Alcaine

ABSTRACT

Although comeal abrasions are commonly seen in primary care settings, the primary care literature contains scant references on detecting and managing this problem. This article provides an overview of corneal abrasion asse#ment and treatment. Four common etiologies of abrasion are discussed: traumatic abrasion, contact lens abrasion, forein body abrasion, and recurrent erosion. Parameters for the history and physical examination are outlined, Including sections on contact lens removal, lid eversion, and fluorescein staining. Treatment regimens for each of the etiologies are discussed, with a focus on current research on using pressure eye patches as an Intervention. Indications for referral to an ophthalmologist are noted.

Corneal abrasions caused by trauma or a foreign body are among the most common patient complaints presented in ophthalmologists' offices; such complaints are commonly seen in primary care settings as well.' Corneal epithelial defects account for up to 10% of admissions in eye emergency departments (EDs).2 Because an epithelial defect usually heals in 2 to 3 days without sequelae, little attention has been given to improving the treatment of this common problem.

The management of corneal abrasions has changed little over the past several decades. Although abrasions are not a blinding or serious disorder, they are uncomfortable for the patient.3 Further, scant references for detecting and managing this problem exist in the primary care literature. Thus, this article reviews the assessment and current recommended treatment regimens for corneal abrasions. Relevant anatomy and physiology and etiologies are presented first, followed by pertinent points for the history and physical examination and approaches to treatment and referral.

Anatomy and Physiology

The cornea is a clear, avascular, curved structure comprising approximately onefifth of the eyeball's outer circumference and is continuous with the sclera at the limbus. The only purpose of the cornea is to refract light rays. The average adult cornea is about 0.65 mm thick and about 11.5 mm in diameter and is composed of five layers (see Figure 1).4

The epithelium is the external nonkeratinized layer. It consists of five or six cell layers. Its surface is regular and smooth; it has its own basement membrane; and it can regenerate and heal without a scar. Corneal epithelial defects heal by migration and proliferation of cells at the abrasion's margins over the denuded area. Most corneal abrasions heal within 3 days.

Bowman's layer is an acellular membrane that is nonregenerative and therefore, when damaged, heals with a scar. The stroma, which accounts for 90% of the corneal thickness, is composed of loose bundles of collagen fibrils. Damage to the stroma results in scarring.

Descemet's membrane is an elastic membrane on the stroma's inner surface. In acute ulceration, the membrane functions as a barrier to perforation. The endothelium is a single layer of cells that act as a water pump. These cells do not regenerate but slide over to take the place of damaged cells.4

The cornea is densely innervated by sensory nerve fibers from the fifth cranial nerve. The corneal nerves are among the most sensitive in the body. Even a minor injury often results in considerable pain, induced by the exposure of nerve endings in the epithelium. Blinking exacerbates the pain.5

Etiologies

Traumatic Corneal Abrasion

Usually an intact blink reflex is sufficient to prevent corneal damage. Traumatic corneal abrasions result in the partial or complete removal of a focal area of epithelium on the cornea.6 This type of abrasion is usually limited to the superficial corneal epithelium and often results from trauma induced by a finger, branch, paper, metal, hairbrush, or mascara wand.7,8The use of a sunlamp or a welding or carbon arc without proper eye protection can induce a corneal abrasion by causing ultraviolet burns of the cornea.8

Contact Lens Abrasion

Contact lens abrasions have become increasingly common because of the large number of people (approximately 25 million) wearing contact lenses in the United States.9 Abrasions from contact lenses may be caused by: (1) a foreign body between the lens and the cornea; (2) improper contact lens fit; (3) overwear with secondary corneal edema; or (4) damage to the epithelium upon inserting or removing the contact lens.6,

Contact lens complications range from minor irritations to corneal ulceration and infection. In ulcerative keratitis, a break in the corneal epithelium (ulceration) is associated with underlying suppuration. This process is usually secondary to a bacterial infection, usually with Pseudomonas species.

Pseudomonas and other bacteria associated with contact lens-related keratitis cannot usually penetrate the corneal epithelial barrier to initiate infection. For corneal suppuration to occur, contact lens-associated hypoxia or mechanical abrasion must disrupt this barrier.9 Although ulcerative keratitis can occur with all types of lenses, use of extended wear soft lenses increases the risk by tenfold to fifteenfold over that of daily wear soft lenses.910

Corneal Foreign Bodies

Foreign bodies may be single or multiple and may be grossly visible or barely detectable, even with a slit-lamp examination. The most common foreign bodies are rust, dirt, glass, and hair.

