Chapter 159. Corneal Foreign Body Removal

Corneal foreign bodies are a common complaint confronting Emergency Physicians and account for approximately 35% of all eye injuries seen.1 Many objects have been implicated as a source of corneal foreign bodies including, but not limited to glass, metal, wood, dirt, dust, insects, and plant particles.1 The majority of ocular foreign bodies require prompt removal. More than 75% of retained foreign bodies present on the eye surface are corneal in nature, and if left in place for more than 3 days will result in a keratitis.2

The prevailing symptom that forces patients to seek treatment is the sensation of an ocular foreign body or simply the pain associated with the foreign body. A variety of techniques exist for removal of ocular foreign bodies. A discussion of each of these techniques is necessary to determine the proper technique for a given situation.

Many foreign bodies are diverted from the surface of the eye by the rapid blinking action of the eyelids and the eyelashes. A foreign body may not necessarily lodge itself into the cornea or the surrounding scleral surface if it is able to get past the eyelids and eyelashes. It may be washed to the inner canthus by a combination of blinking and tear flow. The foreign body may occasionally be carried away via drainage through the lacrimal ducts.2 Objects that resist these means of diversion may be found in the upper or lower fornices, the channels created by the fold of the inner surfaces of the eyelids in communication with the conjunctival surface of the eye. The foreign body in the upper fornix is typically found lodged in the subtarsal groove on the inner surface of the upper eyelid, inferior to the tarsal plate.2 Foreign bodies may also travel deeper into the respected fornices where they may be difficult to find. Foreign bodies may lodge themselves into the surface of the conjunctiva overlying the sclera or into the cornea itself, which obviously carries the most risk of serious injury or permanent scarring.

The cornea is <1 mm thick. It is comprised of five layers (from outer to inner layer): epithelium, Bowman's membrane, stroma, Descemet's membrane, and the endothelial layer that lies directly over the anterior chamber.3 The surface epithelium itself has five layers of squamous cells. Most superficial corneal foreign bodies become embedded in this layer and do not result in scarring. Bowman's membrane has no regenerative capacity, and if injured, may result in scarring and permanent injury.4 Foreign bodies that violate Bowman's membrane are considered deep corneal injuries. The stroma is composed of collagen and accounts for the largest portion of the cornea. Descemet's membrane is a basement membrane that can be regenerated if injured. The final component of the cornea is the endothelial layer that is composed of a single row of cuboidal cells that can regenerate if damaged.

Healthy cells adjacent to the injury slide over the damaged site and eventually replicate to the previous number of cells present when the corneal epithelium is injured.3 Conjunctival epithelium migrates over the cornea to aid in its repair. This is true even if the entire surface epithelium of the cornea is removed.

Corneal innervation is provided by sensory nerve fibers located in the surface epithelium. These are concentrated primarily in the center of the cornea and sparsely located in the periphery.5,6 Injuries to the corneal epithelium produce pain, tearing, photophobia, and the sensation of a foreign body.6 More pain occurs when the central portion of the cornea is affected due to the larger distribution of sensory nerves.6

Patients are fairly adept at identifying the location of an embedded foreign body due to the corneal innervation. A study evaluated 50 patients with corneal foreign bodies and their accuracy in identifying the foreign body location.7 Eighteen patients (36%) were unable to identify the foreign body location, 14 (28%) were able to identify the exact location, and 18 (36%) were partially correct in identifying the location based upon vertical and horizontal components. Always acknowledge the patient's sensation of an ocular foreign body and evaluate the area thoroughly.

The presence of a metallic foreign body in the cornea can result in a rust ring. This is identified as a brownish ring surrounding the foreign body. The rust ring, and the metallic foreign body, must be removed from the cornea. The rust ring may be removed at the time of the foreign body removal or within 24 hours by an Ophthalmologist. Refer to Chapter 160 for the complete details of rust ring removal.

