NCLE Basic Exam Study Guide
Questions and Answers13
Diffused Illumination - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--More sensitive map of the cornea
Questions and Answers13
Diffused Illumination - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--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 - ANSWERS--More sensitive map of the cornea
