Which of the following best describes the primary defect in accommodative esotropia?

Explanation

## Accommodative Esotropia: Pathophysiology **Key Point:** Accommodative esotropia occurs when the convergence response to accommodation is abnormally high relative to the amount of accommodation stimulus — characterized by a high AC/A (accommodation-convergence to accommodation) ratio. ### Mechanism **High-Yield:** The AC/A ratio is the amount of convergence (measured in prism diopters) induced per diopter of accommodation. - Normal AC/A ratio: 3–5 prism diopters per diopter of accommodation - In accommodative esotropia: AC/A ratio is **>5** (often 8–10 or higher) ### Pathophysiology 1. Patient has uncorrected hypermetropia 2. To achieve clear vision, excessive accommodation is required 3. Each unit of accommodation triggers excessive convergence (due to high AC/A ratio) 4. Result: **esotropia that appears or worsens with near fixation** ### Clinical Presentation - Onset typically between 18 months and 4 years of age - Esotropia worse at near than distance - Often associated with uncorrected hypermetropia (typically +2.00 to +6.00 D) - May be fully accommodative, partially accommodative, or non-accommodative component present ### Management **Clinical Pearl:** The primary treatment is **full hypermetropic correction** with spectacles. This reduces the accommodation demand and thereby reduces the convergence stimulus. - If fully accommodative: spectacle correction alone resolves the esotropia - If partially accommodative: spectacles + possible surgery for residual deviation - Bifocals or progressive lenses may be added if AC/A ratio is very high **Mnemonic: ACHE** — **A**ccommodative esotropia, **C**orrection with glasses, **H**ypermetropia, **E**sotopia at near