An Update on the Management of Intraocular Foreign Bodies

Raj Rathod, MD • William F. Mieler, MD

Advances in vitreoretinal surgery have allowed more successful treatment of ocular injuries with retained intraocular foreign bodies. IOFBs can be found in up to 40% of penetrating or open-globe ocular trauma cases.^1,2 Vision loss can be devastating as a result of endophthalmitis, retinal detachment or metallosis. However, timely and appropriate management often leads to favorable anatomic outcomes with restoration of good visual function in the majority of cases.

MECHANISM OF INJURY

Young men are most prone to sustaining open-globe injuries with retained IOFBs, with the majority of injuries occurring at the workplace. Hammering, using machine tools, shooting weapons and being in proximity to explosions are among the most common mechanisms involved in retained IOFB cases. Less common causes include assault, motor vehicle accidents, lawn mower injuries and insect stings. The foreign bodies produced by hammering tend to be small, sharp projectiles that penetrate the eye with less disruption and carry a more favorable prognosis (Figure 1). Roughly 90% of the involved projectiles are metallic, and over half of these are magnetic. The other mechanisms of injury tend to produce projectiles that are larger and blunter, consequently causing more damage to the eye on penetration, oftentimes leading to a more guarded visual prognosis.^3-5

Figure 1. An intravitreal metallic IOFB with a moderate amount of vitreous hemorrhage, which was sustained while hammering metal on metal. The IOFB was removed via pars plana vitrectomy techniques and an internal magnet and forceps. The final visual outcome was 20/20.

Iron, lead, copper, zinc, silver, gold, platinum, nickel, glass, plastic and wood are the most frequently encountered materials. Entry into the eye can occur through the cornea (65%), sclera (25%) or at the limbus (10%). The final location of the IOFB is found to be in the vitreous cavity (61%), anterior chamber (15%), retina (14%), lens (8%) and/or subretinal space (5%). Occasionally, the IOFB can perforate the globe and lodge within the posterior sclera or orbit.^6-8

EVALUATION

As with all vision-threatening injuries, evaluation begins with a thorough history, including setting of the trauma, time of injury, use of safety glasses, possible materials involved in the injury, and any events or interventions since the time of injury. There must be a high suspicion for a retained IOFB in the setting of hammering, sawing, drilling, grinding or an explosion. It should be assumed that ocular injuries sustained in these types of settings potentially harbor an IOFB until proved otherwise.

A thorough ocular examination should follow, including visual acuity assessment, pupillary evaluation, and external slit-lamp and fundus examination, dependent upon the extent of the injury. Intraocular pressure may be measured if the procedure will not place undue force on the globe. Subtle signs, including focal lens opacities, IOP asymmetry, pupil asymmetry, iris heterochromia or small self-sealing wounds, may suggest the presence of an IOFB.

Ocular imaging is an essential part of evaluating a suspected retained IOFB and should be considered in all open-globe traumatic injuries.⁹ Computed tomography has become the modality of choice as it affords a high sensitivity, can accurately localize single or multiple IOFBs regardless of location, requires little patient cooperation, and does not cause globe manipulation. The composition of the IOFB may also be ascertained by radiodensity evaluation. The imaging protocol should include images in both axial and coronal planes with cuts ideally <1.5 mm. Limitations of CT scanning include the potential of missing small fragments <0.7 mm in size, wooden foreign bodies or IOFBs in the scleral wall, or glass near the lens.^10-12

Echography is a valuable tool that can augment the information obtained from other imaging modalities. Although it must be used cautiously, as in the setting of an open-globe injury, there is a risk of prolapsing the intraocular contents if inappropriate pressure is placed on the eye. Echography has a high sensitivity and can readily detect the presence and location of IOFBs, both radiolucent and radiodense. Additional information about the intraocular status can be obtained simultaneously, including retinal and choroidal detachments, vitreous hemorrhage and posterior exit wounds.¹³

Magnetic resonance imaging can be used in specific cases in which a plastic or wooden IOFB is suspected and not detected by other imaging modalities. It should only be used after the presence of metallic IOFBs has been excluded, as the magnetic forces can alter the position of a metallic IOFB and cause further injury to the eye.^14,15

MANAGEMENT

Definitive management of an IOFB injury consists of timely repair of the entry site, removal of the IOFB and attention to concomitant ocular damage. However, prior to surgery, several important preparatory measures should be taken. The eye should be protected with a Fox shield at any time when the eye is not being examined. Tetanus status should be addressed and prophylaxis given. If there is any anticipated delay in surgical intervention, antibiotic prophylaxis should be administered as soon as possible. Broad-spectrum intravenous therapy (vancomycin, ancef, ceftazidime and/or newer generation fluoroquinolones) or oral fourth-generation fluoroquinolones (moxifloxacin) are generally acceptable choices.

