COA - Certified Ophthalmic Assistant Tonometry and Glaucoma Questions and Answers

Question 1

A patient's intraocular pressure (IOP) measures 28 mmHg via Goldmann applanation tonometry. Pachymetry reveals a central corneal thickness of 610 µm. How does the corneal thickness likely affect this IOP reading?

Accepted Answer

The true IOP is likely lower than 28 mmHg.

Answer

Goldmann tonometry is calibrated for an average central corneal thickness of about 520-540 µm. A thicker-than-average cornea provides more resistance to the tonometer probe, resulting in a falsely high IOP reading. Conversely, a thinner cornea would lead to a falsely low reading.

Question 2

Which of the following is considered the 'gold standard' for measuring intraocular pressure?

Accepted Answer

Goldmann applanation tonometry

Answer

Goldmann applanation tonometry (GAT) is widely considered the international gold standard for measuring intraocular pressure due to its accuracy and reproducibility. It works by measuring the force required to flatten a specific area of the cornea.

Question 3

A patient presents with a sudden onset of severe eye pain, nausea, blurred vision, and halos around lights. Tonometry reveals a very high IOP. Which type of glaucoma is most likely responsible for these symptoms?

Accepted Answer

Acute angle-closure glaucoma

Answer

Acute angle-closure glaucoma is a medical emergency characterized by a sudden blockage of the eye's drainage angle, leading to a rapid and severe spike in intraocular pressure. This causes symptoms like intense eye pain, redness, blurred vision, halos, headache, and nausea. Primary open-angle glaucoma, the most common form, is typically painless and develops slowly.

Question 4

During Goldmann applanation tonometry, the fluorescein mires are observed to be very thick and wide. This is most likely to cause what type of error in the IOP measurement?

Accepted Answer

A falsely high reading

Answer

Excessive fluorescein in the tear film creates thick mires. The width of the mire band adds to the area of applanation, meaning less force is required from the tonometer dial to align the inner edges. This leads the operator to record a pressure that is falsely high. Conversely, too little fluorescein (thin mires) can lead to a falsely low reading.

Question 5

What is the generally accepted range for normal intraocular pressure (IOP) in the adult population?

Accepted Answer

10-21 mmHg

Answer

The statistically normal range for intraocular pressure in adults is typically between 10 and 21 millimeters of mercury (mmHg). Pressures consistently above 21 mmHg are considered ocular hypertension and increase the risk for developing glaucoma, although glaucoma can also develop at pressures within the normal range (normal-tension glaucoma).

COA - Certified Ophthalmic Assistant Practice Test

COA - Certified Ophthalmic Assistant Practice Test

COA - Certified Ophthalmic Assistant Tonometry and Glaucoma Questions and Answers