Corneal Atlas: Part III
From Abrasions to Burns, How to Manage Corneal Injuries

NSAIDs and Steroids For Corneal Trauma
Is the Pressure Patch Obsolete?
Removing Tissue Not a Once-and-Done Deal
Acid Burns vs. Alkali Burns

Corneal trauma comes in many forms. Your appropriate management of these ocular emergencies can subdue sight-threatening insults.

by Alan G. Kabat, O.D. and Joseph W. Sowka, O.D, Contributing Editors

Because the cornea is the most anterior structure in the eye, it's susceptible to insult in many forms—abrasions and lacerations, embedded foreign bodies, and burns resulting from a variety of sources. The cornea has a paradoxical role in trauma. It takes a great deal of punishment, protecting the more delicate ocular structures within the globe. However, many forms of insult can cause structural changes to the cornea. Scarring can render it opaque, resulting in potentially serious visual loss. This article, the third in our series "Corneal Atlas," reviews the varied forms of corneal insult that you'll see in your practice.

Corneal Abrasion
Corneal abrasions are one of the most common ocular injuries; they  comprise about 10 percent of new patient emergency visits.1 They typically result from tangential insult caused by foreign objects such as fingernails, paper sheets, makeup instruments and leaves or branches.

Symptoms. These are fairly straightforward: acute pain and a history of recent trauma. Patients may also complain of photophobia, excessive tearing, blepharospasm and blurry vision. Their discomfort often seems out of proportion to the degree of visible ocular compromise. This is because of the abundance of corneal nerves as well as the likelihood of secondary uveitis with corneal injuries.

Clinical findings. Biomicroscopy will reveal epithelial disruption, with a tissue "flap" sometimes at the edge of the wound. Under white-light illumination, the affected cornea typically shows a loss of luster centrally and ragged irregular edges. Fluorescein will exhibit bright staining in the affected region. Corneal edema ensues in most cases. In severe cases the edema may cause folds to develop in Descemet's membrane.

These patients often complain of extreme pain on presentation. So, we don't hesitate to administer one drop of 0.5 percent proparacaine when the patient won't cooperate due to pain. This technique is both palliative and diagnostic; patients with corneal injury respond rapidly and exquisitely; those who do not respond as well have more severe ocular inflammation involving the uveal tissues.

Management. Once you complete the exam, you must "trim" the abrasion of any loose epithelial flaps or tags with a wet cotton-tipped applicator. You might use a foreign body spud, jeweler's forceps or even an Alger brush if the wound involves significant amounts of tissue. Although it may be tempting to replace the remaining epithelium back over the wound, this is a clinical error. Unless the abrasion is less than an hour or two old, the detached epithelium is no longer viable tissue. If you place it within the wound bed, it will become antigenic and induce even more pronounced inflammation. Also, this dead tissue can impede the growth of new epithelium which, under normal circumstances, will expand to fill the wound in 24-48 hours.

After debridement, your goals of management become threefold:

• Prevent further inflammatory sequelae. You can instill cycloplegic agents in the office during your diagnosis, since you'll see these patients daily until the abrasion resolves. We recommend 0.25 percent scopolamine for most cases.

• Prevent opportunistic infection. The compromised epithelium can provide a vehicle for opportunistic bacterial flora, so topical antibiotics are a key component of therapy. While it is important to utilize a broad-spectrum antibiotic, many of the stronger aminoglycosides (tobramycin, gentamycin, neomycin) may have potentially toxic effects on the cornea and may delay wound healing.2 So, we tend to use better-tolerated agents, such as Polytrim, every 4-6 hours.

• Manage discomfort. Anti-inflammatory agents help manage both post-traumatic pain and tissue swelling. Many doctors withhold these agents, particularly corticosteroids, for fear of delayed wound healing and increased propensity toward opportunistic infection. However, NSAIDs have been shown to be quite safe and effective in treating corneal abrasions short-term.3 Agents such as Voltaren (diclofenac) every 2-4 hours are excellent for pain management and mild to moderate inflammation.

