Topography

Question 1

What does topography measure?

Answer 1

Measures the curvature of cornea and corneal abnormality/astigmatism.
Most evaluate 8,000-10,000 specific points across the corneal surface

Question 2

When is topography used?

Answer 2

Preferred in pt’s with K’s less than 46D
- Fitting of RGP
- Annual eval of corneal changes
- Implanting IOL’s
MANDATORY in corneal reshaping and for advanced keratoconus

Question 3

Tangential map

Answer 3

AKA True map
-Represents actual map of cornea
-More sensitive than axial, but used less often
- Yields smaller patterns than axial
- Measures power and curvature
- Evals central & peripheral` cornea
- Offers better visualization and precise location of corneal defects
- Same colors as axial
Useful post surgery/pathology

Question 4

Evaluation map

Answer 4

Important when first fitting CLs on an irregular cornea.
Helps decide best fitting lens design (corneal vs scleral)
most useful in predicting fluorescein patterns with RGP

Question 5

Refractive map

Answer 5

Often used to evaluate visual performance in post refractive surgery
Only measures curvature values from anterior surface

Question 6

Axial map

Answer 6

AKA power map
- Simplest of all displays
- Uses color to represent a dioptric value and shows variations in corneal curve
Warm colors- Steep
Cool colors- Flat
Ideal for base curve selection

Question 7

Pellucid Marginal Degeneration

Answer 7

PMD
- Degenerative corneal condition
- Presents with painless vision loss affecting both eyes
- Non-inflammatory, non-hereditary cause of corneal ectasia with bilateral clear inferior (4-8oclock)
- Peripheral corneal thinning

Question 8

With the rule VS Against the rule

Answer 8

With : Vertical, blue to the sides
Against: Horizontal, blue to top and bottom

Question 9

Keratoconus

Answer 9

Corneal disease, thinning and cone shaped cornea, usually affecting both eyes
Mild <45D
Moderate 45-52D
Advanced >52D