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B2.2-2.4: Prismatic effect, effective power and thick lenses

A base-out prismatic effect is induced on a spectacle lens when
a) Optic centre of a plus lens is decentred outwards
b) Eyes look inwards in plus lenses with respect to the optic centre
c) Eyes look outwards in minus lenses with respect to the optic centre
d) All of the above
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Terms in this set (88)
A base-out prismatic effect is induced on a spectacle lens when
a) Optic centre of a plus lens is decentred outwards
b) Eyes look inwards in plus lenses with respect to the optic centre
c) Eyes look outwards in minus lenses with respect to the optic centre
d) All of the above
d
A man wearing a spectacle lens of +3 D experiences a prismatic effect of 4.2 ∆ BD when looking through the lenses at a particular gaze. Is he looking up or down with reference to the optic centre of lens and by how much?
a) 12.6 cm up from the optic centre of the lens
b) 1.4 cm up from the optic centre of the lens
c) 1.4 cm down from the optic centre of the lens
d) 12.6 cm down from the optic centre of the lens
b
An individual has a prescription of -3.00 DS in the right eye and +2.00 DS in the left eye. What will be horizontal prismatic imbalance of the eye when the person looks 10 mm inside from the optic centre from each eye?
a) 1 ∆ BI right eye
b) 5 ∆ BI right eye
c) 1 ∆ BI left eye
d) 5 ∆ BO left eye
a - RE prismatic effect: 3∆ BI, LE prismatic effect: 2∆ BO. Both prisms will make conjugate movements so the prismatic imbalance: 1∆BI right eye.
The right lens of a pair of eyeglass lenses has 2.0 ∆ BU and the left lens has 3.0 ∆ BD. What is the net prismatic effect or prismatic imbalance between these two lenses?
a) 5 ∆ BD right eye
b) 5 ∆ BD left eye
c) 1 ∆ BU left eye
d) 1 ∆ BD right eye
b - These prisms will make disjunctive eye movements, so we add the prisms. This can also be written as 5 ∆ BU right eye
For a myopic eye that can be corrected with a -12.00 D spectacle lens mounted 12 mm in front of the cornea, what would be the required contact lens power?
Hint: K = K/1-dK
a) -9.64 D
b) -10.49 D
c) -12 D
d) -4.92 D
b