Contact Lens Equipment and Measurements : Keratometer / Slit Lamp Flashcards
What describes the curvature of a surface by stating the length of the curve’s radius?
Radius of Curvature
What does a short radius mean?
Steeper Curve
What does a long radius mean?
Flatter Curve
What will the radius be if the curve is steep?
Short
What will the radius be if the curve is flat?
Long
What is radius of curvature measured in?
mm
What determines corneal power?
Curvature
What does the radius of curvature converts to?
Dioptric Power
What keratometer provides power in values in dioptres?
Manual
What keratometer provides values in mm and dioptres?
Automater
What is the conversion formula?
P=(n-1)/r
What is P in the conversion formula?
Curvature power in dioptres
What is N in the conversion formula?
Index of refraction
What is R in the conversion formula?
Radius of curvature
What should you convert the radius of curvature to?
meters
What is the index of refraction for the eye?
1.3375
What is the average corneal power value?
43.50D
If the value is high, will the cornea be steeper or flatter?
Steeper
If the value is low, will the cornea be steeper or flatter?
Flatter
What device measures corneal curvature?
Central 3mm
Keratometer
What are the purposes of keratometer?
Measures amount and type of astigmatism
Information to help select contact lens base curve
Corneal distortion
Assess tear layer
Is the cornea a convex or concave mirrored surface?
Convex
What type of astigmatism is when the horizontal is the flatter meridian?
With the Rule
What type of astigmatism is when the vertical is the flatter meridian?
Against the Rule
What is the purpose of slit lamp?
Examine anterior and posterior segment of eye
Can you take photos with slit lamp?
Yes
What can you evaluate with slit lamp? examples?
Evaluate contact lenses
Evaluate for dry eyes
