Corneal Abrasion

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Most people fully recover from minor corneal abrasions without permanent eye harm. However, deeper scrapes can cause corneal infections, corneal erosion, or scarring of the cornea. If not treated decently, these complications can result in long-term vision problems. Any unusual symptoms, including a recurrence of agony following healing, should be reported to your eye doctor.

Corneal abrasion is most likely the most common eye injury and perhaps one of the most neglected. It occurs because of a disruption in the integrity of the corneal epithelium or because the corneal surface is scraped away or denuded as a result of physical outward coerces. Corneal epithelial abrasions can be puny or large (see the photos below).

Corneal abrasions usually heal rapidly, without serious sequelae. Consequently, they are often considered of little consequence. However, deep corneal involvement may result in irregularity of the corneal epithelium or scar formation in the stroma.

Corneal abrasions occur in any situation that causes epithelial compromise. Examples include corneal or epithelial disease (eg, dry eye), superficial corneal injury or ocular injuries (eg, those due to foreign bods), and contact lens wear (eg, daily disposable soft lenses, extended-wear soft lenses, gas-permeable lenses, hard polymethylmethacrylate lenses). Spontaneous corneal abrasions may be associated with map-dot-fingerprint dystrophy or recurrent corneal erosion syndrome.

A traumatic corneal abrasion is the classic corneal abrasion in which mechanical trauma to the eye results in a defect in the epithelial surface. Common causes of traumatic corneal abrasions include the following:

Foreign body–related abrasions are defects in the corneal epithelium that result from removal of or spontaneous dislodgement of a corneal foreign figure. Foreign figure abrasions are typically caused by chunks of metal, wood, glass, plastic, fiberglass, or vegetable material that have become embedded in the cornea.

Contact lens–related abrasions are defects in the corneal epithelium that are left behind after the removal of an overworn, improperly fitting, or improperly cleaned contact lens. In these cases, the mechanical insult is not from outer trauma but rather from a foreign bod that is associated with specific pathogens.

Spontaneous defects in the corneal epithelium may occur with no instantaneous antecedent injury or foreign bod. Eyes that have suffered a previous traumatic abrasion or eyes that have an underlying defect in the corneal epithelium are prone to this problem.

The diagnosis of corneal abrasion can be confirmed with slitlamp examination and fluorescein instillation (see Workup). Prophylactic topical antibiotics are given in patients with abrasions from contact lenses, who are at enlargened risk for infected corneal ulcers, but many emergency physicians have stopped using these agents for minor injuries. Patching the eye is a traditional measure, but it is not supported by research and should not be performed in patients at high risk of eye infection. Agony ease is significant. (See Treatment.)

Anatomy

The cornea is a semitransparent tissue over the anterior part of the eye that serves several purposes: protection, refraction, and filtration of some ultraviolet light. It has no blood vessels and receives nutrients through tears as well as from the aqueous humor. It has sensory innervation from the ophthalmic division of the trigeminal nerve.

The cornea is composed of the following five layers (anterior to posterior):

Pathophysiology

A corneal abrasion is a defect in the surface of the cornea that is limited to the most superficial layer, the epithelium, and does not penetrate the Bowman membrane. In some cases, the bulbar conjunctiva is also involved. Corneal abrasions result from physical or chemical trauma. Severe corneal injuries can also involve the deeper, thicker stromal layer; in this situation, the term partial-thickness corneal laceration may be used.

The conjunctival response to corneal wounding has been known since 1944, when Mann very first observed that peripheral corneal abrasions heal by the sliding of limbal cells to cover the epithelial defect. [1] This response is split into two phases: (1) the response of the limbal epithelium, which is the source of the fresh corneal epithelial stem cells, and (Two) the response of the conjunctival epithelium itself.

Under normal circumstances, the limbal epithelium acts as a barrier and exerts an inhibitory growth pressure that prevents the migration of conjunctival epithelial cells onto the cornea. Like the rest of the surface of the bod, the conjunctiva and the cornea are in a constant state of turnover. Corneal epithelial cells are continuously shed into the rip pool, and they are at the same time replenished by cells moving centrally from the limbus and anteriorly from the basal layer of the epithelium.

Movement from the basal to superficial layers is relatively rapid, requiring 7-10 days. However, movement from the limbus to the center of the cornea is slow and may require months.

This normal physiologic process is exaggerated in the case of a corneal abrasion. During corneal healing of a lesion, corneal epithelial cells become flattened, they spread, and they stir across the defect until they cover it fully. Cellular proliferation, which is independent of cell migration, starts approximately twenty four hours after injury.

