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Tonometry and Keratometry Flashcards

7 cards from real COT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which type of tonometer is most appropriate for an uncooperative child or a patient who cannot be positioned at a slit lamp?

    Answer: Rebound (iCare) tonometer

    Rebound tonometers like the iCare require no anesthetic, minimal cooperation, and can be used handheld in any position.

  2. The refractive index assumed by most manual keratometers when converting radius of curvature to diopters is approximately:

    Answer: 1.3375

    Most manual keratometers use a standardized keratometric refractive index of 1.3375 to convert corneal radius to diopters.

  3. What is diurnal variation of IOP, and when is IOP typically highest?

    Answer: IOP varies throughout the day; typically highest in the early morning

    IOP follows a circadian rhythm and is typically highest in the early morning hours, which can be clinically significant for glaucoma monitoring.

  4. When performing keratometry on a patient with dry eye, the technician observes mires breaking up quickly. The BEST approach is to:

    Answer: Instill artificial tears, wait briefly, then reattempt measurement

    A dry, irregular tear film disrupts the reflected mires; lubricating drops temporarily stabilize the tear film for a more accurate reading.

  5. Which statement about the Perkins tonometer is TRUE?

    Answer: It is a hand-held version of Goldmann applanation tonometry

    The Perkins tonometer is a hand-held applanation device that uses the same Goldmann applanation principle, useful for supine or pediatric patients.

  6. When recording keratometry results, 43.50 D @ 180° / 45.00 D @ 90° represents a cornea with:

    Answer: 1.50 D of with-the-rule astigmatism

    With-the-rule astigmatism means the steeper meridian is near 90°; here 45.00 D @ 90° is steeper, giving 1.50 D WTR astigmatism.

  7. Which medication instilled before tonometry can falsely lower IOP measurements by reducing aqueous production during the exam?

    Answer: Topical beta-blocker (timolol)

    Topical beta-blockers like timolol reduce aqueous production and can lower IOP, potentially affecting the accuracy of a baseline pressure reading.