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Anterior Segment 2 > Evaluation of the Cornea and Conjunctiva > Flashcards

Evaluation of the Cornea and Conjunctiva Flashcards

1
Q

What are the top 3 functions of the cornea?

A
  1. Refracts; Transmits light
  2. Transparency
  3. Protection
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2
Q

How many diopters does the cornea refract?

A

43-48D

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3
Q

T or F: The curvature of the anterior and posterior surface contributes more to the refractive power

A

True

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4
Q

What corneal factors does the refractive power depend on?

A
  1. Change in refractive index from air to cornea
  2. Curvature of anterior surface
  3. Corneal thickness
  4. Curvature of posterior surface
  5. Change in refractive index from cornea to aqueous
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5
Q

Transparency can occur due to:

A
  1. minimal scattering and distortion
  2. regular arrangement of collagen
  3. smooth optical surface by tear film
  4. avascular tissue
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6
Q

The cornea protects the eye with the use of __?

A

Zonula Occludens/Tight junctions

Allows transport of materials through cells but not between them

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7
Q

What is the horizontal diameter of the front cornea?

A

12 mm

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8
Q

What is the anterior vertical diameter of the front cornea?

A

11mm

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9
Q

What is the horizontal and vertical diameters from behind?

A

11.7mm

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10
Q

The cornea is ___ in the center and ___ in periphery

A

steeper, flatter

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11
Q

What is the anterior radius of curvature?

A

7.8mm

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12
Q

What is the posterior radius of curvature?

A

6.5mm

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13
Q

70-80 large nerves from branches of the long and short ciliary nerves enter at what 3 nerve networks in peripheral stroma?

A
  1. Midstroma
  2. Bowman’s layer
  3. Epithelium
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14
Q

This effect influences corneal metabolism and aid in tissue maintenance

A

Neurotrophic effect

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15
Q

Measuring corneal sensitivity due to the density of nociceptors is called what?

A

Esthesiometry

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16
Q

What two things are very common to decrease corneal nerve sensitivity?

A

CLs overwear

Herpes Simplex Virus

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17
Q

This device is used to measure tactile sensitivity of the eye by using controlled pulses of air as stimulation

A

Corneal Aesthesiometer

- can use cotton wisp test for this as well

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18
Q

Corneal Metabolism relies upon what 2 things?

A

Oxygen and Glucose

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19
Q

Oxygen for corneal metabolism comes from what 3 places?

A
  1. atmosphere (mostly)
  2. aqueous humor
  3. limbal capillaries
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20
Q

What 2 places does glucose come from for corneal metabolism?

A
  1. From aqueous thru leaky endothelium

2. Small amounts come from the limbal capillaries

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21
Q

This illumination without fluorescein will cause corneal iron lines to appear black and in a linear, arcuate or circular pattern

A

Cobalt Filter Illumination

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22
Q

This illumination is great to view fleischer rings in keratoconus

A

Cobalt filter

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23
Q

This illumination occurs when the microscope and illumination system are set at equal angles of incidence and reflection

A

Specular Reflection

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24
Q

This technique is useful in evaluating the corneal endothelium, anterior and posterior lens.

A

Specular Reflection

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25
Q

This illumination is great for view corneal gutatta

A

Specular Reflection

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26
Q

This illumination is when the microscope is focused on an area immediately adjacent to illuminated tissue

A

Indirect illumination

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27
Q

This illumination is useful for evaluating refractile, non-opaque corneal lesions like microcysts and EBMD.

A

Indirect illumination

28
Q

This illumination causes light to be reflected off the anterior surface of the iris as the cornea is in focus

A

Retroillumination of the Iris

29
Q

This illumination has the slit beam directed straight through the dilated pupil, the light will reflect off the fundus through the pupil forming a red reflex

A

Retroillumination of the fundus

30
Q

This illumination uses the internal reflection characteristics of the cornea are used to evaluate its transparency while the observe looks outside of the slit lamp

A

Sclerotic Scatter

31
Q

This illumination is most commonly used to evaluate central corneal clouding, will appear as grey areas in the cornea.

A

Sclerotic Scatter

32
Q

This vital stain permeates into the intercellular space associated w/ any epithelial cellular disruption

A

Sodium Flurorescein

33
Q

This vital stain stains dead and devitalized cells and mucus.