In general, all foreign bodies involving the eye must be removed. They do not all need to be removed immediately in the Emergency Department. Foreign bodies that are superficial and located on the cornea, sclera, eyelid, upper fornix, or lower fornix can safely be removed in the Emergency Department by the Emergency Physician. Metallic foreign bodies require prompt removal to avoid the formation of a rust ring. If a rust ring is also present, the foreign body should be removed in the Emergency Department and the rust ring can be removed by the Emergency Physician or by the Ophthalmologist at the 24-hour follow-up visit. Vertical abrasions on the cornea during the fluorescein examination are indicative of a foreign body under the eyelid. This requires the upper eyelid to be everted to evaluate for the presence of a foreign body under the eyelid.

Corneal foreign bodies located in the direct axis of vision can cause permanent visual disturbances if improperly removed.4 Consult an Ophthalmologist before removing these foreign bodies, as they often prefer to remove them. Deeply embedded objects or multiple foreign bodies that would require extensive debridement can result in significant scarring.1 Consult an Ophthalmologist before attempting to remove these foreign bodies. Avoid any manipulation of the eye if a perforated globe is suspected based upon either the direct examination of the eye or the mechanism of injury. Foreign bodies embedded deeply within the cornea may be left in place if they are composed of an inert substance such as glass.1 This will avoid the possibility of additional scarring from extensive debridement as long as the object is well below the corneal surface to allow for healing of the epithelium over the object. This decision must be made in conjunction with an Ophthalmologist. Consult an Ophthalmologist if an infection is associated with the foreign body (e.g., corneal edema, corneal clouding, or a purulent discharge). Refer injuries to an Ophthalmologist that are old, those in which the foreign body has been covered by epithelium, and foreign bodies resistant to removal. Do not attempt to extract a corneal foreign body if the patient is confused or uncooperative as this can result in a perforated globe. Consider the use of intravenous sedation, procedural sedation (Chapter 129), or general anesthesia to extract the foreign body in these patients after consulting an Ophthalmologist.

• Slit lamp
• Cotton-tipped applicator
• Corneal spud
• Ringer's lactate solution or normal saline
• Intravenous (IV) tubing
• 25 or 27 gauge needle
• Tuberculin syringe with needle
• Topical ocular anesthetic solution (e.g., proparacaine and tetracaine)
• Topical ophthalmic antibiotic
• Cycloplegic agents (e.g., cyclopentolate, homatropine, and tropicamide)
• Fluorescein strips or liquid
• Electric burr drill and burrs
• Eye patches
• Adhesive tape
• Benzoin solution
• Wood's lamp (if slit lamp is not available)
• Eidolon BLUMINATOR® (Eidolon Optical LLC, Natick, MA) (if slit lamp is not available)

Having the availability of a slit lamp is preferred when removing a corneal foreign body. There are alternatives if a slit lamp is not available or the Emergency Physician does not feel comfortable with using a slit lamp. The Wood's lamp can provide the appropriate blue light required for fluorescein staining and rust ring removal. This portable device has a built in magnification lens. It has several disadvantages including having to be plugged into an outlet, an awkward shape, and a heaviness that must be balanced while using it. A newer device is the Eidolon BLUMINATOR®. It is small, handheld, self-contained, battery powered, and includes a 7× magnification lens.

Perform a complete eye examination prior to removing a foreign body. Measure visual acuities prior to any ocular procedure and following the procedure to document any changes. Refer to Chapter 153 for the complete details regarding the eye examination. Apply a topical ocular anesthetic agent into the affected eye. Note any irregularities in the contour of the eye, any loss of anterior chamber depth, prolapse of the iris through a corneal laceration, focal injection, a hyphema, or lens opacification. All of these signs may indicate a ruptured globe that requires an emergent Ophthalmology consultation.4 Vary the beam of light from the slit lamp in its direction of illumination from direct exposure to indirect exposure, and even tangential exposure, to highlight any surface defects.8 Examine the anterior chamber for cells and flare that occurs in older injuries as a result from a secondary iritis. The patient typically suffers from the discomfort of an anterior uveitis rather than the foreign body itself.1

Stain the eye with fluorescein dye. Fluorescein can permanently stain contact lenses and should not be used in their presence. Illuminate the eye with a cobalt blue light, looking for the green reflection of a corneal abrasion. Observe the site for the flow of fluorescein stain away from the site of a corneal puncture as anterior chamber fluid flows forth, otherwise known as the Seidel sign.4,8 A positive Seidel sign indicates a ruptured globe. Irrigate the fluorescein stain from the eye after the examination is complete to avoid any chemical-induced irritation.

