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Tonometry and Glaucoma Flashcards

6 cards from real COA 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. Goldmann applanation tonometry (GAT) measures intraocular pressure by determining the force required to flatten a corneal area of what specific diameter?

    Answer: 3.06 mm

    The Goldmann tonometer prism flattens a circular corneal area of 3.06 mm diameter. At this diameter, the forces of surface tension and corneal rigidity cancel each other out, providing an accurate IOP reading.

  2. A patient's IOP is measured by GAT as 14 mmHg OD and 15 mmHg OS. The COA notes the corneal pachymetry is 490 microns OU. How should the COA interpret this?

    Answer: IOP may be falsely low; thin corneas tend to underestimate true IOP with GAT

    GAT assumes a standard central corneal thickness (CCT) of ~550 microns. Corneas thinner than 550 microns are more easily applanated, requiring less force, causing GAT to underestimate true IOP. A CCT of 490 microns is significantly thin.

  3. Which type of glaucoma is characterized by a narrow or closed iridocorneal angle that obstructs aqueous outflow?

    Answer: Angle-closure glaucoma (ACG)

    Angle-closure glaucoma results from apposition or adhesion of the peripheral iris against the trabecular meshwork, blocking aqueous humor outflow through the iridocorneal angle and causing IOP elevation.

  4. What is the recommended first step before performing Goldmann applanation tonometry?

    Answer: Instill a topical anesthetic and fluorescein

    GAT requires topical anesthesia for patient comfort and fluorescein sodium to create the characteristic tear film meniscus rings that enable proper mire alignment. Both are instilled before the procedure.

  5. The optic nerve cup-to-disc ratio (CDR) is evaluated during ophthalmic assessment. Which CDR value is MOST suggestive of glaucomatous optic nerve change?

    Answer: 0.8 OD with inferior rim thinning

    A CDR of 0.8 is large and, combined with inferior rim thinning (loss of the ISNT rule pattern), is highly suspicious for glaucomatous optic neuropathy. Both the ratio and the rim quality must be assessed.

  6. Non-contact tonometry (NCT or 'air puff') measures IOP by analyzing what?

    Answer: The time or force required for an air pulse to applanate the cornea

    The NCT instrument delivers a rapid air puff that deforms the cornea. An infrared detection system measures either the time required to flatten a standard corneal area or the force of the puff at the moment of applanation, which correlates with IOP.