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Low Vision Aids
Cataract & Refractive Surgery
Key Points
- •Low vision (WHO): BCVA <6/18 to >=3/60 in the better eye; rehabilitation uses four types of magnification: relative distance, relative size, angular (telescopes), and electronic (CCTV)
- •Kestenbaum's rule: reciprocal of the Snellen distance fraction = approximate add power needed (VA 6/36 → +6D add; VA 6/60 → +10D add)
- •AMD (central scotoma): needs magnification + eccentric viewing training (combined > either alone); glaucoma/RP (peripheral loss): needs field expansion (reverse telescopes, prisms), NOT magnification
- •CCTV (desktop video magnifier) is the gold standard for high-magnification sustained reading (up to 60x); stand magnifiers are best for patients with hand tremor; high-add spectacles for hands-free moderate magnification
- •Always optimise spectacle correction and illumination first - uncorrected refractive error is the most common correctable cause of visual impairment; improved task lighting (500–1000 lux) can be as helpful as a magnifier
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- Definition
- Epidemiology
- Aetiology and causes
- Pathogenesis
- Classification
- Risk factors and associations