NCLE Exam Prep Questions And
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optic zone - ANSWER✔✔ the central portion of a contact lens which contains the
refractive power and generally corresponds to the central corneal cap
posterior apecal radius - ANSWER✔✔ 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 - ANSWER✔✔ occurs when the posterior radius of curvature is
decreased (i.e. 8.4 to 8.1 mm)
flatter base curve - ANSWER✔✔ occurs when the posterior radius of curvature is
increased (i.e.8.1 to 8.4 mm)
bicurve lens - ANSWER✔✔ 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 - ANSWER✔✔ 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 - ANSWER✔✔ contains a base curve and three or more peripheral
curves. usually a larger lens.
junctional zone - ANSWER✔✔ the junction of two curves
blending - ANSWER✔✔ the smoothing of a junctional zone by removing the sharp
line between the zones
lens diameter or chord diameter - ANSWER✔✔ the width of a lens or the
measurement from one edge of the lens to the opposite edge
curve widths - ANSWER✔✔ the width of the CPC, PPC, or IPC
central thickness - ANSWER✔✔ separation between the anterior and posterior
surface at the geometric center of the lens. minus lenses are thinner, plus lenses
are thicker
ballasted lens - ANSWER✔✔ lens with a heavier base which becomes oriented
inferiorly or downward when the lens is worn
prism ballated lens - ANSWER✔✔ a ballasted lens which utilizes a prism wedge
designed to weight the lens
truncated lens - ANSWER✔✔ 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 - ANSWER✔✔ effective power of a lens when measured from
the back surface
wetting angle - ANSWER✔✔ 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 - ANSWER✔✔ lenses with different radii of curvature
in each meridian which are used to correct astigmatism
principal meridians - ANSWER✔✔ the meridians of shortest and longest radii
which differ by 90 degrees
front surface toric lens - ANSWER✔✔ a lens in which the anterior surface has two
different radii and the posterior surface is spherical
back surface toric lens - ANSWER✔✔ a lens in which the posterior surface has two
different radii and the anterior surface is spherical
bitoric lens - ANSWER✔✔ a lens in which both the posterior and anterior surfaces
contain two different radii
lenticular bowl - ANSWER✔✔ 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
, spin-cast soft lens - ANSWER✔✔ a mentioned of manufacturing soft contact
lenses whereby a liquid material is revolved in a mold at a controlled speed and
temperature which produces the desired curvature, design, and power
acuity - ANSWER✔✔ clearness; visual ________ is measured by the smallest
object that can be seen at a certain distance
adnexa oculi - ANSWER✔✔ accessory structures of the eye, such as the lacrimal
appatatus and the eyelids
albinism - ANSWER✔✔ heredetary loss of pigment in the eye, skin, hair, usually
associated with lowered visual acuity, nystagmus and light sensitivity
amblyopia - ANSWER✔✔ loss of vision without any apparent disease of the eye
ametropia - ANSWER✔✔ a refractive error in which the eye, when in a state of
rest, does not focus the image of an object upon the retina; includes hyperopia,
myopia, and astigmatism. see also refractive error
aniridia - ANSWER✔✔ congenital absence of the iris
aniseikonia - ANSWER✔✔ a condition in which the ocular image of an object as
seen by one eye differs so much in size or shape from that seen by the other eye
that the two images cannot be focused into a single impression
aniscoria - ANSWER✔✔ inequality of the pupils in diameter
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