Six-year-old with a constant esotropia and hyperopic anisometropia: prescribing, dispensing and the first six months
A 6-year-old boy is brought by his mother to a Ministry of Health polyclinic optometry room after his school screening flagged reduced vision in the right eye. He has never worn glasses and has no known health problems; birth and development were normal. Unaided acuity with a crowded picture test is 0.16 OD and 0.8 OS. Cover testing shows a constant right esotropia of about 20 prism dioptres at both distance and near, and on alternate cover he prefers to fixate with the left eye. Cycloplegic retinoscopy 40 minutes after cyclopentolate 1% gives +5.00/−0.75×180 OD and +1.50 DS OS. Anterior segments are clear, fundi are healthy, and there is no manifest latent nystagmus. The optometrist is working alone; there is no orthoptist on site and the next paediatric ophthalmology clinic is 8 weeks away. The boy starts Grade 1 in three months and his mother is anxious about the squint being noticed.
1. Interpret the findings. What is the working diagnosis, how do the refractive and binocular findings relate, and why is the full cycloplegic prescription prescribed rather than a reduced 'comfort' power?
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Working diagnosis. A constant right esotropia with hyperopic anisometropia, that is, an accommodative (refractive) esotropia with an anisometropic amblyopia of the right eye superimposed.
What the numbers say.
- Spherical equivalent OD = +5.00 + (−0.375) = +4.63 D; OS = +1.50 D; anisometropia about 3.1 D.
- The more hyperopic eye is also the deviated and amblyopic eye (0.16 vs 0.8). That is the classic pattern: a blurred retinal image and strabismic suppression are acting on the same eye, so the amblyopia is likely to be denser than the acuity alone suggests.
- A constant 20 Δ esotropia at distance and near, with a strong fixation preference and no alternation for distance, means a full accommodative component is likely but a partly accommodative or infantile component cannot be excluded yet.
Why the full cycloplegic result. Undercorrecting hyperopia in an esotropic child leaves residual accommodative demand, which drives accommodative convergence and holds the deviation present. Undercorrecting the more ametropic eye additionally widens the anisometropia and blunts later amblyopia therapy, because the amblyopic eye keeps the poorer image. So the full +5.00/−0.75 and +1.50 are ordered, with no routine 'adaptation' reduction; the refraction is repeated at review and dynamic retinoscopy over the new glasses confirms the child is actually accommodating through the correction.
2. Write the dispensing plan: exact prescription for each eye, lens and frame choices for a 6-year-old, and the instructions you give the mother about wear time and what to expect.
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Prescription (full cycloplegic result). OD +5.00/−0.75×180; OS +1.50 DS. Full-time wear from waking; off only for bathing.
Lens decisions.
- 1.50 or polycarbonate for impact resistance in a young child. A plus lens is thinnest at the edge anyway, so a high index buys almost nothing and costs Abbe number.
- Aspheric design to reduce edge thickness and the small magnification difference between the two eyes. Anti-reflection coating, because the lenses will be dropped and scratched.
- Aniseikonia from roughly 3 D of anisometropia is around 1.5–2.5% - usually tolerated by children, but if he pulls the glasses off or reports 'two sizes', review whether an iseikonic design is needed.
Frame. Small eye size, well-fitting bridge with adjustable pads, cable temples for an active 6-year-old. Avoid oversized frames: weight, slipping and off-axis prism all increase.
Centration. Measure monocular PDs with the fellow eye occluded. Do not use the pupil position of the esotropic eye at the moment of measurement - the deviated eye's pupil is not sitting over the visual axis; mark the corneal light reflex instead.
No prism. Prism does not treat accommodative esotropia and would mask deterioration.
What the mother is told. He must wear them all day, every day, including at school; the first two weeks may bring complaints of blurred floor or mild headache; the glasses will probably straighten the eye within a few weeks but they are not a cure to be stopped when the eye looks straight; a spare pair is worth having; bring him back at 6–8 weeks, or sooner if the eye turns more, the good eye seems worse, or he refuses the glasses.
3. Plan the next six months. How do you treat the amblyopia, when do you escalate, and what would make you refer before the scheduled paediatric slot?
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Phase 1 (0–8 weeks): refractive correction alone. Amblyopia therapy does not start on day one. In refractive accommodative esotropia and anisometropia the glasses themselves often improve acuity substantially, and patching started simultaneously confounds the assessment. Review at 6–8 weeks with crowded logMAR or picture acuity, cover test with glasses at distance and near, and dynamic retinoscopy.
Phase 2: penalisation if acuity has not equalised. Patching 2 h/day (up to 6 h if the gap is large and compliance is good) or atropine 1% drops daily or weekly - trial data show atropine is broadly comparable to patching for moderate amblyopia and is often better accepted by families. Explain light sensitivity and near blur; the penalising agent goes in the good eye, never the amblyopic one, and the good eye must be watched for reverse amblyopia.
Review every 6–8 weeks with acuity and fixation preference until stable, then lengthen the interval.
Refer before the 8-week slot if: acuity falls in the left eye, the deviation increases with glasses, a manifest or latent nystagmus appears, structural disease is suspected, or the child cannot be assessed reliably.
Paediatric ophthalmology referral. Telephone now and ask for an earlier appointment given school entry, and send him routinely regardless for: residual esotropia greater than about 8–10 Δ with glasses after a fair trial, incomitance or a V pattern, no improvement after 12 weeks of documented good compliance, or a need for surgical counselling. Make clear in the letter that any surgery would be for the residual deviation once the refractive component has been treated - not instead of the glasses.