Choosing Lens Material

CR39 pros

• High optical quality (low dispersion)

• More scratch resistant than polycarb

• Least expensive

CR39 cons

• Less impact resistant than polycarb and trivex

• Thicker lenses (lower n)

A lower refractive index will result in…

Steeper curvature → Thicker lens

Polycarbonate pros

• High impact resistant

• Thin lenses

• Built in UV protection

Polycarbonate cons

• Lowest optical quality (more dispersion)

• More expensive than CR39

• Must be anti-scratch and AR coated

Trivex pros

• High impact resistance

• Thinner lenses

• Better optical quality than polycarb

Trivex cons

• More expensive than polycarb

• Lower optical quality than CR39

High index pros

• Thinner lenses

High index cons

• Most expensive

• Lower optical quality than CR39

Rank types of lenses from least expensive to most

CR39 → Polycarb → Trivex → HI 1.67 → Crown glass → HI 1.74

If someone is a polycarb non-adapter, what type of lens should you recommend?

Trivex

If price is a bigger issue → CR39

Rank types of lenses from worse optical quality to best

Polycarb → High index → Trivex → CR39 → Crown glass

What type of lenses should be recommended to children?

Polycarb and trivex for their impact resistance

Rank types of plastic lenses from thickest to thinnest

CR39 → Trivex → Polycarb → HI

Ways that trivex and polycarb are similar

• Impact resistance

• Scratch easier

• UV absorption

Ways that polycarb and trivex are different

• Trivex is more expensive

• Trivex has better optical quality

• Polycarb has higher n