Optical Instrumentation Use Flashcards

A pachymeter is used in optometry and ophthalmology to measure which ocular structure?

Answer: Corneal thickness

A pachymeter measures corneal thickness, which is important for conditions like glaucoma screening and pre-refractive surgery evaluation.

On a manual lensometer, what is the purpose of rotating the eyepiece reticle before beginning a measurement?

Answer: To focus the reticle for the examiner's own eye

Rotating the eyepiece adjusts the reticle to be sharply focused for the individual examiner's eye, correcting for their own ametropia.

When measuring a progressive addition lens (PAL) with a lensometer, where on the lens should you place the distance reference mark?

Answer: At the prism reference point (PRP) or fitting cross

The prism reference point (PRP) or fitting cross is the standard location for placing a PAL in the lensometer to read distance power.

A contact lens thickness gauge (dial gauge) measures which parameter in hundredths of a millimeter?

Answer: Center or edge thickness

A contact lens thickness gauge measures center or edge thickness in increments typically of 0.01 mm.

When using an auto-refractor, the instrument measures which of the following to determine the refractive error?

Answer: The reflection of an infrared target from the retina

Auto-refractors project an infrared target onto the retina and analyze the reflected wavefront to objectively calculate refractive error.

The Humphrey lensmeter (automated lensometer) expresses cylinder in which form by default?

Answer: Both plus and minus, selectable

Most automated lensometers allow the user to select either plus or minus cylinder notation for the displayed prescription.

Which instrument would an optician use to verify that a finished spectacle lens has the correct base curve?

Answer: Geneva lens clock

A Geneva lens clock (lens measure) measures the surface curvature of a spectacle lens to verify its base curve.