NCLE Basic Exam Study Guide Questions and Answers
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Corneal Topography - Tangential Map -Answer -More sensitive map of the cornea
-Calculates corneal curvature based on the tangent to normal
-Found to be more beneficial in identifying corneal pathology
-Not used as frequently to fit CLs
Corneal Topography - Refractive Power Map -Answer -Show spherical aberrations
-More useful when assessing visual performance of post refractive patients
Corneal Topography - Elevation Map -Answer -Shows the difference in the elevation of the
cornea
-Measured in microns
Corneal Topography - Irregularity Map -Answer -Similar to elevation maps
-Uses best fit toric surface as a reference
-Eliminates any toricity from the eye and displays the elevation differences
Corneal Topography - Photokeratoscopic Views -Answer Uses the placido rings which are
reflected onto the eye to subjectively determine the location and regularity of the rings
Corneal Topography - Numerical Views -Answer -Arranges individual keratometric findings
to
,depict curvature readings of the eye
-Extremely useful when fitting specialty contacts
-Corneal topographic software calculates the "average keratometric" value
Corneal Topography - Keratometry Views -Answer -Represent the keratometric readings
along with the axes of the eye's presumed astigmatism
-Dioptric values define the findings from the center of the cornea to the periphery
-This view helps the practitioner to quickly determine if corneal astigmatism is symmetrical
Corneal Topography - Profile Views -Answer -Graphically represent the individual axes of
the
cornea to help depict the 3-D nature of the cornea
Radiuscope -Answer -AKA optic spherometer
-Used to verify base curves, including both spherical and toric curves
-Also used to detect warped CLs
-Tolerance for BC is +/-0.025 mm
Diffused Illumination -Answer -Uses widest slit, longest aperture
-Light source positioned at an angle of 40º-50º
-Used to view overall areas, to observe the ocular adnexa, cornea, sclera, lids, conjunctiva,
lens
, surface, and CL fitting characteristics
Direct Illumination -Answer -Most important/useful illumination
-Light source positioned at an angle of 40º-50º to oculars
-Light beam and oculars are focused in coincidence on area being evaluated
-The difference in the illumination is not the angle used, but where the beam is directed or
focused and the width
-Varying width and aperture creates different illuminations
Optic(al) Section -Answer -Type of direct illumination that uses a narrow beam to create a
cross-section of the cornea
-Used to illuminate and observe individual layers of the cornea and tear film
-Used to evaluate corneal thickness, thinning, distortions, or depth of a foreign body
-Shows corneal-lens relationship
Parallelepiped -Answer -Type of direct illumination
-Uses a 0.5-3.0 mm beam and a 40º-50º angle to create a 3-D cube
-Used to assess width, depth, and height of an object within the cornea
-Useful in observing scars, infiltrates, staining, and the corneal-lens relationship
Indirect Illumination -Answer -Light source is moved out-of-click, the beam is 2-3 mm wide
100% Solved
Corneal Topography - Tangential Map -Answer -More sensitive map of the cornea
-Calculates corneal curvature based on the tangent to normal
-Found to be more beneficial in identifying corneal pathology
-Not used as frequently to fit CLs
Corneal Topography - Refractive Power Map -Answer -Show spherical aberrations
-More useful when assessing visual performance of post refractive patients
Corneal Topography - Elevation Map -Answer -Shows the difference in the elevation of the
cornea
-Measured in microns
Corneal Topography - Irregularity Map -Answer -Similar to elevation maps
-Uses best fit toric surface as a reference
-Eliminates any toricity from the eye and displays the elevation differences
Corneal Topography - Photokeratoscopic Views -Answer Uses the placido rings which are
reflected onto the eye to subjectively determine the location and regularity of the rings
Corneal Topography - Numerical Views -Answer -Arranges individual keratometric findings
to
,depict curvature readings of the eye
-Extremely useful when fitting specialty contacts
-Corneal topographic software calculates the "average keratometric" value
Corneal Topography - Keratometry Views -Answer -Represent the keratometric readings
along with the axes of the eye's presumed astigmatism
-Dioptric values define the findings from the center of the cornea to the periphery
-This view helps the practitioner to quickly determine if corneal astigmatism is symmetrical
Corneal Topography - Profile Views -Answer -Graphically represent the individual axes of
the
cornea to help depict the 3-D nature of the cornea
Radiuscope -Answer -AKA optic spherometer
-Used to verify base curves, including both spherical and toric curves
-Also used to detect warped CLs
-Tolerance for BC is +/-0.025 mm
Diffused Illumination -Answer -Uses widest slit, longest aperture
-Light source positioned at an angle of 40º-50º
-Used to view overall areas, to observe the ocular adnexa, cornea, sclera, lids, conjunctiva,
lens
, surface, and CL fitting characteristics
Direct Illumination -Answer -Most important/useful illumination
-Light source positioned at an angle of 40º-50º to oculars
-Light beam and oculars are focused in coincidence on area being evaluated
-The difference in the illumination is not the angle used, but where the beam is directed or
focused and the width
-Varying width and aperture creates different illuminations
Optic(al) Section -Answer -Type of direct illumination that uses a narrow beam to create a
cross-section of the cornea
-Used to illuminate and observe individual layers of the cornea and tear film
-Used to evaluate corneal thickness, thinning, distortions, or depth of a foreign body
-Shows corneal-lens relationship
Parallelepiped -Answer -Type of direct illumination
-Uses a 0.5-3.0 mm beam and a 40º-50º angle to create a 3-D cube
-Used to assess width, depth, and height of an object within the cornea
-Useful in observing scars, infiltrates, staining, and the corneal-lens relationship
Indirect Illumination -Answer -Light source is moved out-of-click, the beam is 2-3 mm wide
