COT Biometry and A-Scans 2

Question 1

Which IOL formula is generally preferred for eyes with axial lengths greater than 26 mm?

Accepted Answer

Barrett Universal II

Answer

Barrett Universal II performs well across a wide range of axial lengths, including long eyes over 26 mm.

Question 2

In immersion A-scan biometry, the probe is:

Accepted Answer

Submerged in a saline-filled shell over the eye

Answer

Immersion technique uses a saline-filled scleral shell to eliminate corneal compression artifacts.

Question 3

What does the term 'applanation' refer to in contact A-scan biometry?

Accepted Answer

Compressing the cornea with the probe

Answer

Applanation biometry involves the probe touching and slightly compressing the cornea, which can shorten axial length readings.

Question 4

The typical ultrasound frequency used in ophthalmic A-scan biometry is:

Accepted Answer

10 MHz

Answer

Ophthalmic A-scans use 10 MHz ultrasound to achieve adequate resolution for ocular structures.

Question 5

Which structure produces the posterior lens spike in an A-scan waveform?

Accepted Answer

Posterior lens capsule

Answer

The posterior lens capsule generates the second large spike after the anterior lens spike in A-scan.

COT - Certified Ophthalmic Technician Practice Test