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Ocular Considerations: Ectropion, Entropion, Blink, Ptosis, Epiphora
Background
Approximately 2.4 million eye injuries occur each year. Ocular and periocular trauma can occur by a variety of mechanisms, some of the most common including assault and blunt trauma, motor vehicle collisions, gunshot, fireworks, and falls. The cumulative lifetime prevalence of eye injuries in the United States is approximately 1400 per 100,000 population. In one study, medical treatment was not sought for 18% of these injuries. Acute management of traumatic injury necessitates immediate evaluation by an ophthalmologist, as vision loss is a serious risk, and more than half of those with eyelid injury have underlying globe injury. However, in one study 60% of injured eyes showed improvement in visual acuity after treatment.
The United States Eye Injury Registry estimates that periocular injuries occur in 5% of all serious injuries, with 80% affecting the canalicular structures and 70% affecting the eyelids. As discussed in Chapter 1.9 , eyelid lacerations must be repaired to properly align the eyelid structures and avoid the later development of an eyelid notch. Eyelid lacerations, including the canaliculi, require repair and stenting of the canaliculi to prevent future epiphora.
Even if visual function is preserved following an acute periocular injury, scarring can occur, which can further threaten vision years later. Ectropion, entropion, eyelid retraction, ptosis and epiphora can occur months to years following trauma, and may have functional and visual consequences necessitating secondary reconstruction.
Surgical Anatomy
Eyelid and Soft Tissue Anatomy
Knowledge of the normal anatomy of the eyelids is vital to identifying and repairing conditions such as entropion that may interfere with their function.
The peak of the upper eyelid slope is at the medial edge of the pupil. The lateral canthus lies slightly higher than the medial canthus. The palpebral fissure, or vertical distance between the upper and lower eyelid margins is normally about 9 mm. The eyelid height may be measured by the marginal reflex distance 1 (MRD1) and marginal reflex distance 2 (MRD2). The MRD1 is the distance from the pupillary light reflex to the upper eyelid margin, and is normally approximately 4 mm. The MRD2 is the distance from the light reflex to the lower eyelid margin and is typically about 5 mm. The lower eyelid margin normally rests at the inferior junction between the cornea and sclera, the inferior limbus. Lower eyelid retraction is present if the eyelid margin falls below this, and can be quantified by measuring the inferior scleral show, or millimeters of sclera visible between the inferior limbus and the lower eyelid margin.
The eyelids are anchored to the orbital bones by the medial and lateral canthal tendons. The lateral canthus is typically a few millimeters higher than the medial canthus, creating a slight downward slope of the palpebral fissure from the lateral to the medial aspect. The medial canthal tendon divides into anterior and posterior limbs, which attach at the anterior and posterior lacrimal crests, respectively, surrounding the lacrimal sac. The lateral canthal tendon is divided into superior and inferior limbs, which join and attach together at Whitnall's tubercle on the lateral orbital rim.
Beneath the upper and lower eyelid skin lies the orbicularis muscle, which is responsible for eyelid closure and is innervated by the seventh cranial nerve. The pretarsal portion of the orbicularis overlies the tarsal plate, the preseptal portion overlies the septum, and the orbital portion overlies the orbital rim.
The tarsal plate is located posterior to the orbicularis and is made of fibrous tissue. In the upper eyelid, the tarsal plate extends approximately 10 mm above the upper eyelid margin. Posterior to the tarsal plate is the conjunctiva, which contains goblet cells that supply the mucin layer of the tear film.
The two main retractors of the upper eyelid are the levator palpebrae superioris and Müller's muscle. The levator is the primary retractor of the upper eyelid and is innervated by the superior division of the third cranial nerve. Müller's muscle is innervated by sympathetic fibers and extends from the superior border of the tarsus to Whitnall's ligament. Superior to the tarsal plate, the orbital septum, the boundary between the eyelid and orbit, lies posterior to the orbicularis, overlying the preaponeurotic fat. The levator aponeurosis lies posterior to the preaponeurotic fat and anterior to Müller's muscle and conjunctiva.
In the lower eyelid, the orbicularis lies posterior to the skin. The tarsal plate extends 4–6 mm from the lower eyelid margin posterior to the orbicularis, and is lined posteriorly by the conjunctiva. The lower eyelid retractors, or the capsulopalpebral fascia, attach to the inferior aspect of the tarsal plate and are analogous to the function of the levator muscle in the upper eyelid.
The anterior lamella of the eyelids consists of the skin and orbicularis muscle. The posterior lamella includes the tarsal plate and conjunctiva. The gray line, visible at the eyelid margin, marks the boundary between the anterior and posterior lamellae and is a useful anatomical landmark during eyelid surgery.
