China
Africa
Explore chapters and articles related to this topic
Corneal Defects, Abrasions and Foreign Bodies
Published in Amy-lee Shirodkar, Gwyn Samuel Williams, Bushra Thajudeen, Practical Emergency Ophthalmology Handbook, 2019
Corneal defects: Can be seen in dry eyes, corneal ulcers (viral, bacterial, fungal and parasitic), corneal exposure due to lid or lash malposition, chemical or thermal burns, recurrent erosion syndrome due to corneal dystrophies, in the presence of limbal stem cell deficiency or in cases of neurotrophic corneas.
Ophthalmology
Published in Stephan Strobel, Lewis Spitz, Stephen D. Marks, Great Ormond Street Handbook of Paediatrics, 2019
All children with sporadic aniridia should have repeated abdominal ultrasonographic and clinical examinations; molecular genetic evaluation reveals intragenuc mutation only. One protocol advised that the child be seen every 3 months until the age of 5 years, every 6 months until the age of 10, and once a year until the age of 16. If chromosomal deletion is found, 3-monthly scans should be performed and the child transferred to the care of a nephrologist. 50% of patients with aniridia may develop glaucoma and nearly all will develop a keratopathy in adulthood due to limbal stem cell deficiency.
Head and neck
Published in Ian Greaves, Military Medicine in Iraq and Afghanistan, 2018
There are a number of disorders of the ocular surface, including persistent epithelial defects of the cornea, acute chemical burns with long-term loss of integrity of the ocular surface epithelium and conjunctival scarring from mucous membrane disorders, that still pose a clinical challenge in ophthalmic surgery.115,154 The cornea is the most important part of the ocular surface, providing two thirds of the focusing power and maintaining clear and useful vision due to its transparent and avascular nature.155 Amniotic membrane, or amnion, consists of a thick basement membrane and an avascular stromal matrix. Meller et al.154,156 demonstrated that amniotic membrane transplantation is effective in promoting corneal epithelialisation and reducing inflammation, thus preventing later scarring complications. In mild to moderate chemical or thermal burns, the authors found that amniotic membrane transplantation alone rapidly restored both the corneal and conjunctival surfaces.156 In severe burns, amniotic membrane transplantation allowed restoration of the ocular surface without debilitating symblepharon and reduced limbal stromal inflammation but did not prevent limbal stem cell deficiency.156 Nevertheless, these findings support the importance of intervention at the earliest possible stage for eyes with a severely damaged ocular surface.120 The goal of ongoing research is to augment the effects of dry-preserved amniotic membrane for use as an immediate field dressing for ocular burns sustained in the deployed environment.115
Neurotrophic keratopathy: current challenges and future prospects
Published in Annals of Medicine, 2022
Erin NaPier, Matthew Camacho, Timothy F. McDevitt, Adam R. Sweeney
Beyond corneal sensitivity testing, several other tests are helpful to identify comorbid conditions, classify the severity of NK, and monitor response to treatment or disease progression. Assessing tear film health is performed using the Schirmer test and tear osmolarity testing. Tear film health may be followed to assist in tracking subclinical disease progress [2,18]. In vivo confocal microscopy evaluates corneal nerve density in the stromal and sub-basal nerves. Eyes affected with NK can show decreased nerve density, decreased corneal epithelial and endothelial cell density, and increased hyperreflective keratinocytes. Patients who have had long disease duration typically have lower endothelial cell density. Unfortunately, cornea nerve evaluations involving confocal microscopy may have low reproducibility [2]. Ocular surface impression cytology identifies corneal conjunctivalization which can suggest limbal stem cell deficiency.
Temporal Regulation of Notch Signaling and Its Influence on the Differentiation of Ex Vivo Cultured Limbal Epithelial Cells
Published in Current Eye Research, 2020
Kamesh Dhamodaran, Murali Subramani, Lekshmi Krishna, Himanshu Matalia, Chaitra Jayadev, Nandini Chinnappaiah, Rohit Shetty, Debashish Das
The limbus harbors the progenitor ocular/stem cells that play a definitive role in repopulating the corneal surface with epithelial cells.1 These cells migrate centripetally from the peripheral to the central cornea during homeostasis.2 In unilateral limbal stem cell deficiency, limbal epithelial cells from the healthy eye are transplanted to the affected eye either with ex-vivo culturing (cultured limbal epithelial transplantation) or as a limbal biopsy (simple limbal epithelial transplantation).3 The reported rate of success of cell therapy is in the range of 68–72%.4 One of the potential factors influencing the fate of transplanted cells is the underlying signaling mechanisms. Understanding these mechanisms would provide insights into ways to modulate the same for a better clinical outcome.
Limbal Epithelial and Mesenchymal Stem Cell Therapy for Corneal Regeneration
Published in Current Eye Research, 2020
Sachin Shukla, Swapna S Shanbhag, Fatemeh Tavakkoli, Shobhit Varma, Vivek Singh, Sayan Basu
However, subsequently, Thoft and colleagues realized that the limbal epithelium was much more similar to the corneal epithelium than to the conjunctival epithelium.7 This prompted them to propagate the x-y-z hypothesis of corneal epithelial homeostasis. This hypothesis proposed that epithelial cells from the limbus/peripheral cornea migrated centripetally and differentiated to replace the more mature cells in the central cornea.8 Finally in 1986, Schermer et al. in a seminal paper demonstrated the presence of putative stem cells in the basal layers of the limbal epithelium which were slow-cycling, label-retaining and were capable of proliferation in vitro. They proposed that these basal epithelial cells of the limbus transform into transient amplifying cells which in turn give rise to terminally differentiated cells of the corneal epithelium.9 Cotsarelis et al. further elaborated that injury to the central cornea leads to rapid proliferation of otherwise slow-cycling limbal basal epithelial cells.10 Thus, the limbus was established as the central dogma of corneal epithelial regeneration, a paradigm that holds true till this day.10 These important discoveries in the late 1980s led to the coinage of the term ‘limbal stem cells’ to denote the corneal epithelial stem cells and the clinical term ‘limbal stem cell deficiency’ to denote severe ocular surface disease due to limbal stem cell failure.