Stem cells from the limbus also react by proliferating to give rise to daughter cells called transient amplifying cells. These cells migrate to heal the corneal defect and proliferate to replenish the wounded area. The observation of limbal pigment migrating onto the clear cornea provides extra evidence of this process.

The concept that the limbal cells form a barrier to conjunctival cells was supported further by the observation that rabbit eyes treated for one hundred twenty seconds with N -heptanal, which eliminated the corneal and conjunctival epithelium but left the limbal basal cells intact, resulted in healing of the corneal epithelium and had unvascularized corneas. However, when the entire limbal zone was surgically eliminated along with N -heptanal treatment, corneal vascularization and conjunctivalization was observed. [Two]

Demonstration of the centripetal migration of limbal cells (marked by India ink) provided more direct evidence of this concept. These cells migrate in masses as a continuous, coherent sheet, with most cells retaining their positions relative to each other, much like the movement of a herd of cattle.

Rearrangement of intracellular actin filaments plays a role in movement. Cell migration can be inhibited by blocking polymerization of actin, indicating that actin filaments actively participate in the mechanism of cell mobility. Some authors believe that conjunctival and limbal epithelial cells may contribute to the regeneration of corneal epithelium. Marked proliferative responses in the conjunctiva after a central corneal epithelium abrasion have been described.

Why the conjunctival epithelium should proliferate in response to a central corneal wound is unknown. One possibility is that the proliferation replenishes the number of goblet cells, which decreases by up to 50% after corneal wounding. However, proliferation occurs at high levels in the bulbar conjunctiva, which contains few if any goblet cells. The apparent decrease in cell number is more likely the result of mucin secretion rather than actual loss of goblet cells.

Alternatively, conjunctival cells may migrate into the limbus or cornea to help replenish the wound area. No rock-hard data suggest that conjunctival epithelium migrates onto the corneal surface in the presence of intact limbal epithelium. Lastly, healing of the corneal epithelial wound is not finish until the freshly regenerated epithelium has rigidly anchored itself to the underlying connective tissue.

Permanent anchoring units are not formed until the wound defect is covered totally. Epithelial cells migrate rapidly and develop strong, permanent adhesions within one week when the basement membrane is regularly formed and released during the cell migration process.

Albeit transient attachments are regularly formed and released during the cell migration process, formation of normal adhesions takes six weeks, according to Dua et al. [Trio] Little buds of corneal epithelium are present along the contact line inbetween the normal corneal epithelium and the migrating conjunctival epithelium. These buds arise from the corneal epithelium, and normal corneal epithelium emerges to substitute the conjunctival epithelium by step by step pushing it toward the limbus.

The magnitude and extent of both the conjunctival and corneal regenerative responses to a corneal abrasion correlate with the size of the wound. Large epithelial defects were reported to induce a pronounced response in the rate of epithelial cell migration and mitosis at the limbus.

Insults caused by chemical injuries, Stevens-Johnson syndrome, contact lens–induced keratopathy, and aniridia result in limbal harm. These insults cause delayed healing of the cornea, recurrent epithelial erosions, corneal vascularization, and conjunctival epithelial ingrowth.

Role of the epithelial defect

A long-standing clinical observation is that bacterial corneal infections do not occur in patients with an intact, healthy epithelium. Bacterial keratitis and abrasions develop in one of the following three types of patients:

The common feature among the three groups is a defect in the corneal epithelium to which the bacteria must adhere to begin the infection. Mechanisms underlying the development of epithelial defects in the very first two groups are self-evident. In the third group, contact lenses may lead to epithelial injury in any of the following ways:

Defects in the epithelium need not be total thickness. Overnight wearing of soft lenses, which do not provide sufficient oxygen transmissibility to prevent hypoxia, causes superficial desquamation of epithelium and increases the propensity for abrasions and infections.

Corneal full salute induced by overnight wearing of contact lenses is the most significant factor. The cornea normally swells 2-4% during sleep. With a contact lens, overnight erection increases to an average of 15%, and gross stromal edema can be present on awakening. In some patients, induced corneal full salute can be sufficient to cause corneal bullae, which may rupture, leading to epithelial defects.

Etiology

Potential causes of corneal abrasion include the following:

In persons with trachoma, the constant corneal trauma by aberrant lashes and inadequate tears can produce corneal erosions, ulceration, and scarring. These constitute the major pathway to blindness in trachoma.

Contact lens trauma

Contact lens–induced epithelial defects or direct trauma during lens injection or removal can cause corneal abrasions.

