An intraocular foreign body on X-ray. (a) Coronal scan; (b) lateral scan. White arrow shows the IOFB
Computed tomography (CT), with its high resolution and positive rate comparing to X-ray, is considered to be the gold standard for the diagnosis of IOFBs , especially for diagnosing small metallic foreign bodies and nonmetallic foreign bodies. CT helps display the structure of the eyeball and can clearly localize the anatomical position of the foreign body. Furthermore, ophthalmologists can estimate the nature of the foreign bodies according to their CT values and artifacts. Both the plain scan and coronal scan should be taken for accurately locating the IOFBs. Characteristics and images of different IOFBs on CT are shown in Table 4.1 and Figs. 4.2, 4.3, and 4.4. The normal CT values of intraocular structures are shown in Table 4.2.
Characteristics of different IOFBs on CT
Nature of IOFBs
High-density images (CT values, 1000–2000 HU)
Stone, glass, bone, silicon oil, etc.
High-density images (CT values, >300 HU)
Slightly hyperdensity, mixed density, or low-density images
An iron foreign body on CT. Left: plain scan; right: coronal scan
A glass foreign body on CT imaging (white arrow)
A plant foreign body on CT imaging (white arrow)
CT values of intraocular structures
Magnetic foreign body is the contraindication of magnetic resonance imaging (MRI) examination because its translocation under MRI may cause second damage to the eye. An MRI examination is of value when there is a high suspicion of nonmetallic IOFBs, especially wooden foreign body with a negative CT image (Fig. 4.5) . Nonmetallic IOFBs show low signal on both T1W1 and T2W1 sequences. Vitreous and aqueous humor shows low signal on T1W1 sequence and high signal on T2W1 sequence. Nonmetallic IOFBs are easily recognized on T2W1 sequence.
An orbital wooden foreign body on MRI (white arrow)
Under B-scan examination, the appearance of IOFBs could be intraocular strong echoes with posterior acoustic shadow (Fig. 4.6). Combined with single high waves in A-scan, IOFBs can be accurately diagnosed. What should be pointed out is that A/B-scan is not suitable for patients suffering severe traumatic eyeball rupture or combined with complex eyelid laceration before the eye is closed by surgery.
An intraocular foreign body on A/B ultrasound (white arrow)
Ultrasound biomicroscopy (UBM) examination plays an important role in showing anterior segment IOFBs (Fig. 4.7), especially for tiny foreign bodies (<1 mm) which located in the anterior chamber, equator lentis, or near the ciliary body. These kinds of foreign bodies have little influence on visual acuity in the early days after injury and can be hardly found by routine ocular exams. All kinds of foreign bodies could appear strong echoes without posterior acoustic shadow in UBM, no matter it is metallic or nonmetallic foreign bodies.
An intraocular foreign body on UBM (black arrow)
When an IOFB is suspected, the injured eye should be bandaged sterilely and immediately. Anti-infection and anti-tetanus therapies should be performed before the emergency surgery.
The purpose of emergency surgery is to close the wound of the eye, reconstruct the anterior chamber, recover, and maintain the intraocular pressure immediately. For IOFBs, they should be removed as early as possible because of the potential risk of endophthalmitis and its toxicity [4–6]. However, timing of IOFB removal is controversial presently [7, 8]. Magnetic foreign bodies located in the clear anterior vitreous cavity can be attracted out by using a magnet at pars plana sclerotomy site. Foreign bodies in the anterior chamber can be precisely extracted by using different intraocular forceps according to the size of the IOFBs. All kinds of IOFBs can be removed precisely using vitrectomy no matter what characters of foreign body and where the foreign body located in the posterior segment. Meanwhile, the vitreous inflammatory factors, vitreous hemorrhage, IOFB-induced proliferative vitreoretinopathy (PVR), and other disorders in the posterior segment can be completely treated during vitrectomy.
Some complicated cases need secondary surgery to help with the reconstruction of the intraocular structure.
4.3 Illustrative Case(s) of Intraocular Foreign Bodies
Location and size of the IOFBs may result in vision loss independently, regardless of the type of injury and characteristic of the foreign body. The following cases illustrate the IOFBs involved in various parts of the injured eyes and some specific cases. According to recent studies, 58 % IOFB locates in posterior segment, 13–24 % in anterior segment, 7–10 % in lens, 25–48 % in vitreous, 16–44 % in retina, 52 % in both retina and choroid, and 0–15 % subretinally  (Figs. 4.8, 4.9, 4.10, and 4.11).