Explain the process of ocular foreign body removal to the patient and/or their representative. Discuss the benefits and risks of the procedure. Obtain a signed informed consent to perform this procedure. Instill additional topical ophthalmic anesthetic solution as necessary.

Eyelid Foreign Bodies

Evert the upper eyelid.8 Refer to Chapter 153 and Figures 153-12, 153-13, 153-14, and 153-15 for the complete details regarding the eyelid eversion. Instruct the patient to look downward as a cotton-tipped applicator is used to gently press on the upper eyelid over the tarsal plate. Grasp the eyelashes with the thumb and index finger. Pull the upper eyelid outward, downward, and upward to evert it over the applicator. Examine the undersurface of the eyelid for foreign bodies. Remove any foreign bodies by sweeping the area with a saline-moistened cotton-tipped applicator (Figure 159-1). Double evert the eyelid by lifting the inferior edge of the eyelid created by the initial eversion. This is best accomplished by using a cotton-tipped applicator or an appropriate lid retractor. Examine the sclera and conjunctiva for foreign material. Allow the upper eyelid to return to normal. Release the eyelid and instruct the patient to blink their eyes.

Evert the lower eyelid by pulling the lower eyelashes forward while the patient looks upward.4 Examine the area in similar fashion to the upper eyelid. Sweep the scleral and palpebral (eyelid) conjunctival area with a saline-soaked cotton-tipped applicator if the patient experiences a foreign body sensation but no debris can be visualized.

Irrigation

Superficial foreign bodies on the conjunctiva or the cornea can sometimes be removed by using an irrigation technique. A brief description is presented in this section. Refer to Chapter 155 for the complete details regarding eye irrigation. Never use Morgan or Mediflow lenses for eye irrigation in the face of a foreign body as it may lodge the object further into the cornea.

The most appropriate solution to use is Ringer's lactate solution followed by normal saline. Tap water can be used in the prehospital setting. Ringer's lactate solution causes less irritation because the range of its pH (6.0 to 7.2) is closer to the normal pH (7.4) of the eye in comparison to the pH (4.5 to 6.0) of normal saline.4

Place the patient supine with their head tilted toward the side being irrigated to aid in proper runoff of the irrigant. Hang the IV fluid bag above the patient's head. Insert the IV tubing spike into the port on the IV fluid bag. Flush the patient's eye with sterile IV solution through the open end of the IV tubing while holding the patient's eyelids open. Flush from the scleral surface with the flow of solution directed over the cornea, thus washing the object out of the eye.1,4,8 Never direct the solution onto the object in order to avoid embedding it deeper into the soft underlying tissues. Never direct the flow directly onto the surface of the cornea to avoid secondary injury. Use a forceps or cotton-tipped applicator to remove objects flushed onto the palpebral conjunctiva.4 Never use a forceps on the eye itself.

Cotton-Tipped Applicator

Use a cotton-tipped applicator premoistened with saline to remove a foreign body from the conjunctiva overlying the sclera or the eyelids.8 Gently touch the premoistened tip of the cotton-tipped applicator to the conjunctival surface and lift off the foreign body. Do not use the cotton-tipped applicator to remove a foreign body from the cornea.8 It can result in a large corneal abrasion by removing the surface epithelium.

