Accommodation & Effectivity

1. working distance

2. power of the distance spectacle lens

3. distance from the lens to principal planes of eye

what 3 things does the amount of accommodation required to see clearly at near depend on?

T

T/F: spectacle-wearing hyperope will require a near addition to their glasses before a myope will

F

T/F: in spite of differences in required accommodation for contact lens-wearing myopes & hyperopes, a spectacle lens-wearing hyperope will not need bifocals any sooner than a contact lens-wearing myope

T

T/F: as add power increases, the differences in amount of accommodation required for hyperopes & myopes decreases

1.5mm

the primary & secondary principal planes are considered to be _____ behind the cornea

vertex distance + 1.5mm

the distance from spectacle plane to principal planes of the eye =

Ld - Ln

amount of accommodation (AA) =

Ld

vergence of light at principal planes from distant object

Ln

vergence of light at principal planes from near object

hyperope > emmetrope > myope

amount of accommodation required for patients with different REs that wear spectacles

hyperopes

who require a bifocal or progressive first?

hyperope = emmetrope = myope

amount of accommodation required for patients with different REs that wear contact lenses

more

myopes accommodate ______ in contacts than spectacles

less

hyperopes accommodate _____ in contacts than spectacles

accommodate more w/ the correction at the corneal plane

why do some previous spectacle lens-wearing myopes have trouble w/ reading after undergoing refractive surgery?

decreases

as add power increases, differences in amount of accommodation required for hyperopes & myopes ______

1. power of specs affects amount of accommodation required for near viewing

2. specs w/ a large cyl have a considerable difference in refractive power b/t the 2 major meridians

3. single vision lens wearers may require different amounts of accommodation for 1 meridian of the lens than for another when comparing the effectiveness of the lens at distance & near

4. if distance sphere power is large too, the effect can be even larger

5. astigmatism at distance & near are different

6. new amount of astigmatism not fully corrected at near reading distance

why do some non-presbyopes need a different cyl correction for near?

test for cyl pwoer & axis for near vision due to cyclorotation with convergence

what is the best solution for assessing if a non-presbyope needs a different cylinder correction for near?