Entropion is a posterior rotation of the upper or lower lid margin against the globe; the causes include involutional changes within the eyelid tissues or cicatricial shortening of the posterior lamella of the eyelid. Congenital lower lid entropion is rare and results from an excess of skin and orbicularis oculi muscle being only loosely attached to the eyelid retractors. The symptoms of entropion—which include ocular irritation, lid spasm, pain, redness, and watering—are worse in the presence of a keratinized lid margin (occurring in cicatricial disease) and where the ocular surface is compromised. Discomfort may lead to secondary blepharospasm, which exacerbates the entropion by causing the preseptal part of the orbicularis muscle to override the pretarsal component. The eyelids and globe should be examined to identify underlying causative factors—in particular the degree and position of tissue laxity, the position of the eyelid margin and lashes, and the thickness of the tarsus. Any secondary effects of entropion, both within the lid and on the ocular surface, should also be noted. 7-1-1 Tissue Laxity. Aging of collagen and the force of gravity leads to eyelid laxity and an excess of tissues, particularly the anterior lamella of the lid. Stretching of the orbicularis muscle and canthal tendons results in horizontal laxity, and eyelid stability is further compromised by enophthalmos due to age-related fat atrophy. Where there is a relative dissociation between the anterior and posterior lamellae, the preseptal orbicularis muscle overrides the pretarsal muscle, leading to eyelid inversion, and this effect is exacerbated both by laxity of the lower lid retractors and age-related tarsal atrophy. Tissue laxity in the absence of orbicularis overriding tends to cause ectropion; with complete loss of retractor action, this can result in complete eversion of the tarsus (“shelf ectropion”). Horizontal laxity of the eyelid tissues is assessed by grasping the lid skin and applying gentle traction in the appropriate direction. The overall horizontal laxity is judged by the extent to which the eyelid can be parted from the globe—greater than about 6 mm is abnormal for a lower eyelid—and by the speed with which the retracted lid returns to the surface of the globe (the “spring-back” test).
Tracheal pseudomembrane secondary to aspiration pneumonia in a 6-year-old Ragdoll
