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Refracting Skills 2 > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

When the px is behind the phoropter and eye chart is placed at infinity where (feet and meters)

A

20 feet
6 meters

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2
Q

When using the phoropter to measure at near where do we measure (inches and centimeters)

A

16 inches
40 cm

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3
Q

what is the goal when correcting refractive errors

A

To focus the image on the fovea
we use lenses to move the focal point of an image onto the retina

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4
Q

Is retinoscopy objective or subjective?

A

Objective

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5
Q

Parts of retinoscope?

A

-Forehead rest
-Peep Hole
-On/Off
-Magnet for fixation targets (dynamic ret)
-Streak window
-Brightness
-Dust-free sealed optics
-Cross linear polarization filter switch
-Sleeve (ALWAYS DOWN)

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6
Q

Why is it important for the sleeve to be down for ret

A

To produce divergent light rays and a diffuse, unfocused beam of light
This position is termed plano, or plane mirror effect and is required for proper neutralizatino

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7
Q

When the collar is up what does it do?

A

Emits convergent light rays and a sharper beam
-This position is termed concave mirror effect, and is used for certain advanced techniques

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8
Q

Where is the fixation target during ret?

A

-20/200 letter / non accommodative target
-Important to give a target so px is not looking at light // if they look at the light the pupil will constrict and accommodation may be triggered which results in a more myopic result

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9
Q

During ret when the reflection is “off axis” what does this inidicate?

A

Astigmatism

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10
Q

During ret when the light “scissors” what does this indicate?

A

Kerataconus

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11
Q

During ret we evaluate streak at 90,45,180 and 135 .. what do we evaluate?

A

-If the streak looks the same in every direction the refractive error is spherical or close to it
-If the beam is not parallel to the streak this means astigmatism

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12
Q

How to change the angle of the streak on ret?

A

Rotate the collar

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13
Q

how to know if we are working in sphere for ret?

A

Because cyl is always in negative so we work with the more positive (least negative)

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14
Q

Devices used to quantify tonometry

A

-Indentation- Indent (depress) using a fixed weight
-Applanation- Flattening a specific area

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15
Q

Tonometry is good to use for pxs with what?

A

Glaucoma, key in early detection

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16
Q

Successful management of glaucoma

A

-monitoring IOP at regular intervals
-Observing optic nerve
-Verifying the integrity of the pxs visual field

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17
Q

pathway of how acqeuous humor flows through the eye

A

Ciliary body
Pupil
Anterior Chamber
Trabecular meshwork
Schelmms canal
Episcleral veins
Systemic bloodstream

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18
Q

purpose of aqueous humor

A

-provides nutrients to the cornea and lens
-Create an internal pressure necessary to maintain shape of the glope
-If this system falls out of balance then the optic nerve can be damaged which can lead to gluacoma

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19
Q

what happened in 1865

A

Albertch von graefe was one of the first to propose an instrument to assess pxs pressure

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20
Q

what happened in 1884

A

cocaine use to anesthtize the eye

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21
Q

early 1900s

A

Schiotz mechanical tonometer was introduced / became the “gold standard” for measuring IOPS

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22
Q

1950s

A

goldmann applanation tonometer came into use
-this became the preffered method of testing and has remained for 50+ years

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23
Q

What is tonometer measured in

A

mmHG (millimeters of mercury)

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24
Q

Average / normal IOP ??

A

10 to 22 mm Hg

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25
Q

What is ocular hypertension

A

when IOP exceeds 22 mm Hg but other diagnostic testing is normal

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26
Q

Factors affecting IOP

A

-ocular structures
–scleral rigifity
– centreal corneal thickness
-Extraocular influences

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27
Q

Scleral rigity

A

Sclera is abnormally “tough” and resists “give” when an indentation devicfe is applied to the cornea
-Conversely, an abnormally ‘elastic’ sclera gives tooo much causing a false low reading

28
Q

Centreal corneal thickness

A

plays an important role in the accuracy of IOP measurements and in the risk of developing glaucoma

29
Q

Average CCT ?

A

555um (micrometer)

30
Q

Thinner cornea ?

