Definition

A foreign body in the cornea is one of the most common types of eye trauma, second only to surface damage of the cornea. Usually, these foreign objects are minor and do not pose a significant threat to vision. However, they can cause discomfort, often prompting individuals to seek medical attention. The incidence rate varies by population, with one Swedish study indicating about 8 cases per 1,000 people.

Causes

This condition can occur in various situations but is most commonly associated with a failure to use eye protection and high-risk jobs. Foreign bodies can also adhere to the cornea unexpectedly, such as when riding a motorcycle or walking outdoors. The specific foreign objects involved often depend on the person's occupation.

Risk Factor

High-risk occupations for foreign objects impacting the cornea include grinding metal or wood, hammering nails, drilling (on surfaces like asphalt, metal, or wood), and welding. In these types of jobs, small particles of metal, wood, or asphalt are commonly projected towards the eyes, especially if the individual is not wearing protective eyewear. Due to occupational exposure, men under 40 are more frequently affected than women.

Symptoms

When a foreign body is present on the cornea, individuals often feel a distinct sensation, prompting them to seek medical help. Vision disturbances may or may not occur, though light sensitivity is common. Red, watery eyes, especially around the iris, and a visible foreign object may also be present. Pain is frequently experienced due to the high sensitivity of the corneal nerves to any foreign object.

Diagnosis

Before examining the eye, a doctor will ask about the circumstances of the incident to understand what may have adhered to the cornea and how it happened. Vision tests and reflex responses to light may follow, and the inner eyelids may also be examined to detect any additional foreign bodies.

If a foreign object is suspected on the cornea, doctors may apply dye to highlight the corneal area affected and improve the visibility and position of the object. Further examination with an ophthalmoscope or slit lamp may help detect if the foreign body has penetrated deeper into the eye. If discharge is present, lab tests, including blood counts and bacterial cultures, may be conducted to identify potential infections. Additionally, blue light and fluorescent dye can be used to assess for corneal perforation (a hole in the cornea).

Management

Before visiting a doctor, certain precautions should be taken:

1. Avoid rubbing your eye

Even though the foreign object may cause discomfort, rubbing can scratch the cornea. Refrain from touching your eye, especially when working with wood or metal.

2. Do not attempt to remove the object yourself

The cornea is highly sensitive, and foreign objects should only be removed by a trained doctor.

Upon reaching a doctor, medications may be provided, including pain relievers that can be taken orally, through an IV, or as eye drops. Muscle relaxants may be prescribed to alleviate pain, along with an eye patch to cover the unaffected eye, reducing light sensitivity and easing muscle strain.

Foreign bodies should be removed within 24 hours to prevent embedding in the cornea, typically by an ophthalmologist. The eye is flushed with clean water, followed by using a moistened cotton swab to dislodge the object. If necessary, a small needle may be used to extract it.

Afterwards, painkillers are often prescribed as discomfort may persist for a few days, along with muscle relaxants for temporary use. Antibiotics are essential to prevent corneal infection. Follow-up appointments are recommended within 24 hours and periodically for up to two weeks to ensure complete healing of the cornea, and proper visual function, and to monitor for infections.

Complications

Complications from foreign objects in the cornea can vary. If exposure occurs at high speed or if you rub your eyes before the foreign object is removed, you may experience a corneal abrasion, which is a scratch on the cornea. If the foreign object is not removed within 24 hours, it can become embedded in the cornea, potentially interfering with vision, especially if it is located in the center of the cornea.

Foreign objects can lead to corneal infections, known as keratitis, which require treatment with antibiotics. Additionally, high-speed exposure to a foreign object or failure to promptly address a corneal wound can result in holes in the eyeball. These holes must be treated surgically.

Prevention

To prevent foreign bodies from entering the cornea:

• Wear protective eyewear while working with materials that pose a high risk of projecting small particles into the eye.
• Wear a face-covering helmet when riding a motorcycle to minimize exposure to dust or debris.

When to see a doctor?

If a foreign body suddenly enters your eye, try to locate it yourself or with assistance. If it is positioned over the iris or pupil, visit a doctor within 24 hours to remove it before it embeds. In children, symptoms like redness, watering, and pain after eye-rubbing or playing are common indicators. If a foreign object is situated over the iris or pupil, take your child to a doctor immediately.

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