An iron foreign body imbedded in the superficial corneal stroma, with rust ring and corneal edema surrounded. The slit illumination is used in the appreciation of the exact depth of the foreign body
(a) An eye suffered from a penetrating injury including cornea, iris, and lens. An irregular metal IOFB was embedded in the cornea, iris, and lens at 1 o’clock position (black arrow). It has caused the pupil deformation, iris laceration, and focal opacity of the lens. Vision was seriously impaired. (b) An eye suffered from a penetrating injury. An eyelash was located in the anterior chamber and was removed from the anterior chamber during vitrectomy. The removed eyelash is shown on the contact lens (white arrow). The eyelash might bring microorganisms to the eye and cause severe endophthalmitis
(a) An iron IOFB was embedded in the inferior-temporal retina. The obvious retina edema was seen just surrounding the IOFB, which might eventually develop to retinal detachment. A crescented retinal hole was located above the IOFB with tiny retinal hemorrhage (black arrow). It is suspected that the IOFB dropped on the retina resulting in the crescented retinal hole and then bumped to the fixed position of the retina. The best corrected visual acuity (BCVA) was 20/50. (b) B-scan ultrasonography demonstrated the IOFB located in the retina (white arrow)
(a) An irregular glass IOFB was lying on the retinal surface. It has induced a fibrinous reaction around the IOFB. (b) The IOFB was successfully removed by enlarging the sclerotomy
4.3.1 Giant IOFB
A 45-year-old man presented with a 12-h history of a transverse irregular corneal laceration from 3 o’clock to 9 o’clock position with iris and vitreous prolapse after being hit by a piece of iron in the left eye. The wound was closed by primary repair of corneoscleral laceration on the first presentation day. His left eye had best corrected visual acuity (BCVA) of no light perception. Slit-lamp examination presented chemosis, corneal edema, disappearance of anterior chamber, intraocular hemorrhage, and traumatic cataract. Fundus details were not clear due to severe vitreous hemorrhage. B-scan ultrasonography identified a hyperechogenic shadowing that was concerning for an IOFB (Fig. 4.11a). Computed tomography showed a metallic IOFB in the vitreous (Fig. 4.11b). Examination of the right eye was unremarkable.
Eight days after primary repair, we removed the IOFB through an open-sky corneal incision followed by a 23-gauge pars plana vitrectomy (PPV) using a TPK. Firstly, the irrigation-aspiration was performed for removing the exudates and hemorrhage in the anterior chamber (Fig. 4.11c). Then injured cornea was excised using a 7.25-mm trephine (Fig. 4.11d), and the corneal graft was protected by a viscoelastic material and kept in a humid container. After the inflammation tissue of the anterior segment was removed, the IOFB appeared and was separated completely from all surrounding tissues. Then it was grasped with forceps and extracted through the open-sky corneal incision (Fig. 4.11e, f). PPV was performed by using a TPK which included membrane peeling, use of perfluorocarbon liquids, photocoagulation, and silicone oil filling. At the end, the patient’s injured corneal graft was sutured back with 10-0 Vicryl suture.
Removal of a giant IOFB by the traditional technique usually requires a relatively large sclerotomy which can damage the ciliary body and peripheral retina because it is difficult to precisely locate the position of the IOFB and fully expose the posterior globe wall . Similarly, removal of a giant IOFB through the corneal limbus incision combined with PPV also has their limitations. Kunikata et al.  showed two cases of 25-gauge microincision vitrectomy surgery for removal of large IOFB through the 2.4- or 3.0-mm corneal incision. However, this technique is best suited to long slender smooth foreign body and cannot be used for giant and irregular-shaped foreign body.
In this case, open-sky approach presents the following advantages. Firstly, it allows easy and direct access to the giant IOFB, so that the surgical damage to retina, ciliary body, or other ocular structures can be avoided. Secondly, the surgeon can grasp the giant IOFB easily and steadily with forceps, which prevented accidental slippage. Thirdly, it is a useful method in treating patients with giant IOFBs complicated with severe corneal opacity and laceration. The limitation of our method which is open-sky approach itself might threaten the healing of cornea incision and neovascularization.
