CPO FREE CPO Tonometry Principles and Procedures Questions and Answers 3

Question 1

Which of the following tonometry methods is specifically designed to be LEAST affected by corneal biomechanical properties such as thickness and rigidity?

Accepted Answer

Dynamic contour tonometry (DCT)

Answer

Dynamic contour tonometry (DCT) uses a sensor tip with a concave surface that contours to the cornea rather than flattening it. This design principle allows it to measure IOP with minimal influence from corneal properties like thickness, curvature, or rigidity, which are known sources of error for applanation tonometers like GAT and NCT.

Question 2

A patient with significant nystagmus requires an IOP check. Which of the following tonometers would be most challenging to use and likely yield an inaccurate measurement for this specific patient?

Accepted Answer

Goldmann applanation tonometer

Answer

Goldmann applanation tonometry (GAT) requires a stable, centered view of the fluorescein mires for several seconds to obtain an accurate reading. The constant, involuntary eye movements of nystagmus make it extremely difficult to achieve the necessary stability and proper applanation, leading to unreliable measurements. Other methods like Tono-Pen, pneumatonometry, and rebound tonometry take much quicker measurements and are less dependent on prolonged, precise alignment, making them more suitable for patients with nystagmus.

Question 3

When performing a calibration check on a Goldmann tonometer, the feeler arm is tested at positions 0, 2, and 6 on the measurement drum. What does the '2' setting correspond to in mmHg?

Accepted Answer

20 mmHg

Answer

The calibration check points on a Goldmann tonometer correspond to specific pressure levels. The dial setting '0' corresponds to 0 mmHg, '2' corresponds to 20 mmHg, and '6' corresponds to 60 mmHg. This allows for verification of the tonometer's accuracy across a clinically relevant range.

Question 4

A paraoptometric is preparing to measure IOP on a patient who had myopic LASIK surgery two years ago. Compared to the patient's true IOP, a Goldmann applanation tonometer (GAT) reading is most likely to be:

Accepted Answer

Artificially low due to the altered corneal thickness and biomechanics.

Answer

LASIK surgery for myopia involves removing corneal tissue, which thins the central cornea and alters its biomechanical properties. Goldmann tonometry, which was designed for corneas of average thickness, will underestimate the true intraocular pressure in these cases because less force is required to applanate the thinner, more flexible cornea.

Question 5

A patient presents with advanced keratoconus. When using a Goldmann tonometer, the paraoptometric notes that obtaining a clear mire endpoint is difficult due to the irregular corneal shape. The resulting IOP measurement is likely to be:

Accepted Answer

An underestimation of the true IOP.

Answer

In keratoconus, the cornea is typically thinner and has an irregular, conical shape. These factors cause Goldmann applanation tonometry (GAT) to significantly underestimate the true intraocular pressure. The structural changes mean less force is needed to flatten the cornea, leading to a falsely low reading.

(CPO) Certified Paraoptometric Practice Test

(CPO) Certified Paraoptometric Practice Test

CPO FREE CPO Tonometry Principles and Procedures Questions and Answers 3