Describe accommodative esotropia with its management.

Accommodative Esotropia

• Accommodative esotropia is a convergent squint caused by excessive accommodative convergence, either because the child is hypermetropic and over-accommodates, or because the AC/A ratio is abnormally high.
• It is the commonest form of childhood esotropia, and the one that is treatable without surgery.
• The mechanism — accommodation and convergence are yoked. An uncorrected hypermetrope must accommodate constantly to see clearly, and the obligatory convergence that accompanies it overcomes the fusional divergence reserve, so the eye turns in
• Typical onset is 18 months to 4 years, often intermittent at first, worse for near, and precipitated by illness, fever or fatigue — which is when the parents first notice it
• Refractive type — hypermetropia of +3 to +6 dioptres with a normal AC/A ratio. The deviation is similar for distance and near, and is fully corrected by the appropriate spectacles
• Non-refractive (convergence excess) type — a high AC/A ratio with little or no hypermetropia. The deviation is much greater for near than for distance. Treated with bifocals, using an executive segment whose top bisects the pupil.
• Partially accommodative type — glasses reduce but do not abolish the deviation. Surgery is performed for the non-accommodative residue only, and the glasses are continued afterwards. Operating for the whole angle produces a consecutive exotropia when the glasses are worn
• Management:
• 1. Cycloplegic refraction with atropine or cyclopentolate.
• 2. Prescribe the full cycloplegic correction and insist on constant wear. A reduced prescription "to help them adapt" leaves the squint uncontrolled and is a common error
• 3. Treat any amblyopia with occlusion or atropine penalisation
• 4. Bifocals or miotics where a high AC/A ratio leaves a residual near deviation
• 5. Surgery only for the non-accommodative component, and only once the deviation is stable in glasses
• Warn the family in advance that the squint will return whenever the glasses are removed, and that this is expected rather than a failure of treatment — otherwise compliance collapses
• Follow-up — the hypermetropia reduces slowly through childhood, so the prescription must be rechecked under cycloplegia at intervals, and many children can eventually reduce or discontinue the glasses
• Prognosis for binocularity is good where the correction is given promptly, because the eyes were straight before onset and fusion had developed — which is why delay is what costs the binocular vision
• Accommodation and convergence are yoked, so an uncorrected hypermetrope converges every time he focuses