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BOARDS2: Ophthalmic Optics > double vision > Flashcards

double vision Flashcards

1
Q

three main causes of double vision

A

pathology
BV problems
ophthalmic (add type or PDs)

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2
Q 
what amount and direction of prism would be induced in these glasses:
OD:-2.50 DS
OS: -2.00
Add: +2.00, FT 28
Pt PDs: 28/28(distance) and 26/26 (near)
A

0.9PD BI

2mm difference per eye
OD: 0.2x 2.50=0.50PD
OS: 0.2 x 2.00=0.40PD

0.50+0.40=0.90PD BI

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3
Q

what type of mergence movement will be induced by BI prism? what mergence ranges must be large enough to compensate in order to prevent symptoms?

A

divergence

NFV

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4
Q 
what is the image jump when the patient looks into her bifocal
OD:-2.50 DS
OS: -2.00
Add: +2.00, FT 28
Pt PDs: 28/28(distance) and 26/26 (near)
A

1PD BD OU

(.5)(2.00)=1BD

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5
Q

a pair of glasses measures 3BO and 2BU OD and 3 BO and 3 BU OS. what is the total prism?

A

6BO

1BU

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6
Q

to verify the ocular misalignment that would require 6BO and 1BU in glasses, how would the vertical and horizontal lines on Maddox rod appear?

A

right; below

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7
Q

what is the power and orientation needed for fresnel prism to be added to the glasses with 6 BO and 1BU

A

6.08PD at 9.46 degrees

use pythagorean theorem and draw out a vector. solve for C^2 to get the prism. we know the prism must be between 0-90 so pick the one that falls in that range

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8
Q

anytime a question asks to calculate something about a patient looking away from optical center, what is it asking you to do

A

use prentices rule

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9
Q

4 ways to use prentices rule

A

decentration
image jump
vertical imbalance
total prismatic effect

think in cm and draw out prism direction

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10
Q

combining prism between eyes

A

bases opposite=add

bases same=subtract

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11
Q

combing prisms in same eye

A

vector addition

  • draw arrow head towards base
  • use pythagorean theorem
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12
Q

prentices rule

A

PD=dP

d=distance from the optical center in cm
P=power of the lens

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13
Q

BI prism causes images to appear

A

further away

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14
Q

BI prism causes divergence or convergence?

A

divergence

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15
Q

what type of vergences are needed to look through BI prism

A

NFV

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16
Q

PFVs

A

tested directly with BO prism or indirectly with plus lenses. Plus lenses relax accommodation which relaxes convergence. patients must use PFV to counteract this divergence to maintain fusion

BOP

17
Q

exophorias require large ____ranges

A

PFV

18
Q

NFV

A

tested directly with BI prism or indirectly with minus lenses. Minus lenses stimulate accommodation, which stimulates convergence. Patients must use NFV to counteract this convergence to maintain fusion,

19
Q

esophorias require large ____ranges

A

NFV

20
Q

what tests mergence stamina

A

facilities

21
Q

which should you test first, PFV or NFV

A

NFV (BI)

convergence could interfere with the results of the test

22
Q

imAGE jump

A

the amount of prism induced at the bifocal line due to the ADD power when the patient looks into the bifocal segment. calculated using only the add power and the distance between the top of the segment and the optical center of the segment (the style of the bifocal).

23
Q

what is the distance between the optical center and the edge of a FT 28

A

5mm

24
Q

what is needed for imAGE jump

A

add power and the type (the type tells us how far the bifocal is from the optical center

25
Q

what is the distance between the optical center and the edge of a ribbon bifocal

A

7mm

26
Q

what is the distance between the optical center and the edge of a round 22

A

radius (11mm)

27
Q

what is the distance between the optical center and the edge of a executive

A

0

28
Q

what can you do to reduce image jump

A

PAL or executive

29
Q

combining horizontal prism

A
  • if the prism over the left and right eyes are in the same direction (both BI or both BO), ADD the prisms
  • if the prisms over the left and right eyes are in oppose direction (BI in one, BO in the other), subtract the prisms
30
Q

combining vertical prism

A
  • if prisms over the left and right eyes are in the same direction (both BU or both ND), SUBTRACT the prisms to determine the total prism power
  • if prisms over the left and right eyes are in the opposite directions (one BU and one BD), ADD the prisms to determine the total prism power
31
Q

Maddox rod

A

a dissociated, subjective rest that determiners the magnitude and direction of a deviation (cannot tell phoria from tropia). it contains a series of stacked cylinders that forms a line image on the retina when a patient views a light source

32
Q

measuring horiztonal deviation with Maddox rod

A

the Maddox rod striations are oriented horizontally to produce a vertical line image for the eye viewing through the Maddox rod while the fellow eye views a point light source

33
Q

measuring vertical deviation with Maddox rod

A

Maddox rod striations are oriented vertically to produce a horizontal line image for the eye viewing through the Maddox rod while the fellow eye views a point light source

34
Q

uncrossed diplopia on Maddox rod

A

line to the right

35
Q

Maddox rod and right hyper

A

red horizontal line below the point light source

BOARDS2: Ophthalmic Optics (3 decks)

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