Ocular trauma and chemical injury — formative SAQs

SAQ 1 (10 marks)

A 6-year-old is brought to the emergency department immediately after a dishwasher-tablet alkali powder burst into her right eye at home. She is in severe pain, the eye is firmly shut and watering, and the parent rinsed it briefly under the tap before coming in. [5]

Question: Outline the immediate and definitive management of this child, including the irrigation protocol, the grading of severity and the follow-up. (10 marks) [5]

Model answer

Immediate irrigation — the first and most important action (3 marks). A chemical eye injury is irrigated immediately and copiously with saline or Ringer lactate, before any examination and before any pH check, because every minute of retained alkali saponifies lipid membranes and destroys limbal stem cells. Instil a drop of topical anaesthetic to make irrigation tolerable, and irrigate for at least 30 minutes using an intravenous giving set or a Morgan lens. The parent's tap-water rinse was correct first aid and should be continued; the volume and speed of irrigation matter more than the exact fluid. [5] [12]

Fornix clearance and the pH protocol (2 marks). Evert the upper and lower eyelids and sweep the conjunctival fornices to remove any retained particulate matter — a fleck of tablet or cement plastered to the tarsal conjunctiva will keep releasing alkali. After at least 30 minutes of irrigation, check the tear-film pH with indicator paper, wait five to ten minutes, recheck, and continue irrigation until the pH reads 7.0 to 7.2. Only then proceed to the slit-lamp examination. [5]

Examination and grading of severity (2 marks). Record the visual acuity in each eye separately. Examine for conjunctival chemosis, corneal epithelial defects (fluorescein) and, crucially, the extent of limbal ischaemia (pallor). Grade the severity with the Dua classification, which is based on clock hours of limbal ischaemia — the single most important prognostic factor because the limbus holds the corneal stem cells: 0 to 3 clock hours good, 4 to 6 guarded, 7 to 9 poor, 10 to 12 very poor. Marked limbal ischaemia predicts limbal stem-cell deficiency. [4]

Definitive medical management and referral (2 marks). After irrigation, give topical antibiotics to prevent infection, a cycloplegic for comfort and to prevent synechiae, and intraocular-pressure-lowering agents if the pressure rises from trabecular meshwork damage. Refer urgently to ophthalmology; severe limbal ischaemia warrants amniotic-membrane transplantation and, later, limbal-stem-cell transplantation or keratoprosthesis in the worst cases. Explain to the family that the outcome tracks the delay to irrigation and the clock hours of ischaemia. [12] [5]

Disposition, follow-up and prevention (1 mark). Admit or observe as guided by severity and social circumstance. Arrange ocular-surface and intraocular-pressure follow-up, and amblyopia surveillance because the child is in the amblyogenic age range. Counsel the family on household chemical safety and secure storage of cleaning products, because prevention is the most effective treatment. [8]

SAQ 2 (10 marks)

A 9-year-old is struck in the right eye by a dart. On examination the right pupil is teardrop-shaped and peaked toward the nasal limbus, the anterior chamber is shallow, there is a small layered hyphema, and the globe feels soft. [1]

Question: Describe the recognition and stepwise management of this child, including what must be avoided and the indications for surgery. (10 marks) [1]

Model answer

Recognition and diagnosis (2 marks). The diagnosis is a suspected open-globe injury. The teardrop or peaked pupil pointing toward the wound, the shallow anterior chamber, the hyphema, and the soft globe with hypotony after sharp trauma are the classic signs of a full-thickness defect of the globe. In BETT terms this is an open-globe laceration; the iris is likely plugging the wound. This is a sight-threatening emergency requiring urgent ophthalmology. [1] [2]

Protection and preparation for surgery (3 marks). Place a rigid Fox shield over the eye, large enough to cover the orbit and lids and taped so that it does not touch or press the globe. Keep the child nil by mouth and give an antiemetic, because vomiting raises venous pressure and can extrude intraocular contents. Give analgesia and a calm environment. Give intravenous antibiotics with anti-endophthalmitis cover (covering Gram-positive and Gram-negative organisms) and tetanus prophylaxis. Obtain computed tomography of the orbits and brain to confirm the injury, locate any retained foreign body, and assess for associated orbital or intracranial injury; avoid MRI if a metallic foreign body is possible. [1] [8]

What must be avoided (2 marks). Never press on the eye, never apply a pressure patch, never instil drops into the eye, and never measure the intraocular pressure — each can extrude intraocular contents. Do not forcibly pry swollen lids apart; if the lids cannot be opened gently, stop and image. These 'never' actions are the cardinal errors in open-globe management. [1]

Indications for surgery and prognosis (2 marks). Urgent surgical repair by ophthalmology is indicated — primary closure of the wound to restore the globe, with vitrectomy as indicated for a posterior injury, retinal detachment, or a retained intraocular foreign body. The Ocular Trauma Score predicts the final vision from the presenting acuity and the presence of rupture, perforating injury, endophthalmitis, retinal detachment and an afferent pupillary defect; a perforating injury and a poor presenting acuity portend a worse outcome. [3] [2]

Follow-up and safeguarding (1 mark). Arrange amblyopia and vision surveillance, because the developing visual system is unforgiving of deprivation. Watch for endophthalmitis (worsening pain, falling vision, increasing inflammation) and for sympathetic ophthalmia, the rare bilateral granulomatous panuveitis after penetrating injury. Clarify the mechanism and consider non-accidental injury if the history is inconsistent. [8] [1]