Refractive error in children — formative SAQs

SAQ 1 (10 marks)

An 8-year-old girl is brought in because she has been squinting at the board for six months and her distance vision has worsened over the year. Both her parents wear glasses for short-sightedness. Her unaided distance acuity is reduced bilaterally and improves to age-normal with a pinhole. She spends most of the day on screens and little time outdoors. Her parents have read about "atropine drops to stop myopia" and ask whether she should start them. [1]

Question: (a) What is the likely diagnosis and why does a pinhole improve her vision, and what single investigation confirms the refractive state in a child and why? (b) Outline the stepwise management of her myopia, including the non-pharmacological foundation and the pharmacological and optical myopia-control options, naming a specific drug concentration with evidence. (c) What are the red flags that would prompt urgent ophthalmology referral rather than routine spectacles? (10 marks) [12]

Model answer

(a) Diagnosis, pinhole and confirmation (3 marks). The likely diagnosis is myopia — progressive blurred distance vision with clear near vision, squinting, two myopic parents (the strongest risk factor), intense near work and limited outdoor time, in a school-age child. A pinhole improves her vision because it narrows the light bundle entering the eye and reduces the blur circle on the retina, demonstrating that the deficit is refractive rather than organic or amblyopic — but a pinhole never excludes amblyopia or pathology on its own, only separates a refractive cause. The gold-standard confirmation of refractive state in a child is cycloplegic retinoscopy (objective refraction after cyclopentolate), because a child's accommodation can distort measurement and would otherwise mask any coexisting hyperopia. [2] [10]

(b) Stepwise management and myopia control (5 marks). The first step is to correct the distance refractive error with spectacles to the cycloplegic prescription, giving clear distance vision; under-correction is not a myopia-control strategy and does not slow progression. The non-pharmacological foundation of myopia control is increased outdoor time (about two hours a day) and reduced prolonged near work, which slow axial elongation through retinal light exposure. Layered on this, the options are low-dose atropine eye drops, orthokeratology (an overnight rigid lens that reshapes the cornea) and peripheral-defocus contact lenses or spectacles. For atropine, the LAMP trial established that of the low concentrations 0.05, 0.025 and 0.01 percent, 0.05 percent was the most effective over the first year, given as one drop at bedtime; I would explain that myopia control aims to slow, not reverse, axial elongation, and that adherence over years matters. [4] [12]

(c) Red flags for urgent referral (2 marks). The red flags that demand prompt ophthalmology referral rather than routine spectacles are reduced vision that does not improve to age-normal with best correction in either eye (suspect amblyopia or pathology), a new or worsening squint or abnormal head posture, and a rapid or progressive myopic shift, especially in a young child, which may signal a transient refractive change of systemic disease such as poorly controlled diabetes or an ocular pathological cause. None of these is present here, but each is the reason a child with reduced vision is reviewed after correction rather than discharged. [10] [12]

SAQ 2 (10 marks)

A 4-year-old boy is referred after a preschool photoscreen flags a "refer" result. His mother has noticed he screws his eyes up and occasionally one eye turns inward when he is tired. His distance acuity is difficult to measure but appears reduced, and the cover test shows a variable convergent squint. [10]

Question: (a) What is the likely underlying problem and why must you measure refraction under cycloplegia in this child? (b) Outline your management, including the prescribing principle for hyperopia in a young child and the amblyopia risk. (c) Why is a photoscreener a screen and not a prescription, and what would change your management to urgent referral? (10 marks) [2]

Model answer

(a) Likely problem and cycloplegia rationale (3 marks). The likely underlying problem is significant hyperopia driving an accommodative convergent (esotropic) squint: the child accommodates hard to bring the hyperopic focus forward onto the retina, and because convergence is linked to accommodation, the eyes turn inward. I must measure refraction under cycloplegia because a child can accommodate several dioptres, so an undilated test will underestimate or completely mask the hyperopia and may even read the eye as emmetropic — the very error driving the squint. Cyclopentolate abolishes accommodation and yields the true plus error, which is the basis for prescribing. [10] [2]

(b) Management and the prescribing principle (4 marks). Management begins with cycloplegic retinoscopy to measure the true hyperopia, followed by full plus spectacle correction to the cycloplegic measurement. The prescribing principle in a young child is to correct amblyogenic hyperopia promptly to protect visual development and to reduce the accommodative effort — which often reduces or resolves the accommodative squint — balanced against leaving comfortable accommodation. Because the convergent squint and any inter-eye difference risk amblyopia, I would measure each eye's acuity and add occlusion or atropine penalisation of the better-seeing eye if amblyopia is present, treating within the sensitive period. The squint that fails to improve with full hyperopic correction is not a purely accommodative problem and needs ophthalmology and orthoptic review. [10] [2]

(c) Photoscreening as a screen and the urgent thresholds (3 marks). A photoscreener (or autorefractor) is a screen, not a diagnostic refraction: it estimates refractive error and detects amblyopia risk factors in seconds, which is why it is ideal for a preschool child who cannot do optotype testing, but it cannot prescribe the lens — a "refer" result must be followed by cycloplegic retinoscopy to confirm the error and decide the prescription. What would change management to urgent referral is reduced vision that does not improve with correction, a new or fixed squint with reduced vision, or an abnormal head posture with neurological signs — pointers away from simple refractive error toward amblyopia, a motility disorder or, rarely, a cranial nerve palsy or ocular pathology. [10] [2]