Lacrimal System Anatomy
The lacrimal system includes the tear film of the eye and the tear drainage system. The tear film is made up of three layers. The most anterior layer is the oil layer, produced by the meibomian glands and glands of Zeis, and functions to prevent evaporation of the tear film. The middle layer is the aqueous layer, produced by the lacrimal gland and accessory glands of Wolfring and Krause. The mucous layer is the most posterior layer, produced by the goblet cells of the conjunctiva.
The openings to the lacrimal drainage system are the superior and inferior puncta, located medially in the upper and lower eyelid, respectively. Tears travel through the puncta into the superior and inferior canaliculi, which join to form the common canaliculus. The common canaliculus enters the lacrimal sac via the valve of Rosenmuller.
The lacrimal sac lies in the lacrimal fossa, bounded by the anterior and posterior lacrimal crests. The anterior portion of the fossa is made up of a portion of the maxillary bone, and the posterior portion of the fossa is composed of the much thinner lacrimal bone. The blinking action of the eyelids acts as a pump to fill and empty the lacrimal sac. This pumping function is compromised in patients with facial nerve palsy, which is in part responsible for tearing in those patients. The lacrimal sac drains into the nasolacrimal duct, which is lined by mucosa and enters the nose through the valve of Hasner beneath the inferior turbinate in the inferior meatus. Dacryocystorhinostomy surgery bypasses obstruction in the nasolacrimal duct by creating a new orifice into the nose at the level of the lacrimal sac.
Clinical Assessment
History
A thorough history is necessary to guide clinical and surgical decision-making. The mechanism of injury and amount of time elapsed are important elements of the history. Past imaging, if available, should be reviewed. The history of present illness should elicit the patient's primary complaints and allows the surgeon to determine if functional impairment is present. Ocular surface irritation, discomfort, and dryness are common complaints with ectropion, entropion, and eyelid retraction. Corneal epithelial defects or ulcerations may cause significant pain and erythema of the eye. Prior canalicular laceration or fracture through the nasolacrimal duct may result in significant epiphora, which can impair function. Traumatic seventh nerve palsy may result in poor orbicularis function and impairment of the eyelid blink and closure, which can result in ocular surface exposure and desiccation, creating significant discomfort for the patient. Ptosis, which can occur secondary to trauma, can obstruct the superior and temporal visual fields, interfering with visual function. In each case, the surgeon and patient must weigh the risks of surgery against the degree of functional impairment that is present.
Examination
Dilated fundus examination should be performed at the time of initial injury, as there is significant correlation between periocular and concurrent intraocular injuries. Visual acuity, confrontational visual fields, pupils, and ocular motility should be assessed in all patients with a history of trauma. If possible, slit lamp examination should be performed, and should include evaluation of all anterior ocular structures. Careful attention should be paid to the eyelids. MRD1 and MRD2 should be assessed. The patient should be asked to close their eyes gently to assess for lagophthalmos ( Fig. 3.4.1 ). Hertel exophthalmometry can be helpful in the setting of orbital fractures to assess for enophthalmos.
Entropion
Entropion, or posterior rotation of the eyelid margin, with or without trichiasis, may occur after trauma. Although there are several types of entropion, cicatricial entropion is often present in the setting of prior trauma, where scarring and contracture of the posterior lamella rotates the eyelid margin inward. The palpebral conjunctiva of both the upper and lower eyelids should be evaluated, and careful eversion of the upper eyelid should be performed. Scarring of the conjunctiva and posteriorly displaced meibomian gland orifices are suggestive of cicatricial entropion. There may also be concurrent horizontal laxity of the eyelid, which should be evaluated by performing snap-back testing, or pulling the lower eyelid away from the globe and assessing how quickly it snaps back into place. Trichiasis ( Fig. 3.4.2 ) may be present with or without corresponding corneal surface breakdown due to mechanical trauma from eyelashes. Fluorescein staining should be performed if indicated to determine whether the corneal epithelium is intact. In the most severe cases, a corneal epithelial defect may become superinfected to become a corneal ulcer. Corneal ulceration typically appears as focal corneal opacification with overlying epithelial defect, and if present, should be urgently evaluated by an ophthalmologist.
Ectropion
Cicatricial ectropion can also occur after past trauma due to scarring of the anterior lamella, leading to anterior rotation of the eyelid margin ( Fig. 3.4.3 ). The eyelid skin and margin should be assessed for tautness and evidence of scarring. The eyelid should be assessed for horizontal laxity with the snap-back technique. The corneal surface should be examined and fluorescein staining should be performed if indicated. Eyelid retraction may also be present, and the amount of inferior scleral show (the distance from the inferior corneoscleral limbus to the lower eyelid margin) and lagophthalmos should be quantified. In severe cases, exposure of the inferior cornea can cause corneal epithelial breakdown.
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