Neuro-Ophthalmology Vol. 3

Question 1

Approximately how many rods are found within the retina?

Answer 1

80 to 120 million

Question 2

Approximately how many cones are found within the retina?

Answer 2

5 to 6 million

Question 3

Where is the only place that rods are not found within the retina?

Answer 3

Fovea

Question 4

Where is the physiologic blind spot located?

Answer 4

Approx. 17 degrees from the fovea

Question 5

What is the average size of the physiologic blind spot?

Answer 5

5 by 7 degrees

Question 6

What is the smallest subpopulation of cones?

Answer 6

Blue cones

Question 7

What is the only type of cones NOT found at the fovea?

Answer 7

Blues cones

Question 8

Where is the fovea located in relation to the optic disc?

Answer 8

4 mm temporal and 0.8 mm inferior to optic disc

Question 9

What is approximate surface area of the retina?

Answer 9

2500 mm2

Question 10

What calls connect the ganglion cells to the photoreceptors?

Answer 10

Bipolar cells

Question 11

What is the most common type of ganglion calls?

Answer 11

Parvocellular (P cells; 80%)

Question 12

What is the largest type of ganglion cells?

Answer 12

Magnocellular (M cells)

Question 13

What type of ganglion cells are responsible for color perception and have low contrast sensitivity?

Answer 13

P cells

Question 14

What type of ganglion calls are responsible for light contrast and motion?

Answer 14

M cells

Question 15

What type of ganglion cells have the largest field of reception?

Answer 15

M cells

Question 16

Where is the photoreceptor: ganglion cell ratio the highest?

Answer 16

Periphery (1000:1)

Question 17

Where is the photoceptor:ganglion cell ratio the lowest?

Answer 17

Fovea (1:1)

Question 18

Where is the concentration of ganglion cells the highest?

Answer 18

Macula

Question 19

What causes the star-shaped pattern of macular edema?

Answer 19

Radial arrangement of axons of the bipolar cells (e.g. Henle layer)

Question 20

What is the primary neurotransmitter of the retina?

Answer 20

Glutamate

Question 21

What arteries make up the primary blood supply to the optic disc?

Answer 21

Posterior ciliary arteries

Question 22

Where is the ophthalmic artery located in relation to the optic nerve within the optic canal?

Answer 22

The ophthalmic artery is located Inferior to the optic nerve within the optic canal

Question 23

What bone makes up the optic strut?

Answer 23

Lesser wing of the sphenoid

Question 24

What is the average length of the optic canal?

Answer 24

8 to 10 mm

Question 25

What is the average width of the optic canal?

Answer 25

5 to 7 mm

Question 26

In what direction does the optic canal course posteriorly?

Answer 26

Superior and medially

Question 27

What is the most inferior portion of the frontal lobe?

Answer 27

Gyrus rectus (lies above and parallel to the optic nerves)

Question 28

What is the average width and length of the optic chiasm?

Answer 28

12 x 8 mm

Question 29

What is the average thickness of the optic chiasm?

Answer 29

4 mm

Question 30

How far above the sella is the optic chiasm located?

Answer 30

Approx. 10 mm directly superior (though can be anterofixed or postfixed)

Question 31

What percentage of the nasal fibers of the retina desiccate at the optic chiasm?

Answer 31

53%

Question 32

What fibers of the retina are first to cross the optic chiasm?

Answer 32

Inferior fibers

Question 33

Where is the lesion resulting in a superior temporal visual field defect with a central scotoma in the contralateral eye?

Answer 33

Junction of the optic nerve and chiasm

Question 34

Where are the internal carotid arteries found in relation to the optic nerves?

Answer 34

The internal carotid arteries are located inferior to the optic nerves

Question 35

What arteries provide the blood supply to the optic chiasm?

Answer 35

Proximal anterior cerebral and anterior communicating arteries