7 Formation Of Retinal Image

Question 1

(TP) how many photoreceptors are there in the fovea per retinal ganglion cell?

Answer 1

1:1 ratio

Question 2

1 cone in the fovea is equal to _____ arc minute

Answer 2

0.5

A 20/20 letter would need 10 cones to see!!

Question 3

(TP) What’s the approximate width of a foveal cone?

Answer 3

2.5 microns

Question 4

(TP) what’s the visual angle subtended by a foveal cone?

Answer 4

0.5 minutes of arc

Question 5

(TP) how many photoreceptors end-to-end would be used to see entire length of 20/200 snellen E?

Answer 5

100

10x10

Question 6

(TP) which photoreceptors absorb light with a wavelength of approximately 560nm?

L cones

M cones

S cones

Answer 6

L cones

Question 7

You would use spectacles for ______ aniseikonia.

Contacts for ______ aniseikonia

Answer 7

Axial

Refractive

Question 8

What’s a defect of binocular vision in which the two retinal images of an object differ in size?

Answer 8

Aniseikonia

Question 9

What’s the first thing you should think about when an aniseikonia patient comes in and says they have headaches?

Answer 9

Fix their damn glasses

Question 10

Aniseikonia becomes clinically significant at values around -%

Answer 10

3-5%

Question 11

What’s the spectacle magnification formula

Answer 11

M power x M shape

Question 12

What’s the equation for power factor?

Answer 12

1/ 1-dFv

D=vertex distance

Fv= back vertex power

Question 13

Equation for shape factor?

Answer 13

1/ 1-(t/n)F1

T=thickness of lens

N=refractive index

F1=power of FRONT surface

Question 14

The larger the vertex distance, the more ________ you make the image

Answer 14

Magnified