NCLE Basic Exam Study Guide 2023 with complete
solution
Diffused Illumination
-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
-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
-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
-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
-Light source is moved out-of-click, the beam is 2-3 mm wide and is positioned next to the area
being studied
-Illuminated area is translucent or opaque, allowing for observation adjacent to illumination
-Used to observe foreign bodies, corneal nerves, and opacities
-Oscillation of light accentuates details
Retroillumination
-Light source is out-of-click, moved to the side of the area being observed
-Using a 1-3 mm beam, the light is reflected off the iris and used to back-light the area studied
-Useful in examining corneal scars, debris, microcysts, scratches on the lens, sub-epithelial
changes, corneal vascularization, diffuse edema, and surface deposits
Sclerotic Scatter
-Uses a focused parellelepiped placed out-of-click directed at the limbus
-Oculars are not used
-The light is dispersed at the limbus, reflected through the cornea, creating a circumcorneal halo
-Used to observe edema, stromal folds, lens deposits, bubbles under the lens, lens defects, and
scratches
Corneal Topography - Axial Map
, -Most widely understood map of the cornea for many CL fitters
-Overall shape of the cornea
-Colors relate to steepness/flatness
-Sagittal reading measures the curvature of the cornea in diopters and is called the axial power
map
-Calculates curvature rather than power
Corneal Topography - Tangential Map
-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
-Show spherical aberrations
-More useful when assessing visual performance of post refractive patients
Corneal Topography - Elevation Map
-Shows the difference in the elevation of the cornea
-Measured in microns
Corneal Topography - Irregularity Map
-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
Uses the placido rings which are reflected onto the eye to subjectively determine the location and
regularity of the rings
Corneal Topography - Numerical Views
-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
-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
-Graphically represent the individual axes of the cornea to help depict the 3-D nature of the
cornea
Radiuscope
-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
Lensometer
-AKA vertometer, lensmeter, focimeter
-Used to verify power of the lens, optics evaluation, cylinder power, axis location, and prism
-When documenting power, the user should identify whether the reading is in front vertex vs.
back vertex
V-Channel; Hand Measuring Magnifier; or Shadowscope
solution
Diffused Illumination
-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
-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
-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
-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
-Light source is moved out-of-click, the beam is 2-3 mm wide and is positioned next to the area
being studied
-Illuminated area is translucent or opaque, allowing for observation adjacent to illumination
-Used to observe foreign bodies, corneal nerves, and opacities
-Oscillation of light accentuates details
Retroillumination
-Light source is out-of-click, moved to the side of the area being observed
-Using a 1-3 mm beam, the light is reflected off the iris and used to back-light the area studied
-Useful in examining corneal scars, debris, microcysts, scratches on the lens, sub-epithelial
changes, corneal vascularization, diffuse edema, and surface deposits
Sclerotic Scatter
-Uses a focused parellelepiped placed out-of-click directed at the limbus
-Oculars are not used
-The light is dispersed at the limbus, reflected through the cornea, creating a circumcorneal halo
-Used to observe edema, stromal folds, lens deposits, bubbles under the lens, lens defects, and
scratches
Corneal Topography - Axial Map
, -Most widely understood map of the cornea for many CL fitters
-Overall shape of the cornea
-Colors relate to steepness/flatness
-Sagittal reading measures the curvature of the cornea in diopters and is called the axial power
map
-Calculates curvature rather than power
Corneal Topography - Tangential Map
-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
-Show spherical aberrations
-More useful when assessing visual performance of post refractive patients
Corneal Topography - Elevation Map
-Shows the difference in the elevation of the cornea
-Measured in microns
Corneal Topography - Irregularity Map
-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
Uses the placido rings which are reflected onto the eye to subjectively determine the location and
regularity of the rings
Corneal Topography - Numerical Views
-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
-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
-Graphically represent the individual axes of the cornea to help depict the 3-D nature of the
cornea
Radiuscope
-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
Lensometer
-AKA vertometer, lensmeter, focimeter
-Used to verify power of the lens, optics evaluation, cylinder power, axis location, and prism
-When documenting power, the user should identify whether the reading is in front vertex vs.
back vertex
V-Channel; Hand Measuring Magnifier; or Shadowscope
