.
Vanadium inhalation effects on the corneal ciliary neurotrophic factor (CNTF): study in a murine model
Published in Cutaneous and Ocular Toxicology, 2023
Isis Mendoza-Aldaba, Nelly López-Valdez, María Eugenia Cervantes-Valencia, Teresa Imelda Fortoul
The normal corneal epithelium is composed of five layers: the external layer is a non-keratinized well-arrayed stratified epithelium with five to seven cell layers [9]. A study from Tan-Gan et al. [8], reported that exposure to PM2.5 eye drops for 14 days produced a decrease in the number of epithelial layers and their microvilli in the cornea, and also an increase in positive Ki67 cells in the basal layer, and apoptosis [8]. Another study, from Lasagni et al. [22], reported epithelium hyperplasia and disorganised growth, suggesting that these changes could be attributable to oxidative stress in male BALB mice after whole-body exposure to PM10 for 12 weeks. On the other hand, we reported that V inhalation produces oxidative stress in the kidney and in the liver, which is associated with damage in both organs [15,23]. It is possible that V-induced oxidative stress in the cornea might explain the layers’ disarray observed after the 8 weeks of V exposure.
Effects of topical Coenzyme Q10, Xanthan Gum and Sodium Hyaluronate on corneal epithelial wound healing
Published in Clinical and Experimental Optometry, 2022
Leyla Asena, Gülşah Gökgöz, Fatma Helvacıoğlu, Gonca Özgün, Emine Ebru Deniz, Dilek Dursun Altinors
Corneal epithelial defects may occur secondary to chemical injury, neurogenic causes, infectious or immunogenic mechanisms, trauma and corneal epithelial basement membrane pathologies.1 Corneal epithelial integrity is essential for maintaining its barrier function against infective microorganisms, normal stromal hydration and providing a transparent refractive surface. Therefore, careful treatment of corneal epithelial defects is essential. Delayed re-epithelization may lead to persistent epithelial defects, corneal ulcers and infections. Treatment options include topical prophylactic antibiotic drops or ointments, frequently administered preservative-free artificial tears, patching and bandage contact lenses. In unresponsive cases, oral doxycycline, autologous serum, amniotic membrane transplantation, tarsorrhaphy, conjunctival flap and scleral lenses can be added to the treatment.2–4 Conventional treatment options may not be enough in some cases leading to prolonged ocular discomfort, blurred vision and secondary infection, which are all devastating consequences. Therefore, there is still a need for therapeutic agents that can effectively support the healing process.
Black Carbon Induces Complement Activation via NLRP3 Inflammasome in Human Corneal Epithelial Cells
Published in Current Eye Research, 2022
Qin Long, Liqiang Wang, Jing Shang, Ying Liu, Chen Chen
The complement system is composed of three distinct pathways (classical, lectin, and alternative). Formation of the MAC, marked by completion of C5b-9 assembly, reflects the activation of the complement system.15 Due to the pivotal role of the complement system in inflammation, it has been widely linked to a number of disorders within the last 15 years, including ocular inflammatory diseases such as age-related macular degeneration (AMD), 22 pathological myopia (PM), 23 and cornea wound healing.24 Furthermore, multiple complement fragments and receptors have been found to be expressed in the ocular surface tissue of normal cornea, keratitis, and experimental dry eye disease.25–27 Due to direct contact with atmospheric pollutants, the corneal epithelium serves as an essential barrier for maintaining the health of the ocular surface. To our knowledge, there have been no previous reports on the effect of BC particles, including FBC and OBC, on the corneal epithelium.