Corneal Trauma: Abrasions, Lacerations, Foreign Bodies, Burns, and Contact Lenses



Corneal Trauma: Abrasions, Lacerations, Foreign Bodies, Burns, and Contact Lenses


Leejee H. Suh

Daniel L. Overbeek



INTRODUCTION

The surface of the eye, comprised of the cornea and conjunctiva, is susceptible to injuries from exposure or trauma. Eyelids and eyelashes act as physical barriers to the outside environment and, along with the blink reflex, protect the globe from many oncoming threats. Tears bathe the ocular surface with nutrients and immune factors but also trap and sweep away small particles.

The cornea is the eye’s main focusing layer as it bends or refracts light so that images are focused onto the retina. The hallmark transparency of the cornea is caused by the highly organized arrangement of collagen fibers contained in the stroma, which is bordered externally by the corneal epithelium and internally by the endothelium. Disruption of the corneal stroma caused by a laceration results in scar formation, opacification of the cornea, and potential loss of vision.

The endothelium is a single layer of cells on the inner surface of the cornea that maintains desiccation of the stroma. Damage or loss of corneal endothelial cells, which do not regenerate, causes loss of corneal clarity from ensuing corneal edema.

Finally, the cornea is one the most sensitive tissues of the body as it is densely innervated with sensory nerve fibers from the ophthalmic division of the trigeminal nerve, making corneal injuries notably painful.


ABRASIONS

Even minor trauma to the corneal surface can cause epithelial cells to separate from their underlying attachments. A corneal abrasion, also interchangeably called “corneal epithelial defect,” is the loss of part or all of the corneal epithelium without injury to the underlying stroma.


APPROACH/THE FOCUSED EXAM

Common causes of corneal abrasion include injury from fingernails, paper, makeup applicators, tips of eye drop dispensers, dust or dirt particles, and other objects. In chronic contact lens wearers, malpositioned lenses can cause a corneal epithelial injury. If the patient is unable to identify a discrete injury, the physician should be concerned about serious spontaneous causes of an epithelial
defect, which include severe dry eye and exposure keratopathy from incomplete blink or inadequate closure of the eyelids, such as in sedation or an altered mental status, seventh nerve palsy, eyelid deformity, proptosis, floppy eyelid syndrome, and Parkinson disease.

The patient will complain of intense pain, photophobia, and foreign body sensation and tearing and likely have difficulty voluntarily opening the affected eye. For this reason, instillation of a topical anesthetic drop such as proparacaine or tetracaine can temporarily relieve the discomfort and facilitate the rest of the exam.

On examination, the visual acuity of a patient with a corneal abrasion may be decreased if the abrasion disrupts the central cornea. Fluorescein stain and cobalt blue illumination will best highlight the presence and dimensions of a corneal epithelial defect (Figure 35.1). Ideally, the cornea is evaluated with slit lamp magnification, noting the extent of any abrasion and any underlying tissue disturbance. A cotton-tipped applicator soaked in topical anesthetic can be used to debride loose epithelium and aid in a careful evaluation. The de-epithelialized corneal stroma underneath should be smooth and transparent. If the denuded area is not smooth or is disrupted, there may be a laceration or perforation of the cornea. If the area is not transparent, a cellular infiltrate may have caused opacification of the underlying stroma, and infectious keratitis must be considered (Figure 35.2). In either case, immediate evaluation by an ophthalmologist is essential.












In evaluating the anterior chamber, the clinician should look for a normal chamber depth, a normal iris, and a round and reactive pupil. Any disruption of these structures may indicate a perforating injury, with an occult intraocular foreign body presumed to be present.


