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Contact Lenses > Diagnostic Tools and Tests > Flashcards

Diagnostic Tools and Tests Flashcards

1
Q

What is the purpose of Tear tests?

A

They are for contraindication for CL wear

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2
Q

Name 4 tear tests

A
  1. Schirmer Test
  2. Tear Break Up Time (TBUT)
  3. Lacrimal Lake Assessment
  4. Phenol Red Cotton Thread Test
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3
Q

What is the purpose of the Schirmer Test?

A

To evaluate the tear quantity

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4
Q

What do you need to perform the Schirmer Test?

A

Snow strips (Shirmer Strips), Stopwatch and ruler

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5
Q

Explain the steps of a Schirmer test

A
  1. Wash hands and clean work station
  2. Have patient look up and towards their nose.
  3. Pull lower lid down and insert 35x5 mm snow strip (with 5 mm notch) into the outer corner of the eye
  4. Have the patient close their eyes
  5. Start timing
  6. Finish test when the patient has wet 15 mm of the strip or after 5 minutes of timing (which every comes first)
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6
Q

What is an acceptable result from the Schirmer Test?

A

15 mm is wet in 5 minutes.

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7
Q

What is the purpose of the TBUT?

A

To evaluate test quality

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8
Q

What do you need to perform the TBUT?

A

Fluorescein , saline, Burton Lamp or slit lamp with blue cobalt filter.

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9
Q

Explain the steps of the TBUT test

A
  1. Wash hands and clean work station
  2. Remove Fluorescein strip from the package and put 1-2 drops of Fluorescein on the dyed end then swipe fluoroscein strip on the sclera while the patient is looking up and away
  3. Instruct the patient to close their eye and look around (up/down/right/left) to spread tear film across cornea, then blink once and hold open
  4. Have the patient behind the slit lamp (low magnification) with the blue cobalt filter on
  5. Time from the last blink to the first dry spot/streak
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10
Q

What are the objective findings for a TBUT?

A

<7 seconds - contraindicative to CL wear
7-10 seconds - Low TBUT so part time wear , low water lens and comfort drops
10-15 seconds - Average TBUT

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11
Q

What is the Lacrimal Lake?

A

The pooling of tears collected between the lower lid margin and the sclera

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12
Q

What is the purpose of the Tear Lake Test?

A

To evaluate quantity and quality of the tears.

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13
Q

What tools do you need to perform the lacrimal lake test?

A

Slit lamp (can be performed at the same time as TBUT) and observe the tears that are collected

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14
Q

What is the purpose of the Phenol Red Cotton Thread Test?

A

To evaluate tear quantity

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15
Q

What is the procedure of the Phenol Red Cotton Thread Test?

A

Perform the same was as a Schemer test, but with a pre-soaked thread of Phenol Red. When the tears come in contact with Phenol they turn red. Measure after 15 minutes.

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16
Q

What are the uses of Fluoroscein? When would you need to use high molecular Fluoroscein?

A
  1. Stains the corneal surface where epithelial cells have loosened or desquamated (dead/dying)
  2. Evaluates GP/PMMA fit

When wearing soft contact lenses (this will not soak into the lens)

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17
Q

What is Rose Bengal? What is it used for?

Why do we not use it much? What is an alternative?

A

A harmless pink dye. It detects dead/devitalized epithelial cells and those that have lost their protective mucin coating.

Some people complain that it stings. Lisamine Green B

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18
Q

What is a Wratten #12 filter?

A

A filter used to enhance fluoroscein dye in the eye. It is used in conjunction with a Cobalt Blue filter

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19
Q

What is a Burton Lamp? What is a nickname for it?

A

A handhelp 10x magnifier with 2 sets of lights (blue and white). A Poorman’s slit lamp.

20
Q

What can you use a puritan Lamp for?

A
  • TBUT and Tear Lake tests
  • GP fit evaluation
  • Fluoroscein Patterns
21
Q

What is a V-gauge ruler?

A

A ruler with a V-shaped slot which you slide a clean, dry GP lens into to determine the diameter

22
Q

What is a Magnifying loupe/Jeweler’s Loupe?

A

A 7x or 10x magnifier with an eye piece and a ruler on the other to inspect GP lenses for surface quality and edge condition and to measure diameter.

23
Q

How accurate is the measurement of a centre thickness gauge?

A

Up to 100th of a mm (2 decimal places)

24
Q

What are the 5 uses of a radarscope?

A
  1. Base curve (on the back AKA the fitting curve)
  2. Front Curve
  3. Peripheral Curves
  4. Warpage
  5. Surface imperfections
25
Q

What is an astigmatic clock?

