NOCE Optical Instrumentation Usage 5

Question 1

Which instrument provides a topographic map of the entire corneal surface rather than just central curvature readings?

Accepted Answer

Corneal topographer

Answer

Corneal topographers use Placido disc reflection or Scheimpflug imaging to map thousands of points across the entire corneal surface, unlike a keratometer which measures only four central points.

Question 2

When using a lensometer on a trifocal lens, the intermediate add power is calculated as:

Accepted Answer

Half of the total add, measured at the intermediate segment

Answer

The intermediate segment of a trifocal is measured directly through the lensometer, and its power (typically half of the full add) is read at that specific zone.

Question 3

An auto-refractor provides an objective refractive measurement by:

Accepted Answer

Analyzing retinal reflection patterns from projected infrared light

Answer

Auto-refractors project infrared light onto the retina and analyze the reflected wavefront to objectively determine the eye's refractive error.

Question 4

The ANSI Z80.1 standard specifies that for a single-vision distance lens with a power of -5.00 D, the maximum allowable cylinder power error is:

Accepted Answer

±0.13 D

Answer

ANSI Z80.1 allows a cylinder tolerance of ±0.13 D for lenses with sphere powers between ±3.25 D and ±6.50 D.

Question 5

When using a lensometer to verify prism, the amount of prism is measured by:

Accepted Answer

How far the target mires are displaced from the center of the reticle in prism diopters

Answer

Prism is measured by how far the target is displaced from the optical center of the lensometer reticle, with each unit of displacement corresponding to one prism diopter.

NOCE - National Opticianry Competency Examination Practice Test

NOCE - National Opticianry Competency Examination Practice Test

NOCE Optical Instrumentation Usage 5