Intraocular Foreign Bodies (IOFB)
Intraocular foreign body (IOFB) injuries vary in presentation, outcome, and prognosis depending upon various factors. IOFBs can cause perforating or penetrating open globe injuries. The visual prognosis depends on the zone of injury, type and size of foreign body and the subsequent complications. Increased awareness about eye protection, improved surgical techniques, and advancements in bioengineering are responsible for an improved outcome in injuries with IOFB.
Intraocular foreign bodies are seen in 17%-40% of penetrating ocular injuries and represents 3% of all emergency room visits in the United States. Risk factors including metal-on-metal tasks, lack of eye protection, or male gender. These injuries commonly occur at work or at home according to the US eye injury database (Ferenc). The majority of patients injured are between 21 and 40 years of age. The majority of foreign bodies (58-88%) enter the posterior segment.
The location and damage caused by an IOFB depends on several factors including the size, shape, and composition of the object as well as the momentum of the object at time of impact. FBS can cause direct damage via entry into the eye but can also ricochet in the eye causing further damage. Subsequent damage depends on the composition of IOFB.. For example, iron or copper FBs can cause siderosis bulbi or chalcosis, respectively. Inert substances such as glass, stone, and plastic are better tolerated than metals such as copper or iron. Metallic and magnetic objects are the most common IOFBs. Organic material such as vegetable matter or cilia cause severe tissue reaction, are highly contaminated and associated with a significant risk of endophthalmitis. In addition, the mechanism of entry and size of the object are also factors in extent of injury. Foreign bodies entering the sclera usually cause more damage than those entering the cornea. High-speed, small FB will cause a small linear laceration that is less damaging than blunt trauma. Large irregular IOFBs, however, can cause significant initial damage.
A detailed history is very important in IOFB injuries to ascertain the type or material of the foreign body and mechanism of injury. In addition, unilaterality or bilaterality should be determined as well as extraocular injuries to appropriately manage the patient. Explosives and firearms (which are usually a combination of copper and lead) usually cause bilateral ocular damage with multiple foreign bodies. Patients might be asymptomatic or often report a sensation of something entering the eye with no obvious external changes and the incident may be dismissed initially. Other patients may notice decreased vision, a foreign body sensation, redness, tearing, flashes or floaters. Still others might be asymptomatic but on exam an small entry wound is found. History and documentation in the medical record is critical for any medical-legal issues or workman compensation. In addition, the patient should be asked when they last ate or drank for potential surgical planning.
Visual acuity and pupillary examination should be documented with attention to pupil shape, afferent pupillary defect or anisocoria. If a ruptured globe is suspected, applanation tonometry or other exam techniques that put pressure are the globe are typically not suggested until the wound have been closed to prevent expulsion of ocular contents. Careful examination of eyebrows/lids should evaluate for any lacerations, canalicular injury, or small foreign bodies. A full slit lamp examination should be performed. A scleral entry site may be seen with an area of conjunctival injection, hemorrhage, or chemosis with or without a conjunctival laceration. Pigment over the scleral entry site may suggest uveal tissue prolapse. Entry sites in the cornea may be seen as a disruption in the smooth surface with corneal edema surrounding the entry site and/or a positive Seidel test. However, a negative Seidel test does not rule out a penetrating injury and could be present with a self-sealed wound. Iris transillumination defects or iris heterochromia may be also be signs of a perforating injury. Using the entry point either at the cornea or sclera and the disruption point of the iris may help in localizing the IOFB by creating a trajectory path. Close examination of the natural lens for a focal opacity, especially the lens periphery, or phacodynesis may also provide a clue regarding the trajectory of the FB. It is best to examine the iris before dilatation and the lens after dilatation.
Gonioscopy is valuable to visualize the angles if suspicion exists about an IOFB in the angle. However, gonioscopy should be performed carefully to prevent any tissue prolapse and may be deferred if inappropriate. Dilated fundus examination usually reveals the IOFB when it is in the posterior segment. Fundus examination can be difficult if a hyphema or vitreous hemorrhage is obscuring the view. Scleral depression generally is not recommended when an IOFB is suspected and the wound is not self-sealing. However, peripheral retinal examination should be performed as best as possible to look for the IOFB.