Corticosteroids may be too potent for smaller, routine abrasions, but they are certainly indicated for more extensive corneal abrasions and those with secondary uveitis. It is critical to quell the associated corneal and uveal inflammation to enable the epithelial defect to heal. We typically utilize Pred-Forte (prednisolone) or Flarex (fluorometholone) every hour or two for the first 12-24 hours, then taper according to the resolution. In these cases the benefits of corticosteroids outweigh their risks. Withhold them if there is a frank corneal infection associated with the abrasion.

Follow up. See these patients daily. Carefully remove pressure patches or bandage lenses at each visit to evaluate resolution. (See "Is the Pressure Patch Obsolete") With a bandage lens, use copious lubrication to loosen it prior to removal. You don't want to disturb the delicate new epithelium. Significantly large wounds may require treatment for up to 72 hours, but bandaging a patient for this time will invariably increase corneal edema.

You can discontinue topical cycloplegics, antibiotics and anti-inflammatory agents when the corneal defect is at least 90 percent resolved. You may then address residual corneal edema by employing hypertonic solutions (5 percent sodium chloride) every 3-4 hours. Many doctors prescribe hypertonic ointments at bedtime, and continue this regimen for as much as a month or two following the initial abrasion. This helps prevent recurrent corneal erosion (RCE). This is most critical during the first six weeks following the injury.

Corneal Laceration
Corneal lacerations fall into two categories: partial-thickness, or non-perforating; and full-thickness, or penetrating. Since we consider a partial-thickness corneal laceration to be synonymous with stromal corneal abrasion, we will concentrate on full-thickness lacerations.

Symptoms. Patients present in a similar fashion as those with corneal abrasion; they report pain, photophobia, tearing, blurry vision and a history of recent trauma. The agent of trauma, however, usually involves a metallic object such as a hand tool or a knife. If the patient does not seek care promptly, the initial pain may subside due to corneal desensitization.

Clinical findings. Gross inspection reveals a red and swollen eye with significant conjunctival hyperemia and lid edema. The corneal injury is often visible to the naked eye, presenting as a linear or S-shaped "flap." Although it may be difficult to evaluate these patients because of excessive lacrimation or pain, you should measure visual acuity for clinicolegal reasons and perform biomicroscopy to document the extent of the injury.

Biomicroscopy may reveal a shallow or flat anterior chamber, a distorted pupil, or iris prolapse into the wound. Air bubbles in the anterior chamber are a diagnostic finding. If you can view the anterior chamber, you'll see cells and flare from the attendant uveitis. In cases of deeper ocular penetration, you may observe hyphema, iridodialysis and lens dislocation. You must rule out intraocular foreign body in all cases of penetrating injury.  The eye will be hypotonous. Intraocular pressure, if you measure it, generally ranges from 2-6 mm Hg.

Management. Patients with even small corneal lacerations carry a guarded prognosis. Once you identify a penetrating ocular injury, your primary goal is to protect against extrusion of the intraocular contents. This means you must not manipulate the eye excessively, and exert no significant pressure on the globe. Ultrasonography, gonioscopy and applanation tonometry are absolutely contraindicated once the diagnosis is clear. Use non-contact tonometry if you suspect perforating injury and you need an IOP measurement to confirm your diagnosis. In-office use of cycloplegics, corticosteroids or antibiotics is contraindicated in penetrating ocular injury because they're formulated for topical use; their concentrations may have unpredictable and deleterious effects when placed directly on intraocular structures. The use of topical anesthetics is also somewhat risky, although you may need to use one or two drops of proparacaine simply to complete the exam. If this is so, open a new bottle, to minimize the risk of infection. Use all agents sparingly and judiciously in these cases.

From a therapeutic standpoint, the objectives are twofold.

• Protect the eye from further damage and arrange for surgical evaluation and intervention immediately. Lightly dress the involved eye with a protective shield (e.g., a Fox shield). Pressure patching is absolutely contraindicated, as it will cause undue stress on the already-compromised eye. In cases where a pre-manufactured eye shield was not available, several tongue depressors held in place with surgical tape have been used to create a makeshift barrier over the globe. Take care to secure any shield to the brow and orbital ridge, rather than to the lids themselves.

