Foreign body sensation

Foreign body sensation is the feeling that something is in the eye, with grittiness, scratching, irritation and often tearing. It may reflect a true foreign body, or any condition of the cornea, conjunctiva or lids that irritates trigeminal nerve endings.

Anatomy. The cornea is densely innervated by the ophthalmic division of the trigeminal nerve; minor surface disruption causes marked symptoms. Foreign bodies lodge on the cornea, under the upper lid (subtarsal sulcus) or in the conjunctival fornices.

Classification. True foreign body (corneal, conjunctival, subtarsal, intraocular), corneal causes (abrasion, erosion, keratitis, ulcer, dystrophy), lid causes (trichiasis, entropion, blepharitis, chalazion, lid margin lesion), conjunctival causes (conjunctivitis, pinguecula, pterygium, concretions, follicles, papillae), dry eye, and neuropathic causes.

Key distinctions. Vertical linear corneal abrasions suggest a subtarsal foreign body. Metal fragments from grinding or hammering can penetrate the globe. A high velocity injury, severe pain, reduced vision, or irregular pupil suggests an intraocular foreign body.

History. Onset and circumstances (grinding, hammering, drilling, welding, gardening, windy conditions, contact lens insertion), eye protection use, high velocity mechanism, pain, redness, discharge, photophobia, vision change, tearing, previous eye surgery, contact lens use, dry eye symptoms, lid problems (lashes turning in), allergy, and tetanus status.

Examination:

• Visual acuity (before treatment)
• lids (eversion of the upper and lower lids for subtarsal and fornix foreign bodies, lash direction, lid margin)
• conjunctiva
• cornea (foreign body, rust ring, infiltrate, abrasion with fluorescein staining; vertical linear streaks)
• anterior chamber (cells, flare, depth, hyphaema)
• pupil (shape, reaction)
• Seidel test (fluorescein flowing from a wound)
• iris
• lens
• intraocular pressure when no open globe is suspected
• fundus

Topical anaesthetic (proxymetacaine 0.5 percent or oxybuprocaine 0.4 percent) assists examination.

Red flags

• High velocity injury (hammering, drilling, grinding, explosion), or metal on metal
• Reduced vision, irregular or peaked pupil, shallow anterior chamber, Seidel positive, or prolapsed tissue (open globe)
• Hyphaema, hypopyon, lens opacity, or vitreous haemorrhage
• Corneal infiltrate, ulcer or white opacity
• Vegetable matter or organic material (fungal keratitis risk)
• Contact lens wearer
• Chemical exposure
• Severe pain or photophobia not relieved by anaesthetic
• Embedded foreign body that cannot be removed easily or lies over the central visual axis

Special groups. Children: difficult examination (sedation or examination under anaesthesia), non-accidental causes, and fireworks. Pregnancy: avoid oral tetracyclines and fluoroquinolones. Region specific: agricultural injuries and vegetative matter, and fungal keratitis.

Foreign bodies

• Corneal foreign body (metal with rust ring, glass, wood, plant matter), conjunctival foreign body, subtarsal foreign body, fornix foreign body (retained contact lens or fragments)
• Intraocular foreign body, penetrating or perforating injury

Corneal

• Corneal abrasion, recurrent corneal erosion, bacterial, fungal, viral and acanthamoeba keratitis, corneal ulcer, ultraviolet keratitis (welder flash), chemical injury
• Superficial punctate keratitis, filamentary keratitis, exposure keratopathy, corneal dystrophy, contact lens related complications

Lid and conjunctival

• Trichiasis, distichiasis, entropion, blepharitis, meibomian gland dysfunction, chalazion, lid margin lesion
• Conjunctivitis (viral, bacterial, allergic, chlamydial), conjunctival concretions, pinguecula, pterygium, conjunctivochalasis, floppy eyelid, ocular surface tumour

Systemic and neuropathic

• Dry eye disease and Sjogren syndrome, Stevens Johnson syndrome, ocular cicatricial pemphigoid, graft versus host disease
• Neuropathic ocular pain, trigeminal disease, thyroid eye disease

Reasoning. Examine with topical anaesthetic and fluorescein, evert the lids, and decide whether the globe is intact. Image when intraocular foreign body or open globe is possible.

First line. Visual acuity, slit lamp or penlight examination, lid eversion, fluorescein staining, Seidel test, pupil assessment and intraocular pressure (only when open globe is excluded).

Targeted tests.

• CT orbits (thin cuts) without contrast for suspected intraocular or intraorbital foreign body or open globe; MRI is contraindicated when a metallic foreign body is possible; ultrasound is avoided with open globe because of pressure.
• Corneal scraping for Gram stain, culture and fungal stains in suspected infection (by ophthalmology).
• Tear osmolarity, break up time and Schirmer test for dry eye; lid margin assessment for blepharitis.
• Corneal topography and confocal microscopy by ophthalmology when needed.
• Tetanus immunisation status review.

Limitations. Small foreign bodies may be missed on CT. Fluorescein may not show shallow wounds.