Surgery should take place as soon as possible, based on the setting and the availability of proper equipment. Delay in surgery, especially beyond 24 hours, may pose a higher risk of endophthalmitis, development of inflammatory fibrous membranes and/or development or progression of rhegmatogenous or tractional retinal detachments. Depending on the composition of the IOFB, delay in removal can also lead to metallosis. More recently, the United States Armed Forces reported favorable outcomes from their experience with IOFB injuries during the Iraq war, even when surgery was delayed. They reported no cases of endophthalmitis, siderosis bulbi or sympathetic ophthalmia, even up to 661 days after injury. Final outcome was related to the extent of ocular injury rather than the timing of surgery. Antibiotics (most commonly levaquin) were employed immediately and were maintained until IOFB removal.¹⁶

Surgical approach is case-dependent and should take into account the location, size, shape, composition of IOFB and presence of other associated ocular injuries. Closure of the entry wound should be performed initially in order to provide stability to the eye. The IOFB should be removed in a manner that minimizes trauma upon extraction. In general, removal of the IOFB through the entry site is not recommended, as this may cause additional damage. The extraction site, which may be a pars plana or limbal incision, should be adequately prepared. The IOFB should be extracted in the plane of the smallest cross-section.

A variety of tools are available to assist in the removal of IOFBs, including external magnets, internal rare-earth magnets and foreign body forceps. The external magnet is stronger but is bulky and less controlled. The internal magnet is more controlled but is less powerful and therefore restricted to intraocular use, and it requires forceps to assist removal as the force is not strong enough for extraction through a pars plana surgical wound. If forceps are used to engage the IOFB, a second instrument may be used to align the IOFB in the most favorable axis for extraction within the mouth of the forceps.^17,18 A fragmatome set on high aspiration and no ultrasound can also be used to elevate the IOFB to enable grasping with a forceps.¹⁹ Perfluorocarbon can be placed in the eye to minimize impact if there is fear of dropping the IOFB.²⁰

Anterior-chamber foreign bodies are ideally removed through a secondary limbal incision. Removal of the lens is often necessary if there is coexisting injury to this structure or if the IOFB is embedded within it.²¹ Viscoelastics may be employed to maintain the anterior chamber during extraction of the IOFB. If the IOFB is not directly visible but was localized to the anterior chamber by imaging, careful attention must be paid to the angle and the ciliary sulcus, as these locations are potential hiding places for the IOFB.²²

Posterior-segment IOFBs often require pars plana vitrectomy to access the foreign body and address related issues, such as lens removal, endophthalmitis, or repair of associated retinal detachment (Figures 2a and 2b). A magnetic IOFB that is located anterior to the equator and is either intraretinal or subretinal can be removed through a scleral cutdown with the use of an external magnet. Clearly visible magnetic IOFBs posterior to the equator and not embedded in any ocular structure may be removed with an external magnet through a pars plana incision. The majority of remaining cases will require a pars plana vitrectomy approach.²²

Figure 2a. A glass intraretinal foreign body, which the patient sustained while replacing a lighting fixture. The foreign body was removed via pars plana vitrectomy surgery, requiring a small retinotomy, forceps removal, intraocular fluid-air exchange, and placement of demarcating laser.

Figure 2b. The patient two weeks following removal of the glass IOFB. The final visual acuity was 20/25.

ASSOCIATED INJURIES

As previously mentioned, the lens is frequently damaged with the impact of an IOFB. It is reasonable to remove the lens in any case of capsule violation or in cases in which significant lens opacities obscure the ability to view the posterior segment. The approach can be from the anterior segment or pars plana, depending on the extent of injury and location of IOFB. Placement of a secondary intraocular lens is generally not recommended at the time of initial surgery and is highly inadvisable in cases in which endophthalmitis is suspected or risk is high.

