Properties of CL Materials and Lens Polymers

Tri A Wk 2

ideal contact lens

comfort, vision, health and convenience

density is

mass/volume of lens

High density may be disadvantageous due to

heavier lens and may not centre properly

Refractive index determines the

thickness and curvature of lens

Optical transmission is

the ratio of light which passes through material as a %

ability of a lens to rehydrate is important for

dimensional stability

Wettbility of a lens

allow a thick coverage of the tear film, a smooth recovery of tear layer, deposit prevention and good VA

higher the water content the

more comfortable the contact lens but reduction in stability

tensile strength is the

resistance to damage during lens handling and long term durability

tear strength

resistance of material of tear propagation from notch or defect

modulus of rigidity

the stiffness of a material

oxygen permeability

increased water content leads to increased oxygen permeability

toxicity may result in

limbal hyperaemia, peripheral corneal infiltrates and keratic precipitates

further surface damage may result in

patterns of punctate epithelial keratopathy

D is the

diffusion of oxygen through the polymer

k is the

suitability of oxygen in the polymer