Metallic foreign bodies are common in ocular accidents that occur in the workplace. The clinician should determine whether the foreign body is metallic or nonmetallic and, if metallic, whether it is magnetic or nonmagnetic. A magnetic source signals the presence of toxic iron and indicates the possibility of removing the foreign body with a magnetic device.6

Recurrent Corneal Erosion

Of the three types of recurrent corneal erosion, the most common is an acquired erosion caused by a prior linear scratch to the cornea from a fingernail, paper cut injury, or similar trauma. The injury can lead to spontaneous ulceration of the corneal epithelium days, weeks, or even months later, if the basement membrane fails to adequately heal6The basement membrane does not become completely remodeled for up to 3 months after it has been disrupted.8

The second type of recurrent corneal erosion is familial and bilateral and occurs in people with no history of trauma. It occurs more often in women than in men. The third type of recurrent corneal erosion, which also involves no past history of injury, is caused by dystrophic changes that develop spontaneously within the basement membrane.4,6

History

The clinician should ask the patient to describe his or her symptoms in detail. Table 1 lists symptoms attributed to various etiologies of corneal abrasions.

To provide optimal clinical management, the clinician must take a careful history of the injury, determine whether the patient wears contact lenses, and delineate any prior treatment modalities. The history becomes even more important if the injury occurred at work, because the patient may file for worker's compensation or become embroiled in other legal issues. Table 2 lists selected questions for a thorough history.

Physical Examination

Because the affected eye is usually very painful, it may be necessary to instill 1 to 2 drops of a topical anesthetic (such as tetracaine 0.5 % [Pontocaine] or proparacaine HCI 0.5% [Alcaine, Ophthetic, Ophthaine] before undertaking the physical examination. If contact lenses are present, they should be removed using the technique outlined in Table 3.

The clinician should assess visual acuity, extraocular movements, and pupillary responses. The external eye, lid, and conjunctiva must be inspected for masses and redness; the cornea for clarity; and the fundus for any disc abnormalities.5 The eye is then directly visualized with a strong light source, and the cornea is inspected under magnification, if possible. When foreign bodies are suspected, the lids must be everted using the method described in Figure 2.

Fluorescein staining is done to detect and outline any damaged corneal epithelial cells. Fluorescein (AK-Fluor, Fluorescite, Fluor-I-Strip) is a hydrophilic dye that is repelled by the lipid cell membrane of the epithelial cells and that stains areas in which epithelium is missing.8

Sterile, single-use, fluorescein-impregnated paper strips are dampened with sterile saline. The strip is touched to the inferior cul-de-sac while the patient looks upward. The patient is asked to blink once.5 Denuded areas of epithelium produce a bright green color when viewed by normal light. The color is intensified when fluorescent lighting is used.

A contact lens abrasion may look different, dependent on the etiology. Diffuse central staining and haziness indicate lens overwear, an overly tight lens, or failure to wash off lens cleaner sufficiently. Small, irregular abrasions indicate difficulty in inserting or removing the lens. Irregular linear scratches suggest the presence of a foreign body between the lens and the cornea.6,8

A slit lamp is usually not available in primary care settings. This instrument may be on hand in EDs or occupational health settings. The slit lamp is a biomicroscope that provides a well-illuminated, highly magnified view of the eye's anterior segment.6 Tests such as ultrasound scans, radiography, and computed tomography are usually performed by an ophthalmologist.

Differential Diagnosis

The clinician should exclude other disorders that can cause eye pain. These include extraocular disorders such as hordeolum, chalazion, and conjunctivitis; intraocular conditions such as acute angle-closure glaucoma, anterior or posterior uveitis, and refractive error; orbital disease such as tumor or inflammatory disease; and referred pain from other sources such as sinusitis, tension headache, tooth abscess, or temporal arteritis.5

The clinician should also exclude other ocular disorders that can produce staining of the denuded corneal epithelium by fluorescein and would require different forms of therapy before treating the patient for a corneal abrasion. Such disorders include herpetic keratitis, which looks like a branching dendritic ulcer; corneal ulcers; corneal dystrophy; and recurrent corneal erosion. If a deep corneal foreign body has penetrated the anterior chamber, fluorescein dye will reveal a leak of aqueous humor at the perforation site.'

Treatment

Patients should be assessed for tetanus immunization status and given tetanus prophylaxis if necessary.8 A followup appointment should be scheduled within the next day or 2 to assess symptoms and corneal healing. Because bacterial corneal ulceration is a potential complication of a simple corneal abrasion, every patient should be followed until the epithelium is intact.

