Foreign Body in the Eye

Foreign bodies (FBs) in the eye are a common problem. If the mechanism involves the foreign body travelling at high speed, it is important to consider the possibility of a penetrating eye injury. The growing use of contact lenses means that individuals are increasingly presenting with problems relating to these such as a piece of lens being retained in the eye. Most cases are trivial but some require referral to an ophthalmologist.

You may find our records on Eye Trauma, Conjunctival Problems (which includes a section on conjunctival FBs) and Contact Lens Problems helpful.

• FBs in the eye are a very common cause for seeking attention at an Emergency or Minor Injuries department.
• Penetrating injuries and trauma are more common in men.
• Risk factors include certain jobs (e.g. car mechanics) and some sports (particularly outdoor sports), especially if protective goggles are not worn.
• Pepper spray, used as an offensive weapon in law enforcement or by ordinary citizens, can produce corneal abrasions.¹

History

• When did this occur?
• What was the patient doing?
• Were goggles worn?
• What is or might be the nature of the foreign body?
  • Organic vs. inorganic
  • Did it enter the eye at speed?
  • Might there be more than one FB? (e.g. twig vs. grains of sand)
• Is there a definite history of a foreign body? A number of conditions, particularly involving the cornea, may feel like a FB.
• Has the patient taken any action (e.g. irrigate the eye)?

Symptoms

• Pain, relieved by a topical anaesthetic
• Sensation of a foreign body relieved considerably by topical anaesthesia
• Photophobia
• Tearing
• Red eye

Patients are quite reliable at being able to say where the foreign body is located.²

There may be no symptoms if the foreign body is below the surface of the conjunctival epithelium. Over a few days epithelium often grows over small corneal foreign bodies with reduction in pain.

Examination

You may need to put a drop of local anaesthetic in the affected eye at the start of examination.

• When examining a patient for a FB, check the acuity of both eyes and look at the structures of the eye, working from front to back, starting with the lids and ending with the fundus.
• The lower and upper lids need to be everted to look for additional FBs, particularly if there is the ongoing sensation of the presence of a FB. If a superficial foreign body is suspected but not found, double eversion of the upper lid to search for a foreign body is required.
• Fluorescein staining of the cornea is essential to detect any epithelial defect caused either by a FB lying on the cornea or a FB lying under the lid and scratching the corneal surface (look for linear abrasions) as the person blinks.
• If you suspect that the FB has penetrated the globe, you may perform a Seidel test first to confirm this; if in doubt, do not hesitate to refer.

You may find our record on Examination of the Eye helpful; this explains how to perform all examinations and how to do a Seidel's test.

Signs

Findings may be:

• Normal or decreased visual acuity
• Conjunctival injection
• Ciliary injection, especially if an anterior chamber reaction occurs
• Visible foreign body
• Rust ring, especially if a ferrous foreign body has been embedded for hours or days
• Epithelial defect that stains with fluorescein
• Corneal oedema
• Anterior chamber cell or flare

Worrying signs

• A cloudy cornea: this may represent oedema or infection - the former a sign of potentially significant injury and the latter an important condition to treat promptly.
• The eye will be red but any additional signs of inflammation (such as a corneal infiltrate or inflammatory cells in the anterior chamber) should prompt a referral.
• Any pupil, iris or fundal abnormality.

Extraocular

Superficial FBs (e.g. particles of steel or sand) are often washed away by tears but they may also adhere to the ocular or conjunctival surface. If they become stuck under the lid, they may produce linear corneal abrasions and if they lodge within the conjunctival fornix, they can give rise to a chronic conjunctivitis. Occasionally, a very high velocity foreign body may penetrate the cornea or sclera.

Corneal

Look for a little dark speck on the corneal surface. They can become quite embedded and ferrous foreign bodies can give rise to rust staining on the bed of the abrasion (a 'rust ring') if left for more than a few days.

Metallic foreign bodies are often sterile (there is an acute rise in temperature in their transit through air) but organic and stone foreign bodies carry a higher risk of infection. Discharge or evidence of uveitis (red eye, pain, photophobia) should prompt an immediate referral.

Intraocular

A history of a high velocity injury (e.g. during grinding) should raise suspicion of an intraocular foreign body. Symptoms typically include decreased or double vision and pain but equally, the patient may be asymptomatic and not present for many years! Intraocular foreign bodies can be:³

• Poorly tolerated, leading to inflammation e.g. organic matter and sometimes, copper, iron and steel
• Reasonably tolerated, producing a low-grade inflammatory reaction e.g. copper alloys that are less than 85% copper (e.g. bronze), nickel, aluminium, mercury, zinc
• Well tolerated e.g. carbon, coal, stone, glass, plastic, rubber, steel and most other metals

• Corneal abrasion
• Keratitis, bacterial or fungal
• Herpes simplex keratitis
• Iritis or uveitis

Most superficial foreign bodies require no special investigations other than a good look with a slit-lamp (including the surface of the cornea with fluorescein) and a fundal examination with an ophthalmoscope.

