COT Biometry and A-Scans 5

Question 1

The 'effective lens position' (ELP) in IOL formulas refers to:

Accepted Answer

The predicted postoperative position of the IOL principal plane

Answer

ELP is the predicted postoperative location of the IOL's principal plane, which significantly affects refractive outcome prediction.

Question 2

A-scan biometry in a pseudophakic eye (already has an IOL) requires:

Accepted Answer

A specific pseudophakic velocity setting for the IOL material

Answer

PMMA, silicone, and acrylic IOLs each have different sound velocities, requiring appropriate settings for accurate measurement.

Question 3

Which parameter does the Holladay 1 formula use in addition to axial length and keratometry?

Accepted Answer

Surgeon factor (SF)

Answer

Holladay 1 uses the surgeon factor (SF) to predict ELP based on axial length and keratometry.

Question 4

Which of the following axial length ranges classifies an eye as 'long'?

Accepted Answer

>24.5 mm

Answer

Eyes with axial lengths greater than 24.5 mm are generally classified as long, corresponding to myopic eyes.

Question 5

What is the purpose of taking multiple A-scan measurements and averaging them?

Accepted Answer

To improve accuracy and reduce variability from fixation or probe alignment

Answer

Averaging multiple readings minimizes random errors from eye movement or slight probe misalignment during the exam.

COT - Certified Ophthalmic Technician Practice Test