• Refer directly to an ophthalmic surgeon. This is true in all cases of penetrating ocular injury. Typically, the surgeon will ask to meet the patient at the hospital emergency room. In the interim, you must instruct the patient not to eat or drink anything (NPO) prior to seeing the surgeon. Surgical management may involve suturing, cyanoacrylate glues or even emergency keratoplasty in severe cases. Small, uncomplicated corneal lacerations have been treated successfully using only a bandage soft contact lens and aggressive drug therapy.9 Parenteral antibiosis is also recommended for all patients with perforating corneal injuries.10

Corneal Foreign Body
Corneal foreign body is second only to corneal abrasion as the most common form of ocular trauma.11,12 Most of these injuries involve metal fragments and are associated with high-risk activities that involve hammering, grinding, drilling, etc. (e.g., auto repair, carpentry).10 Even so, foreign bodies can consist of practically any material—soil, wood, glass, plastic, sand and even insect parts. While many of these are inert, metallic foreign bodies and those of organic origin tend to produce a more significant inflammatory reaction.

Symptoms. These patients generally present with mild to occasionally severe pain, depending upon the location and extent of the object. Sometimes they describe the discomfort merely as a scratchiness or "foreign-body sensation." Excessive tearing, blurred vision and photophobia are also common.

Clinical findings. Upon inspection, you may note edema of the lid, focal or circumlimbal conjunctival injection, and a mild to moderate anterior chamber reaction. The most critical sign is particulate matter, either on the corneal surface or embedded into it. With metallic foreign body, a rust ring may appear around the object. You may also note a ring of infiltrate at the site of the offending agent if it has been present for more than 24 hours.

Management. As in corneal abrasion, the primary concern in managing foreign body is the attendant inflammation and risk of secondary infection. In most cases foreign objects act as an antigen to set off an inflammatory cascade, resulting in dilation of the surrounding vessels and subsequent edema of the cornea, conjunctiva and lids. This process also liberates white blood cells, resulting in corneal infiltration and an anterior chamber reaction. If the foreign body is not removed, infection and/or necrosis can result.

With all foreign bodies, it is important to first ensure that the object has not perforated the cornea. Even if biomicroscopy does not demonstrate foreign matter in the anterior chamber, you should still do the Seidel test. If you don't notice penetration, you may remove the object under topical anesthesia. We recommend using the least invasive means necessary, proceeding in a stepwise fashion. Smaller objects may simply involve a direct stream of sterile irrigating solution or a moistened cotton-tipped applicator. More deeply embedded objects may require a flexible loop, a foreign body spud, or a bent 25- or 27-gauge needle. You may have to resort to Jeweler's forceps to extricate stubborn foreign bodies and/or clear away loose epithelial tissue. It is also important to inspect the fornices and palpebral conjunctiva for additional foreign matter that may exacerbate the condition.

Once you've removed the object, use a foreign body spud or Alger brush to eliminate any remaining cellular debris or rust, as well as any ragged or non-viable epithelial tissue surrounding the wound. Even a small amount may impede resolution.15 When the region is free of all particulate matter, the wound essentially represents an iatrogenic corneal abrasion. Treat it as such, depending on its size, severity, and significance of the inflammatory response.

Follow-up. This is the same as that for a corneal abrasion: See these patients daily until resolution. Residual scarring is not uncommon, unfortunately, so inform patients at the initial evaluation that these injuries might scar and cause reduced vision. This is particularly true when the foreign body encroaches upon the visual axis.

Chemical Burns
Corneal burns secondary to chemical insult constitute a true ocular emergency. The duration of time between injury and intervention is perhaps most critical in determining their outcome. First- line therapy consists of immediate, copious irrigation of the ocular surface. This dilutes the chemical, so the first 2-3 minutes after the injury are most critical.10 If the patient telephones to report a chemical injury, instruct him to irrigate the eye for 30 minutes before he comes to your office. A garden hose or the kitchen sink is the best means to accomplish this, but any bland liquid is acceptable if there's no water nearby.

Symptoms. The diagnosis of chemical trauma is typically based more upon the history than the signs and symptoms. In many cases the initial contact is by telephone, with patients declaring that they've sprayed or splashed something into their eyes. They may report varying degrees of pain, photophobia, reduced vision and colored haloes around lights. The tissue of the lids and adnexa may be burned and swollen as well. 