Localization and confirmation of diagnosis
Localization of the IOFB is the prime aspect of management. The first question to answer is whether the IOFB is in the eye (anterior or posterior) or in the orbit. Before the development of CT scans, a standard X-ray was used for localization. Plain X-ray is useful in radio-opaque foreign bodies only and will not detect radiolucent IOFBs such as wood or glass. The standard “foreign body x-ray series,” includes Water’s, Caldwell, and lateral views. Plain x-ray films, with Caldwell or Water’s projections, may demonstrate the presence, but not the location of the IOFB.
The Sweet localization technique involves frontal and lateral projections. A foreign body within the globe can be localized with a bone-free examination by eye movement. This study localizes the foreign body to either the anterior or the posterior segment of the eye. If the foreign body is in the anterior segment, the object will rotate in the same direction as the eye and if it’s in the posterior segment, it will move in the opposite direction as the eye.
Localization using metal locators either placed on the eye with a contact lens or sutured to limbus may also be done. This may help by localizing the foreign body either to the anterior or the posterior segment of the eye. The various metal locators are Berman, Roper-Hall, and Bronson-Turner.
Computed tomography provides much more reliable information regarding the size, shape, and localization of the foreign body and is the preferred imaging modality. MRI is not used for metallic IOFB given the potential to dislodge the foreign body and cause further destruction and should never be the initial imaging modality of choice after trauma. MRI may be more effective in localizing nonmetallic IOFB such as wood, but should only be used if there is 100% certainty that the object is non-metallic. Ultrasound can be a useful adjunct in localizing IOFB and to determine if the object is metallic. It should be performed carefully in cases of an open globe injury. Ultrasonography is useful to determine the extent of the intraocular damage, retinal detachment, double perforation, as well as foreign bodies not seen on x-ray studies particularly in cases with intraocular blood. Ultrasonography can assist in identifying the nature (air, glass,etc) and shape of the IOFB. Ultrasound biomicroscopy and/or gonioscopy can be used if FB in the angle is suspected. These tests should be performed with caution to prevent expulsion of intraocular contents.
Treatment of the injured eye with an IOFB includes protection of the globe with a shield, not a patch, avoiding any pressure over the globe. Tetanus status should be determined and updated as needed. The surrounding area should be cleaned and small pieces of foreign bodies around the eye should be removed, especially in cases of explosives. A delay in management can increase the risk for infection. Broad-spectrum intravenous antibiotic prophylaxis should be started especially that covers virulent pathogens including Bacillus and Clostridium. Vegetable matter poses high risks for endophthalmitis and should be removed urgently. High-speed small metallic objects that usually self-sterilize and inert FB may be removed at a later time after the initial wound is closed. The definitive management is surgical. During surgery, the conjunctival opening should be carefully created, taking care to remove superficial foreign bodies and to avoid any damage to prolapsed uveal tissue.
It is necessary to determine if IOFB is anterior or posterior to the iris because the surgical approach will vary. The eye is stabilized by closing the open wound first. If the IOFB is in the anterior chamber, it can often be removed using a limbal incision and using viscoelastic solution/OVD to maintain the chamber and protecting the corneal endothelium. Special techniques may be needed to remove the FB embedded in the iris, ciliary body or the lens. Pars plana vitrectomy (PPV) is used to remove IOFBs from the posterior chamber. The technique of extraction depends on the composition and the size of the object. Retinal tears and detachment are treated with gas or oil tamponade after the FB is removed. Intravitreal antibiotics with vancomycin and ceftazidime may be considered for contaminated FBs.
