Chapter 24

INTRAOCULAR FOREIGN BODIES

Ferenc Kuhn, Viktória Mester, and Robert Morris

IOFBs are traditionally defined as intraocularly retained, unintentional projectiles, although surgeons commonly remove objects of different types from the eye (see Table 24–1). IOFBs have typically caused so much concern to both patients and health care providers (from ancient barbers to modern ophthalmologists) as to prompt urgent extraction. This urge all too commonly has taken precedence over the most important goal: vision.¹

HISTORY

Ferenc Kuhn, Viktoria Mester, and Robert Morris

IOFB extraction dates back thousands of years²; the first successful magnetic IOFB removal was reported in 1624.³ The EEM, introduced by Hirschberg in 1789, became the ultimate tool with a high success rate in extracting fresh ferrous IOFBs, even if these were invisible. The EEM also served diagnostic purposes,⁴ verifying the IOFB’s magnetic nature by inflicting pain on the unanesthetized patient. The introduction of vitrectomy not only improved the results considerably: it refocused the ophthalmologist’s attention from IOFB removal to complex visual rehabilitation.⁵

EPIDEMIOLOGY AND PREVENTION

Incidencea:

• 18–41% among open globe injuries^6–9 (USEIR: 16%).

Age (years):

• average: 29–38^8,10–13 (USEIR: 31);

• range: 3–79^8,10–12 with 66% between 21 and 40¹⁴ (USEIR: 2–76 with 61% between 21 and 40 and only 3% being 60).

Sex: males in 92–100%^{8,10–13,15,16} (USEIR: in 93%). Place:

• work in 54–72%^8,12,13,16 (USEIR: 33%);

• home in 30%^8,16 (USEIR: 42%).

Cause:

• hammering in 60–80%^14–17 (USEIR: 53%);

• power or machine tools in 18–25%^14,17;

• weapon-related in 19% (USEIR).

IOFB injury is rare in persons wearing eye protection^10,18; in the USEIR, only 3% of patients claimed having safety goggles on when the injury occurred.

Occasionally, an IOFB has so much momentumb that the damage is incompatible with anatomical reconstruction (see Chapters 8 and 31). However, in the vast majority of cases the injury allows globe preservation via appropriate surgery, during which typically the following consequences must be addressed:

• entrance wound (must have occurred by definition);

• inflammation; and

• immediate and secondary

physical (mechanical);

chemical; and

other complications (e.g., endophthalmitis; see Table 24–2).

Entrance Wound

The IOFB must possess certain energy to perforate the eye’s protective wall. The length of the entry wound is predictive of the risk of retinal damage: the shorter the wound, the less energy to be lost during penetration (see Table 24–3).

Mechanical Intraocular Damage

Little or no damage is expected if the IOFB has completely lost its kinetic energy upon entry. Typically, however, intraocular tissue injury also occurs. The primary impact may be followed by additional impaction(s) via ricocheting (see Table 24–4 and the following). Blunt IOFBs are more destructive than sharp objects.²²

Source: F. Kuhn and R. Morris, unpublished data from the USEIR.

Inflammation

Breach of the eyewall, intraocular hemorrhage, and lens/vitreous admixture, among other lesions, incite an inflammatory response. Inflammation can cause synechia formation and IOP elevation and has been implicated in the development of PVR.²⁴

Chemical Implications

Metallic IOFBs are rarely pure.²⁵ The damage an alloy inflicts is generally proportional to the content of the harmful component.²⁶ Toxicity is more closely related to the active surface area than to the volume of the IOFB.^27,c

Siderosis

IOFB-related corrosion is caused by the interaction between trivalent iron ions and proteins primarily in the eye’s epithelial cells. The cytotoxicity involves enzyme liberation and lysosome breakdown, leading to cell degeneration.²⁸ The ferric iron, stored in siderosomes as ferritin, is thought to be toxic by generating free radicals.²⁹

Siderotic changes include the following clinical findings:

• iron deposits on the corneal endothelium;

• chronic open-angle glaucoma;

• brownish discoloration of the iris, leading to conspicuous heterochromia in people with light-colored irises^d;

• dilated, nonreactive pupil (another common first sign³²),^e which may also show light/near reaction dissociation and supersensitivity to weak miotics³³;

• yellow cataract with brown deposits on the anterior capsule;

• pigmentary retinal degeneration, eventually leading to attenuated vessels and visual field loss; and

• optic disk swelling/hyperemia.³⁴

The clinical diagnosis is confirmed by characteristic ERG changes such as:

• increased A wave initially; and a

• progressive reduction of the B wave subsequently.

The threat of siderosis is a powerful argument to remove all fresh ferrous IOFBs. Nevertheless, siderosis is not inevitable; see Table 24–5 for various misconceptions. If there is associated IOP elevation despite removal of the foreign body, filtration surgery may be required.

It is best to discuss all treatment options with the patient, who must make the ultimate decision in cases of a chronic IOFB with threatening or existent siderosis (see Table 24–6 for our guidelines). If an IOFB is retained, regular follow-up of the informed patient is necessary using visual acuity, slit lamp, IBO, ERG, and diagnostic x-ray spectrometry.³⁹ The ERG is especially important because electrophysiologic signs of siderosis may arise earlier than clinical changes.40 If the patient is not expected to return for follow-up, IoFB removal should be recommended.