Abrasions occur more frequently with rigid lenses than with other lenses, possibly because of their puny diameter and the acute corneal defects they cause. Rigid contact lenses can lead to relative corneal hypoxia, epithelial edema, and epithelial breakdown. Corneal abrasions due to soft lenses are observed most frequently with taut or extended-wear lenses. In these situations, acute epithelial hypoxia impairs attachment of the epithelium to the Bowman membrane.

The most common trauma is an inferior abrasion of the cornea caused by lens removal. Sometimes, the person’s fingernail slices the contact lens and also the cornea. More often, the lens becomes slightly dehydrated at the end of the day because of insufficient blinking. The lens adheres to the cornea, removing the epithelium. This area may not heal well, especially if the epithelial cells are continually ripped away. After the contact lens is eliminated, the patient may feel discomfort; however, no ache occurs when the lens is worn because it acts as a bandage. Patients who incompletely blink and those who work in a dry environment, read most of the day, or look at TV or computer screens should be warned about this complication.

A foreign figure may become trapped under a contact lens and produce linear scrape marks on the cornea. The total irregularity of these wavy abrasions is the clue to this cause of injury.

A soft lens offers no protection against blunt trauma to the eye, but it does not pose any extra jeopardy in terms of eye trauma. For example, a soft lens does not adversely affect an eye injured by a knuckle or a ball. In industrial settings, a soft lens is not a substitute for safety glasses.

Rigid contact lenses may break or chip, causing punctate epithelial keratopathy.

Adverse corneal events, such as corneal abrasions, have been reported with mechanisms of overnight corneal reshaping with orthokeratology. Lang concluded that corneal compromise and poor compliance can cause adverse events with corneal reshaping. [6] The need for ongoing patient education is significant in both children and adults who wear contact lenses.

Sports-related injury

Corneal abrasions can occur in almost all sports. They most frequently occur in youthfull people.

In places where soccer is played frequently, influence with the soccer ball causes approximately one third of all sports-related eye injuries. Contrary to previous ophthalmologic instructing that testicles larger than four inches in diameter infrequently cause eye injury, 8.6-inch soccer testicles cause most soccer-related eye injuries, both serious (eg, hyphema, vitreous hemorrhage, retinal rip, chorioretinal rupture, angle recession) and minor (eg, corneal abrasions, contusions). [7]

Approximately one in ten college basketball players has an eye injury each year. Most basketball-related eye injuries are corneal abrasions caused by an opponent’s finger or elbow striking the player’s eye.

The incidence of severe eye injuries in wrestling is low. In a examine at Michigan State University, Legitimate.4% of wrestlers had eye injuries that were relatively mild (eg, lacerated eyebrows, corneal abrasions) and that left no permanent harm. [8] The average college team with twenty five players and two thousand six hundred athlete exposures should expect 1-2 eye injuries each season, with a significant injury every 9-10 seasons. [9]

Albeit significant eye injuries are not a major risk in equestrian events other than polo, cross-country riders frequently have corneal abrasions from hitting tree branches overhanging the trail. Wearing spectacles with polycarbonate lenses provides adequate protection against this risk.

Albeit cross-country skiing causes fewer musculoskeletal injuries than alpine skiing, cross-country skiers are more likely than alpine skiers to have eye injuries, especially corneal abrasions from contact with tree twigs. [Ten] Both cross-country and downhill skiers can have solar keratopathy (snow blindness) and injuries due to accidents with ski poles.

Eyelid surgery

In patients undergoing eyelid surgery, corneal abrasion can result from sutures inadvertently placed through the tarsus or conjunctival surface. After sutures are placed, the lid should be everted to check that they are not exposed.

The globe and cornea should be protected during lid dissection and suture placement. A contact lens corneal protector or lid plate can be used.

Anesthesia

General anesthesia is more likely to cause adverse systemic effects than local or ocular complications. Ocular problems that do occur are usually not serious and include corneal abrasion, chemical keratitis, hemorrhagic retinopathy, and retinal ischemia (infrequent).

The incidence of corneal abrasion due to general anesthesia is as high as 44%. Plain precautions, such as instilling a bland ointment or taping both pairs of eyelids closed in the case of nonocular surgery and the lids of the nonoperative eye in the case of ocular surgery, may prevent surface trauma produced by the surgical drape, anesthetic mask, or exposure. Decreased rip production under general anesthesia, proptosis, and a poor Bell phenomenon may worsen corneal exposure, requiring eyelid suturing in some susceptible patients.

Argon laser trabeculoplasty

Corneal abrasion is one of the complications of argon laser trabeculoplasty. Others include the following [11] :

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