Tvrda gas-propusna (RGP) kontaktna sočiva Koncepcija

Slide 12
Kontinualni ne-sferčni dizajn
• Jedna kontinualna kriva
• Aproksimira oblik kornee
• Asferična
• Oblik se obično dobija iz konusnih preseka
• Više od jednog konusnog preseka se koristi da
bi se dobila kontinualna kriva
Rigid Gas Permeable Contact Lenses Design
Continuous Non-Spherical Design
Surface designs (front or back) don’t have to be limited to designs based on a circle. The
concept of the cornea not being spherical has been accepted for more than a century
(Senff, 1846).
The attraction of a continuous single curve which more nearly approximates the cornea’s
actual shape is obvious. Such surface designs are referred to as ‘aspheric’ and represent a
deliberate attempt to improve on designs which are ‘spherical’. (The term ‘spheric’ is not
normally used but is still correct.)
The family of curves from which such surface shapes can be derived, which also includes
a first order approximation to the shape of the cornea, is called conic sections.
Conic sections can be combined to form compound continuous curves. Combinations of
conic and nonconic sections have also been used. The advent of computers and computeraided
manufacturing means that very complex continuous curves are possible.
Kontinualni ne-sferčni dizajn
Dizajn površine (prednje ili zadnje) ne mora biti ograničen samo na krugu. Oblik kornee
nije sferni što je ustanovljeno pre više od jednog veka (Senff, 1846).
Privlačnost jedne kontinualne krive koja vrlo blisko aproksimira oblik kornee je
očigledna. Takav oblik je asferični i predstavlja promišljen pokušaj da se popravi sferični
dizajn (Izraz “sferni” normalno ne koristi iako je korektan.
Familija krivih od kojih se može dobiti oblik površine, što takođe uključuje prvu
aproksimaciju oblika kornee, se zove konusni preseci.
The family of curves from which such surface shapes can be derived, which also includes
a first order approximation to the shape of the cornea, is called conic sections.
Konusni preseci se mogu kombinovati da bi se dobila složena kontinualna kriva. Takođe
se može koristiti i kombinacija konusnih i ne-konusnih preseka. Korišćenje kompjutera
omogućava vrlo kompleksne kontinualne krive.