Free previewYou're reading the free part of this topic. The rest is included with Clinical.See what's included
Contact lens optics
Anatomy & Optics
Key Points
- •The tear lens formed between an RGP lens and the cornea corrects corneal astigmatism - this is why RGP lenses are first-line for keratoconus and irregular astigmatism
- •Vertex distance correction is clinically significant for powers >±4 D: moving a minus lens closer to the eye makes it less minus; moving a plus lens closer makes it more plus
- •Minimum Dk/t for safe daily wear is >24 barrer/cm (Holden-Mertz); for overnight wear >87 barrer/cm (Harvitt-Bonanno)
- •Daily disposable silicone hydrogel lenses are the safest option with the lowest risk of microbial keratitis
- •Overnight/extended wear is the single greatest risk factor for contact lens-related microbial keratitis (5-15x increased risk)
Free preview ends here
Keep reading Contact lens optics
17 more sections are included with the Clinical plan.
- Definition
- Epidemiology
- Aetiology and causes
- Pathogenesis
- Classification
- Risk factors and associations