If there is suggestion of infection, swabs should be taken. If a penetrating foreign body is suspected it may be apparent on x-ray but that depends upon its composition. CT is sometimes used but MRI must be avoided if there is any chance that the body may be metallic. Ultrasound can be used and is usually performed in the Eye Unit.

The aims of management are to relieve pain, avoid infection and prevent long term loss of function. Shield (do not patch) the eye of patients with a suspected intraocular foreign body and refer to the ophthalmologists for a dilated fundus examination, an ultrasound scan (done in clinic) and assessment of collateral ocular damage with a view of surgical removal and repair.

Initial management: irrigation

Irrigation of the eye is always a good starting point. It will wash away loose matter and so can help with completing your examination. It may be the only action required. If there are residual FBs, you may need to add another drop of anaesthetic at this point as any previously applied drops will have worn off or been washed away.

Removal

The first approach is to sit the patient at a slit lamp, anaesthetise the eye if you have not done so already and try to remove the FB. Use a cotton-tipped bud with a gentle twisting motion over the FB, so trying to 'scoop' it up from the surface. If this does not work and you feel comfortable working at the slit-lamp, use a 25G sterile needle to dislodge the FB. This is tricky on the conjunctival surface as its high vascularity causes it to bleed and so obscures your operating field very quickly. If in doubt or if there is likelihood of penetration through more than 25% of the cornea, refer.

The longer the time the FB remains on the cornea, the greater likelihood of complications (e.g. infection).⁴ After removal, treat as a corneal abrasion and advise the patient to return if the symptoms do not begin to resolve over the following 24 hours. Residual rust rings should be removed using an Alger brush or automated sterile burr. This procedure should only be used if you are competent with the slit-lamp and have had training and experience in FB removal. Rust ring removal may need to happen a few days later when the it becomes more superficial.

Drugs used

• Antibiotic drops or ointment should be prescribed until any epithelial defect heals to prevent infection. Drops are easier to instil than ointment and less sticky and uncomfortable but the duration of action of drops is very much shorter than for ointment.
• A topical cycloplegic like cyclopentolate 1%, 2 to 4 times daily is useful for pain and photophobia.
• Topical ophthalmic NSAIDs can reduce pain without impairing healing.⁵

Surgical management

Intraocular foreign bodies must be removed in the operating theatre using a microscope. These injuries are often vision threatening and should be treated quickly.

The issue of patching

Traditionally, an eye with a corneal abrasion following a FB has been patched for 24 hours in order to relieve pain and protect the cornea by keeping the lids shut over it and preventing them rubbing against it during blinking. However, evidence is emerging that the cornea actually heals faster and with less pain when it is not patched⁶ and so many are dropping this practice or suggesting a short period of patching only (e.g. overnight). Patched patients should not drive.

A patch must not be used with any of the following as there is high risk of serious complications:

• The possibility of a perforation of the globe exists
• A corneal infiltrate is present
• A possible retained intraocular foreign body
• The mechanism of injury involves vegetable matter or false finger nails³

If you decide to patch, prepare two sterile surgical eye pads and adhesive tape. Fold one pad in half and place it over the closed eye (it works best with the fold edge up and the curved side pointing down). Place the second pad over the first and apply the tape. A single pad will not keep the eye shut and will cause more discomfort.

If you are unable to remove the FB, refer the patient to an ophthalmologist. Other indications for referral include:

• Lid oedema
• Diffuse subconjunctival haemorrhage
• Persistent corneal defect or corneal opacity
• Diffuse corneal damage (focal or diffuse opacity)
• Scleral or corneal laceration
• Hyphaema (blood in the anterior chamber)
• Abnormally shallow or deep anterior chamber compared to the fellow eye
• Post-traumatic dilation of pupil or abnormal shape of pupil
• Any case with possible full penetration of the cornea or sclera

• When a corneal foreign body encroaches on the visual axis, tell the patient about potential loss of visual acuity due to unavoidable scarring. This should be documented for medico-legal purposes.
• Residual impaired corneal sensation causing increased risk and poor healing of corneal abrasions may heal poorly.

If superficial FBs are completely removed, recovery should be full with no sequelae. Residual FB may remain inert in the eye for many years and not cause any problems if they are clear of the visual axis. Others may cause an inflammatory reaction. If this occurs or if there is a more extensive injury to the eye, the prognosis can be more guarded and is related to the extent of the injury.

Safety goggles must be worn where working conditions demand. An employer who does not enforce this is failing to comply with health and safety legislation.

Goggles are becoming standard equipment for squash. A squash ball and the base of a shuttlecock are the same size as the orbit of the eye and so represent a much greater risk than a cricket or football.

Airbags represent a significant safety features in cars, in addition to seat belts. However, they can cause eye injuries. Depowered airbags are safer than powered airbags in terms of reducing eye injuries.⁷