optic zone - - - the central portion of a contact lens which contains the refractive power and
generally corresponds to the central corneal cap
posterior apecal radius - - - this term is generally used in reference to
...
optic zone - - - the central portion of a contact lens which contains the refractive power and
generally corresponds to the central corneal cap
posterior apecal radius - - - this term is generally used in reference to spin-cast soft lenses. the
curvature of the posterior surface of the lens changes with the refractive power. the radius of
curvature is measured at the apex of the posterior surface.
steeper base curve - - - occurs when the posterior radius of curvature is decreased (i.e. 8.4 to 8.1
mm)
flatter base curve - - - occurs when the posterior radius of curvature is increased (i.e.8.1 to 8.4
mm)
bicurve lens - - - a contact lens which contains two curves: one base curve and one secondary
curve. it is usually small 7.5 to 8.8 mm on diameter, relatively steep and made with narrow
peripheral curves about 0.2 mm. lenses are usually intrapalpebral lenses, designed to fit within
the palpebral fissure limits.
tricurve lens - - - a contact lens which contains three curves: a base curve, an outer peripheral
posterior curve (PPC), and an intermediate posterior curve (IPC). lenses are generally larger, 9.5
mm or greater.
multicurve lens - - - contains a base curve and three or more peripheral curves. usually a larger
lens.
junctional zone - - - the junction of two curves
blending - - - the smoothing of a junctional zone by removing the sharp line between the zoneslens diameter or chord diameter - - - the width of a lens or the measurement from one edge of the
lens to the opposite edge
curve widths - - - the width of the CPC, PPC, or IPC
central thickness - - - separation between the anterior and posterior surface at the geometric
center of the lens. minus lenses are thinner, plus lenses are thicker
ballasted lens - - - lens with a heavier base which becomes oriented inferiorly or downward when
the lens is worn
prism ballated lens - - - a ballasted lens which utilizes a prism wedge designed to weight the lens
truncated lens - - - a lens which has been cut off, usually 0.5-1.5 mm along its lower edge, to
form a horizontal base. double ________ along the top and bottom portion of the lens is
sometimes done to help improve stabilization
back surface power - - - effective power of a lens when measured from the back surface
wetting angle - - - the angle that the edge of a bead of water makes with the surface of the plastic,
the smaller the angle the greater the wetting ability
toric lenses or toroid lenses - - - lenses with different radii of curvature in each meridian which
are used to correct astigmatism
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