NCLE Basic Exam Study Guide 2023 with complete solution

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