1.By material
(1) Hard contact lenses.
(2) Soft contact lenses.
2, according to wearing time
(1) daily wear: lenses are taken off every night for cleaning and disinfection.
(2) long wear: lenses worn overnight, regardless of consecutive days.
(3) flexible prescription: for occasional overnight wear, no more than two nights per week.
3. By use cycle
(1) Disposable lenses: discarded after use, without care and maintenance products.
(2) Frequent replacement lenses: discarded within three months, care products required.
(3) traditional lenses: more than three months, using about 12 months
4. Percentage of water content in lenses according to water content
1, water content = water content in the lens / total weight of the lens × 100% soft lenses.
2, routinely divided into two categories: low water content 50% oxygen permeability is proportional to the water content.
5, FDA soft lens material classification method
(1) low water content non-ionic water content 35% – 50% conventional type of ultra-thin lenses ideal material.
(2) high water content non-ionic water content 51%-81% disposable lens ideal material low water content ionic DD easy to produce precipitates; high water content ionic DD easy dehydration, premature yellowing, sensitive to PH, in acidic solution can produce size curvature change.
6.By function
(1) vision correction lenses: for refractive error, aphakic eyes or cone corneas.
(2) Cosmetic lenses: for those who change the hikari angle of the eye.
(3) treatment lenses: for the treatment of various eye diseases.
(4) Color blindness lenses: for color blindness patients to improve color discrimination.