How can I differentiate between a corneal abrasion and a foreign body in the eye during examination?

To differentiate between a corneal abrasion and a foreign body in the eye during clinical examination, start with a detailed history and symptom assessment, noting pain, photophobia, tearing, and foreign body sensation, which are common to both but may be more localized in foreign body cases.

Examination should include visual acuity testing and careful inspection of the eyelids and conjunctiva for any embedded foreign material. Use fluorescein staining and cobalt blue light to identify corneal epithelial defects characteristic of abrasions, which appear as linear or irregular staining patterns on the cornea.

In contrast, a foreign body may be directly visible on the corneal surface or conjunctiva, sometimes with localized rust rings if metallic. Removal attempts should be cautious, and if the foreign body is embedded, it may require specialist intervention.

Corneal abrasion typically presents with diffuse epithelial loss without a retained object, whereas a foreign body is a discrete, often visible particle causing localized irritation and possibly a focal epithelial defect around it.

Additional signs such as conjunctival injection, lid edema, and tearing are common to both but do not reliably differentiate them. If a foreign body is suspected but not visible, eversion of the upper eyelid is essential to check for hidden particles.

In summary, the key clinical differentiators are the direct visualization of a foreign body and the pattern of fluorescein staining: diffuse epithelial loss for abrasion versus localized defect with or without visible foreign material for foreign body. Prompt referral is advised if the foreign body is embedded or if there is suspicion of deeper injury ¹ (Heath Jeffery et al., 2022).