NCLE Basic Exam Study Guide latest updated, Exams of Nursing

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NCLE Basic Exam Study Guide 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 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 - Answer- -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 - Answer- -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 - Answer- -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 - 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 Intermediate Anterior Curvature (IAC) - Answer- -The curvature on the anterior lens surface between the central anterior curve and the peripheral anterior curve -Present in high plus lenses with a lenticular flange to increase edge thickness or in high minus lenses to reduce edge thickness -Expressed in mm of radius of curvature Peripheral Anterior Curve (PAC) - Answer- -Lies between the IAC and the edge of the lens -Expressed in mm -Generation and polishing are considered part of the edging process of manufacture -Previously called the front bevel Diameter - Answer- -Linear measurement of lens' chord length, passing through its geometrical center -Commonly called size or width -Expressed in mm Edge - Answer- -Junction of the PAC and PPC -Blended and polished with a high speed buffing wheel or is cut or ground in any number of specific manners -The edging process is considered part of the generation and polishing of the peripheral curves -Should only be refered to as the edge, rather than bevel or secondary curve Power - Answer- -Should be read/expressed as BVP -Expressed in diopters Thickness - Answer- -Measured at geometrical center -Variable: depends on power, CPC, index of refraction of plastic being used, and diameter -A lens is generally ordered with a specific diameter and CPC. If so, the manufacturer will select a CAC that will yield minimal central thickness -If a lenticular type lens is used, the flange thickness is measured at the junction of the CAC and IAC -Measured in hundredths of millimeters Optical Zone (OZ) - Answer- -Area on the posterior lens surface -The linear diameter of the CPC -Determined by subtracting TWICE the widths of the PPC and various IPC from the overall diameter -HINT: Peripheral and intermediate curves are on BOTH sides of the lens Find the Optical Zone: PPC: 0.4mm IPC1: 0.2mm IPC2: 0.2mm Lens Diameter: 9.5mm - Answer- Optical Zone: 7.9mm 0.8mm x 2 = 1.6mm 9.5mm - 1.6mm = 7.9mm Lacrimal Lens - Answer- -AKA tear lens -Layer of tears between the back surface of the lens and the front surface of the cornea -If a lens is fit directly on the cornea, the lacrimal lens on zero -If a lens is fit steeper than the cornea, then a plus lacrimal lens is created and must be compensated for: steeper add minus (SAM) -If a lens is fit flatter than the cornea, then a minus lacrimal lens is created and must be compensated for: flatter add plus (FAP) -Will take on the properties of a lens when in contact between the cornea and contact lens A lens with a steep CPC that vaults the corneal apex and touches the cornea at its peripheries is considered a ____ fittinglens. This lens will not ride freely over the cornea and will generally cause corneal edema and subsequent spectical blur. - Answer- tight A ____ fitting lens is fitted flatter than K and will touch at the corneal apex with excessive movement over the cornea. It is not uncommon for this lens to fall off the eye or become easily decentered. Such a lens may cause abrasions at the corneal apex and may also cause corneal edema. - Answer- loose If the lens is too flat, the fitter will generally ____ the fit by going ____ . - Answer- tighten, steeper 4 refractive mediums - Answer- -Cornea -Aqueous -Crystalline Lens -Vitreous Index of refraction of the cornea - Answer- 1.37(6) (Avg. dioptric power: 43D) Index of refraction of the aqueous - Answer- 1.33 Index of refraction of the Crystalline lens - Answer- 1.42 (Avg. dioptric power: 17D) Index of refraction of the vitreous - Answer- 1.33 Index of refraction of the tear film - Answer- 1.33 Index of refraction of the lens material - Answer- Varies depending on the material, but generally close to 1.33 The lacrimal lens will have a refractive power ____ ____ to the dioptric value of the steepness or flatness in relationship to the cornea. - Answer- proportionally equal -Example: a lens fit 0.50D steeper than K will have a lacrimal lens of +0.50D "K" is the ____ of the two meridians - Answer- flatter Sagittal Value - Answer- The distance from the geometrical center of a lens on its posterior surface, perpendicular to its corneal diameter Bitoric Lens - Answer- A contact lens that has two different and perpendicular radii of curvatures on both the anterior and the posterior surfaces Front Surface Toric Lens - Answer- -A contact lens that has two different and perpendicular radii of curvature on its anterior surface only -Has a spherical posterior surface -Must be stabilized by truncation and/or prism ballast -Used when a spherical GP lens results in unacceptable residual astigmatism -When corneal astigmatism is less than refractive astigmatism, a special anterior surface may be needed Back Surface Toric Lens - Answer- -A contact lens that has two different and perpendicular radii of curvature on its posterior surface only -Has a spherical anterior surface -Only functional when manifest cylinder is 1.5 times greater than corneal astigmatism -Only used when the corneal toricity is so great that alignment in all meridians is not possible -Toric curves on the posterior surface are required when a spherical lens results in areas of excessive clearance or bearing example: -2.00-4.00x180 42.00@180/45.00@90 Refractive Cyl: 4.00D Corneal Cyl: 3.00D Delta K (∆K) - Answer- -Difference in the powers in the two principal meridians on the cornea -True corneal astigmatism is when ∆K equals the manifest cylinder, both in power and in axis If corneal astigmatism falls between 0 and 1.75D, you would start by going ___ ___ than K. - Answer- +0.50 steeper example: flattest meridian is 42.50. Going steeper by +0.50 brings it to 43.00, which would be the starting BC