Lensometer Basics
This is the standard name of the tool used to measure the prescription of a lens
What is a lensometer?
This prescription component measures the amount of nearsightedness or farsightedness.
What is sphere?
This adjustment is made to bring the reticle into focus for clear measurements.
What is focusing the eyepiece?
If the internal lines appear blurry while measuring, this part of the lensometer likely needs adjustment.
What is the eyepiece?
A prism correction is used to address these types of eye misalignments.
What are strabismus or eye alignment issues?
This part of the lensometer allows the user to bring internal lines into focus for proper measurement.
What is the eyepiece?
The cylinder measurement in a prescription corrects for this vision problem.
What is astigmatism?
The concave side of the lens should face this direction when placing the lens on the lensometer rest.
What is downward?
When the optical center of the lens is not properly aligned, this error in measurement can occur.
What is a prism reading?
To measure prism accurately, the lens should be centered on this part of the lensometer.
What is the prism ring or risley prim?
Before measuring, you must set the lensometer to this to ensure accurate readings.
What is zero or infinity?
When a lens has no cylindrical power, this word is used to describe the cylinder component in the prescription.
What is plano?
This control on a lensometer is used to measure and read the cylinder power.
What is the axis wheel?
This issue occurs when there is a discrepancy between the measured and prescribed axis values.
What is an off-axis alignment?
Progressive lenses require special attention because they do not have this standard reference point.
What is the optical center?
A lensometer measures the focal length of a lens to determine these three main prescription values.
What are sphere, cylinder, and axis?
The measurement of a prism correction is given in these units.
What are prism diopters?
When aligning a multifocal lens, you should focus on this part first.
What is the distance portion?
A distorted or incorrect reading can happen if you forget to do this crucial step before starting a measurement.
What is zero the lensometer?
When measuring bifocal lenses, this part of the lens is measured separately from the main portion.
What is the segment (or add segment)?
This type of lensometer uses digital displays to show readings automatically, reducing manual adjustments.
What is an automated lensometer?
This number in a prescription specifies the orientation of the cylindrical correction.
What is the axis?
If you detect two different line patterns in a lensometer, this indicates the presence of this component in the prescription.
What is astigmatism?
If the lines in the lensometer are not aligning no matter how much adjustment is made, this might indicate that the lens has this issue.
What is a warped or defective lens?
The amount of prism in a lens is indicated by the displacement of this point.
What is the optical center?