Ophthalmology – Intraorbital Foreign Body

Basics

Description

An intraorbital foreign body (IOFB) is an object that penetrates and becomes retained within the orbit. It most commonly results from a high-velocity penetrating injury or direct impalement by a sharp object.

Foreign bodies may enter through the eyelid or conjunctiva and can damage the globe, extraocular muscles, optic nerve, orbital vessels, orbital walls, or even extend intracranially. The severity depends greatly on the composition, size, velocity, and location of the object and the associated injuries produced at the time of penetration.

Epidemiology

Most patients with intraorbital foreign bodies are young males, commonly younger than 30 years of age. This pattern reflects greater exposure to occupational, recreational, projectile, and traumatic injuries.

Prevention

The most important preventive measures are education and appropriate protective eyewear during high-risk occupational and recreational activities.

Eye protection is particularly important when working with machinery, metal, wood, construction materials, firearms, or other sources of high-velocity projectiles.

Pathophysiology

An IOFB develops when an object penetrates the periocular tissues and enters the orbit through the eyelid, conjunctiva, or adjacent structures.

The foreign body can cause immediate mechanical damage to orbital structures. Subsequent complications depend heavily on the material retained.

Organic materials, particularly wood and plant matter, provoke substantial inflammation and can introduce microorganisms into the orbit. They therefore carry a high risk of infection, abscess formation, and chronic granulomatous inflammation.

Many inert inorganic materials, such as certain metals, glass, or plastic, may remain relatively well tolerated when deeply located and not causing functional problems.

Etiology

Projectile injuries are an important cause. Metallic foreign bodies may result from BB or pellet injuries, firearms, industrial accidents, or fragments produced during metalworking.

Nonmetallic objects may also penetrate the orbit. These can be organic, such as tree branches or wooden fragments, or inorganic, such as glass, plastic, and stone.

The nature of the material is clinically important because organic material generally produces a much greater inflammatory and infectious response than inert inorganic material.

Diagnosis

History

A history of periocular or orbital trauma is usually present, but the original injury may appear deceptively minor.

Delayed presentation is not uncommon. This is particularly important in children or in patients who were intoxicated or otherwise unable to provide an accurate history at the time of injury.

A retained foreign body should therefore be considered in a patient with otherwise unexplained recurrent orbital inflammation, orbital cellulitis, draining sinus, abscess, proptosis, or ocular motility disturbance, particularly when there is a remote history of trauma.

The mechanism of injury should be established whenever possible because it provides information about the likely material, trajectory, velocity, and risk of intracranial penetration.

Physical Examination

Visual acuity should be assessed as soon as safely possible. Vision may range from completely normal to profound or complete visual loss depending on associated globe, optic nerve, or orbital injury.

An afferent pupillary defect may indicate significant optic nerve or retinal involvement.

Extraocular movements should be assessed carefully. Limitation of movement may result from direct extraocular muscle injury, mechanical restriction, inflammation, or nerve injury.

Other possible findings include blepharoptosis, proptosis, orbital swelling, and inflammation.

A foreign body located near the orbital apex may occasionally produce gaze-evoked visual loss, suggesting compression or compromise of the optic nerve or its blood supply with certain eye positions.

The periocular skin and conjunctiva should be examined carefully for an entry wound. The conjunctival fornices deserve particular attention because a small penetration site may easily be overlooked.

The examination must also determine whether there is an associated open-globe injury, which substantially changes subsequent management.

Laboratory Investigation

If infection is suspected, material from the wound or foreign body should be submitted for appropriate aerobic, anaerobic, and fungal cultures.

A complete blood count may demonstrate leukocytosis in patients with significant acute or chronic orbital infection or inflammation, although normal laboratory findings do not exclude a retained foreign body.

Imaging

CT Scan

Orbital CT is generally the key initial imaging study in penetrating orbital trauma. It is particularly effective at identifying and localizing metallic and glass foreign bodies and evaluating associated orbital fractures.

Thin-section images in appropriate planes help determine the foreign body’s location and relationship to the globe, optic nerve, extraocular muscles, and orbital walls.

Wooden foreign bodies can be challenging because their CT appearance changes depending on their water content and duration within the orbit. Dry wood may have very low attenuation and can resemble air, while retained wood may later become more conspicuous as it absorbs fluid and induces inflammation.

MRI

MRI can be useful when CT is unrevealing but there remains strong clinical suspicion for an organic or other radiolucent nonmetallic foreign body.

However, MRI should not be performed until a ferromagnetic metallic foreign body has been reliably excluded, because movement of ferromagnetic material within the magnetic field can cause additional tissue injury.

Ultrasonography

Ultrasound can occasionally assist in localization, particularly for more anterior lesions, but it is less reliable for evaluating the orbital apex.

