Ophthalmic Instruments and Lens Materials:
Measurement and Safety Exam 2026-2027 Questions
And Answers Graded A+
What are horizontal and vertical prism bars used for?
To measure the amplitude or power of fusion and sometimes in the cover-uncover
test for strabismus in children.
How are horizontal and vertical prism bars oriented?
They can be set in a horizontal direction (base in or out) or in a vertical direction
(base up or down).
What is Risley's rotary prism?
A device consisting of two counter-rotating prisms that allows for rapid adjustment
and measurement of prism power strength.
What does a lensmeter measure?
It determines the dioptric vertex power of a lens, the axis, the optical center, and
the presence and direction of a prism.
What is the function of the Geneva lens measure?
, It measures the radius of curvature of the lens surface and records it in diopters.
What is a disadvantage of the Geneva lens measure?
It is calibrated for crown glass only and can give incorrect measurements for hard
resin lenses and aspheric surfaces.
What is the purpose of the Posner diagnostic and surgical gonioprism?
It is used for viewing the anterior chamber and observing the alignment of
intraocular lens feet.
What is a gonioscope?
A handheld microscope combined with an illuminating system used for
gonioscopy of the angle structures.
What does keratometry measure?
It measures the central anterior curvature of the cornea and is valuable for
detecting corneal astigmatism.
What is the Bausch & Lomb keratometer known for?
It is the standard on which other keratometers are based for measuring corneal
curvature.
Measurement and Safety Exam 2026-2027 Questions
And Answers Graded A+
What are horizontal and vertical prism bars used for?
To measure the amplitude or power of fusion and sometimes in the cover-uncover
test for strabismus in children.
How are horizontal and vertical prism bars oriented?
They can be set in a horizontal direction (base in or out) or in a vertical direction
(base up or down).
What is Risley's rotary prism?
A device consisting of two counter-rotating prisms that allows for rapid adjustment
and measurement of prism power strength.
What does a lensmeter measure?
It determines the dioptric vertex power of a lens, the axis, the optical center, and
the presence and direction of a prism.
What is the function of the Geneva lens measure?
, It measures the radius of curvature of the lens surface and records it in diopters.
What is a disadvantage of the Geneva lens measure?
It is calibrated for crown glass only and can give incorrect measurements for hard
resin lenses and aspheric surfaces.
What is the purpose of the Posner diagnostic and surgical gonioprism?
It is used for viewing the anterior chamber and observing the alignment of
intraocular lens feet.
What is a gonioscope?
A handheld microscope combined with an illuminating system used for
gonioscopy of the angle structures.
What does keratometry measure?
It measures the central anterior curvature of the cornea and is valuable for
detecting corneal astigmatism.
What is the Bausch & Lomb keratometer known for?
It is the standard on which other keratometers are based for measuring corneal
curvature.
