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Refraction & Optical Assessment
High YieldManual refraction, automated refraction, and optical imaging assessment
Refraction is the most frequently performed procedure in ophthalmology, yet a sloppy endpoint can mask pathology or trigger unnecessary investigations. Retinoscopy remains the definitive objective technique — indispensable in children, uncooperative patients, and as a cross-check before refractive surgery. This section covers subjective and objective refraction methods with their pitfalls and clinical applications.
Key Points
- Manifest refraction follows a systematic protocol: fog → MPMVA → JCC axis → JCC power → sphere refinement → duochrome → binocular balance → near add (if ≥40)
- Retinoscopy is the gold standard objective refraction — with-motion = add plus, against-motion = add minus; neutralisation point = endpoint minus working distance correction
- Cycloplegic refraction (cyclopentolate 1% or atropine 1%) is mandatory in all children <10 years and young hyperopes — eliminates accommodative spasm that masks true hyperopia
- JCC (Jackson Cross Cylinder) refines cylinder axis (handle on axis, flip for preference) and power (minus axis on trial axis) — ±0.25 D flips
- Vertex distance correction needed for lenses ≥±4 D — spectacle Rx at 12 mm vertex differs from contact lens power at cornea
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