Several treatment maxims pertain to providing ocular care in the primary care setting. First, ointment should not be instilled into the eye if penetrating injury is suspected, because the injury may allow access to the anterior chamber. Second, patients with abrasions or foreign bodies should not be maintained on topical anesthetics, which prevent healing and cause epithelial breakdown. Third, patients with abrasions or foreign bodies should not receive topical steroids, because these steroids greatly increase the risk of secondary infection.b8

Traumatic Corneal Abrasions

Treatment of corneal abrasions has traditionally consisted of three steps: the instillation of a short-acting cycloplegic agent such as cyclopentolate HCl 1% (Ak-Pentolate, Cyclogyl, Pentolair) to reduce discomfort from ciliary muscle spasm; the instillation of an antibiotic ointment such as bacitracin zinc plus polymyxin B sulfate (Polysporin) or gentamicin (Garamycin, Genoptic); and the application of a pressure patch dressing for 24 to 48 hours.

After the dressing has been removed, topical antibiotic ointment or the instillation of drops two to three times daily is continued for 4 days to protect against infection. Analgesics may be prescribed for pain.'

Recently, the use of pressure patching for corneal abrasions has been questioned. The rationale for using a pressure patch is that it presumably reduces friction between the healing corneal epithelium and the eyelid, thus permitting healing to occur quickly. The patch also prevents blinking, which has been thought to hasten healing. However, pressure patch use is not completely benign because it removes binocular vision with a subsequent reduction in visual field and depth perception.' It can also be uncomfortable for the patient and may actually impede healing.

A pressure patch covering a closed eyelid decreases corneal oxygenation, thus causing anaerobic metabolism. This situation leads to a depletion of corneal glycogen reserves and decreased production of energy for vital corneal function.7 The patch raises the corneal temperature, thereby potentially slowing healing and predisposing the cornea to infection.lz

To study the potentially adverse effects of patching, the Corneal Abrasion Patching Study Group conducted an investigation of pressure patching versus no patching in 223 subjects with noninfected, non-contact lensrelated traumatic corneal abrasion or foreign bodyrelated corneal abrasion.7

The researchers found that patients treated with antibiotic ointment and mydriatics alone had significantly faster healing times, lower pain levels, and better compliance with treatment protocols than those who wore a pressure patch in addition to those drugs. The author of a similar study of 30 subjects found no difference in healing rates between patched and nonpatched groups, although the patched group had more discomfort than the nonpatched group."

The Corneal Abrasion Patching Study Group noted that the extra expense and risk of pressure patching is unnecessary and may even be detrimental. They recommended that superficial corneal abrasions caused by trauma or foreign body removal be treated with a broadspectrum antibiotic ointment such as erythromycin (Ilotycin) or bacitracin zinc plus polymyxin B sulfate, a short-acting mydriatic, and no pressure patch.7

Because pain is the major complaint in corneal abrasions, the Corneal Abrasion Patching Study Group conducted another study looking at the efficacy of topical nonsteroidal anti-inflammatory drops in the treatment of noninfected, non-contact lens-related traumatic corneal abrasions.3 All patients received cycloplegic drops and antibiotic ointment. Subjects were randomized to receive either ketorolac tromethamine (Toradol, Acular) or control drops.

Both groups had similar healing times; however, the group taking ketorolac had significantly less pain, photophobia, and foreign body sensation at 24-hour followup. Considering these results and prior work, the authors recommend the following for patients with significant pain from traumatic, non-contact lens-related corneal abrasions: cycloplegic drops, if needed; ketorolac tromethamine four times daily for 3 days (or less, if the patient is comfortable); antibiotic ointment three times daily for 3 days or until the abrasion is completely healed; and no pressure patching unless the area of the abrasion is greater than 10 mm2.3

Contact Lens Abrasions

Treatment of hard contact lens abrasions includes a cycloplegic agent initially, followed by antibiotic ointment or drops two to three times daily for 4 days.6 Because of the potential for infection, corneal abrasions secondary to contact lenses are not patched.9,13

An antibiotic with coverage against Pseudomonas, such as an aminoglycoside, polymyxin B sulfate, or bacitracin, should be chosen. Erythromycin and sulfa compounds are inadequate.9 Because corneal stromal suppuration can develop rapidly, patients should be seen again within 24 hours.

For soft contact lens abrasions, a potential Pseudomonas infection must be suspected. The abrasion should be cultured and treated with an antibiotic such as tobramycin (Tobrex) drops every hour for 6 hours and then every 3 hours while the patient is awake, until the patient is seen the following day.6

For both hard and soft lenses, the patient should be discouraged from inserting contact lenses until complete healing has been documented.9 Lenses may be worn again 2 days after the cornea has healed.6.8

Corneal Foreign Bodies

Corneal foreign bodies are difficult to remove because the cornea is delicate, easily damaged, and covers the visual axis.14 Intervention in the primary care setting is usually limited to irrigation. More extensive removal interventions, such as forceps, cotton-tipped applicators, needles, dental spuds, and burrs, may be used by the practitioner working in the ED or occupational health setting. If irrigation fails to remove the foreign body or if the foreign body is deeper than superficial, referral to an ophthalmologist is warranted.