What does it look like and how is it used?

A

An eye chart used to detect unresolved astigmatism

In a clock formation, there are 3 evenly weighted parallel lines at each hour. Ask the patient if they can see all the lines at equal thickness. If any lines are not equal then they have some unresolved astigmatism at that axis.

26
Q

What is a Keratometer? What is another name for it?

A

An instrument that measures the corneal curvatures (in Diopters) in the central 3-5 mm of the corneal cap.

AKA Ophthalmoteter

27
Q

What is the normal measurement range of a Keratometer? How can you extend this range?

A

+36.00 to +52.00 D

You can extend this by placing trial lenses infront of the barrel
-1.00 lens: take the readings and subtract 6.00 D
+1.00 lens: take the readings and add 9.00 D

28
Q

What is a secondary use for a keratometer?

A

Can evaluate the fit of a SCL in situ.

29
Q

Define the Slit Lamp

A

A binocular microscope that is used to examine the eye, tear film, CL fit, growths and irregularities and examine corneal layers.

30
Q

What is Tyndall’s effect?

A

Using a darkened room and a narrow beam of light, one can see things that one cannot see under normal conditions (dust particles in the air when at the movies)

31
Q

What is a placebo disk? What does it look like?

A

A handheld device used to detect irregular astigmatism. A disk with concentric rings (alternating black and white) with a hole in the centre.

32
Q

How do you use a placedo disk?

A

The cornea is used as a convex mirror the reflects the pattern. if there is broken or asymmetrical reflection the patient has irregular corneal astigmatism.

33
Q

What is a Soper Topographer?

A

An attachement to the keratometer that maps several central and mid-peripheral points on the cornea.

34
Q

What is a spot/Streak Retinoscope used for?

A

To evaluate SCL fit in situ. Checks the reflex of the light beam. It is the most sensitive indicator of a marginally tight lens (Only used by OD and OMD)

35
Q

What is a Pachometer?

A

A device mounted on a slit lamp that is used to measure corneal thickness or size of the anterior chamber

36
Q

When is corneal mapping helpful?

A

Post-surgical fitting of contact lenses and measuring irregular corneas.

37
Q

What is the Ishihara Colour Test?

A

Test for Red-Green colour deficiency. Circles of different shades of green and red - classic colour test

38
Q

What can case a loss of chromatic discrimination?

A

Diabetes, AMD, Glaucoma, Plaquenil

39
Q

Define a Snellen Chart. What does 20/40 mean?

A

A chart for vision testing.

20 - distance the patient is standing
40 - maximum legible viewing distance

This patient can see at 20 ft what most people can see at 40 ft.

40
Q

What is the cover test?

A

Measures how well two eyes work together. When looking at an object in the distance/near the OD will cover one eye, pause and uncover it. The OD will examine the eye as it is uncovered and refixates on the target. It helps detect stray, amblyopia or a decrease in depth perception

41
Q

What is the Ocular Motility Test? When is it used?

A

Saccades are assed by having the patient move their eye quickly from R/L/U/D or “follow my finger”. It is especially useful when the patient complains of double vision or the OD suspects neurological disease

42
Q

What is the Broad H test?

A

A motility test used to test the horizontal rectus muscle. The overreaction or under action of one eye or double vision in any position are recorded and can indicate problems

43
Q

What is the duo chrome test?

What principle is this using?

A

A subjective refraction - comparing the sharpness of black targets of similar sizes on a red/green background

  • Too much plus: red background is sharper
  • Too much minus: green background is sharper

Chromatic aberration and assumes when the eye is looking in the distance it is focused on the yellow part of the visible spectrum

44
Q

What is an amsler grid?

A

A test for Wet AMD. If there is any waviness or missing parts of the grid this can indicate wet AMD - Good home monitoring tool

45
Q

What do Mydriatic Drops do?

What are they used for?

Examples

A

They act on the muscles of the iris to dilate the pupils

Dilating the pupil for a fungus exam

Mydriacyl and Phenylephrine

46
Q

What do Cycloplegic Drops do?

What are they used for?

Examples

A

Act on the iris AND ciliary body - dilates the pupil and paralyzes the focusing muscles to eliminate accommodation

Essential for refracting children and iritis therapy

Atropine

47
Q

What do Miotic Drops do?

What are they used for?

Examples

A

Spimulate the sprinter muscles of the iris to cause constriction.

Treatment of Strabismus and Glaucoma

Eserine, Hydrochloride and Pilocarpine nitrate

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