Corneal Foreign Body

Updated: Feb 13, 2024
  • Author: Siddharth Nath, MD, PhD; Chief Editor: Hampton Roy, Sr, MD  more...
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Overview

Practice Essentials

Corneal foreign bodies are a commonly encountered presentation in the ambulatory urgent care and emergency room setting, second only to corneal abrasions in their frequency. Often, corneal foreign bodies are the result of inadequate eye protection coupled with a risky activity, such as grinding metal-on-metal. Most corneal foreign bodies do not cause significant mortality or morbidity, however, those in the visual axis, and those that strike the eye at high speed, carry the potential for sight-threatening complications. Timely recognition and appropriate removal of a foreign body is key to ensuring an optimal patient outcome.

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Background

A corneal foreign body is any material embedded within the cornea that disturbs its normal structure, and sometimes, function. A foreign body may be composed of such items as metal, glass, inert element (eg, silica), plastic, or organic matter, to name a few. 

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Pathophysiology

Corneal foreign bodies represent a form of ocular trauma. The cornea is directly exposed to the external environment and thereby susceptible to traumatic injury. Potential foreign bodies may be released during certain activities (grinding metal, high-speed biking, etc), or may be intentionally directed towards the eye or face in an injurious fashion. 

Upon contact with the cornea, depending on the speed, angle of entry, and structure of the foreign body, it may either ricochet off the cornea, or become embedded within, penetrating initially through the corneal epithelium, and then, through Bowman's layer, the corneal stroma, and Descemet's membrane. If a foreign body strikes the cornea with sufficient force, it may continue through into the endothelium and into the anterior chamber, creating a penetrating injury, which is beyond the scope of this article. 

Foreign bodies that do not penetrate through the cornea remain embedded within and incite a strong inflammatory reaction. Dilation of ciliary vessels, liberation of white blood cells into the anterior chamber, and edema of the cornea are common. If a foreign body is contaminated with microorganisms, or if it is organic in nature, often, an infectious keratitis also will result. Failure to adequately remove a corneal foreign body in a timely manner can result in infection and continuation of the inflammatory cascade.

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Epidemiology

Frequency

Corneal foreign bodies are an exceptionally common cause for emergency health care visits. Although true frequencies are difficult to estimate, given the varied etiologies that can result in a foreign body within the cornea, estimates within the literature place the incidence at 40% of ocular injuries as a whole (which occur at 8.1 per 1000).

Mortality/Morbidity

Generally, superficial foreign bodies that are removed soon after the injury leave no permanent sequelae, though in some cases, corneal scarring or infection may occur, which are discussed in detail later in this article. The longer the time interval between the injury and treatment, the greater the likelihood of complications.

A foreign body is considered an intraocular foreign body if it completely penetrates into the anterior or posterior chambers. When this occurs, ocular morbidity is much more likely. Injury can occur to the iris, lens, and retina, and vision loss may be permanent. Any intraocular foreign body can cause infection and endophthalmitis, a potentially catastrophic condition that can result in loss of the eye. Discussion of penetrating injuries and intraocular foreign bodies is beyond the scope of this article.

Sex

Similar to other traumatic injuries, the incidence in males is much higher than in females.

Age

Similar to most other traumatic injuries, the peak incidence is found in the second decade and generally occurs in people younger than 40 years.

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Prognosis

Superficial corneal foreign bodies that are not in the visual axis have good prognosis if removed in a timely manner. Incomplete removal, damage to ocular tissue during removal, or positioning within the visual axis, carry a more guarded prognosis as prolonged inflammation and scarring may affect final visual acuity. 

Corneal foreign bodies that penetrate the globe (discussed elsewhere) typically carry a poorer prognosis.

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Patient Education

Remind patients of the importance of wearing protective eyewear. Patients who are monocular should wear a pair of glasses with polycarbonate lenses, regardless of whether they require refractive correction, at all times.

Eyes should not be rubbed while working with wood or metal particles.

If a foreign body enters the eye, the eye should not be touched and no attempt should be made by the patient to remove the foreign body. Patients should attend to their nearest emergency department or urgent care centre for appropriate evaluation at the slit lamp.

For excellent patient education resources, visit eMedicineHealth's Eye and Vision Center. Also, see eMedicineHealth's patient education articles Eye Injuries and Foreign Body, Eye.

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