NCLE Study Guide Questions with Correct Answers

NCLE Study Guide Questions with Correct Answers Back Surface Power - Answer-Effective power of a lens when measured from the back surface. Back Surface Toric Lens - Answer-A lens in which the posterior surface has two different radii and the anterior surface is spherical. Ballasted Lens - Answer-A lens with a heavier base which becomes oriented inferiorly or downward when the lens is worn. Bicurve Lens - Answer-A contact lens which contains two curves: one base curve and one secondary curve. It is usually small (7.5 to 8.8 mm in diameter), relatively steep, and made with narrow peripheral curves (about 0.2 mm). Bicurve rigid lenses are usually intrapalpebral lenses, designed to fit within the palpebral fissure limits. Bitoric Lens - Answer-A lens in which both the posterior and anterior surfaces contain two different radii. Blending - Answer-The smoothing of a junctional zone by removing the sharp line between the zones. Central Thickness - Answer-Separation between the anterior and posterior surface at the geometric center of the lens. Minus lenses are thinner, plus lenses are thicker. Curve Widths - Answer-The width of the CPC, PPC, or IPC. Flatter Base Curve - Answer-Occurs when the posterior radius of curvature is increased (i.e. 8.1 to 8.4 mm). Front Surface Toric Lens - Answer-A lens in which the anterior surface has two different radii and the posterior surface is spherical. Junctional Zone - Answer-The junction of two curves. Lathe Cut Soft Lens - Answer-A method of manufacturing soft contact lenses in which a machine lathe is used to grind lens designs, size and power. Lenticular Bowl - Answer-A lens design generally used in higher plus powers which consists of a central optic zone and a surrounding non-optic peripheral or "carrier" portion. Against-the-rule Astigmatism - Answer-The horizontal meridian (180°) of the cornea is steeper. Binocular Vision - Answer-The ability to use two eyes together, which is integral to stereoscopic vision. Biomicroscope (Slit Lamp) - Answer-An instrument with high-intensity light source and a biomicroscope, used to examine the anterior and posterior segments of the eye. The binocular slit-lamp gives a stereoscopic and magnified view.