COT Refraction and Retinoscopy 5

Question 1

If a spectacle Rx is −10.00 D at a vertex distance of 12 mm, what is the approximate contact lens power needed?

Accepted Answer

−9.00 D

Answer

For high minus lenses, moving the lens to the cornea reduces effective power; the CL power is approximately −9.00 D at the corneal plane.

Question 2

During retinoscopy, the reflex in the 90° meridian neutralizes with +1.00 D and the 180° meridian with +3.00 D. The resulting refraction in plus cylinder form is:

Accepted Answer

+1.00 +2.00 ×090

Answer

The least plus meridian (90°) becomes the sphere (+1.00), and the cylinder is the difference (+2.00) with axis at the least plus meridian (090).

Question 3

A patient's cycloplegic refraction is +2.00 D OU. After cycloplegia wears off, they accept only +0.50 D during manifest refraction. The remaining +1.50 D is called:

Accepted Answer

Latent hyperopia

Answer

Latent hyperopia is the portion of total hyperopia that cannot be relaxed voluntarily and is only detected under cycloplegia.

Question 4

Which instrument performs an objective, automated refraction by measuring wavefront aberrations or Purkinje images?

Accepted Answer

Autorefractor

Answer

An autorefractor objectively measures the refractive error by analyzing reflections from the retina or measuring wavefront errors without patient response.

Question 5

When refining cylinder axis with the Jackson cross cylinder, the patient reports that flip position 1 and flip position 2 look equally blurry. This means:

Accepted Answer

The axis is correctly positioned

Answer

Equal blur in both JCC positions means the cylinder axis is correctly placed at the midpoint between the two flip orientations.

COT - Certified Ophthalmic Technician Practice Test

COT - Certified Ophthalmic Technician Practice Test

COT Refraction and Retinoscopy 5