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OP3.6 | Conjunctival Foreign Body Removal in Simulation — SDL Guide (Part 2)

Technique: Conjunctival and Subtarsal FB Removal in Simulation

The standard technique for conjunctival and subtarsal FB removal at the primary-care or emergency department level uses a torch, a slit-lamp (if available), topical local anaesthesia, and a moistened cotton bud or, for adherent FBs, a 25-gauge hypodermic needle tip. This technique is appropriate for superficial conjunctival and subtarsal FBs only — corneal FBs with stromal embedding should be referred. Understanding the rationale behind each step of the procedure is as important as memorising the steps themselves, because an understanding of the rationale allows you to safely improvise when equipment is unavailable and to recognise when a step that is going wrong should trigger a halt rather than continued effort. The procedure described below assumes that the pre-removal assessment has confirmed no red flags — if you encounter any finding during the procedure that suggests a penetrating injury (a shallow anterior chamber, uveal tissue prolapse, or a wound track visible in the cornea), stop immediately and convert to emergency referral. Equipment needed and the procedure steps are as follows.

Equipment required:
- Topical local anaesthetic: oxybuprocaine (benoxinate) 0.4% or proxymetacaine 0.5% drops.
- Torch or slit-lamp.
- Fluorescein strip or drops + cobalt-blue light.
- Sterile cotton bud (moistened with saline).
- 25-gauge needle (for adherent FBs).
- Topical antibiotic (chloramphenicol or ciprofloxacin).
- Eye pad and bandage (if needed post-procedure).

Step-by-step procedure:

Step 1 — Instil topical local anaesthetic:
Instil 1–2 drops of oxybuprocaine 0.4% into the conjunctival sac of the affected eye. Wait 1 minute for full effect. This reduces pain, blepharospasm, and involuntary squeezing, allowing safe examination and removal. IMPORTANT: Do not give the patient a bottle to take home — repeated self-use of topical local anaesthetic causes corneal epithelial toxicity (anaesthetic keratopathy), impairing epithelial healing and masking the sensation of corneal damage.

Step 2 — Identify the FB:
For a subtarsal FB: Evert the upper eyelid. Ask the patient to look downward. Place a cotton bud horizontally at the upper border of the tarsal plate. Grip the upper lid margin lashes gently and fold the lid forward and upward over the cotton bud, exposing the palpebral conjunctiva. Inspect the subtarsal sulcus for the FB under torch light.

For a bulbar conjunctival FB: Inspect the exposed surface directly under the torch.

Step 3 — Remove the FB:
For a loose FB on the palpebral conjunctiva or subtarsal sulcus: use the moistened tip of a sterile cotton bud to gently sweep across the surface. The FB should adhere to the wet cotton tip. Use minimal pressure — you are sweeping the surface, not scraping.

For a more adherent FB: use the bevel of a 25-gauge needle tip (held tangentially, NOT perpendicular to the surface) to gently lift the FB edge. This should be performed under slit-lamp magnification or a bright torch with 2.5× loupes. This step requires specific training — do NOT attempt with a perpendicular needle angle, which risks a corneal laceration.

Step 4 — Check for complete removal:
Re-inspect the subtarsal sulcus after removal. Instil fluorescein and examine under cobalt-blue light. The epithelial defect from the FB site should be visible (stains green). The vertical linear scratches from a subtarsal FB should still be present initially — they will resolve with re-epithelialisation within 24–48 hours.

Step 5 — Instil topical antibiotic and pad the eye:
Instil topical chloramphenicol 0.5% drops or ointment to the eye. Pad the eye with a clean eye pad for 4–6 hours if there is a significant corneal epithelial defect. Advise the patient to return if pain worsens, vision decreases, or symptoms do not improve within 24 hours.

Post-Removal Care and Referral Criteria

Post-removal management is as important as the removal itself. Poor aftercare can convert a successfully managed conjunctival FB into a missed secondary infection or an undetected penetrating injury. The corneal epithelial defect left by a FB or by the removal procedure is a temporary open wound — susceptible to infection, painful without lubrication, and a site of ongoing discomfort until re-epithelialisation is complete. The post-removal protocol is therefore designed to achieve three goals simultaneously: prevent secondary bacterial infection of the epithelial defect, reduce discomfort during healing, and ensure that any delayed-onset complication (a rust ring at 24 hours, a worsening infection, an unsuspected penetrating injury that declares itself as the patient's VA deteriorates) is detected promptly. Each element of the post-removal care plan below serves one or more of these goals.

Standard post-removal care for simple conjunctival/subtarsal FB:
- Topical antibiotic: chloramphenicol 0.5% drops 4× daily for 5–7 days to prevent secondary bacterial infection at the corneal epithelial defect.
- Eye pad: if there is a significant corneal epithelial defect (visible on fluorescein), pad the eye for 4–6 hours to reduce blinking-induced friction during early healing. Do NOT pad a suspected infected eye (pad creates a warm, moist environment that promotes bacterial growth).
- Patient instructions: return if (a) pain worsens rather than improves over 24 hours, (b) VA decreases, (c) the eye becomes more red rather than settling, (d) purulent discharge appears.
- Follow-up in 24 hours: to confirm re-epithelialisation of the defect and to remove any rust ring if present.

