Optics

Question 1

Indirect ophthalmoscopy:
the image formed is:

Answer 1

-vertically and horizontally inverted

-real

-located between the observer and the lens, at or near the second principle focus

-located about 40-50 cm from the observer who must accommodate to view the image

Question 2

An indirect ophthalmoscopy , how does emmetropia affect the image

Answer 2

the image size is the same regardless of position of lens

Question 3

An indirect ophthalmoscopy , how does myopia affect the image

Answer 3

image size increases as lens moves away from eye and reduces nearer eye (image within 2nd principle focus)

Question 4

An indirect ophthalmoscopy , how does hyperopia affect the image

Answer 4

image size decreases as lens moves away from eye and increases nearer eye (image outside 2nd principle focus)

Question 5

In indirect ophthalmoscopy,

stronger condensing lenses produce:

Answer 5

-less angular magnification

-an increased field of view

-an increase in laser spot magnification

Question 6

In indirect ophthalmoscopy,

Weaker condensing lenses produce:

Answer 6

more angular magnification
less field of view
less laser spot magnification

Question 7

advantages of indirect over direct ophthalmoscopy:

Answer 7

binocular view (compared to uni-ocular view for direct)

wider field of view (about 25 degrees compared to about 6 degrees with direct)

Question 8

disadvantages of indirect compared to direct ophthalmoscopy:

Answer 8

less magnification

image is inverted (image is upright for direct)

Question 9

What is the formula to calculate the power needed to change from glasses to contact lenses?

Answer 9