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]