Week 2 - Objective Flashcards
What are the 6 parts to an objective assessment?
1 - Visual acuity
2 - Keratometry
3 - Corneal Topography
4 - Slit lamp assessment
5 - Lens fitting
6 - Observe CLs fit
Do we take VAs at the start of the evaluation with the ROOM LIGHTS ON without gls and cls in/on?
Yes
What do we record when we take VA measurements?
-Distance and near VA’s
-binocular
-monocular recording
We measure the VAs with and without cls in.T/F
True
What is keratometry? 2
-is the measurement of the corneal apex of the cornea.
-Measures the flattest and steepest curves of the cornea
What does a keratometer measure? 4
- the corneal radius of curvature
-corneal astigmatism
-the quality of the corneal refracting surface
-the base curve selection for contact lens (GP + Soft lenses)
In contact lens fitting,
the keratometer should be used on
every new patient and on rechecks T/F
True
What is the K measurement?
the measurement that parallels the steepest zone of the flattest primary meridian
What is the steepest zone in the cornea?
the apex of the cornea
What unit is used with K readings?
Dioptres
Dioptric values can be converted to mm to figure out base curve T/F
True
If the mires are CLEAR BLURRY CLEAR (clear before the blink/blurred right after the blink/clear again) how do the soft contact lenses fit?
The lens fits flat, try a steeper fit
If the mires are BLURRY CLEAR BLURRY (blurry before the blink/clear right after the blink/blurry again) how do the soft contact lenses fit?
The lens fits steep, try a flatter fit
What charts are used to measure VAs (distance and near) ? 3
Snellen
Digital VA chart
Reading Card
What do we make sure we note when we write the VAs down?
OD/OS/OU - keep track of the eye being measured
When do you move on with the line or stop and record during the VA measurements?
When they get the majority of the letters correct
How do you write the VAs if they dont get the entire row but can read some of the one below or above?
For examples
20/40+1 if they got the entire row of the 20/40 and 1 letter of the 20/30
20/20-2 if they got the majority on that row apart from 2 letters.
What are the 3 types of corneal astigmatism?
-‘with the rule’ astigmatism
-‘against the rule’ astigmatism
-oblique astigmatism
What is the steepest meridian in with the rule astigmatism ?
Vertical Meridian
How will a patients prescription reflect they have an with the rule astigmatism?
- rx will have an axis within 30° of the 180 line
-it will fall within 001 -30 or between 150-180 degrees.
In glasses with the rule astigmatism is corrected with a minus cylinder in the horizontal axis. Why?
This creates a steeper
horizontal meridian
thereby neutralizing or
balancing the steepness of
the vertical meridian of the eye.
What is the steepest meridian in against the rule astigmatism?
Horizontal meridian
How will a patients prescription reflect they have an against the rule astigmatism? 2
-The pxs prescription will reflect this by having an axis
within 30° of 090 line
-The axis will fall somewhere
between 060-120°
In glasses against the rule astigmatism is corrected with a minus cylinder in the vertical axis. Why?
This creates a steeper
vertical meridian
thereby neutralizing or
balancing the steepness of the horizontal meridian of the eye
Where is the steepest curve in oblique astigmatism?
outside of the vertical and horizontal meridians
What is considered a steep K reading?
-Greater than 45 Dioptres
How will a patients prescription reflect they have an oblique astigmatism? 2
-The px rx will have an axis that is NOT within 30° of 090 or 180
-An oblique meridian falls between 120°-150° and 30°- 60°
What is considered a medium K reading?
-42.00 - 45.00 Diopters
What is considered a flat K reading?
-Less than 42.00 Diopters
Why would we do a corneal topography?
To gain a comprehensive understanding of the shape of the cornea.
Different patters in the corneal topography graph can indicate different issues. T/F
True
such as pellucid marginal degeneration, keratonconus or kertoglobus
What is the purpose of a slit lamp? 3
-provide a closer look at the different structures at the front of the eye and inside the eye
-assessing eye health
-ensuring a proper fit for contact lenses
What are 5 other contact lens observations that can be done during the objective part of the cls appt?
- HVID (horizontal visible iris diameter)
- PA / PF (palpebrae aperture/fissure)
- Lid Eversion
- Tear Break Up Time
- Tear Prism
What meridian does the + and - represent in a keratometer?
+ = horizontal meridian
- = vertical merdian
How is the keratometer reading recorded?
Horizontal first then Vertical @ the axis
for example
45.00/45.50 @ 090
This is also an example of with the rule astigmatism as the steepest meridian is in the vertical
What are the concentric rings on a corneal topography known as?
placido disc
How would we find the corneal astigmatism when given K readings?
find the difference between the two K readings
What do we check for during diagnostic lens evaluation once the lens have been placed on the cornea? 3
-lens fit
-comfort
-final power verification
What do we use the fluorescein (orange) dye for? 2
-stain tear film and devitalise tissue
-used to evaluate GP fit
Fluorescein (orange) is most commonly used to asses GP fit. What kind od fluorescein can be used to check the fit of soft cl?
High molecular weight
What is rose bengal (red) staining agent used for? 3
-stain devitalized tissue
-Shows deficiency of preocular tear
film protection
-diagnose ocular surface disorders
What is lissamine green staining agent used for? 2
-Used to stain devitalized tissue.
-Also stain epithelial cells that are
unprotected by mucin or glycocalyx.
If the mires are CLEAR CLEAR CLEAR (clear before the blink/clear during the blink/clear again) how do the soft contact lenses fit?
good fit