Chalcosis

Once the danger of the acute reaction has passed, however, the risk of toxicosis drops dramatically and the IOFB may be tolerated for many years without complications.

Copper tends to deposit in membranes (e.g., Descemet’s, lens capsules, ILM^2,44) and causes destruction by increasing lipid peroxidation.²⁶ The typical clinical findings include:

• copper particles in the aqueous;

• green discoloration of the iris;

• greenish/brown-colored sunflower cataract with spokes of copper deposits radiating from a central ring;

• copper particles in the vitreous; and

• copper deposits on the retinal surface.²

Unlike siderosis, chronic chalcosis rarely leads to blindness, and even the associated cataract does not severely impede vision. Improvement may occur spontaneously or after surgical removal⁴⁵; conversely, the chalcosis may intensify despite successful IOFB removal due to the intraocular retention of copper powder².

“Inert” Substances

Substances generally well tolerated inside the eye (e.g., gold, glass, plastic, porcelain) may on occasion cause substantial damage⁴⁰:

• hot plastic can lead to massive foreign body reaction and eventual loss of the eye⁴⁶;

• aluminum may result in metallosis⁴²;

• sharp edges of glass can inflict secondary mechanical damage⁴⁷;

• lead may result in medically uncontrollable glaucoma⁴⁸;

• nucleus material left in the vitreous after cataract surgery may cause a foreign body reaction⁴⁹ (see Chapter 21).

EVALUATION

Based on a detailed history, inspection at the slit lamp and by ophthalmoscopy, and certain diagnostic tests (see later in this Chapter and Chapter 9), the ophthalmologist should (be able to) determine whether an IOFB is indeed present. The medicolegal implications are considerable; missed IOFBs constitute up to 56% of all trauma-related legal claims (see Chapter 7).⁵⁰ The following basic questions must be answered:

• Is there a foreign body?

• Is the foreign body truly in the eye (IOFB) or is it in the orbit?

• Are there multiple IOFBs?

• Exactly where inside the eye is the IOFB situated?

• What were the circumstances of the injury?

• What associated conditions are present (e.g., endophthalmitis, vitreous hemorrhage) or threaten (e.g., retinal detachment)?

History

Ask specific questions to determine the circumstances of the injury (when, where, how, by whom and what, distance, energy, material, etc.), and keep in mind that:

• most patients seek medical attention shortly after injury because of pain and/or visual complaints;

• if the history is suspicious but no IOFB is found, it is best to continue the search for an elusive IOFB54,55;

• IOFBS may not be discovered until siderotic signs appear³³.

External Inspection and Slit Lamp

An anterior entrance wound is commonly visible to the naked eye (use a penlight if necessary) or there may be warning signs (e.g., hemorrhage over the sclera, localized corneal edema, nonsurgical hole in the iris^g).

Reports on wound size vary widely (1 to 17 mm^16,60); most wounds are <5 mm. Slit-lamp biomicroscopy is mandatory, and a 90–diopter lens can provide additional information regarding IOFB position and com-position as well as the associated intraocular damage. Gonioscopy, performed after wound closure, may also be helpful (see Table 24–7 for literature data on the distribution of the entry sites).

Ophthalmoscopy

By also showing the damage to intraocular tissues (see Table 24–8 for literature data on risk factors) and the IOFB’s relationship to these tissues, information provided by direct visualization is superior to that by any other diagnostic technique.¹⁰ Especially if located anteriorly, however, IOFBS may be missed, even in the presence of clear media.²⁹

Ultrasonography

In the hands of an experienced clinician, ultrasonography is a very effective method to detect the presence and location of even nonmetallic IOFBs. It is the best indirect method to find associated tissue injuries such as choroidal and vitreous hemorrhages and retinal detachment^10,62 and to follow eyes after the primary repair.

With extreme caution, ultrasonography may be performed on eyes with an open wound;⁶³ alternatively, it is used on the operating table once the wound is closed. The B scan tends to overestimate the size of the IOFB and should not be used for measuring purposes.⁶⁴

For finding and localizing small, nonmetallic IOFBS in the anterior segment, ultrasound biomicroscopy is superior to CT, MRI, and contact B-scan ultrasonography.^65,66 It is limited in its ability, however, to distinguish between different materials and cannot be used if the globe has an open wound.⁶⁵

Although still widely used, this traditional method is slowly being replaced by CT as the primary radiological diagnostic tool. Inaccuracies have been described in numerous individual case reports and large studies.17,31,67–73 Screening by plain x-ray has been found unnecessary.74 Dental x-ray is more helpful by virtue of its bone-free image.

