Horizontal Prism at Near Only

1. AC/A ratio is either high or low

2. periodic strabismus is present

3. noncomitant strabismus is present

what are some reasons for horizontal prism at near only?

plus, in

because the segment is just a small _____ lens, when the segments are moved nasally, they will create a base ____ prismatic effect

T

T/F: if there is a difference b/t distance cyl values & near cyl values in a non-presbyopic patient, a second, single vision pair of glasses is needed for near work

yes

will this situation possibly call for a prescription for horizontal prism at near only?

there is a periodic strabismus at near only

T

T/F: when correcting horizontal prism at near w/ 2 pairs of glasses, the distance Rx is given w/o prism, a second pair for near viewing is given & includes both horizontal prism & the near add power

larger

the least expensive method for correcting horizontal prism at near w/ a MF lens is to use a ________ FT segment, these segments are decentered more or less than they normally would be for the near PD

1. 2 pairs of glasses

2. Fresnel press on prism for near only

3. larger seg FT lenses & decentration

4. split lenses

5. cement seg construction

6. neurolens

what are the options for creating horizontal prism at near only?

larger-segment flat-top lenses & decenter

• least expensive option to create horizontal prism at near only

• decentration depends on power of the near add

neurolens

contoured prism that gradually increases in amount b/t distance & near-viewing areas to correct for gradually changing convergence insufficiency

in

when the segment OC is decentered nasally, this creates base ____ prismatic effect

inward

if base in prism is prescribed, the additional seg inset will be ____

outward

if base out prism is prescribed, the additional seg inset will be ____

1. cannot move segment far enough due to lens size

2. segment is too small, edge will be too close to the LOS, not enough reading area

3. large eye size, decentered lens blank may not be large enough

4. large amount of outward decentration for BO prism at near can cause blank size problems

what are some restrictions on near segment decentration?