vision

Question 1

what and where is the retina

Answer 1

very thin layer of tissue lining inner part of eye; blood vessels get thinner as go away from optic disc

Question 2

retina function

Answer 2

captures light rays which are sent to brain via optic nerve

Question 3

where does optic nerve connect

Answer 3

back of eye near macula

Question 4

what is the optic disc

Answer 4

visible portion of optic nerve

Question 5

where is the physiological blindspot

Answer 5

where the optic nerve meets the retina (optic disc), as no light-sensitive cells; brain covers with surrounding visual stimuli

Question 6

where is the macula located

Answer 6

centre of retina, temporal to optic nerve

Question 7

what is the macula, including colour and size

Answer 7

small and highly sensitive part of retina responsible for detailes vision (appreciate detail, read etc.); yellow and 6mm in diameter

Question 8

what is the very centre of the macula called, and why does it form

Answer 8

fovea, forms pit at centre as absence of overlying ganglion layer

Question 9

cones and rods in fovea, and clinical assessment

Answer 9

highest concentration of cones (1:1 ratio with neurones, so photons coming from different sources stimulate different receptors -> distinguish between different light sources; perceive detail), lowest concentration of rods; assessed with optical coherence tomography exam

Question 10

how many layers in retina

Answer 10

3

Question 11

what is present in outer layer (behind retinal pigment epithelium, which is in contact with choroid -> sclera)

Answer 11

photoreceptors (1st order neuron) - cones and rods; light comes in, hits and reflects off retinal pigment epithelium, and then detected

Question 12

function of outer layer

Answer 12

detection of light

Question 13

what is present in middle layer

Answer 13

bipolar cells (2nd order neurons) and horizontal and amacrine cells

Question 14

function of middle layer

Answer 14

local signal processing to improve contrast sensitivity, and to regulate sensitivity

Question 15

what is present in inner layer

Answer 15

retinal ganglion cells (3rd order neurons)

Question 16

function of inner layer

Answer 16

axons of optic nerve transmit signal from eye to brain

Question 17

diagram of retinal structure

Answer 17

slide 28

Question 18

2 classes of photoreceptors in retina

Answer 18

rod and cone

Question 19

segments of cones and rods

Answer 19

nucleus -> inner segment -> connecting cilium -> outer segment

Question 20

disk pathway in photoreceptors

Answer 20

proteins synthesised in inner segment -> transported through connecting cilium -> distal migration in outer segment -> shed from tips

Question 21

diagram of cones and rods

Answer 21

slide 29

Question 22

outer section: cone vs rod

Answer 22

rod has longer outer segment, with photo-sensitive pigment

Question 23

sensitivity to light: cone vs rod

Answer 23

rod is 100x more sensitive

Question 24

response to light: cone vs rod

Answer 24

cone is much faster response (rod is higher spatial and time summation)

Question 25

type of vision: cone vs rod

Answer 25

rod is responsible for night vision (scotopic), peripheral vision and motion, cone is responsible for day light fine vision, central vision and colour vision (photopic vision)

Question 26

number: cone vs rod

Answer 26

120 million rods, 6 million cones

Question 27

where is blindspot angle relative to fovea

Answer 27

20 degrees

Question 28

where is highest concentration of rod photoreceptors in retina relative to fovea

Answer 28

20-40 degrees relative to fovea

Question 29

where is highest concentration of cone photoreceptors in retina relative to fovea

Answer 29

0 degrees (at fovea)