4.3.2 Posterior Segment Intraocular Metallic Foreign Body Existence of 10 Years Causing Chronic Uveitis and Secondary Glaucoma
A 49-year-old man presented with a progressive blurred vision, pain, photophobia, and redness in the left eye for 10 years and worsened for 3 months. He had a history of penetrating injury in the left eye 10 years ago and was diagnosed traumatic cataract and IOFB. There was no information about the ophthalmic examination and ocular symptoms of the patient at that time. He underwent a successful cataract surgery and intraocular lens implantation 5 months after the injury. However, it was unknown whether the foreign body was removed or not. Three months ago, he returned with visual impairment and intraocular inflammation in the left eye, and topical antibiotics and medical treatment were given for photophobia, pain, and redness. However, the symptoms were not alleviated. On presentation, the visual acuity was light perception and IOP was 46 mmHg in the left eye. The left eye examination revealed chemosis, corneal edema, flare in the anterior chamber, and stale iris laceration. The fundus was not clear. Ocular ultrasonography demonstrated only a vitreous opacity in the left eye (Fig. 4.12a). Neither X-ray nor CT revealed an IOFB (Fig. 4.12b). Systemic and topical antibiotics as well as steroids were given, but no improvement was seen in vision and sign. Because of a clinical suspicion of an IOFB in posterior segment and secondary glaucoma, a 23-gauge vitrectomy combined with trabeculectomy was performed. A 2-mm long metallic foreign body was found at 6 o’clock of ora serrata and was removed from the sclerotomy site (Fig. 4.12c, d). The stale iris laceration induced by IOFB and iridectomy for trabeculectomy was seen clearly (Fig. 4.12d). Two months after the foreign body removal, the symptoms of uveitis and glaucoma disappeared. The final BCVA was 20/100 and IOP was 13 mmHg without intraocular inflammation (Fig. 4.12f). The visual field defect significantly appeared at the final follow-up (Fig. 4.12g).
(a) B-scan ultrasonography indicated a hyperechogenic shadowing that was concerning for a foreign body. (b) CT demonstrated a metallic IOFB in the vitreous cavity. (c) The irrigation-aspiration was performed for removing the exudates and hemorrhage in the anterior chamber. (d) The injured cornea was excised using a 7.25 mm trephine. (e, f) The foreign body was grasped with forceps and extracted through the open-sky corneal incision. It was an irregular-shaped and measured of 10 mm long, 7 mm wide, and 4 mm thickness foreign body
4.4 Current Consensuses on Intraocular Foreign Bodies
4.4.1 General Rules
As a general rule, a fresh IOFB should not be left in the eye after open-globe injury. However, if the IOFB is verifiable inert, and no signs of endophthalmitis was observed, early surgery should be considered carefully for its risk of potential complications may possibly bring more damage to the eye than the IOFB itself. In cases of posterior segment IOFBs, a decision of vitrectomy or not must be made in time: the more severe tissue damage is, the more indication of vitrectomy is given to remove the IOFB and prevent subsequent damage to the intraocular structure . An invisible IOFB due to severe vitreous hemorrhage or inflammation is an absolute indication. Furthermore, decisions must be made depending on the condition of instruments, surgical timing, and preoperational prophylactic antibiotics .
The surgical plan should be well discussed once the IOFB has been accurately localized. Some IOFBs may be well tolerated, such as glass particles or alloys, and a decision of observation could be made in the first instance. This especially applies when the visual acuity remains fine. When an IOFB is decided not to be removed immediately, intravitreal antibiotics is wildly accepted and used as a prophylactic measurement against infectious endophthalmitis . IOFBs in the posterior segment require to be carefully analyzed for the risks of endophthalmitis. Ophthalmologist should also consider the surgeon’s experience and expertise, the equipment availability (at night versus in the daytime), the patient’s general condition, and the legal environment .
4.4.3 Instruments and Management
Magnets are commonly employed for the majority of magnetic IOFBs (Fig. 4.13). Two types of magnets exist: internal rare earth magnets and external magnets. The iron content of the IOFB, location, and visibility within the globe determine which one to be used [15, 16]. External magnets are capable of generating great force but are bulky, restricted to use outside the eyes, and therefore, provide less control. Rare earth magnets are smaller, create a more unidirectional magnetic field, and are capable of fine control. They generated less force and are consequently restricted to intraocular use where they can be placed in close proximity to the IOFB. Their use in the posterior segment requires concurrent pars plana vitrectomy surgery. Inaccurate localization of an IOFB or incorrect use of magnets may cause numerous complications, including inadvertent traction on vitreous base and retina, or impaction of the IOFB into the lens . The internal rare earth magnet requires the use of intraocular foreign body forceps for extraction since the type of magnet lacks the strength for trans-scleral IOFB delivery . In most cases, even with external magnet, the IOFB is generally aided with forceps through the scleral as well .
(a–g) A 49-year-old man presented with a progressive blurred vision, pain, photophobia, and redness in the left eye for 10 years and worsened for 3 months. He had a history of penetrating injury in the left eye 10 years ago. Traumatic cataract surgery was performed successfully after initial ocular injury. Whether the IOFB was removed or not was unknown. (a) B-scan showed a vitreous opacity in the injured eye. (b) CT didn’t reveal an IOFB. (c) A 2-mm long metallic foreign body was found at 6 o’clock of ora serrata in the surgery (white arrow). (d) The foreign body was grasped and extracted by an intraocular forceps (white arrow). (e) The stale iris laceration induced by IOFB and iridectomy for trabeculectomy can be seen clearly. (f) The optic nerve atrophy was revealed, and the ratio of C/D was 0.9. (g) Visual field defect appeared at the final follow-up