Eyedocs instruments

Question 1

The principle of diffraction is used in what?

Answer 1

multi-focal intraocular lenses - interference of waves of light to creat multi-focality

Question 2

What is the primary focal point?

Answer 2

It is the object location associated with a parallel ray LEAVING the lens

Question 3

What is the secondary focal point?

Answer 3

It is the image location associated with a parallel ray ENTERING the lens

Question 4

What is the conjugate point?

Answer 4

Two points that are an object and image of each other

Question 5

What is the far point?

Answer 5

The point in visual space conjugate with the retina when the eye is not accommodating

Question 6

What is the aim of spectacle / CL correction?

Answer 6

Place a lens in front of the eye so that the secondary focal point of the lens coincides with the far point of the eye

Question 7

What is the vertex distance?

Answer 7

the distance between the eye and its corrective lens is the vertex distance (from corneal surface to back of lens)

Question 8

What is the near point?

Answer 8

The point in space conjugate to the retina when the eye is fully accomodated

Question 9

What is the distance between far point and near point called?

Answer 9

the accomodative range

Question 10

What does a spherocylindrical lens consist of?

Answer 10

two cylindrical lenses of differing dioptic powers orientated 90 degrees apart

Question 11

What is the circle of least confusion?

Answer 11

section of the conoid in which incoming light is the most focused (most-point like)

The smaller the COLC, the better the vision

Question 12

What are the two techniques used to correct the astigmatic patient?

Answer 12

1. Retinoscopy
2. Jackson-Cross

Question 13

What are the refractive types of astigmatism? (5)

Answer 13

1. Compound myopic (both focal lines in vitreous)
2. Compound hyperopic (both focal lines behind eye)
3. Simple Myopic (one line in vitreous, one on retina)
4. Simple Hyperopic (one line behind eye, one on retina)
5. Mixed (one in vitreous, one behind eye)

Question 14

What does a -2 sphere do in astigmatism in retinoscopy?

Answer 14

Pushes entire focal lines back - aim is to keep anterior focal line on the retina

Question 15

What does a +1 cylindrical lens do in astigmatism in retinoscopy?

Answer 15

pulls the posterior focal line forward

Question 16

What is a Jackson Cross lens?

Answer 16

It is a spherocylindrical lens containing plus and minus cylinders of equal and opposite powers orientated 90 degrees apart with no net spherical equivalent power

Question 17

What is the main property of the jackson cross lens?

Answer 17

It does not move the circle of least confusion when placed before an astigmatic eye as it has no sphere power

Question 18

What should you aim for for a Jackson Cross Lens?

Answer 18

Aim for mixed astigmatism with circle of least confusion on the retina before cylinder is introduced

Question 19

What is with the rule astigmatism?

Answer 19

vertical meridian (180) is steeper than horizontal meridian (90) (squeezing a ball in the vertical axis)

Question 20

How do you correct with the rule astigmatism?

Answer 20

1. minus cylinder at 180 degrees (vertical mer)
2. plus cylinder at 90 degrees (horizontal mer)

Question 21

How do you correct against the rule astigmatism?

Answer 21

1. minus cylinder at 90 degrees (horizontal)
2. plus cylinder at 180 degrees (vertical)

Question 22

How do you change prescription from positive cylinder to negative cylinder?

Answer 22

1. Add sphere to cylinder
2. change cylinder sign
3. axis Change by 90 degrees

Question 23

Large convex lenses (aphakia) produce what effects? (4)

Answer 23

1. pin-cushion effect
2. ring scotoma
3. jack in the box phenomenon
4. spherical aberration

Question 24

Large concave lenses produce what effects (1)

Answer 24

1. Barrel disrotion effect of images

Question 25

What are the contraindications of LASIK surgery (3)

Answer 25

1. Long term topical/oral corticosteroids 2. Immunocompromised 3. Chronic ocular conditions (incl keratoconus with risk of ectasia)

Question 26

What are base-in prisms used for?

Answer 26

1. measurement of horizontal fusional amplitude

Question 27

What are base-out prisms used for?

Answer 27

1. Management of esophoria 2. Management of VI nerve palsy 3. Improve convergence in patients with convergence insufficiency 4. 4 prism base-out prism is used for suppresion scotoma of microtropia

Question 28

WHich children's test uses crowded letters? Which children's test uses letters singly?

Answer 28

1. Sonksen-Silver 2. Sheridan-Gardiner

Question 29

What is the difference bewteen Kay, Keeler and Cardiff Cards?

Answer 29

Kay - matching pictures Keeler - preferential grating Cardiff cards - simplistic pictures in white

Question 30

What is the purpose of a maddox rod?

Answer 30

Identifies presence of - horizontal deviations - vertical deviations - torsional deviations - latent and manifest strabismus

Question 31

What is a maddox rod?

Answer 31

series of parallel cylinders lying 3mm apart that converts a POINT source of light to a LINE image.

Question 32

What are the contraindications to ICG? (5)

Answer 32

1. Pregnancy 2. Seafood Allergy (not in FFA) 3. Iodide Allergy (not in FFA) 4. Kidney Failure 5. Liver Disease (not in FFA)

Question 33

What are the contraindications to FFA? (4)

Answer 33

1. Previous allergy to fluorescein 2. Breastfeeding (not in ICG) 3. Kidney failure 4. Pregnancy