DIFFERENTIAL DIAGNOSIS

Corneal abrasions are usually easily diagnosed. Entities that present in a similar fashion include infectious keratitis (corneal ulcer from bacterial, fungal, or viral etiologies), recurrent erosion syndrome, ultraviolet keratitis (welder’s “burn”), and severe dry eye syndrome. Recurrent erosion syndrome is a common condition of the epithelial and/or epithelial basement membrane characterized by recurrent corneal abrasions that typically occur on awakening when the eyelids are rubbed and opened. Common etiologies include a history of traumatic corneal abrasion and anterior corneal basement membrane dystrophy. Finally, one must entertain a very high degree of suspicion for infectious keratitis in any patient who has a history of injury from organic matter or one who wears contact lenses, particularly with overnight lens wear, poor contact lens hygiene, and a history of sleeping and/or swimming with contacts.


MANAGEMENT

The prognosis for corneal abrasion is excellent because the corneal epithelium will usually regenerate without scar formation within 1 week and restore normal visual acuity. The primary complication of concern, however, is secondary infectious keratitis, which can cause scarring and subsequent vision loss. For this reason, all patients with a corneal abrasion are started on prophylactic topical antibiotics. Proper topical antibiotic selection is important and may not be the same in all cases. For a noncontact lens wearer, topical ophthalmic erythromycin ointment, bacitracin or bacitracin/polymyxin ophthalmic ointment or polymyxin B/trimethoprim drops are all commonly used. If the patient is a contact lens wearer, or the injury was from a fingernail or organic matter (eg, tree branches), a broader spectrum antibiotic, such as a topical fourth generation fluoroquinolone such as moxifloxacin, is usually the antibiotic of choice.

Antibiotic treatment is typically continued for 5 to 7 days 4 times daily or until the epithelial defect has resolved. In the case of abrasions from organic matter, the patient must be followed by an ophthalmologist to monitor for delayed-onset fungal infection. For large abrasions, a cycloplegic agent (ie, cyclopentolate 1%) is often used to reduce photophobia caused by ciliary body spasm. Contact lens wearers should forgo any contact lens wear for at least 1 week beyond full recovery and the completion of a complete antibiotic course. The patient should then be referred to an ophthalmologist for continued care to ensure appropriate healing and resolution and to confirm that no secondary keratitis is present. Patching the eye can be considered for pain control but should not be done if the injury involves fingernails or organic matter or if the patient wears contact lenses, because in these cases patching may enhance bacterial growth.1


LACERATIONS

A corneal laceration is caused by a sharp object cutting through the epithelium and into the stroma. When a laceration is full thickness, it is termed a corneal perforation and results in an open globe. These wounds can often be self-sealing, especially when caused by a high-velocity projectile. The patient may report significant pain, photophobia, and reduced vision, as in a corneal abrasion, or may have more subtle symptoms.

Slit lamp examination should include examination of not only the cornea but also the adjoining conjunctiva and sclera to look for extension beyond the peripheral cornea. The anterior chamber depth of the affected eye should be compared with the contralateral eye as a shallower anterior chamber signifies a wound leak and likely full thickness laceration.

A Seidel test is very useful in identifying a wound leak from a corneal perforation. In this test, the eye is anesthetized with topical anesthetic, and then a moistened fluorescein strip is applied directly over the potential site of perforation while observing the area under the cobalt
blue light in slit lamp examination. If there is a wound leak, the fluorescein dye will be diluted by the escaping aqueous humor and appear as a green stream (Figure 35.3). This is called a “positive Seidel test.”

Once a corneal laceration and perforation are detected, immediate ophthalmology evaluation is required to decide whether treatment can be performed at the slit lamp or with surgical intervention. Full thickness corneal lacerations greater than 2 mm generally require surgical intervention in the operating room with primary closure (Figure 35.4). If the anterior chamber is flat, the repair should be done within 24 hours to avoid permanent damage to the lens and cornea and creation of peripheral scarring or synechiae between these two areas. If there is concomitant iris prolapse through the corneal laceration, repair should be done in the operating room to either reposition the iris into the anterior chamber or debride areas that appear necrotic or
infected. Extensive lacerations with avulsion and large amount of tissue loss may require corneal transplantation.

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Apr 18, 2023 | Posted by in OTOLARYNGOLOGY | Comments Off on Corneal Trauma: Abrasions, Lacerations, Foreign Bodies, Burns, and Contact Lenses

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