Anterior Intraocular Foreign Body (IOFB anterior to the iris plane)
No lens involvement:
If the lens is not involved, the pupil should not be dilated or constricted by miotics to prevent any further injury to the lens. A careful examination to look for the entry wound should be performed and if needed, the suspected wound can be explored. Any wound that is not self-sealing is closed using the suture of choice for the specific tissue. Reforming and maintaining the anterior chamber (AC) depth is of utmost importance prior to removing the IOFB. Usually an injection of balanced salt solution or a viscoelastic through the paracentesis port is recommended. Even self-sealed entry wounds can re-open while forming the anterior chamber, so careful manipulation is suggested. Injection through the entry site should not be done. Viscoelastic solutions are preferred for their ability to better maintain AC depth and protect the corneal endothelium. It is important to remove any residual viscoelastic at the end of surgery to reduce the risk of intraocular pressure rise. Removal of the IOFB is not recommended through the original entry wound. The foreign body should be removed through a surgical incision depending on the location and size of the foreign body. Usually a shelved incision that is the size of the IOFB is created either in clear cornea or sclera. A 20-gauge rare earth magnet may retrieve the object through the surgical incision if it is metallic and small. Nonmagnetic objects or large magnetic objects are best managed with intraocular forceps. Care should be taken while removing the foreign bodies to avoid any injury to surrounding tissue. Samples of any anterior chamber aspirate maybe sent for microbiological evaluation if signs of infection are present or infection is suspected.
With lens involvement :
If the IOFB has damaged the lens or caused subluxation, lensectomy should be performed. Generally, patients are young with a soft nucleus that can be removed via phacoemulsification or a manual extracapsular cataract extraction (ECCE) may be performed. Concurrent intraocular lens (IOL) insertion is usually not performed because calculation of the IOL power may not be exact and to avoid postoperative complications such as severe inflammation as is expected in such cases. Anterior capsule rim should be saved where possible, for future IOL implantation.
Posterior Intraocular Foreign Body
External approach - Small magnetic IOFB in the region of the pars plana.
Accurate localization is necessary to mark the incision point. Preoperative ultrasound biomicroscopy helps to localize the metallic foreign body in the pars plana region. Careful conjunctival opening should be performed, as the foreign body may be present just external to the eye in the sub-conjunctival space. If necessary, the rectus muscles are isolated and tagged for better exposure. Either a partial-thickness scleral flap or a full-thickness sclerotomy is performed after localizing the IOFB precisely. Diathermy is applied to the choroid. A pre-placed mattress suture is placed. Anterior chamber paracentesis is performed to avoid any prolapse of intraocular contents. An external electromagnet is placed over the sclerotomy site and turned on. The choroid should tent indicating the magnetic IOFB is in this location. Occasionally, the IOFB will directly extrude through the choroid when the electromagnet is on; however, an incision in the choroid is usually required for the IOFB to pass through the choroid. Diathermy at this point would be helpful to avoid any bleeding. If vitreous it noted to prolapse with the IOFB, sharp scissors are used to cut the vitreous. It is better to avoid cutting the prolapsed uveal tissue to avoid bleeding and to instead cauterize the prolapsed uveal tissue. When the IOFB is removed, the sclerotomy site is closed with the pre-placed mattress suture. Indirect ophthalmoscopy is performed to detect and treat any retinal tears that may be present.
Major complications of the external approach are extrusion of intraocular contents with retinal incarceration and possible hemorrhage. Reducing the intraocular pressure with AC paracentesis and external pressure on the globe at the time of IOFB removal reduces this complication. Occasionally, the IOFB is difficult to remove with the external electromagnet because the magnetic strength is not sufficient to overcome the force holding the IOFB due to encapsulation. In such situations, an internal approach is recommended.