Clinical findings. There is an accepted classification for chemical injuries, but we tend to categorize most as either mild, moderate or severe. Mild burns may present with lid erythema, conjunctival hyperemia, punctate corneal epithelial erosion and slight corneal haze. Moderate burns usually demonstrate mild ischemic necrosis of the lids and conjunctiva, interspersed blanching of the conjunctival and scleral vessels, total epithelial erosion of the cornea, and moderate corneal haze. Fluorescein staining may be absent in cases of complete corneal erosion.

Severe burns present with scarred, necrotic lid tissue, complete blanching of the conjunctiva and sclera with necrotic edema, and significant or total corneal opacification. Associated uveitis ensues with moderate to severe burns, although you may have difficulty seeing it because of corneal haze and conjunctival blanching. 

The pH of the ocular surface is around 7.0, with the tear film slightly more acidic than the corneal surface. When we discuss chemical injury to the eye we usually focus on strong alkalis (pH >10) and acids (pH <4). While these have the most potential for serious injury, you must also consider aromatic compounds (gasoline, solvents and alcohol), household cleaning agents (soaps and detergents), and pepper-based products (Mace, Tabasco sauce). Chemically, these are usually either weak acids or bases (pH = 5-9), but can still cause severe irritation to the cornea and other ocular tissues.

Management. Repeat irrigation in the exam room and test the eye with litmus paper to establish the nature of the offending agent. When the pH of the eye is near neutral, you may discontinue the lavage. You may evaluate visual acuity at this point, as well as other necessary preliminary testing. 

Inspect the lids and fornices meticulously with the biomicroscope. As with other corneal injuries, you must remove necrotic epithelial tissue to initiate healing. We recommend using a cotton-tipped applicator moistened with a topical antibiotic for this task.

Perform tonometry, if possible. Significantly elevated IOP may occur due in part to corneoscleral shrinkage. If media clarity permits, also do a fundus examination. Following the examination, instill a strong cycloplegic agent and topical antibiotic in the involved eye. Depending on the severity of the corneal erosion, you may need to use a pressure patch. Bandage contact lenses are contraindicated because the residual chemical substance in the ocular tissues may damage the contact lens polymer.

The best way to address elevated iop is with an oral agent, such as methazolamide 50mg BID. You may add topical agents such as beta-blockers (or CAIs) later if the IOP remains high. Patients with chemical injury may complain of severe pain, so it is often necessary to prescribe oral pain medication. OTC ibuprofen or naproxen sodium may provide significant relief in most cases. For patients in greater discomfort, codeine (Tylenol #3) and propoxyphene (Darvocet) may be indicated.

Mild acid and alkaline burns typically resolve in two to three days when the corneal defect is healed, IOP is stable and no uveitis is present. More severe chemical burns may take weeks to resolve and require more aggressive therapy. The use of topical corticosteroids has been studied extensively in the treatment of these injuries.16-19 Steroid use on an acid burn is no more risky than in any other corneal injury, and may actually aid in wound healing because the epithelial cells adhere poorly to an inflamed stroma.16 In patients with significant anterior segment inflammation, we recommend using topical steroids every hour or two, along with cycloplegics administered TID-QID. In alkaline burns, some studies suggest that corticosteroids may promote corneal melting by creating the potential for tissue collagenase. 17-18

Corticosteroids may aid treatment of alkaline burns for the first 7-10 days, but taper them quickly. Additional topical agents that are sometimes employed in alkaline burns include 10-20 percent acetylcysteine and 10 percent sodium citrate. The former is a potent collagenase inhibitor, which may counteract corneal melting. It is not commercially available in ophthalmic form, so an experienced pharmacist must make this for you. Sodium citrate has been shown to significantly decrease the incidence of corneal ulceration and perforation.20 Like acetylcysteine, it is only available from limited sources and must be compounded.

Both Drs. Kabat and Sowka are associate professors at Nova Southeastern University College of Optometry in Fort Lauderdale, Fla.

