Limbal stem cells, also known as corneal epithelial stem cells, are stem cells located in the basal epithelial layer of the corneal limbus. They form the border between the cornea and the sclera. Characteristics of limbal stem cells include a slow turnover rate, high proliferative potential, clonogenicity, expression of stem cell markers, as well as the ability to regenerate the entire corneal epithelium. Limbal stem cell proliferation has the role of maintaining the cornea; for example, by replacing cells that are lost via tears. Additionally, these cells also prevent the conjunctival epithelial cells from migrating onto the surface of the cornea. Medical conditions and treatments
Damage to the limbus can lead to limbal stem cell deficiency (LSCD); this may be primary - related to an insufficient stromal microenvironment to support stem cell functions, such as aniridia, and other congenital conditions, or secondary – caused by external factors that destroy the limbal stem cells, such as chemical or thermal burns, radiation, surgery, infection, use of contact lenses, or certain drugs. Signs and symptoms include: conjunctivalisation, corneal vascularisation, edema, ocular discomfort or pain, visual impairment, and blindness, which are likely associated with failure in the process of regenerating the corneal epithelium. Immediate management aims to limit traumatic or chemical damage to the limbus, control inflammation, and help achieve a healthy corneal epithelium. Initial treatment after trauma/injury includes preservative-free artificial tears, topical steroids, ‘bandage’ contact lenses, and autologous eye drops (eye drops manufactured from the patients own blood serum and plasma).
Treatment
Neonatal acne will typically resolve by itself in 2-6 months. In mild cases, cleansing the face daily with gentle soap and water while avoiding use of potential comedogenic soaps, lotions and oils is often enough. Further treatment is not necessary but in severe or persistent cases topical therapy can be initiated. Benzoyl Peroxide
Topical benzoyl peroxide (BPO) may be indicated in persistent or inflammatory cases. BPO is a lipophilic agent that penetrates into sebaceous glands and generates reactive oxygen species that kill P. acnes. It also has comedolytic and anti-inflammatory properties and can prevent development of antimicrobial resistance. Topical Retinoids
Topical retinoids can be used alone or in combination with BPO. Retinoids are derived from vitamin A. They bind to retinoic receptors to normalize the rate of keratinocyte growth and prevent inflammation. Overactive keratinocyte production can lead to comedone formation. Topical Antibiotics
In cases where scarring is a concern, topical antibiotics may be recommended. Topical clindamycin and erythromycin are the most commonly prescribed options for acne. Antibiotics kill P. acnes on skin that could be causing inflammation. With the emergence of resistant P. acnes, experts recommend topical antibiotics to be used in combination with BPO to reduce the risk of development of antimicrobial resistance. The most common side effects of topical antibiotics are stinging, burning and redness at the site of application. Topical antifungals
Some experts suggest the use of topical ketoconazole in newborns with more pustular neonatal acne as there is evidence it shortens duration of lesions.