Unit 3 Flashcards
P=(n-1)/r where:
P= curvature power in diopters
n= 1.3375 (index of refraction for eyes
r= radius of curvature IN METERS
Average corneal power
43.50 D
Steeper cornea is higher or lower diopter value
Higher
Flatter cornea is higher or lower diopter value
Lower
With the rule astigmatism Is steeper at what axis?
90 degree (vertical axis)
Against the rule astigmatism is steeper at what axis?
180 degrees (horizontal)
What kind of astigmatism looks like a red eight
With the rule
What kind of a stigmatism looks like a red Bow tie
Against the rule
Purposes of keratometry
-Detect amount and type of astigmatism
-Determine initial contact lens shape
-Intraocular lens implant selection
-Indicate a compromised cornea
-Diagnose keratoconus
-Assess tear layer and quality
Radius of curvature should be written in this unit of measure
Metres
As the radius of corneal curvature gets bigger the K reading does this
Gets smaller
What does MCAR stand for
Mires clear and regular
What does corneal topography do
Describes the shape of the corneal surface and all meridians
In topography normal corneas are represented by these colours
Greens and yellows
In topography flatter areas are represented by these colours
Blues or cool colours
In topography steep areas are represented by these colours
Reds or hot colours
All corneal topography devices display this information
-Keratometry values
-Power and access of the flattest meridian
Purposes of corneal topography
-Screen for corneal changes
-Monitor corneal ectasia
-Fitting contact lenses
-Pre-and post refractive surgery
-Post keratoplasty
-Ocular surface disorders
What does a placido disc do
Determines the shape of the anterior cornea only
What does slit scanning and Scheimpflug technology do
Take a series of 2-D images and reconstruct them into 3-D image of the front and back surface of cornea
Axial maps are good for this
-Corneal power
-Good overview
Tangential maps are good for this
-Power and curvature at individual points
-Most accurate
Elevation maps
Placido- calculate elevation
Scheimpflug- Actual elevation measured
Corneal thickness map is taken by these machines
-Scheimpflug
-scanning slit
Review manual keratometer labelling answer key
Try to name the parts based only on the numbers