Ultrasonography also requires particular caution when an open-globe injury is suspected, because pressure on a potentially ruptured globe should be avoided.

Intracranial Extension

Any penetrating injury with a trajectory toward the orbital roof, superior orbital fissure, or orbital apex should raise concern for orbitocranial penetration.

This is especially important in children because their orbital bones are relatively thin. Appropriate CT imaging should evaluate the orbit, brain, and suspected trajectory of the penetrating object.

Additional Diagnostic Testing

When an iron- or copper-containing foreign body lies close to the sclera or globe, electroretinography (ERG) may occasionally be useful to evaluate retinal toxicity.

The need for additional testing depends on the composition and location of the foreign body and associated ocular injury.

Pathological Findings

Retained organic foreign bodies commonly produce chronic inflammation. Histopathology may demonstrate a foreign-body granulomatous reaction, fibrosis, inflammatory cellular infiltration, and occasionally abscess formation.

This strong inflammatory response explains why retained wood and other organic materials generally require removal.

Differential Diagnosis

A retained IOFB should be distinguished from conditions producing similar orbital inflammation or mass effect, particularly orbital cellulitis, idiopathic orbital inflammation, and orbital neoplasms.

In a child with unexplained orbital inflammation or an apparent orbital mass, an occult penetrating injury and retained foreign body should remain in the differential diagnosis.

Treatment

Management depends on the material, location, accessibility, associated injuries, infection, ocular motility, neurologic status, and visual function.

The presence of a foreign body does not automatically mean that every object should be surgically removed. Attempted removal of a deeply located inert object can sometimes cause more damage than leaving it undisturbed.

Medical Treatment

Patients with contaminated penetrating injuries require appropriate tetanus prophylaxis according to their immunization status and wound characteristics.

When orbital cellulitis or another infection is present, broad-spectrum antimicrobial treatment is required. Coverage should reflect the mechanism of injury and suspected organisms, with appropriate anaerobic coverage for contaminated wounds.

Organic foreign bodies have a particularly high risk of polymicrobial and fungal infection and require aggressive evaluation and management.

Surgical Treatment

Surgical removal is generally indicated when the foreign body causes neurologic compromise, significant ocular motility restriction, infection, abscess formation, optic nerve compromise, or other orbital complications.

Organic foreign bodies should generally be removed because of their high risk of infection and chronic inflammatory reactions.

Accessible foreign bodies in the anterior orbit are also more likely to be removed because surgery can often be performed with relatively limited risk.

In contrast, a deeply located inert inorganic foreign body in the posterior orbit may sometimes be observed when it is not causing infection, visual dysfunction, motility disturbance, or other complications. Attempting to retrieve an object adjacent to the orbital apex or optic nerve may itself threaten vision.

Intraoperative imaging or localization techniques, including ultrasound or fluoroscopy, may occasionally assist in identifying difficult-to-localize foreign bodies.

Associated globe injuries should be addressed appropriately as part of the overall surgical plan.

Referral and Multidisciplinary Management

Patients require urgent ophthalmologic assessment, particularly when there is decreased vision, suspected open-globe injury, optic neuropathy, significant motility disturbance, or orbital infection.

An oculoplastic or orbital surgeon may be required for removal of complex foreign bodies.

If imaging demonstrates or strongly suggests intracranial penetration, neurosurgical involvement is essential.

Follow-Up

Follow-up should assess visual acuity, pupillary responses, ocular motility, globe integrity, optic nerve function, orbital inflammation, and signs of infection.

Patients in whom an inorganic foreign body is intentionally retained require ongoing observation for delayed complications.

Organic foreign bodies require particularly careful follow-up because infection or inflammatory complications may develop even after an initially quiet period.

Prognosis

Visual prognosis depends primarily on the severity of the initial injury, particularly damage to the globe, retina, optic nerve, or orbital apex.

Many retained inert metallic foreign bodies are well tolerated and may have a good prognosis when they do not directly damage important orbital structures.

The composition of the metal matters. Copper-containing foreign bodies can provoke severe chronic inflammatory or suppurative reactions.

Organic materials have a less favorable prognosis because they carry a substantially greater risk of orbital infection, abscess formation, chronic inflammation, and intracranial infection.

Complications

Potential complications include orbital cellulitis, orbital abscess, chronic suppurative inflammation, sterile abscess formation, orbitocutaneous fistula, orbital wall osteomyelitis, ocular motility abnormalities, optic nerve injury, and permanent visual loss.

Penetrating injuries extending beyond the orbit may produce intracranial infection, cerebral injury, meningitis, or brain abscess, making recognition of orbitocranial extension particularly important.