COT - Certified Ophthalmic Technician Optics and Lensometry Questions and Answers

Question 1

A technician uses a manual lensometer to neutralize an unknown spherical lens. The target mires come into sharp focus when the power wheel is set to -3.25 D. What does this measurement represent?

Accepted Answer

The back vertex power of the lens.

Answer

The front vertex power of the lens.

Answer

The equivalent spherical power.

Answer

The prismatic power of the lens.

Question 2

A patient's prescription is +3.00 D sphere in the right eye. If the patient looks 5 mm down from the optical center of the lens, what is the magnitude and direction of the induced prism according to Prentice's Rule?

Accepted Answer

1.5 Δ Base Up

Answer

3.0 Δ Base Down

Answer

1.5 Δ Base Down

Answer

3.0 Δ Base Up

Question 3

An optical lab requires a prescription to be in minus cylinder form. Which of the following is the correct transposition of the prescription -1.00 +2.50 x 110?

Accepted Answer

+1.50 -2.50 x 020

Answer

-3.50 -2.50 x 020

Answer

+1.50 +2.50 x 020

Answer

-1.00 -2.50 x 020

Question 4

A patient wearing high-power spectacle lenses complains of seeing color fringes, especially around lights and high-contrast objects. This optical phenomenon is known as:

Accepted Answer

Chromatic aberration

Answer

Spherical aberration

Answer

Coma

Answer

Pincushion distortion

Question 5

When neutralizing a pair of progressive addition lenses (PALs) in a manual lensometer, what is the correct procedure to determine the near add power?

Accepted Answer

Measure the sphere power in the distance portion, then measure the total sphere power in the near portion; the difference between these two values is the add power.

Answer

Measure the power at the fitting cross and subtract it from the power in the near viewing zone.

Answer

Focus the mires on the distance verification circle, then move to the near verification circle and read the new spherical power directly.

Answer

Add +2.50 D to the distance power, as this is the standard add power for all progressive lenses.

Question 6

Which of the following best defines the 'base curve' of a spectacle lens?

Accepted Answer

The standard, foundational curve on a lens surface from which all other curves are calculated.

Answer

The dioptric power of the cylinder component of the prescription.

Answer

The thickest edge of a prism-containing lens.

Answer

The curvature of the lens surface closest to the eye.

A technician uses a manual lensometer to neutralize an unknown spherical lens.The target mires come into sharp focus when the power wheel is set to -3.25 D.What does this measurement represent?

A technician uses a manual lensometer to neutralize an unknown spherical lens.
The target mires come into sharp focus when the power wheel is set to -3.25 D.
What does this measurement represent?