1. Chiapella AP, Rosenthal AR. One year in an eye casualty. Br J Ophthalmol 1985; 69:865-70.
2. Stern GA, Schemmer GB, Farber RD, et al. Effect of topical antibiotic solutions on corneal epithelial wound healing. Arch Ophthalmol 1983; 101:644-7.
3. Kaiser PK, Pineda R 2nd. A study of topical nonsteroidal anti-inflammatory drops and no pressure patching in the treatment of corneal abrasions. Corneal Abrasion Patching Study Group. Ophthalmology 1997; 104:1353-9.
4. Kaiser PK. A comparison of pressure patching versus no patching for corneal abrasions due to trauma or foreign body removal. Corneal Abrasion Patching Study Group. Ophthalmology 1995; 102:1936-42.
5. Kirkpatrick JNP, Hoh HB, Cook SD. No eye pad for corneal abrasion. Eye 1993; 7:468-71.
6. Arbour JD, Brunette I, Boisjoly HM, et al. Should we patch corneal erosions? Arch Ophthalmol 1997; 115:313-7.
7. Wedge CI, Rootman DS. Collagen shields: efficacy, safety and comfort in the treatment of human traumatic corneal abrasion and effect on vision in healthy eyes. Can J Ophthalmol 1992; 27:295-8.
8. Hamill, MB. Corneal injury. In: Krachmer JH, Mannis MJ, Holland EJ, eds. Cornea. St. Louis: Mosby, 1997. 1403-21.
9. Leibowitz HM. Hydrophilic contact lenses in corneal disease IV. Penetrating corneal wounds. Arch Ophthalmol 1972; 88:602-6.
10. Parrish CM, Chandler JW. Corneal trauma. In:  Kaufman HE, Barron BA, McDonald MB, eds. The Cornea, 2nd Edition. Boston: Butterworth-Heinemann, 1998. 633-71.
11. Monestam E, Bjornstig U. Eye injuries in northern Sweden. Acta Ophthalmol 1991; 69:1-5.
12. Banerjee A. Effectiveness of eye protection in the metal working industry. BMJ 1990; 301:645-6.
13. Arnold RW, Erie JC. Magnetized forceps for metallic corneal foreign bodies (letter). Arch Ophthalmol 1988; 106:1502.
14. Weiss JS, Kachadoorian H. Removal of corneal foreign bodies with ocular magnet (letter). Ophthal Surgery 1989; 20:378-9.
15. Jayamanne DGR, Bell RW. Non-penetrating corneal foreign body injuries: factors affecting delay in rehabilitation of patients. J Accident Emerg Med 1994; 11:195-7.
16. Donshik PC, Berman MB, Dohlman CH. Effect of topical corticosteroids on ulceration in alkali-burned corneas. Arch Ophthalmol 1978; 96:2117-20.
17. Brown SI, Weller CA, Vidrich AM. Effects of corticosteroids on corneal collagenase of rabbits. Am J Ophthalmol 1970; 70:744-7.
18. Koob TJ, Jeffrey JJ, Eisen AZ. Regulation of human skin collagenase activity by hydrocortisone and dexamethasone in organ culture. Biochem Biophys Res Commun 1974; 61:1083-8.
19. Berman M, Winthrop S, Ausprunk D, et al. Plasminogen activator (urokinase) causes vascularization of the cornea. Invest Ophthalmol Vis Sci 1982; 22:191-9.
20. Pfister RR, Nicolaro ML, Paterson CA. Sodium citrate reduces the incidence of corneal ulcerations and perforations in extreme alkali-burned eyes—acetylcysteine and ascorbate have no favorable effect. Invest Ophthalmol Vis Sci 1981; 21:486-90.

NSAIDs and Steroids For Corneal Trauma

The American Society of Cataract and Refractive Surgeons (ASCRS) recently issued a warning regarding the use of topical NSAIDs. The organization says that a survey conducted of its members demonstrated numerous cases of "severe complications including corneal melting ..." with topical NSAIDs used postoperatively. 