An internal approach is used in cases with opaque media and large, nonmagnetic, or subretinal IOFB that cannot be managed through an external approach. A standard 3-port vitrectomy is performed. Sclerotomy incision should avoid the area of the entry wound to prevent further damage to intraocular tissues if any incarceration is suspected. The first goal of the vitrectomy is to remove any adhesions of the IOFB, to avoid any pull on the retina. Once the foreign body is free from all the adhesions, it can be removed with forceps or a magnet. Before removing the foreign body, peripheral examination of the retina and removal of the peripheral vitreous should be performed to avoid any traction while removing the foreign body through the sclerotomy. If the IOFB is larger than the sclerotomy site, enlargement of the sclerotomy in a circumferential direction may be necessary. A very large IOFB is best managed through a limbal incision after a lensectomy. A limbal or scleral tunnel is created and should be large enough to accommodate the IOFB. The IOFB is grasped and brought into the AC through the pupil. The corneal endothelium should be protected with viscoelastic solution. The infusion line is turned off to reduce the risk of iris prolapse. A second forceps is introduced through the limbal incision to grasp the IOFB and extract it out of the eye. The limbal incision is closed. If the IOFB is intraretinal or subretinal, the IOFB is grasped and may be removed through the retinal impact or entry site. Retinal blood vessels should be cauterized to avoid any pre-retinal or subretinal hemorrhage. If the foreign body is encapsulated, the capsule needs to be dissected with forceps or scissors. Once the foreign body is free from the capsule, it can be removed with a magnet or forceps through the sclerotomy. Care should be taken to avoid any injury to the peripheral retina while removing the IOFB through the sclerotomy. Retinal tears/retinal detachment can be caused by the foreign body or by manipulation during the procedure.
Use of intravitreal antibiotics should be considered in contaminated cases. For endophthalmitis prophylaxis, intravitreal vancomycin (1.0mg/0.1ml) and ceftazidime (2.25mg/0.1ml) is given. In patients allergic to penicillin, intravitreal amikacin (0.4mg/0.1ml) may be given instead of ceftazidime. In cases where fungal infection is suspected, intravitreal amphotericin or voriconazole is indicated. Systemic antibiotics (oral or intravenous) are usually used for a week as well.
Frequent post-operative examinations are performed in ensuing weeks and months for evaluation of any post-operative complications such as the following:
- Endophthalmitis: Infection is reported in 2% - 48% of IOFB cases; a higher rate is noted if organic FB is involved. The risk factors for developing an infection include delayed removal of IOFBs, posterior open globe injury, a contaminated setting, a large wound, delayed administration of antibiotics, and lens capsule injury. If signs of infection (hypopyon, increased pain with vitritis) are noted, prompt treatment with intravitreal and systemic antibiotics is recommended. An emergent PPV should be performed in a setting of retained IOFB with endophthalmitis.
- Anterior segment injuries including corneal scar, traumatic cataract, or hyphema can be seen in up to 60-75% of cases with IOFBs that progress with time and need to be addressed medically or surgically. Angle recession glaucoma can also be seen.
- Retinal tear or detachment is seen in 5%-40% of eyes with IOFBs. Post-operative RDs have a poor visual prognosis.
- Proliferative vitreoretinopathy (PVR): Extensive fibrous growth and contraction of scar tissue can be seen in eyes with open globe injury. the development of PVR may depend on the extent of injury and the size of the FB.
- Sympathetic ophthalmia is seen in 0.2% - 2.0 % of cases. Clinical symptoms include photopsias, pain, decreased vision with signs of red eye, uveitis, vitritis, creamy white deep retinal nodules, vasculitis and choroiditis in the fellow eye. It is managed with steroids with immune modulation therapy.
- Optic neuropathy can be seen acutely with direct trauma to the optic nerve by the FB. Metallosis (siderosis, chalcosis) due to retained FBs (iron, copper, zinc or nickel) can also give optic neuropathy with time.
Prognosis largely depends upon multiple factors (see Table):
|Better visual prognosis||Poor visual prognosis|
|Normal lens||Poor presenting visual acuity|
|Absence of lens injury||APD|
|Decreased wound length||Increased wound length|
|Anterior segment IOFB||Posterior segment IOFB|
|Older age||Younger age|
|Use of PPV rather than magnets for posterior located IOFB||No PPV for posterior IOFB|
|Lack of RD||RD|
|Absence of endophthalmitis||Endophthalmitis|
|Culture of nonvirulent organism|
|Metal-on-metal mechanism of injury|
- Features of the ophthalmic exam that may be predictive of long-term visual acuity using the "OCULAR TRAUMA SCORE" include:
- Presenting visual acuity
- The presence or absence of endophthalmitis
- Globe rupture
- Perforating injury
- Retinal detachment
- Afferent pupillary defect
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