NCLE Prep Exam 3 of 4 | with COMPLETE SOLUTION

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The tolerance for the overall lens diamter according to the ANSI standards is: A. +/-0.005mm B. +/-0.05mm C. +/-0.01mm D. +/-0.1mm - ✔✔B. According to the ANSI standards (Z80.2-1989), the tolerance for the overall diameter of a contat lens is +/-0.05mm. ANSI standards have been developed to maintain quality in the contact lens industry. It is important to have an understanding of the ANSI guidelines. All of the following will enable the practitioner to verify the overall rigid gas permeable lens diameter except: A. Slot gauge B. Shadowgraph C. Measuring magnifer D. Radiuscope - ✔✔D. Radiuscope The slot gauge, shadowgraph and measuring magnifier will all enable the practitioner to verify the overall lens diameter of rigid gas permeable lens. The radiuscope is an instrument that will measure the base curve of a rigid lens. Placing the concave side of a rigid gas permeable lens against the lens stop of the lensometer, will provide you with which of the following? A. Back vertex power B. Front vertex powerC. Best vertex power D. Closest vertex power - ✔✔A. Back vertex power By placing the back (posterior) surface of the rigid gas permeable lens against the lens stop, the reading that results will be in back vertex power An instrument that allows simultaneous verification of lens diameter, optic zone width and peripheral curve width is: A. Measuring magnifier B. Ophthalmometer C. Profile analyzer D. Radiuscope - ✔✔A. Measuring magnifier An ophthalmometer, another name for the keratometer, cannot measure the listed parameters. The profile analyzer evaluates the peripheral curve blends and the radiuscope measures the base curve of the rigid contact lens. The measuring magnifier is the only instrument that will measure the parameters listed. Assessment of the quality of the peripheral curves (blends) of a rigid contact lens is achievable by the use of the: A. Profile analyzer B. Shadowgraph C. Profile analyzer D. Burton lamp - ✔✔A. Profile analyzer All of the listed instruments show that a rigid contact lens has blends. However, the only instrument that can adequately assess the quality of the blends between the peripheral posterior curve (PPC), intermediate posterior curve (IPC) and the central posterior curve (CPC), is the profile analyzer

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