Ophthalmic Lens Characteristics

Question 1

What is plano-concave often used for?

Answer 1

High minus prescription

Question 2

True or false:

Plano-convex is not used for ophthalmic lenses.

Answer 2

True

Question 3

What is bi-convex often used for?

Answer 3

High plus prescription

Question 4

What is bi-concave often used for?

Answer 4

used rarely for very high minus prescription

Question 5

Plano-cylinder form

Answer 5

patient with astigmatism but no myopia or hyperopia

one flat lens surface and one cylindrical lens surface

Question 6

Sphero-cylinder form. What side is the spherical surface on?

Answer 6

patient with astigmatism plus myopia or hyperopia
Spherical surface on one side and a toric surface on the other

-spherical surface on the front

Question 7

______________ or best-form lenses are designed to minimize monochromatic lens aberration

Answer 7

Corrected curve

Question 8

______________ lenses are now the most common lens form.

Answer 8

Corrected curve

Question 9

__________ is the distance between a point on the circle and the midpoint of a chord of the circle

Answer 9

Sagitta

Question 10

measures sagittal depth of lens surface

Answer 10

lens clock

Question 11

________ formula for sagitta is only necessary for highly curved surfaces (contact lenses)

Answer 11

Exact

Question 12

____________ formula is used when s is small in relation to r (ophthalmic spectacle lenses)

Answer 12

approximate

Question 13

For a crossed cylinder lens, ____ cylinder ground on the front surface and _____ cylinder ground on the back surface, with the axis 90° apart

Answer 13

plus; minus

Question 14

for ___________ tilt, the axis meridian is the 180° meridian, therefore the sagittal meridian is the horizontal meridian

Answer 14

pantoscopic