Open globe or intraocular foreign body (emergency). Shield (rigid, not touching the eye), no pressure, no topical drops or ointment, no removal of embedded material, nil by mouth, analgesia and antiemetic (ondansetron 4 mg IV, maximum 16 mg in a single dose; QT warning), tetanus prophylaxis, IV antibiotics (ceftazidime 1 g IV every 8 hours plus vancomycin 1 g IV every 12 hours, or ciprofloxacin 400 mg IV every 12 hours with adjustment to creatinine clearance), and emergency ophthalmology.

Corneal and conjunctival foreign body.

• Topical anaesthetic (proxymetacaine 0.5 percent 1 drop) for examination and removal only; do not prescribe for home use.
• Remove superficial foreign body by irrigation with saline, moistened cotton bud, or a sterile needle under the slit lamp by a trained clinician; remove the rust ring or refer for removal when deep or central. Do not use a needle at the bedside in a child.
• Chloramphenicol 0.5 percent drops 4 times daily or ointment 3 to 4 times daily for 5 days (ofloxacin 0.3 percent 1 drop 4 times daily in contact lens wearers), lubricants, cycloplegic drops for severe pain (cyclopentolate 1 percent 1 drop), and oral analgesia (paracetamol 1 g every 4 to 6 hours, maximum 4 g in 24 hours; ibuprofen 400 mg every 6 to 8 hours with food, maximum 2.4 g in 24 hours). No eye patch.
• Review at 24 hours for large abrasions or rust ring and at 48 to 72 hours if not healed. Tetanus prophylaxis for contaminated wounds when immunisation is incomplete.

Subtarsal foreign body. Evert the lid and remove with a moist cotton bud, irrigate, then chloramphenicol 0.5 percent drops 4 times daily for 5 days and review at 24 to 48 hours.

Corneal abrasion. Chloramphenicol 0.5 percent drops 4 times daily for 5 days, with lubricants and oral analgesia; healing typically within 24 to 72 hours.

Recurrent corneal erosion. Lubricating ointment at night for 3 to 6 months, hypertonic saline 5 percent drops 4 times daily, and ophthalmology for micropuncture or phototherapeutic keratectomy.

Keratitis and corneal ulcer. Same day ophthalmology: corneal scraping, then ofloxacin 0.3 percent or moxifloxacin 0.5 percent 1 drop every 15 to 60 minutes initially (fortified antibiotics or antifungal natamycin 5 percent for fungal disease), cycloplegic drops, and no patching.

Ultraviolet keratitis. Lubricants, cycloplegic drops, oral analgesia and review within 24 hours; healing in 24 to 72 hours.

Chemical injury. Immediate irrigation with at least 1 to 2 L of saline or water until pH is 7.0 to 7.4, then same day ophthalmology.

Trichiasis and entropion. Epilation of aberrant lashes, then electrolysis, cryotherapy or surgery for recurrent disease; trachoma related trichiasis needs surgery. Entropion: tape (temporary) and lid surgery.

Dry eye and blepharitis. Lubricants (hypromellose 0.3 percent or sodium hyaluronate 0.1 to 0.2 percent, 1 drop 4 to 6 times daily, preservative free when frequent), warm compress and lid hygiene, and doxycycline 100 mg orally daily for 6 to 12 weeks for meibomian gland dysfunction (avoid in pregnancy and in children under 12 years).

Conjunctivitis. Treat by cause (viral: lubricants and hygiene; bacterial: chloramphenicol 0.5 percent drops 4 times daily for 5 days; allergic: olopatadine 0.1 percent drops twice daily).

Pinguecula and pterygium. Lubricants, sunglasses, short course topical steroid or antihistamine for inflammation, and surgical excision for visual axis involvement or persistent symptoms.

Conjunctival concretions and floppy eyelid. Removal of concretions under topical anaesthesia; lid shield and sleep apnoea screening in floppy eyelid syndrome.

Neuropathic ocular pain. Specialist assessment, topical autologous serum, oral gabapentin 300 mg at night increased every 3 to 7 days (adjust to creatinine clearance), or amitriptyline 10 mg at night increased by 10 mg weekly to 25 to 75 mg.

Prevention. Protective eyewear (goggles, face shields) for grinding, hammering, drilling, gardening and sport.

Monitoring. Review at 24 to 48 hours after removal of a foreign body, and at 1 week for ulcers. Check visual acuity and fluorescein staining at each review.

Referral and escalation. Same day ophthalmology for open globe, intraocular foreign body, deep or central foreign body, rust ring that cannot be removed, infiltrate or ulcer, reduced vision, contact lens related pain, or chemical injury. Oculoplastic referral for trichiasis and entropion surgery.

Admission criteria. Open globe, intraocular foreign body, severe chemical injury, infectious keratitis needing intensive treatment, or paediatric examination under anaesthesia.

Discharge and safety netting. Advise not to rub the eye, to avoid contact lens wear until healed, and to wear eye protection. Return for increasing pain, reduced vision, light sensitivity, discharge, redness, or no improvement in 48 hours.