An IOFB should always be suspected and ruled out in cases of ocular or orbital trauma. In most cases, an IOFB is either observed, or it is suggested by the presence of an entry site or the reported mechanism of injury. A detailed history helps the clinician assess the likelihood of the presence of an IOFB. As previously discussed, ocular imaging can be very helpful in the detection of IOFBs (Fig 18-6). If surgical removal of an IOFB cannot be accomplished promptly, intravitreal injection of antimicrobial agents should be considered to minimize the risk of endophthalmitis developing.
Surgical techniques for removal of intraocular foreign bodies
In the case of an IOFB, surgical planning should address the following issues:
location of the foreign body in the eye
surgeon’s ability to visualize and localize the foreign body
size and shape of the foreign body
composition of the foreign body (ferromagnetic vs nonferromagnetic)
encapsulation of the foreign body
Figure 18-6 Images from a patient with an intraocular BB pellet. Axial (A) and coronal (B) computed tomography views show the pellet’s position to be in the superior and posterior globe. B-scan echography (C) shows retinal detachment (arrow) and subretinal hemorrhage (H). A characteristic reverberation of echoes between the front and back surfaces of the round pellet gives a “trail of echoes” artifact that extends posterior to the foreign body on B-scan (asterisk) and on A-scan (D)
Pars plana vitrectomy allows removal of traumatized vitreous and facilitates controlled microsurgical extraction of IOFBs as well as media opacities such as cataract and hemorrhage (Video 18-1). Before forceps extraction is attempted, the IOFB should be freed of all attachments. A small rare-earth magnet may be used to engage and separate the foreign body from the retinal surface. Although small foreign bodies can be removed through enlargement of the pars plana sclerotomy site, it may be safer to extract some large foreign bodies through the corneoscleral limbus or the initial wound to minimize collateral damage.
Removal of large metallic intraocular foreign body.
Courtesy of Nur Acar, MD.
Access all Section 12 videos at www.aao.org/bcscvideo_section12.
Retained intraocular foreign bodies
The reaction of the eye to a retained foreign body varies widely and depends on the object’s chemical composition, sterility, and location. Inert, sterile foreign bodies such as stone, sand, glass, porcelain, plastic, and cilia are generally well tolerated. If such material is found several days after the injury and does not appear to create an inflammatory reaction, it may be left in place, provided it is not obstructing vision.
Zinc, aluminum, copper, and iron are metals that are commonly reactive in the eye. Of these, zinc and aluminum tend to cause minimal inflammation and may become encapsulated. However, any very large foreign body may incite inflammation and thereby cause proliferative vitreoretinopathy. Epiretinal proliferations, tractional retinal detachment, and phthisis bulbi may result in complete loss of vision. Migration of the foreign body also can occur, especially if it contains copper.
Chalcosis Pure copper is especially toxic and causes acute chalcosis. Prompt removal is required to prevent severe inflammation that may lead to loss of the eye. Foreign bodies with a copper content of less than 85% (eg, brass, bronze) may cause chronic chalcosis. Typical findings in chronic chalcosis are deposits in Descemet membrane (a sign similar to the Kayser-Fleischer ring in Wilson disease and the result of copper’s affinity for basement membranes), greenish aqueous particles, green discoloration of the iris, lens capsule (“sunflower” cataract), brownish-red vitreous opacities and strand formation, and metallic flecks on retinal vessels and the internal limiting membrane in the macular region. Late removal of copper may not cure the chalcosis; in fact, dissemination of the metal during surgery may worsen the inflammatory response.
Siderosis bulbi In siderosis bulbi, iron from IOFBs is deposited primarily in neuroepithelial tissues such as the iris sphincter and dilator muscles, the nonpigmented ciliary epithelium, the lens epithelium (see BCSC Section 11, Lens and Cataract, Chapter 5, Fig 5-14), the retina, and the RPE. Retinal photoreceptors and RPE cells are especially susceptible to damage from iron (Table 18-2). Electroretinography (ERG) changes in eyes with early siderosis include an increased a-wave and normal b-wave, a progressively diminishing b-wave amplitude over time, and eventually an undetectable signal during the final stage of iron toxicity of the retina. Serial ERGs can be helpful in monitoring eyes with small retained foreign bodies. If the b-wave amplitude decreases, removal of the foreign body is generally recommended.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.