CT

With a sensitivity of 45 to 65% for IOFBs < 0.06 mm³and of 100%⁷⁵ for IOFBs >.06 mm³, CT is the best indirect method for both detecting and localizing IOFBs. Appropriate software and technique allow some differentiation of IOFB composition, although CT still cannot distinguish between various types of metals.^62,76,77

Although both are able to find IOFBs as small as 0.048 mm^3,75 helical (spiral) CT:

• provides an image superior to that of a conventional axial CT^80,81;

• has a shorter examination time;

• has the ability to reconstruct coronal/sagittal images without further scanning; and

• reduces motion artifacts and radiation.⁸²

MRI

A powerful tool for cross-sectional and soft-tissue analyses, MRI is very sensitive in detecting IOFBs, allowing discovery even when performed for nonophthalmological indications.⁸³

Having been supplanted by superior diagnostic methods90 or because they are not commercially available,³⁹ metal detectors are rarely used today.

Table 24–9 summarizes certain shortcomings of ultrasonography, plain x-ray, and CT; Table 24–10 shows some of the potential diagnostic traps, threatening even when different evaluation methods are combined.¹⁰ It must be emphasized that in the vitrectomy era:

• accurate preoperative IOFB localization is less important;⁵⁵ and

• the IOFB may move from its predetermined position before or during surgery.³⁷

MANAGEMENT STRATEGY AND COUNSELING

Before designing and discussing with the patient the management plan, all data must be analyzed carefully to answer the following crucial questions:

• Is this a high-risk injury?^j If yes, immediate intervention is advised.

• Is a retinal break and/or detachment present? The more likely that retinal damage has occurred (see Table 24–4), the more urgent the intervention. If media opacity prevents retinal visualization, use indirect clues such as:

wound length (see Table 24–3);

circumstances of the injury (the greater the kinetic energy of the object and the sharper it is, the more likely that deep penetration has occurred); and

wound location (i.e., corneal vs. scleral).

Additional helpful factors to consider are:

• IOFB characteristics (see Table 24–11);

• risks and types of associated intraocular tissue damage (see Table 24–8);

• the surgeon’s experience, expertise, and the equipment available; and

• the legal environment.

FIGURE 24–2 shows the management options; remember that:

• if they are fresh, even inert IOFBs are best removed (see Figs. 24–3 and 24–4, and Table 24–12);

• if IOFB removal is decided upon and the eye shows associated tissue damage, it is better to perform complex reconstruction simultaneously than as a secondary reconstructive procedure because:

vision is not improved just by IOFB removal;¹⁴ and

the risk of endophthalmitis is reduced only if the “cultured media” (i.e., vitreous) is also promptly removed^9,23;

• in cases of posterior segment IOFBs, a decision must be made whether to perform vitrectomy:

the more extensive the intraocular tissue damage, the more vitrectomy is indicated to treat existing lesions and to prevent subsequent retinal detachment⁹¹;

an IOFB invisible due to vitreous hemorrhage is an absolute indication.

In addition, decisions must be made regarding:

• instrumentation (see later in this Chapter);

• timing (see later in this Chapter); and

• the use of prophylactic antibiotics (see Chapter 28 and the Appendix).

General anesthesia is preferred, especially if the IOFB is in the posterior segment. If the intervention is urgent (high-risk case) and the patient ate recently, alternative methods are available (see Chapter 8).

SO has become so rare (see Chapters 8 and 29) that we feel it justified not to consider it as a major factor when the management plan is designed. The patient must nevertheless be fully informed (see Chapter 7), especially when deciding whether to retain a permanently blind eye, and careful follow-up is always advised.

TIMING

Literature data regarding the optimal time for intervention are conflicting. Endophthalmitis prevention is the primary goal (Table 24–13), for which as early surgery as reasonably possible is recommended for both medical and legal reasons.^k Conversely, a recent study has confirmed earlier reports that there is no difference whether surgery is performed in the first 48 hours or later.⁹² Delaying the intervention never-theless requires vigilance (see Chapter 28) to quickly note signs of a developing infection.^l

• IOFBs in the AC are usually removed at the time of primary repair.

• Intralenticular IOFBs are typically extracted in conjunction with cataract removal.

• IOFBs in the posterior segment require careful analysis of the risks and advantages (see Table 24–14).

Certain additional factors to consider (see Chapter 8 for details):

• less experienced surgeons may want to delay the intervention because:

the earlier the surgery is performed, the greater the danger of the development of difficult-to-control intraoperative hemorrhage;

spontaneous detachment⁹³ makes the critical step of posterior hyaloid face removal technically easier⁴² while significantly improving the prognosis⁹⁴;

early intervention may reduce⁹¹ the current 11%²⁴ incidence of PVR development;

• especially in cases of central corneal wounds, edema may initially prevent adequate visualization; intensive steroid therapy can substantially improve conditions in just a few days;

• the delay should not exceed 14 days: a few weeks will increase almost fourfold the risk of proliferation and subsequent tractional retinal detachment⁹³;

• no statistically significant visual/anatomical difference is seen whether vitrectomy is performed during the first or the second week after injury⁸;

• spontaneous posterior hyaloid detachment may occur in a few days,^95,m especially if vitreous hemorrhage is present.⁹⁶

Stay updated, free articles. Join our Telegram channel

Join

Full access? Get Clinical Tree