Pre-Operative Biometry (M)

Question 1

What takes an electrical charge and turns it into a digital output to determine aberrations?

Answer 1

CCD sensor

Question 2

What is the imaging device that has a tilted image and object plane to get objects in focus at the same time? 1. What is the advantage of this? 2

Answer 2

1. Scheimpflug

2. Gives maximum depth of focus and minimal image distortion for an obliquely tilted object

Question 3

Does diffraction increase or decrease with a decreased in pupil size?

Answer 3

increase

Question 4

What type of spherical aberrations come into focus just before the retina?

Answer 4

(+) spherical aberrations

Question 5

What types of aberrations are associated with high sphere?

Answer 5

spherical aberrations

Question 6

Do aberrations increase or decrease with a decreased in pupil size?

Answer 6

decrease

Question 7

What are the five measurements taken by a Pentacam?

Answer 7

• Pachymetry
• Topography
• Corneal Curvature (Ant/Post)
• Astigmatism Determination
• Scheimpflug Imaging of Lens

Question 8

How many diopters change is associated with a 1mm axial length change?

Answer 8

3D

Question 9

What type of spherical aberrations come into focus just behind the retina?

Answer 9

(-) spherical aberrations

Question 10

What is a procedure to analyze an ocular response?

Answer 10

corneal hysteresis (normal corneas have higher values)

Question 11

What types of aberrations are associated with keratoconus or pellucids?

Answer 11

coma

Question 12

What are some of the available aberrometers?

Answer 12

1. visx
2. iProfiler
3. Allegro

Question 13

How does the measurement from a contact A-scan differ from a non-contact?

Answer 13

0.2 to 0.3mm shorter because of corneal compression