Accommodation-related presbyopia occurs primarily because of which age-related change?
- A Weakening of the zonular fibres reduces ciliary body tension
- B Increased lens nuclear sclerosis and reduced lens elasticity prevents adequate shape change despite normal ciliary muscle contraction ✓
- C Reduced ciliary muscle contractility due to autonomic denervation
- D Vitreous liquefaction reduces posterior zonular tension
Explanation
The Helmholtz theory of accommodation states that for near focus, the ciliary muscle contracts, zonules relax, and the crystalline lens becomes more curved (increased power). In presbyopia, the lens nucleus becomes increasingly sclerotic and inelastic with age, preventing adequate curvature change despite maintained or even increased ciliary muscle contraction. Scheimpflug studies confirm that in presbyopia the lens does not change shape adequately on accommodation. Ciliary muscle function is largely maintained until late middle age. This explains why reading adds are needed, and forms the basis for corneal inlays (e.g., KAMRA), multifocal/EDOF IOLs, and lens-refilling procedures under development.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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