Optics

Question 1

What works on principal of total internal reflextion

Answer 1

Fibre optic cables
Endolaser fibreoptic probe

Question 2

How can anisekonia be reduced in hypermetropic anisometropia

Answer 2

Anisekonia - different sized images

Decrease distance between lens and cornea - less powerful lens, less magnification

Question 3

Purkinje sanson images

Answer 3

1,2,3 - convex - erect virtual

4 concave - inverted, real

Question 4

Images in compound mciroscope

Answer 4

First image real
Second (observed) is virtual

Question 5

What can the porro prism be used for

Answer 5

To shorten instruments
Inverted, deviated 180 degrees

Question 6

What formula requires AC depth

Answer 6

Haigis

Question 7

Power cross

-0.75 at meridian 110
+1.25

Answer 7

-0.75DS/+2.0DCx110

Because the x110 is the axis of the +2dc meridian

Question 8

How can spherical aberration be reduced

Answer 8

Decrease aperture in front of lens

Question 9

What does excess pressure on the cornea in A scan result in

Answer 9

Excess pressure, lower axial length

SRKT = A - 2.5AL - 0.9K

Means higher powered lens

Meaning moer myopia

Question 10

Diagnosis of thyrotoxicosis?

Answer 10

High T3,T4
Low TSH