Certified Ophthalmic Assistant (COA) – Ophthalmic Equipment Practice Questions and
Answers Study Guide
The use of red and green letters for 'fine-tuning' the refraction. - ANS ✔✔Duo chrome Test
A tray of lenses and accessories used to determine the refractive error of an eye. - ANS ✔✔Trial
case
An entire trial set of lenses mounted on a circular wheel so that each lens can be brought before
the aperture of the viewing system by turning a dial. - ANS ✔✔Phoropter or Refractor
Most valuable instrument in determining the refractive error of an eye. Determines the total
objective refractive error of an eye and may be the only means of assessing refractive error in
infants and small children. - ANS ✔✔Retinoscope
A caliper used to measure the vertex distance. - ANS ✔✔Distometer
Term to describe the distance from the cornea of the patient's eye to the back surface of the
lens inserted in the trial frame, refractor, or glasses. - ANS ✔✔Vertex distance
A triangular, or wedge-shaped, piece of plastic or glass that has the property of displacing a
bundle of light. - ANS ✔✔prism
Instrument used to determine 1. the dioptric vertex power of a lens, 2. the axis, 3. the optical
center of a lens, and 4. the presence fo prism and the direction of its base - ANS ✔✔lensometer
(also can be known as lensmeter or vertometer)
Measures the radius of curvature of a lens surface and records it in diopters. - ANS ✔✔Geneva
lens
Answers Study Guide
The use of red and green letters for 'fine-tuning' the refraction. - ANS ✔✔Duo chrome Test
A tray of lenses and accessories used to determine the refractive error of an eye. - ANS ✔✔Trial
case
An entire trial set of lenses mounted on a circular wheel so that each lens can be brought before
the aperture of the viewing system by turning a dial. - ANS ✔✔Phoropter or Refractor
Most valuable instrument in determining the refractive error of an eye. Determines the total
objective refractive error of an eye and may be the only means of assessing refractive error in
infants and small children. - ANS ✔✔Retinoscope
A caliper used to measure the vertex distance. - ANS ✔✔Distometer
Term to describe the distance from the cornea of the patient's eye to the back surface of the
lens inserted in the trial frame, refractor, or glasses. - ANS ✔✔Vertex distance
A triangular, or wedge-shaped, piece of plastic or glass that has the property of displacing a
bundle of light. - ANS ✔✔prism
Instrument used to determine 1. the dioptric vertex power of a lens, 2. the axis, 3. the optical
center of a lens, and 4. the presence fo prism and the direction of its base - ANS ✔✔lensometer
(also can be known as lensmeter or vertometer)
Measures the radius of curvature of a lens surface and records it in diopters. - ANS ✔✔Geneva
lens
