Cicatricial entropion causes misdirection of lashes when shortening of the posterior lamella follows contraction of scar tissue. The underlying pathology can vary and includes infection (trachoma chlamydia, chronic blepharoconjunctivitis and Herpes Zoster Ophthalmicus), toxic epithelial necrolysis (Stevens-Johnson syndrome), pemphigoid and trauma (chemical, thermal and mechanical). Histology is sometimes required to determine the nature of the condition.
Repair of these conditions not only includes rotation of the lid margin but modification or the addition of material to the foreshortened posterior lamella. Replacing like with like is a standard maxim so the posterior lamella requires replacement with tarsoconjunctiva if at all possible. When this is not readily available various auto-, homo- and allografts may be used, which all attempt to lengthen the tarsoconjunctival surface and allow the lashes to point away from the globe. The upper lid graft has one main objective and that is to maintain a moist surface in contact with the cornea. Gravity and muscle dynamics keep the tissues in contact. The lower lid, which works against gravity, requires a more rigid scaffold to support the skin and mucosal surface against the cornea. Material can be harvested from various sites and includes hard palate mucosa, nasal septal cartilage and ear cartilage. This requires a separate mucosal lining in order to protect the eye. Hard palate mucosa that has sufficient collagen matrix to remain rigid is probably the best form of substitute that can be adapted for both the lower and upper lid if tarsoconjunctival tissue is unavailable.
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