Manual Extraction

Extract the foreign body with a corneal spud or hypodermic needle if it is not removed via irrigation or if it is embedded superficially into the corneal surface. A corneal spud is a stainless steel device that comes in a variety of shapes. It generally consists of a sharpened metal tip attached to a handle.1 It is used to lift off or to carve out a corneal foreign body.1 Many physicians prefer to use a tuberculin syringe. It allows for better control of the needle by using the syringe portion as the grip. The author always uses a saline-filled tuberculin syringe. This allows the Emergency Physician to apply saline drops to moisten the eye as well as to flush away the foreign body after it is dislodged from the cornea. An 18 gauge needle has been described for the removal of large foreign bodies because of its wide diameter.1 The instrument used is physician dependent. Proper explanation of the extraction procedure using a needle will often ease a nervous patient and ensure better compliance by limiting unexpected movements.

Perform the procedure under direct visualization with the slit lamp. Place the patient seated at the slit lamp with their head firmly in place against the forehead rest to avoid any unexpected movement (Figure 159-2A). If a slit lamp is not available, the foreign body can be removed using the blue light of a Wood's lamp or Eidolon BLUMINATOR®. Hold the needle, or spud, between the thumb and index finger of the dominant hand as one would a pencil with the bevel facing the Emergency Physician. Stabilize the dominant hand on the patient or the slit lamp apparatus using the remaining fingers. Instruct the patient to focus their vision on a given point to avoid any eye movement.

Approximate the tip of the needle, or spud, to the foreign body with the naked eye before utilizing the slit lamp microscope in order to avoid inadvertent injury. Approach the foreign body from the periphery and not across the patient's field of vision (Figure 159-2B). Gently tease out the foreign body using the beveled edge of the needle, or spud, in a tangential direction in relation to the eye to avoid inadvertent deep puncture if the patient suddenly moves (Figure 159-2C). Use the tip to gently pry the foreign body loose if absolutely necessary, but extreme care must be exercised (Figure 159-2D). Remove the loose foreign body with a moistened cotton-tipped applicator or with gentle irrigation.

Electric Burr Drill Extraction

An electric battery powered drill equipped with various sized diamond dental burrs, if available, can be used for foreign body removal (Figure 159-3). Its use is typically associated with an increased tissue defect when compared to using a needle or a spud.9 Use caution as the burr drill can also embed the foreign body deeper into the cornea.

Choose a burr size that is slightly larger than the diameter of the foreign body. Load the burr onto the drill. Grasp the device like a pencil using the thumb and middle finger. Press the finger bar on the drill with the index finger to turn on the drill and rotate the burr bit. Approach the foreign body tangentially to the eye (Figure 159-4). Gently place the rotating burr bit on the area to be debrided using short applications of one to two rotations of the burr. Lift the burr from the cornea after each application to examine the area and determine if the foreign body has been removed.

Carefully examine the cornea under the slit lamp with and without the use of fluorescein dye. Ensure that the foreign body is completely removed. Consult an Ophthalmologist if the foreign body has broken off, is deeply embedded within the cornea, or is associated with a rust ring. Measure and record the patient's visual acuity after the extraction procedure. Compare this to the pre-extraction visual acuity. Consult an Ophthalmologist if there is a difference in the pre-extraction and post-extraction visual acuity.

A corneal abrasion will be present upon removal of the foreign body. The defect is usually larger than the original foreign body and should be treated as a typical corneal abrasion. Place a broad-spectrum ophthalmic antibiotic ointment (e.g., an aminoglycoside) on the eye. Instruct the patient to instill topical broad-spectrum antibiotics every 4 hours if the eye is not patched.1,4,5,8 The ophthalmic nonsteroidal anti-inflammatory drugs are safe to use and provide effective pain relief.12–14 Currently available are bromfenac, diclofenac, and ketorolac.

The use of an eye patch is controversial and usually not required. Refer to Chapter 161 regarding the complete details of eye patching. The use of eye patches should be considered cautiously as they may be associated with additional discomfort, delayed healing, and the conversion of a corneal abrasion into a corneal ulcer.10 Consider patching the eye closed if the defect is large and painful. Avoid pressure patching the eye in the case of small, superficial, or minimally painful abrasions. Avoid the use of eye patches in cases of organic foreign bodies and in patients who wear contact lenses, as the bacterial milieu is favorable for the development of a local infection.4 Since most patients will not need eye patching, it is best to consult an Ophthalmologist before patching an eye.