Rust ring management:
When a metallic FB has been in contact with the corneal epithelium for more than a few hours, iron oxidises to form a brown rust ring in the corneal epithelial cells around the FB site. The rust ring is mildly toxic to the corneal epithelium and must be removed — but it should be removed at 24-hour review, not immediately (it is easier to debride after softening overnight). Removal with a rotating burr (Alger brush) under slit-lamp, or gentle cotton-bud debridement, is the standard approach.

Indications for immediate specialist referral after initial assessment:
- Any penetrating injury sign (listed in previous section).
- FB suspected to be in the corneal stroma (embedded — cannot be lifted with cotton bud from the surface).
- FB associated with reduced VA, photophobia, or hypopyon.
- Any injury from copper or brass (chalcosis risk).
- Chemical injury (alkali or acid splash) — requires immediate copious irrigation, NOT FB removal as the primary action.
- Paediatric patients — less cooperative; higher risk of incomplete removal; refer to ophthalmologist.

Applied Practice: Simulation Scenarios

Working through structured scenarios before your skills laboratory session builds the decision-making framework so that the technique practice is purposeful rather than mechanical. For each scenario, decide before reading the outcome: safe to remove at primary care, or refer? In the skills laboratory, the technical procedure is practised on a simulation model and the assessment is on technique. But the more important decision — the one that determines patient safety — is the go/no-go decision: does this FB meet the criteria for primary-care removal, or does one of the red flags require immediate referral? This go/no-go decision cannot be practised on a simulation model; it must be practised through case scenarios, and it must become automatic before your clinical posting. The three scenarios below span the three most important categories: a safely manageable conjunctival FB, a corneal FB requiring specialist referral, and a penetrating injury requiring emergency management.

Scenario 1 — The simple subtarsal FB (proceed):
A 30-year-old teacher has gritty irritation in the right eye since a dust storm 6 hours ago. VA is 6/6. Pupil round and reactive. Fluorescein staining shows 4 fine vertical scratches on the superior cornea. No FB visible on the bulbar conjunctiva. No subconjunctival haemorrhage.
- Decision: vertical scratches + history of dusty environment + no red flags → suspect subtarsal FB. Evert upper lid. Remove with moistened cotton bud after instilling oxybuprocaine. Apply chloramphenicol. Review in 24 hours.
- Key learning: the FB was not visible until the lid was everted — eversion is mandatory whenever vertical scratches are present.

Scenario 2 — The corneal FB (refer):
A 22-year-old welder has a painful, watering right eye since a spark hit it 2 hours ago without protective goggles. VA is 6/9. Pupil round. A small grey metallic spot is visible on the cornea at the 10 o'clock position, surrounded by a faint brownish ring. Fluorescein staining shows a localised punctate defect at the spot. The slit-lamp shows the FB is embedded in the anterior stroma, not just the epithelium.
- Decision: embedded corneal FB + rust ring beginning → DO NOT attempt removal (will deepen the wound). Apply topical antibiotic, pad the eye, and refer to ophthalmology.
- Key learning: a metallic FB embedded in the stroma requires specialist removal with a slit-lamp and appropriate instruments to avoid deepening the perforation.

Scenario 3 — The penetrating injury (emergency referral):
A 45-year-old factory worker was operating a lathe when a fragment struck his left eye. His vision is 'blurry' and the eye is very red. VA is 6/36, not improved on pinhole. The pupil is oval and slightly peaked at the 7 o'clock position. The cornea appears dull and slightly opaque at one point. There is a band of subconjunctival haemorrhage extending to the posterior limit of the visible sclera.
- Decision: reduced VA + peaked pupil + subconjunctival haemorrhage to posterior limit + mechanism (high-velocity lathe fragment) → penetrating eye injury. Do NOT instil drops. Do NOT pad tightly. Call ophthalmology emergency. Keep patient supine. NBM (nil by mouth) in case of emergency surgery. Document all findings.
- Key learning: the combination of reduced VA + peaked pupil + posterior haemorrhage in a high-velocity injury is a penetrating eye injury until proven otherwise.

Self-Assessment

Before your skills laboratory session, assess whether you can answer the following questions without consulting your notes — they represent the minimum competency for the OP3.6 assessment: The questions below test both factual recall (red flags, rust ring management, anaesthetic keratopathy) and clinical reasoning (when to stop and refer, how to counsel a patient about take-home drops). For the OP3.6 OSCE assessment, the examiner will look for a student who performs the technical steps fluently and recognises — without prompting — when the scenario has changed from a safe removal to an emergency referral situation. If you cannot rapidly recall the answer to any of the questions below, that topic area represents a priority for revision before your skills laboratory. The most safety-critical question is number 5 — the rule about pressure and the open globe; this is the one fact in this entire module where an incorrect answer in a clinical scenario is immediately life-affecting for the patient.

1. Name three red flags that should stop you from attempting FB removal and trigger immediate referral.
2. What do vertical linear corneal scratches on fluorescein staining indicate, and where should you look next?
3. Why should topical local anaesthetic NOT be given to the patient as a take-home drop?
4. What is a rust ring, how soon after FB removal should you attempt to remove it, and why not immediately?
5. What is the single most important rule about padding a suspected penetrating eye injury?

If you cannot answer question 5 ('pad without pressure — never apply pressure to an open globe'), this is the highest-stakes point in the entire module. Re-read the penetrating injury sections before your skills laboratory.