Retinal breaks are a common coincident injury in cases of IOFBs. Different opinions regarding treatment of breaks without detachment exist. Some surgeons believe the impact itself creates enough of an adhesion that additional treatment is not necessary. Others recommend laser or cryotherapy to all visualized breaks. Some authors recommend treatment prior to surgery, with time allowed for the scars to mature (typically one to two days). If the retinal break is associated with a retinal detachment, treatment of the break is universally recommended. Reattachment techniques include pars plana vitrectomy, retinopexy, gas tamponade and a scleral buckle procedure.^23-25

Endophthalmitis is a potentially devastating consequence of ocular trauma and develops in 8% to 13% of IOFB cases.³ Presentation >24 hours after injury, age >50 years, IOFBs composed of steel, and organic or soil-contaminated IOFBs are all risk factors for endophthalmitis. In cases in which endophthalmitis is suspected, antibiotics must be started immediately, and removal of the IOFB should proceed as soon as possible. As previously noted, systemic antibiotics with broad-spectrum coverage and adequate intraocular penetration are preferred (cefazolin, ceftazidime, vancomycin, and third- or fourth-generation fluoroquinolones are potential choices) in all cases. Oral fourth-generation fluoroquinolones (gatifloxacin and moxifloxacin) have also been shown to achieve significant levels of penetration into the vitreous cavity.^26,27

Intravitreal injection at the time of surgery is a critical component of management of cases of endophthalmitis with IOFB. A combination of vancomycin and either ceftazidime (preferred due to less retinotoxicity) or amikacin (better coverage of Bacillus species) should be used. If the situation involves a delay in surgical management, there may be a role for intravitreal antibiotic injection at the time of presentation with plans for surgical remediation as soon as feasible. The use of intravitreal antibiotics in cases without signs of infection is debated as the potential for side effects, such as allergy, toxicity and development of resistance, must be weighed against the potential benefits. Subconjunctival and topical antibiotics, in general, do not provide adequate penetration into the vitreous.^21,28

A pars plana vitrectomy is often necessary and, in fact, preferred for purposes of clearing inflammation, obtaining culture studies, decreasing infection load, irrigating toxins and allowing better distribution of antibiotics. The indications for pars plana vitrectomy from the Endophthalmitis Vitrectomy Study were limited to postoperative infections and do not apply in cases of trauma and IOFBs associated with endophthalmitis.²⁹

Adequate intraocular specimens, including the aqueous and vitreous and of the IOFB itself, should be sent for microbiology studies (gram stain and aerobic, anaerobic and fungal cultures). The clinical exam must be used in conjunction with the culture results as not all specimens from eyes with active infection will yield a positive result. Additionally, IOFBs can yield positive culture results, even in the absence of intraocular infection. The most common species of bacteria involved are Bacillus, Staphylococcus epidermidis, and Streptococcus species. Bacillus in particular tend to be aggressive and frequently cause rapid destruction of ocular tissues.³⁰

METALLOSIS

Retention of metallic IOFBs can lead to further damage to ocular structures. The two most concerning culprits are iron and copper. Siderosis bulbi, a result of iron retention, is characterized by iris heterochromia, mydriasis, decreased vision, lenticular deposits and cataract, as iron is accumulated in metabolically active cells. Electroretinographic changes are common and often irreversible; however, prognosis for siderosis can be good.³¹

Ocular damage from copper retention, or chalcosis, depends on the concentration of copper in the IOFB. Pure copper causes a fulminant panophthalmitis with poor prognosis that requires immediate treatment and removal of the retained material. If the copper content of the material is >85%, deposits accumulate on ocular structures and are visible clinically as Kayser-Fleischer rings, sunflower cataracts, iris and vitreous discoloration, and greenish refractile deposits on the retinal surface.³²

OUTCOMES

IOFB injuries carry a fairly good prognosis overall, with 60% of eyes achieving vision of ≥20/40 and 80% reaching ≥5/200.^3,33,34 Better outcomes are seen in cases of sharp mechanism of injury, anterior wound location, absence of lens damage, and wound <10 mm in maximum extent. Afferent pupillary defect, lens injury, dense vitreous hemorrhage, wounds >10 mm, large IOFB, posterior wounds, postoperative retinal detachment, BB gun injury, blunt force injury, extensive retinal damage and intraretinal IOFB all portend a less favorable outcome.^3,33,34

Proliferative vitreoretinopathy is an often-encountered sequela that can limit visual recovery. The risk of developing PVR seems to be related to intraretinal location of IOFBs, the presence of retinal breaks, choroidal hemorrhage, and multiple operations. Complete pars plana vitrectomy with removal of the posterior hyaloid may reduce the risk of PVR. Antiproliferative medications have been used with uncertain benefit.^25,34

Subretinal neovascularization may develop in any area where Bruch's membrane has been disrupted. Significant vision loss can result from neovascularization. Reports on management with laser photocoagulation in this setting are limited. Treatment with anti-VEGF agents has not yet been reported at the present time.²⁵

SUMMARY

Any case of an open-globe injury may harbor a retained IOFB, and it is essential to always rule out a foreign body in this setting. While these injuries have the potential to cause devastating visual loss, the majority of cases can be successfully managed with current surgical techniques. RP

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