NCLE 2025 EXAM PREP WITH ACCURATE SOLUTIONS- GUARANTEED A+
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 zones
lens 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
principal meridians
the meridians of shortest and longest radii which differ by 90 degrees
front surface toric lens
a lens in which the anterior surface has two different radii and the posterior surface is
spherical
back surface toric lens
a lens in which the posterior surface has two different radii and the anterior surface is
spherical
bitoric lens
a lens in which both the posterior and anterior surfaces contain two different radii
lenticular bowl
a lens design generally used in higher plus power which consists of a central optic zone
and a surrounding non-optic peripheral or "carrier" portion
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 zones
lens 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
principal meridians
the meridians of shortest and longest radii which differ by 90 degrees
front surface toric lens
a lens in which the anterior surface has two different radii and the posterior surface is
spherical
back surface toric lens
a lens in which the posterior surface has two different radii and the anterior surface is
spherical
bitoric lens
a lens in which both the posterior and anterior surfaces contain two different radii
lenticular bowl
a lens design generally used in higher plus power which consists of a central optic zone
and a surrounding non-optic peripheral or "carrier" portion