A

<555um
will elicity artifically low IOP due to less resistance by cornea

31
Q

Thicker cornea?

A

> 555um
will yield falsely high IOP readings

32
Q

what are some extraocular influences?

A

-body position
-diurnal curve
-ocular profusion pressure

33
Q

what can body position effect IOP

A

-IOP is lowest in a sitting position
-increase overnight when in a reclining position

34
Q

Diurnal curve

A

over a 24 hr period, IOP normally fluctuates 2 to 6 mm Hg
-In glaucoma pxs, can be greate than 10 mm Hg

35
Q

Ocular profussion pressure

A

relationship between IOP and systemic blood pressure
-Systemic blood pressure drops, it decreases the OPP

36
Q

Clinical skills

A

-Palpation
-Indentation
-Applanation (contact / non contact)

37
Q

Palpation

A

-Tacticle or digital palpation
-Eye w. elevated pressure will feel more rigid

38
Q

Palpation advantages

A

-no special equipment is needed
-can be performed in any location
-anesthic drops are not required m
-SImple, non threatening means to guage IOP in young children

39
Q

Palpation technique

A

Ask the px to close their eyes - not to squeeze them shut
-W/ the index and middle finger, gently press on the central globe through the eyelid

40
Q

Indentation

A

-Measure the distortion of the cornea when acted upon by an external force
-Converted to an equivalent IOP

41
Q

Indentation tool

A

Schiotz tonometer
-Premier indentation tonometer

42
Q

Indentation technique

A

-Instil topical anesthetic
-have px recline
-hold eyelids open and ask px to breath slowly and fixate on the ceiling
-footplate is slowly lowered perpendicularly onto the cornea
-record the measurment and use the chart to convert the reading to mmHg

43
Q

Applanation

A

-Measure the force required to flatten a standard area of the cornea
-displaces much less aqueous in comparission to indentation

44
Q

Tools for applantation

A

-goldmann applanation tonometry
-perkins
-pneumotonometer
-Icare
-Tono pen
-Dynamic contour tonometry

45
Q

Goldmann applanation tonometry

A

-consists of a funnel shaped prism with a flat applanating surface
-tip creates two semicircular mires when applied to the corneal surface

46
Q

Technique of Goldmann applanation tono

A

-instill combined anesthetic drop w. fluroscien dye into the eye
-seat px comfortably at the slit lamp. Examine the corneal surface to make certain its healthy
-Swing tonometer into position. Prism should be rotated to the 180 degree position (unless there is 3D or more of cyl)
-Set mag to lowest power, switch cobalt blue, open the light to the biggest section and position light at an angle between 45 and 60
-move the prism forward until it makes contact w the central cornea
-turn the force adjustment knob until the inner edges of the mires are just toughing eachother

47
Q

How to record pressure from goldmann applanation

A

read the number on the force adjustment knob. Multiply the reading by 10 to convert it to IOP in mm Hg

48
Q

how to disinfect goldmann tip

A

-soak in hydrogen peroxide 0.3 or household bleach for 10 mins. Rinse with saline and pat dry

49
Q

Perkins

A

-Hand-held battery-operated, portable applanation tonometer
-principles are essentially the same as goldmann

50
Q

If a px had a high IOP and we were doing palpation how would it feel?

A

It would feel hard / firm

51
Q

Pneumotonometer

A

-Regulated flow of air runs from an internal pump through a tube to a probe-The probe detects the force of air flowing through it and the force of resistance as it slightly indents the cornea
-The balance of these two forces represents the IOP

52
Q

Technique of pneumotonometer

A

-Turn on device
-Ensure good air flow (no kinks in the hose)
-Administer anesthetic and have px focus straight ahead
-Gently place the tonometer tip against the pxs central cornea
-A “beep” (change in tone) will signal when a measurement has been obtained

53
Q

Icare

A

-Utilizes the principle of “rebound technology”
-Magnetized coils propel a tiny, disposable probe onto the cornea
-bounces back once it makes contact
-the firmer the eye (higher the IOP), the faster the probe rebounds
-Useful as a screening tool for uncooperative pxs or children
-Home-monitoring device where the px is trained to use themselves

