What is the appropriate workup for a patient with a foreign body sensation in the eye?

Workup for Foreign Body Sensation in the Eye

The workup for a patient with foreign body sensation requires immediate visual acuity testing, systematic slit-lamp examination with fluorescein staining, and eversion of the upper eyelid to exclude hidden foreign bodies—this approach identifies both common corneal pathology and the frequently missed subtarsal foreign bodies that cause chronic symptoms. 1, 2, 3

Initial Assessment and Red Flags

Immediate Visual Acuity Testing

• Measure visual acuity before any intervention to establish baseline function and identify acute vision loss requiring urgent ophthalmology referral 2
• Test with current correction at distance and near as appropriate 1
• Perform pinhole testing to assess best-corrected visual potential 1

Critical Red Flags Requiring Immediate Ophthalmology Consultation

• High-velocity mechanism of injury (grinding, hammering, metal work) mandates immediate referral due to risk of globe penetration 2, 4
• Irregular pupil after trauma indicates penetrating injury 2, 4
• Eye bleeding or vision loss after trauma 5
• Central corneal infiltrate >2mm with suppuration or feathery margins suggesting bacterial keratitis 5

Systematic External and Slit-Lamp Examination

External Examination Components

• Assess for proptosis, blepharoptosis, lagophthalmos, or floppy eyelid syndrome 1
• Evaluate eyelid position, character, lashes, and lacrimal apparatus 1
• Check for facial asymmetry, scarring, or malfunction (poor blink, incomplete closure) 1
• Examine pupillary function including size, response to light, and relative afferent pupillary defect 1

Detailed Slit-Lamp Biomicroscopy

• Systematically examine eyelid margins and lashes, tear film, conjunctiva, sclera, cornea, anterior chamber depth, iris, lens, and anterior vitreous 1
• Use sclerotic scatter, specular reflection, and indirect illumination techniques to evaluate all corneal layers 1
• Look for epithelial breakdown, stromal infiltration, foreign bodies, or corneal edema 1
• Assess for keratic precipitates, anterior chamber reaction, or sectoral corneal edema suggesting endotheliitis 1

Essential Diagnostic Maneuvers

Fluorescein Staining

• Apply fluorescein to identify corneal epithelial defects, which become more apparent after 2 minutes and are best visualized with cobalt blue light and yellow filter 1
• Exposure-zone (interpalpebral) punctate or blotchy staining suggests dry eye 1
• Diffuse corneal and conjunctival staining may indicate viral keratoconjunctivitis or medicamentosa 1
• Inferior corneal staining patterns suggest staphylococcal blepharitis, meibomian gland disease, or lagophthalmos 1

Upper Eyelid Eversion

• Always evert the upper eyelid to examine the superior palpebral conjunctiva, as concealed foreign bodies in this location are frequently missed and cause chronic unresolved ocular pain 3
• Foreign bodies can be minute (iron shards, eyelashes, sand grains) and hide without typical pathognomonic signs 3
• This step is critical because hidden foreign bodies often masquerade as dry eye or are misdiagnosed as neuropathic pain 3

Corneal Sensation Testing

• Test corneal sensation before placing any drops, especially topical anesthetics, using a cotton-tip applicator twisted to a fine point or unflavored dental floss 1
• Reduced or absent sensation suggests neurotrophic keratopathy 1

Additional Testing When Indicated

Intraocular Pressure Measurement

• Measure IOP using Goldmann applanation tonometry when possible 1
• Defer contact tonometry if suspected ocular infection or corneal trauma is present 1
• Alternative methods include pneumotonometer, handheld electronic applanation, or rebound tonometry for abnormal corneas 1

Tear Film Assessment (If Dry Eye Suspected)

• Schirmer test without anesthesia: <10mm wetting in 5 minutes suggests abnormality, <5.5mm is diagnostic of aqueous tear deficiency 1
• Tear breakup time evaluation 1
• Rose bengal or lissamine green staining for conjunctival involvement 1

Fundus Examination

• Examine mid and posterior vitreous, retina, vasculature, and optic nerve through dilated pupil when appropriate 1
• Rule out posterior segment pathology that may present with referred ocular discomfort 1

Common Pitfalls to Avoid

• Failing to evert the upper eyelid is the most common cause of missed foreign bodies leading to chronic unresolved symptoms 3
• Not testing visual acuity before other interventions prevents establishing baseline function 2
• Overlooking high-velocity injury mechanisms that require immediate ophthalmology referral regardless of initial examination findings 2, 4
• Misdiagnosing chronic foreign body sensation as dry eye or neuropathic pain without thorough examination 3
• Using topical anesthetics before testing corneal sensation 1

Contact Lens Wearers: Special Considerations

• Contact lens wearers with foreign body sensation require topical antibiotics with antipseudomonal coverage (fluoroquinolones preferred) due to dramatically increased infection risk 5
• Never patch the eye in contact lens wearers as this increases bacterial keratitis risk 5
• Instruct immediate discontinuation of lens wear until cleared by eye care provider 4