Visual development, amblyopia and vision screening in childhood — formative SAQs

SAQ 1 — The child who sees well with both eyes open (10 marks, 15 minutes)

A five-year-old girl attends school-entry vision screening. With both eyes open she manages perfectly, but when the right eye is occluded she reads only the top line of the chart with the left (an acuity of about 6/60, or 1.0 logMAR) that does not improve with a pinhole. The eyes are structurally normal, the red reflexes are symmetric, and the cover test shows no manifest turn. [2]

a) Define amblyopia and explain why this is a cortical rather than an ocular problem. (2 marks) [2]

b) State the screening acuity refer threshold that should have triggered referral, and explain why a both-eyes-open check can miss this deficit. (2 marks) [1]

c) Outline the stepwise management, naming the first intervention and the two occlusion or penalisation options supported by the Pediatric Eye Disease Investigator Group trials. (4 marks) [4] [5]

d) Give the population-level justification for universal preschool screening in one sentence. (2 marks) [7]

SAQ 2 — The white pupil at the six-week check (10 marks, 15 minutes)

A two-month-old baby is brought because the parents noticed a white pupil in a flash photograph. On examination the red reflex is absent in the left eye and normal in the right. The baby is otherwise well. [10]

a) What are the two can't-miss diagnoses, and what is the appropriate referral timeframe? (3 marks) [10]

b) Explain why deprivation amblyopia is the densest type and why the timing of surgery for a visually significant congenital cataract is measured in weeks rather than months. (3 marks) [2]

c) Name two further can't-miss mimics of a white or poor red reflex that you would want excluded at ophthalmology assessment. (2 marks) [10]

d) Contrast this with the common, reassuring finding of pseudostrabismus: name the discriminating bedside features that separate it from a real strabismus. (2 marks) [2]