54
Q

ICare technique

A

-No calibration or anesthetic needed
-Insert a fresh probe into the base
-Hit the measurment button once (00 will appear)
-Adjust forehead support so the device is aligned properly
-Ask the px to look straight ahead. Press the measrument botton
-Six measurments are made consecutively.
-Once all 6 are obtained, the IOP reading will be displayed following a “P”

55
Q

Tono-Pen

A

-Translate mechanical deformation of the cornea into an electrical signal
-Some devices require daily calibration prior to use
-Portable and easy to use in any position
-Not very accurate when testing in the very high or very low ranges

56
Q

Tono-Pen techniques

A

-Administer anesthetic drops
-Instruct the px to focus on a distant object
-Ensure a fresh tip cover is in place (confirm px does not have latex allergy)
-Direct the tip perpendicularly to within 1/2inch of the center of the pxs cornea.
-Press the operators button once (8888) will appear on display “====” should appear followed by a beep / begin measuring
-Briefly touch then remove the tonometer tip from the corneal surface
-A chirp will sound when a valid IOP is obtained
-After a given number of valid measruments are acquired a final been will sound

57
Q

Dynamic contour tonometry (DCT)

A

-Eliminates errors inherent in measuring IOP caused by corneal rigidity or thickness
-A microscope analyzes the force measurements and the ocular pulse amplitudes
-Takes 100 readings per second
-Measures pulsatile IOP directly and continuously (dynamically)
-Attaches to the slit lamp

58
Q

Cons with Dynamic contour tonometry

A

Takes longer than GAT
Increased contact time with cornea
Price

59
Q

Non contact applanation tonometry

A

-Air puff tonometer
-Diation
-Ocular response analyzer 8 (ORA)

60
Q

Air Puff Tonometer

A

-Uses infared and photoelectric sensors to calculate the time it takes for a standardized pulse of air to flatten the cornea
-Great screen device
-Tend to read IOP 2.7 to 3 mmHg higher compared to GAT / confirm suspicious measurments with GAT

61
Q

Air puff tonometer - does a soft eye take longer or shorter

A

Takes a shorter amount of time in comparison to a firmer one

62
Q

Diaton

A

-Hand-held, pen like device that takes IOP transpalpebrally (through the eyelid) px is looking up
-Essentially we are measuring the scleral not the cornea
-Does not directly touch the cornea
-Works on “ballistic principle”, which is similar to indentation
-Discrepancy between the diaton and GAT
-Accurate readings require precise placement of the tip of the correct eyelid location

63
Q

Ocular Response Analyzer 8 (ORA)

A

-Emits a noncontct pulse of air, which pushes the cornea in until it becomes slightly concanve (past the usual depth achieved by applanation)
-The cornea rebounds to its original convex shape
-The system captures both readings
-The difference between these readings is the corneal hysteresis (CH)
-Numbers are averaged and converted to IOP

64
Q

what does CH stand for and mean?

A

Corneal hysteresis
-CH is the ability of the cornea to absorb and dissipate energy

65
Q

Potential risks of tonometry ?

A

-Any method of tono should be avoided in all cases of corneal ulcer or orbital trauma
-Caution when taking IOP on an infected eye (may spread infection to the opposite eye or other pxs)
-Corneal abrasion / scratch
-Rubbing the eye while anesthetized

66
Q

what is Vasovagal Reaction and what can happen to px

A

-Result of a stimulation in one branch of vasovagal nerve which can cause you to faint
-Px may become very quiet and suddenly feel unwell
-Nauseous or warm
-Pale, sweaty, or clammy

67
Q

What to do when Vasovagal reaction happens to a px

A

-Stop procedure
-Have px lower their head or recline chair backward to bring hear at/or below level of the heart
-Tell px to take slow, cleasning breaths
-Call for help, DO NOT leave px unattended
-Reaction usually last for less than a min with a full recovery
-Be cautions of a second reaction when the px stands up
-Check blood pressure and pulse before allowing px to leave
-Document reaction in the chart for future refrence

Refracting Skills 2 (5 decks)

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