What are the key clinical features to differentiate a corneal abrasion from other ocular injuries?

The key clinical features used to differentiate a corneal abrasion from other ocular injuries primarily involve assessing the nature of the symptoms, the appearance of the eye, and the presence of specific 'red flag' signs that indicate more severe or different conditions ¹.

• Typical Corneal Abrasion Features: A corneal abrasion typically presents with symptoms such as pain, a foreign body sensation, photophobia (light sensitivity), and redness ¹. Visual acuity may be affected, especially if the defect is in the visual axis or accompanied by corneal oedema ¹. Diagnosis is often confirmed by applying fluorescein dye, which stains the area of epithelial defect, making the abrasion visible under cobalt blue light ¹.
• Differentiating from Penetrating Eye Injury or Intraocular Foreign Body: Suspect a penetrating eye injury or intraocular foreign body if the injury resulted from high-velocity incidents (e.g., drilling, hammering, lawn mowing) or sharp objects (e.g., glass, knives) ¹. Red flag features include severe pain, a significant reduction in visual acuity, irregular, dilated, or non-reactive pupils, hyphema (blood in the anterior chamber), hypopyon (pus in the anterior chamber), or corneal opacity ¹. A visible foreign body protruding from the globe should not be removed in primary care ¹.
• Differentiating from Chemical Injury: A chemical injury is an emergency requiring immediate and copious irrigation of the eye for 20-30 minutes with fluid like lactated Ringer's solution, normal saline, or water, followed by urgent ophthalmology referral ¹.
• Differentiating from Retained Foreign Bodies (beyond simple abrasion): If a foreign body cannot be safely removed in primary care, or if it is composed of organic material (e.g., seeds, soil, insect scales), or located in or near the centre of the cornea, it warrants referral to ophthalmology due to increased risk of infection and complications ¹. Vertical scratch marks that stain with fluorescein may indicate a subtarsal foreign body under the upper eyelid ¹. Metallic foreign bodies can leave a rust ring, which requires removal by ophthalmology within 1-2 days ¹.
• Differentiating from Infection or Ulcer: Worsening eye pain, irritation, redness, or a decrease in visual acuity, along with the development of a corneal infiltrate or ulcer, suggest infection and necessitate urgent review or referral to ophthalmology ¹. An abrasion that does not improve or worsens 24 hours after treatment, or does not resolve completely within 3-4 days, also indicates a need for referral ¹.
• Differentiating from Recurrent Erosion Syndrome: If recurrent erosion syndrome is suspected, discussion with or referral to ophthalmology is indicated ¹. This condition involves recurrent episodes of epithelial breakdown (Ramamurthi et al., 2006).
• Differentiating from Child Maltreatment: In children, suspect child maltreatment if there are retinal haemorrhages or an eye injury without major confirmed accidental trauma or a known medical explanation, including birth-related causes ².