After the foreign body has been removed, the eye is treated for a traumatic corneal abrasion. More extensive reepithelialization may take longer to heal and may require extended days of treatment. Ointment should not be instilled if a penetrating eye injury is suspected; the injury might allow it to enter the anterior chamber of the eye. A protective metal shield and cotton pads should be placed over the eye and the patient referred for surgical management.6

If the foreign body is metallic, referral to an ophthalmologist may be warranted. Metal objects that remain in the cornea for more than 3 hours oxidize and stain adjacent epithelial cells a reddish-brown color in a circular shape known as a rust ring. The rust ring may be accompanied by an underlying ring of infiltrate.' These stains may wash out spontaneously over time, leaving a white, nebulous scar. Therefore, they are usually removed with specialized instruments such as a brush or burr at the time of foreign body removal or within 1 to 2 days after foreign body removal.1,6

Recurrent Corneal Erosion

Recurrent erosion is treated with antibiotic ointment and pressure patching for 24 hours. Over the next several months, copious use of artificial tears every 2 to 3 hours and antibiotic or artificial tear ointment at bedtime should be used to prevent another erosion. The tears and ointment lubricate the interface between the lid and corneal epithelium.6 Severe cases, which should be treated by an ophthalmologist, may call for constantwear therapeutic soft contact lenses with artificial tears or the debridement of defective epithelium.4,6,8

Referral

Even seemingly minor ocular injuries have the potential for severe complications such as infection and vision loss. Although superficial corneal abrasions can safely be treated in the primary care setting, close follow-up is needed to ensure that healing occurs and that the original diagnosis was correct. Referral to an ophthalmologist is desirable if the patient suffers acute vision loss, a corneal ulcer or an abrasion that does not heal within 48 hours, a herpes lesion, hyphema, penetrating trauma, chemical or alkali burns, a metallic foreign body, or a foreign body that irrigation cannot remove.

REFERENCES

1. Cakanac CJ, Ajamian PC: Cornea and Conjunctiva: Clinical Procedures. Boston, Mass.: Butterworth-Heinemann; 1996:1-22.

2. Chiapella AP, Rosenthal AR: One year in an eye casualty clinic. Br J Ophthalmol 1985;69:865-70.

3. Kaiser PK, Pineda R, Corneal Abrasion Patching Study Group: A study of topical nonsteroidal anti-inflammatory drops and no pressure patching in the treatment of corneal abrasions. Ophthalmology 1997;104:1353-59.

4. Boyd-Monk H, Steinmetz CG: Nursing Care of the Eye. Norwalk, Conn.: Appleton and Lange; 1987:195-217.

5. Steinert RF: Evaluation of eye pain. In: Goroll AH, May LA, Mulley AG, eds. Primary Care Medicine: Office Evaluation and Management of the Adult Patient, 3rd edition. Philadelphia, Pa.: J.B. Lippincott Co.; 1995:964-66.

6. Pavan-Langston D: Burns and trauma. In: Pavan-Langston D, ed. Manual of Ocular Diagnosis and Therapy, 4th edition. Boston, Mass.: Little, Brown; 1996:31-44.

7. Kaiser PK, Corneal Abrasion Patching Study Group: A comparison of pressure patching versus no patching for corneal abrasions due to trauma or foreign body removal. Ophthalmology 1995;102:1936-42.

8. Deutsch TA, Feller DB: Paton and Goldberg's Management of Ocular Injuries, 2nd edition. Philadelphia, Pa.: WB. Saunders Co.; 1985:61-131.

9. Schein OD: Contact lens abrasions and the nonophthalmologist. Am J Emerg Med 1993;11:606-608.

10. Schein OD, Glynn RJ, Poggio ED, et al.: The relative risk of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses: A case-control study. N Engl J Med 1989;321:773-78.

11. Hulbert MFG: Efficacy of eyepad in corneal healing after corneal foreign body removal. Lancet 1991;337:643.

12. Kirkpatrick JNP, Hoh HB, Cook SD: No eye pad for corneal abrasion. Eye 1993;7:468-71.

13. Clemons CS, Cohen EJ, Arentsen JJ, et al.: Pseudomonas ulcers following patching of corneal abrasions associated with contact lens wear. Contact Lens Association Opthalmologists J 1987;13:161-64.

14. Santen SA, Scott JL: Ophthalmologic procedures. Emerg Med Clin North Am 1995;13:681-701.

ABOUT THE AUTHOR

Sue Wingate, RN, CS, CRNP, DNSc, is an adult nurse practitioner in Gaithersburg, Md.

Copyright Springhouse Corporation Jun 1999
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