Auto-refractors, Lensometry, Keratometry Flashcards
what refractor is simple to operate, but may have refractometric results that are variable and not accurate enough to allow prescription without refinement?
Objective refractors
What refractor requires a skilled, well trained operator and may allow for testing of both near and distance vision?
Subjective refractors
This refractor requires operator skill and knowledge for accurate refinement and eliminates the need for the traditional 20-foot testing distance required by manual refinement
Combination objective/subjective refractor
A procedure used to measure the prescription of a patient’s existing eyeglass lenses or the power of contact lenses is called
Lensometry
Lensometry measures 4 principal properties of lenses, what are they?
spherical and cylindrical power in diopters; axes, if the lenses have a cylinder component; presence and direction of a prism incorporated into the lenses; optical centers
instruments used to perform lensometry may be ____ or _________ and are known as ________
A. manual or automated
B. lensmeter/lensometer
What are the 4 elements of lensometry?
- Focusing the instrument eyepiece, 2. positioning the eyeglass lens to be measured on the spectacle table of the lensometer, 3. measuring the sphere power and, if present, the cylinder and axis, 4. marking the optical center (optional)
The measurement of a patient’s corneal curvature is known as
Keratometry
The instrument used to measure corneal curvature is
Keratometer/ophthalmometer
What are the 4 conditions that must be met simultaneously for a proper keratometry measurement?
The reticule is in the center of the bottom-right circle. The keratometer is focused with fusion of the bottom-right circles. The pluses between the circles are in the same plane and are fused. The minuses between the circles are in the same plane and are fused.