This new information has many eye doctors questioning the routine use of topical NSAIDs. Our opinion: This class of drugs is safe and effective in cases of non-iatrogenic corneal trauma, particularly corneal abrasions. Studies corroborate our sentiment.3 

Consider that the vast majority of cases ASCRS cites involve postsurgical complications involving one drug, generic diclofenac. The doctors surveyed may have been using this drug very aggressively. For the record, we still recommend the judicious use of topical NSAIDs to manage the pain of traumatic corneal injuries until there's greater evidence linking it to potential complications.

Regarding topical corticosteroids, we have for many years maintained that these agents do more good than harm, and that their negative press is undeserved. We recognize that corticosteroids may impede epithelial regeneration to some degree in cases of corneal trauma. However, it is also true that epithelial defects are incapable of resolving in the face of active stromal inflammation.

In these more severe cases, corticosteroid use becomes critical to wound resolution. You must take care not to prescribe these agents in cases that may be associated with herpetic or fungal infection. But when secondary inflammation of the stroma or uvea ensues, don't withhold corticosteroid use simply because an epithelial defect exists. This can only delay resolution.

top

Is the Pressure Patch Obsolete?

The traditional mainstay of corneal abrasion therapy, the pressure patch, has spurned a debate over the past few years over whether this is truly the most effective means of managing corneal abrasions.3-6

Today, most investigators and clinicians agree that patching is really not necessary for small, routine corneal abrasions. For larger abrasions, some clinicians do still utilize pressure patching, although many have switched to the use of bandage contact lenses in these instances.

Our experience with bandage contact lenses has proven quite successful, even in abrasions involving more than 80 percent of the corneal surface. These patients retain cosmesis, comfort, binocularity, and the ability to administer topical medications on a regular basis even with the contact lens in place.

Using a bandage contact lens speeds resolution of corneal edema because it allows the cornea to deturgesce far more readily than it would with the lid closed and patched.

top

Removing Tissue Not a Once-and-Done Deal

How much corneal tissue should you remove in cases of foreign body? How deep should you "dig" into the stromal tissue to extract rust or debris?

Most experts agree that it is important to remove as much of the affected epithelial tissue as possible to enable healing, but this may be difficult if the patient doesn't cooperate or the foreign body has been embedded for days.

You don't have to complete the procedure in one sitting. In some cases, you may need to debride the wound more than once to complete the task.

At the initial visit, we'll sometimes utilize an antibiotic ointment with a light patch for several hours or overnight, along with cycloplegia and anti-inflammatory therapy. This helps "soften" the epithelium and makes it much easier to debride the remaining tissue when the patient returns.

As for removing rust from the corneal stroma, this isn't necessary in most cases unless the foreign body has actually penetrated to that depth. Rust staining of the stroma will almost invariably produce scarring, but so too will manipulation of the stromal tissue. Most stromal rust rings eventually migrate to the surface with the normal sloughing of dead cells, and at that point are easy to remove without risk of scarring. Although we suggest being aggressive when removing epithelial tissue, we advise caution once you get below Bowman's membrane.

top

Acid Burns vs. Alkali Burns

The composition of the substance that causes a chemical burn—whether acid or akaline—determines your management approach.

Acids have a propensity to bind with tissue proteins, essentially "cooking" the surface tissue and forming a barrier to further penetration. The damage at the initial presentation of an acid burn, whatever the severity, is about as bad as it gets.

Acid burns may result from exposure to sulfuric acid (battery acid), muriatic acid (a form of hydrochloric acid used in swimming pools) and even vinegar (acetic acid). Expect acid burns to look a little better on day two than on day one.

Alkaline burns are more common because these substances are found in many household and industrial products, including ammonia, lye and lime (a component of cement). They're also more ominous than acid burns: These substances act to saponify the fatty acids in the cell membranes of the cornea, softening the tissue.

This mechanism destroys not only the epithelial cells but also deeper cellular structures. Penetration into the stroma is inevitable, and tissue damage may continue long after the initial trauma; sequelae of severe alkaline burns may occur in the retina.

It's not uncommon for alkaline burns to be worse at follow-up, so you should repeat a full evaluation. It's also important to sweep the fornices and ocular surface at each follow-up, especially if the offending agent was in particulate form (e.g., calcium carbonate). Repeated swabbing helps to remove embedded debris and necrotic tissue, and prevents symblepharon formation.

top

| | | | | |