Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Pathology > Optics > Flashcards

Optics Flashcards

1
Q

A Scan:

1D IOL difference in axial length?

A

0.4mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Normal torsional cyclo vergence fusional amplitude?

A

2-3 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Point of reversal reach in retinoscopy?

A

When patient’s FAR point = observer’s NODAL point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How does pinhole increase acuity?

A

Improves irregular astigmatism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Decentring convex lens

A

Where P is the induced prismatic power in prism dioptres; F is the power of the
decentered lens in dioptres; and D is the decentration in centimetres.
The easiest way to determine the direction of prism power is to imagine convex
lenses as two prisms attached base to base and concave lenses as two prisms
attached apex to apex. Thus when a convex lens is decentred the base of the lens
is always towards the optical centre, i.e. in the same direction as the lens is moved,
whereas the opposite is true for concave lenses.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Pair/Peye = (nIOL - nair)/ (nIOL - neye)

A

Intraocular lens (IOL) powers are labelled according to their power immersed in aqueous humor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Stiles-Crawford effect no.2

A

In addition to changes in the efficiency with which photons are captured as a function of angle of incidence, there is also a shift in the hue and saturation of monochromatic lights depending on the angle of incidence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

doublet

A

reduces spherical aberation

Principal lens + weaker lens cemented together to reduce power of periphery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Oblique astigmatism

A

line of light not parallel with principal axis of lens

worse in biconvex and biconcave lenses than in meniscus lenses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

AC/A Ratio heterophoria method

A

IPD (cm) + (Ocular deviation for near (D) - for distance(D)/near fixation distance (D)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

AC/A Ratio: Gradient method

A

Ocular deviation for distance - for near)/minus lens dioptre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Image formed: Concave

A

Real

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Image formed: Convex

A

Virtual

Minified - always

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

PRK - below which diameter can cause haloes?

A

Diameter < 4mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Spot factor magnification

A

size of spot at retina / size of setting at laser machine

Lens

Image Magnification Laser Spot
60D

1.15 0.87
78D

          0.93              	1.08 90D

0.76 1.32
Volk Superfield

0.76 1.32
Volk Super 66

1.00 1.00
Volk Digital 1.0

1.00 1.00
Volk Digital Clear Field

2.79 0.36
Volk Digital High Mag

1.30 0.77
Volk Digital ClearMag

3.89 0.26
Volk Digital Wide Field

0.72 1.39

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Syntophere

Angle of anomaly

A

AOA = OA - SA
normal retinal correspondence (NRC), the SA is equal to OA and the AOA will be zero.
In unharmonious ARC, the SA will be less than the OA (but the SA will not be zero)
In harmonious ARC, the SA will be zero, so the AOA will be equal to the OA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Effective power of lens formula

A

d is POSITIVE If moves towards eye

d is NEGATIVE if moves away from eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

RSM of aphakic spectacle

A

1.33

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

iseikonic lens

A

no power lens
but increases the magnification by increasing hte visual angle subtended to by the eye
pure magnification - front lens surface and thickness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Near visual point (bifocals)

A

Should be 2mm nasal and 8mm inferior to distance visual point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where should the top of the near visual point be placed?

A

tangential to the inferior limbus

Children - lower margin of pupil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How can prismatic jump be reduced?

A

If the optical centres of the lens lies near or at the junction of the 2 portions
incorporating base-up prism in near segment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Effect of tear lens on steeper base curve

A

makes acial hight greater, and therefore more positive (convex)

24
Q

What dioptre is a limitation to soft contact lenses in corneal astigmatism?

A

1.5-2D

25
Q

decentring Myopic prismatic effect

A

temperoally: Base in prism
Nasally: Base out
Inferiorly: Base up
Superiorly: Base out

26
Q

Increasing the negative power of the contact lens

A

increasing temperature (evaporation)

27
Q

Assessing microtropia

A

4D bae OUT prism

28
Q

Power of refractive surface

A

(n2 - n1)/r1

29
Q

Diffraction and wavelength

A

INCREASES with wavelength

30
Q

Minimum angle of RESOLUTION

A

Visual acuity is reciprocal

31
Q

Image found anywhere in convex mirror

A

Found within centre of curvature, erect, laterally inverted

32
Q

Total internal reflection

A

Light travels from higher refractive index to lower

Incident ray > critical angle

33
Q

Axial magnification

A

magnification of the depth of the image along the optical axis

34
Q

Correcting eso/exotropia with prisms

A

Usually correction split between the two eyes
To correct convergence: prism must be base OUT
To correct divergence: prism must be base IN
To correct vertical deviation: prism opposite for both eyes

35
Q

Contact lens nomenclature

A

base curve/diameter/power

36
Q

Reducing lens movment

A
  1. Increase contact lens diameter
  2. Decrease base curve of CL
  3. Increase thickness of CL
37
Q

A change in the radius of corneal curvature of 0.1 mm produces a change in refraction of what in contact lens fitting?

A

0.5 dioptres.

38
Q

Aspheric lens

A

radius changes from the center to the outside (becomes less curved usually)

39
Q

Hyperope and contact lens

A

Will use less accomodation with contact lenses

40
Q

Angular magnification

A

Power eyepiece/power objective

Eyepiece lens is more powerful > objective

object is not changed in position or size, but has an optical system interposed between the object and the eye to make the object appear larger.
Angular magnification takes into account not only the size of an image, but also its distance from the observer

41
Q

Should hyperopes/myope use round or flat top bifocals?

A

Myope - flat top

Hyperope- round top

42
Q

Mode lock pulse

A

30 pico seconds

x100 powerful than Q switch

43
Q

Ionisation lasers

A

Ng-YAG

Argon-fluride excimer

44
Q

Thermal lasers

A

CO2 lasers

45
Q

Photochemical

A

Argon lasers for retinal photocoagulation

46
Q

Back vertex power

A

1/posterior vertex focal length

47
Q

Captoptric images

A

1- keratometry
1+2 - corneal thickness
2+3 - AC depth
3+4 - accomodation

48
Q

Chromatic aberation

A

NOT affected by refractive index

affected by dispersive power

49
Q

Spherical abberation reduced by what in the eye?

A
  • aplantic curvature of cornea
  • iris - stop light coming obliquely
  • lens - nucleus higher refractive index
  • Retina - cones sensitive to light paraxially
50
Q

What do Best form lenses improve?

A

spherical and oblique astigmatism

51
Q

What is vergence power affected by?

A

RI on each side of medium
thickness of lens
Vergence power of each surface

52
Q

Angular magnification

A

Quotient of angle subtentded by image OVER object

53
Q

How do fresnel prisms reduce VA?

A

Chromatic aberration

54
Q

Absolute RI

A

velocity of light in vacuum/velocity of light in medium

55
Q

Tear lens

A

K>BC = convex
K < BC = concave
K = BC = plano

Pathology (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions