Ocular trauma and chemical injury — branching viva

Opening question

Examiner: Two children have just arrived. The first has an alkali powder burst to the eye; the second has a teardrop pupil and a soft eye after a dart. Take me through your first 60 seconds with each. [5]

Candidate: These are the two time-critical paediatric ocular emergencies, and the order of first aid decides the outcome. For the alkali splash, I irrigate immediately and copiously with saline or Ringer lactate, before any examination and before any pH check, because every minute of retained alkali destroys limbal stem cells. For the dart injury, the teardrop pupil and soft eye mean a suspected open globe, so I shield it with a rigid Fox shield and apply no pressure, keep the child nil by mouth with an antiemetic, and call ophthalmology for urgent surgery. Irrigate the chemical injury, shield the open globe — that is the frame. [5] [1]

Examiner: Why must you not examine the chemical-injury child before irrigating? [5]

Candidate: Because the history of a splash is enough to start irrigating, and the slit-lamp examination and the pH measurement each take minutes during which the alkali keeps liquefying tissue and killing stem cells. The delay to irrigation is the single biggest determinant of outcome, so irrigation is the assessment that comes first; the detailed examination follows once the eye is being flushed and the pH is on its way to neutral. [5]

Branch 1 — classification (BETT) and pathophysiology

Examiner: Use the Birmingham Eye Trauma Terminology to classify the dart injury. [1]

Candidate: The dart injury is an open-globe laceration — a full-thickness wound of the globe wall from a sharp object. BETT separates closed globe, where the wall is intact (contusion, lamellar laceration, superficial foreign body), from open globe, where there is a full-thickness defect (a rupture from blunt inside-out force, or a laceration from a sharp object). Within laceration I distinguish a penetrating wound — an entrance only — from a perforating wound, which has an entrance and an exit. A retained intraocular foreign body is its own open-globe injury. [1] [2]

Examiner: Why does alkali injure more than acid? [5]

Candidate: Alkali saponifies the lipid membranes of cells, causing liquefactive necrosis that melts tissue and penetrates through the stroma into the anterior chamber, where it destroys limbal stem cells and the trabecular meshwork. Acid coagulates surface proteins into a coagulum that acts as a barrier and limits deeper penetration. Hydrofluoric acid is the exception among acids, because its fluoride ion penetrates deeply and it injures like an alkali. [5]

Branch 2 — irrigation protocol and grading

Examiner: Walk me through your irrigation protocol for the alkali eye. [5]

Candidate: I instil a drop of topical anaesthetic, then irrigate with saline or Ringer lactate for at least 30 minutes using an intravenous giving set or a Morgan lens. I evert the lids and sweep the conjunctival fornices to remove any retained particulate matter, because a fleck of tablet plastered to the tarsal conjunctiva will keep releasing alkali. After at least 30 minutes I check the tear-film pH with indicator paper, wait five to ten minutes, recheck, and continue until the pH reads 7.0 to 7.2. If only tap water was available at the scene, the family did the right thing — volume and speed matter more than the exact fluid. [5]

Examiner: How do you grade the severity, and what does it tell you? [4]

Candidate: I grade chemical-burn severity with the Dua classification, based on clock hours of limbal ischaemia — the single most important prognostic factor, because the limbus holds the corneal stem cells. Zero to three clock hours is a good prognosis, four to six guarded, seven to nine poor, and ten to twelve very poor with likely limbal stem-cell deficiency. Severe ischaemia warrants urgent ophthalmology for amniotic-membrane transplantation and, later, limbal-stem-cell strategies. [4]

Branch 3 — the open-globe pathway and the Ocular Trauma Score

Examiner: For the dart injury, what will you do and what will you avoid before theatre? [1]

Candidate: I place a rigid Fox shield over the eye with no pressure, keep the child nil by mouth, give an antiemetic, and give intravenous antibiotics with anti-endophthalmitis cover plus tetanus prophylaxis. I never press on the eye, never apply a pressure patch or drops, and never measure the intraocular pressure — each can extrude intraocular contents. I obtain CT of the orbits and brain to confirm the injury, locate any foreign body and assess associated injury, and I avoid MRI if a metallic foreign body is possible. [1]

Examiner: How do you prognosticate, and what worsens the outlook? [3]

Candidate: The Ocular Trauma Score predicts the final vision. It starts from the presenting acuity — no light perception 60, light perception or hand motions 70, one over two hundred to nineteen over two hundred around eighty, six over sixty to six over fifteen ninety, and six over twelve or better one hundred — and subtracts for rupture twenty-three, endophthalmitis seventeen, perforating injury fourteen, retinal detachment eleven, and an afferent pupillary defect ten. The worse the raw score, the worse the predicted final vision. [3]

Branch 4 — hyphema and sympathetic ophthalmia

Examiner: A third child has a hyphema after a ball to the eye. How do you manage it? [6]

Candidate: I manage most hyphemas conservatively — restrict activity, elevate the head, avoid aspirin and other antiplatelet agents, and review daily for the rebleed, which classically occurs on day two to five, and for the intraocular pressure. I screen at-risk children for sickle cell, because sickled cells block the trabecular meshwork and even a small hyphema can spike the pressure and threaten the optic nerve, lowering the threshold for surgery. The Cochrane review found no clear benefit of aminocaproic acid or systemic steroids, so pharmacological prophylaxis is not routine. Surgical evacuation is for complications — corneal blood staining, uncontrolled glaucoma, a large clot, or a persistently raised pressure in sickle-cell disease. [6] [7]

Examiner: What is sympathetic ophthalmia, and how is it prevented? [1]

Candidate: Sympathetic ophthalmia is a rare bilateral granulomatous panuveitis that follows a penetrating injury to one eye — the exciting eye — causing inflammation in the previously uninjured sympathising eye, from days to years later with a peak around three months. It is treated with systemic immunosuppression. Enucleation of a blind, severely injured exciting eye within 14 days of the injury may prevent it, which is one reason a hopelessly injured eye is sometimes removed rather than repaired. [1]

Wrap

Examiner: Summarise paediatric ocular trauma in one sentence. [8]

Candidate: The whole skill is in the first 30 seconds: a chemical splash is irrigated immediately and copiously, before any examination, because every minute of retained alkali destroys limbal stem cells; and a suspected open globe is shielded with a rigid Fox shield and never pressed, because pressing a full-thickness wound extrudes the eye — get those two moves right and you have done more for the child's vision than any operation that follows, then grade the injury with BETT and the Dua clock hours, prognosticate with the Ocular Trauma Score, and never forget amblyopia surveillance. [5] [1]