Topography, Corneal Refractive Surgeries (M)

Question 1

Which type of topography gives the most accurate elevation data?

Answer 1

elevation based

Question 2

How many microns per pulse does an Excimer laser remove?

Answer 2

0.25microns

Question 3

What is a tangential map a measure of? 1. What is it good for? 2

Answer 3

1. good for local changes

2. determining cones and PMD

Question 4

What is the post-op regimen for LASIK?

Answer 4

1. fluoroquinolone QID x1wk
2. pred forte QID x1wk
3. topical NSAID QID x1wk

Question 5

What is a axial map a measure of? 1. What is it good for? 2

Answer 5

1. curvature

2. base curves

Question 6

What is a refractive map a measure of? 1. What is it good for? 2

Answer 6

1. refractive power across cornea

2. LASIK or monitoring ortho-k

Question 7

What type of damage does excimer laser ablation cause? 1. Femptosecond laser? 2

Answer 7

1. photodisruptive and photochemical

2. photodisruptive

Question 8

What is the incisional refractive surgery that has peripheral elevation the results in relative central corneal flattening? 1. What is the incisional that corrects for astigmatism?

Answer 8

1. radial keratotomy

2. astigmatic keratotomy

Question 9

How quickly does the epithelium typically heal in PRK

Answer 9

3 to 5 days

Question 10

Which procedures are variants of PRK and differ in how the epithelium is removed? 1. Do they have an epithelial flap? 2

Answer 10

1. LASEK and epi-LASIK

2. yes

Question 11

What are the preferred patients and advantages of PRK?

Answer 11

1. indicated for low amounts of ref error

2. thin corneas can be considered

Question 12

If the high point and low point of a cornea have a difference of 350um or over, what should be fit?

Answer 12

scleral lens

Question 13

What are the different laser properties that have been developed?

Answer 13

1. full beam (causes central islands)
2. scanning slit
3. flying spot (optimal to minimize thermal effects)

Question 14

What is the procedure in which the corneal epithelium is removed and frozen donor tissue is placed under the peripheral annular keratotomy?

Answer 14

epikeratophakia

Question 15

What are the ways to remove the epithelium in PRK?

Answer 15

1. mechanical (blade, alcohol, Amoils brush, trans epithelial)
2. alcohol
3. laser or trans epithelial

Question 16

What are the different types of ablation laser techniques (and how do higher order aberrations relate to each)?

Answer 16

1. conventional (increase HOAs)
2. wavefront (keep HOAs the same)
3. topography guided (eliminates some HOAs)

Question 17

What is a elevation map a measure of? 1. What is it good for? 2

Answer 17

1. height of cornea from a reference surface

2. fitting irregular corneas with contact lenses

Question 18

What are the two types of flap creation options for LASIK?

Answer 18

1. femptosecond laser

2. microkeratome

Question 19

What is the Munnerlyn approximate ablation depth formula?

Answer 19

(optic zone)^2*D/3
D=refractive error
in microns

Question 20

What is the post-op regimen for PRK?

Answer 20

1. antibiotic
2. steroid
3. bandage CL
4. prophylactic mitomycin C

Question 21

What is the procedure in which a corneal flap is created and artificial lens or donor lens is placed under the flap? 1. What is it used for? 2

Answer 21

1. keratophakia

2. high hyperopia or aphakia

Question 22

What corneal laser procedure involves epithelial and epi BM removal?

Answer 22

PRK

Question 23

What are the general limits of excimer laser?

Answer 23

1. less than -12 D
2. less than -4D cyl
3. +0.50 to +6