A

Rose Bengal

34
Q

This vital stain stains dead and degenerate cells in the epithelium or conjunctiva, but not healthy epithelial cells

A

Lissamine Green

35
Q

Fluorescein is best observed __ minutes after instillation.

A

2 minutes

36
Q

Mucins and other tear film components block this type of staining.

A

Rose Bengal

37
Q

This dye also stains healthy epithelial cells.

A

Rose Bengal

38
Q

What dye is deemed slightly toxic?

A

Rose Bengal

39
Q

How long should you wait until you check Rose Bengal Staining?

A

5 minutes

40
Q

This is a synthetically produced, organic dye that has been historically used in food products.

A

Lissamine Green

41
Q

What stain is useful in HSV diagnosis?

A

Lissamine green

42
Q

Lissamine green is best observed __ minutes after instillation.

A

2 minutes

43
Q

In a patient with DES, we will find lissamine green staining where?

A

at the limbus and bulbar conjunctiva

44
Q

Sodium fluorescein must have ___ illumination.

A

high illumination

45
Q

Rose bengal needs ____ illumination.

A

high illumination

46
Q

Lissamine green needs _____ illumination.

A

low illumination

47
Q

Corneal topography captures how many mm of the central cornea?

A

10 mm

48
Q

What are the 4 things corneal topography is useful for?

A
  1. CL fitting
  2. Corneal Reshaping
  3. Dx of corneal disease
  4. Pre/Post Sx eval
49
Q

What are the 4 limitations of corneal topography?

A
  1. Non-repeatable measurements
  2. Depend on ocular surface cond.
  3. Must use same topographer to compare pt data
  4. Scale must be set the same for each test on the same patient
50
Q

What are the 4 types of corneal maps?

A
  1. Axial Power/Curvature
  2. Tangential Power
  3. Refractive
  4. Elevation
51
Q

This map displays power/curvature in diopters/mm relative to the keratoscope axis; most common map

A

Axial Power/Curvature

52
Q

This map shows power of the eye in its refractive state. Great for assessing results of refractive or corneal reshaping sx

A

Refractive

53
Q

This map is the most sensitive for periphery. Best map for analysis keratoconus.

A

Tangential Power

54
Q

This map shows difference in height or elevation of the cornea in microns from a reference surface. Best to determine pathology

A

Elevation

55
Q

This map is best for describing general corneal shape and detecting changes over time.

A

Axial power/curvature

56
Q

This map is most useful for analysis of keratoconus or transition areas in corneal reshaping therapy or refractive surgery.

A

Tangential power

57
Q

Pellucid marginal degeneration is what?

A

inferior thinning of cornea

  • Known as crab claws or kissing doves
58
Q

T or F: Keratometry does not directly measure refractive power.

A

True.

Measurement is written in diopters, but doesn’t measure refractive power

59
Q

What are the 6 limitations of keratometry?

A
  1. Relies on proper alignment
  2. Must be perfectly focused
  3. Instrum. errof of 0.37D possible
  4. Assumes corneal is spherical
  5. Loses accuracy above 50D
  6. Only central 3mm of cornea
60
Q

What are the 2 indication of corneal OCT indications?

A
  1. Keratoconus
  2. LASIK
  3. Planning PTK
  4. Detecting Corneal Dystrophy
  5. Tear meniscus measurement
  6. Corneal power measurement for post lasik IOL calculation
  7. Details of angle structures for glaucoma
61
Q

Corneal OCT will show greater curvature on anterior and posterior surfaces for what disease?

A

Keratoconus - can detect early, focal thinning

62
Q

What is the average corneal thickness?

A

535-555 microns +/- 30 microns

63
Q

This is commonly used in glaucoma diagnosis, refractive surgical evaluations, and monitoring corneal edema is?

A

Pachymetry

64
Q

This non-invasive technique is used to assess the corneal endothelium; cornea MUST BE CLEAR.

A

Specular Microscopy

65
Q

What techique is used to evaluate donor corneas?

A

Specular Microscopy

66
Q

This technique is used in research and is good for viewing endothelium in edematous, cloudy corneas.

A

Confocal Microscopy

67
Q

This technique is an ultrasound biomicroscopy that uses a high frequency probe (50 Hz) in glaucoma, uveitis, trauma, tumors, sclerits or any other disease of the anterior chamber.

A

high resolution Ultrasound

Anterior Segment 2 (14 decks)

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