The proper method of applying an eye patch is to first administer all necessary medications. Instruct the patient to close both eyes. Apply a folded patch to the affected eye (rounded edge pointed downward) over which is placed an unfolded patch. Prep the skin with a benzoin solution to aid with tape adherence. Apply strips of tape from the medial aspect of the forehead, over the patch, and to the lateral cheek. Apply the tape tightly enough to prevent eye opening but lightly enough to not cause discomfort. Apply strips of tape repeatedly over the patch until it is entirely covered. Apply the final pieces of tape over the center of the patch while holding the cheek soft tissue superiorly. This will ensure that the cheek, when released, will pull the bandage taut and avoid loosening.4,8

Cycloplegics (e.g., 1% cyclopentolate) can be used to alleviate pain or to limit pain in cases of significant corneal defects or an anterior uveitis.1 Topical steroids have no place in the treatment of traumatic corneal defects.1 Oral analgesics are appropriate in cases of persistent discomfort. Do not prescribe topical ocular anesthetic agents due to their abusive potential and the direct deleterious effects of the anesthetic on the corneal epithelium.4

Refer all patients to an Ophthalmologist for reexamination in 24 hours, especially if an eye patch has been applied. A rust ring can be removed by the Ophthalmologist at the follow-up visit. Instruct the patient not to operate a vehicle if the eye is patched closed. These instructions also hold true if the eye is not patched but a procedure was performed to remove a foreign body.

Many eye injuries occur while at work due to failure to comply with wearing eye protection, resulting in a significant loss of working hours.6,7,11 Take the time necessary to explain the importance of wearing safety goggles if the injury occurred while at work, gardening, or participating in hobbies (e.g., woodworking, drilling, auto repair, etc.).

A foreign body will occasionally not be able to be removed in the Emergency Department. Refer the patient to an Ophthalmologist for definitive treatment before further attempts at removal result in severe ocular injury and the potential for violation of the anterior chamber (i.e., perforation of the globe). Notify an Ophthalmologist immediately if inadvertent puncture of the globe occurs from attempts at foreign body removal as a surgical emergency now exists.

Improper placement of eye patches can cause a corneal ulcer or delayed corneal healing.8 Caution the patient against driving while the eye is patched due to impaired depth perception.8

Continued discomfort at the 24-hour follow-up may indicate the foreign body was not completely removed, a corneal rust ring from a metallic object has formed, a penetrating eye injury, anterior uveitis, or an infection.1 Contaminated corneal foreign bodies or those consisting of vegetative material can also lead to corneal ulceration from the introduction of bacteria.1

Corneal defects will not always be completely healed at the 24 hour follow-up. The eye may require one additional day of patching if the defect is still a significant size. Treat the defect by applying a topical antibiotic for several more days if the defect is markedly smaller than the original injury.1

Care must be taken to avoid further damage to the eye when treating children or patients who are uncooperative. Intravenous sedation and analgesia can be used in these situations. Consult an Ophthalmologist for treatment under general anesthesia if sedation is contraindicated or if the Emergency Physician is not comfortable with removing the foreign body under procedural sedation.4

Corneal foreign bodies are routinely encountered in the Emergency Department. They must be definitively treated in order to avoid long-lasting ocular disability. Documentation of a complete history and physical examination of the eye is mandatory before attempting to remove a foreign body. The most reliable method of corneal foreign body removal is the use of a hypodermic needle or corneal spud, taking care to avoid additional ocular trauma. Administer appropriate antibiotics and/or cycloplegics after removal of the foreign body. The application of an eye patch is not required after the foreign body is removed in most cases. The decision to apply an eye patch is best done in consultation with an Ophthalmologist. Refer the patient to an Ophthalmologist in 24 hours for evaluation of proper healing and the immediate treatment of any evolving complications.