CC3: Visual Field Defects

Question 1

Perimetry (kinetic vs static)

Answer 1

used to assess, diagnose & monitor progression of opthalmologic & neurologic conditions

• kinetic perimetry: testing visual field by moving things in periphery
• static perimetry: object presented in our visual field but doesn’t move; instead object is made dimmer/brighter

Question 2

The blind spot is about 17 degrees towards temporal field. Why is there a blind spot but we don’t really notice it?

Answer 2

• blind spot is where optic nerve is
• brain fills in our blind spot = “filling in phenomenon”
• aka scotoma
• no photoreceptor cells

Question 3

Binocular visual field involves?

Answer 3

Right and Left nasal fields = 120 degrees

Question 4

How does binocular visual field differ from monocular field (aka monocular temporal crescent)?

Answer 4

binocular vision involves using both eyes together. monocular field involves field above 60 degrees (ex. looking at an object at the corner of one eye)

Question 5

Traquair’s island of vision is a 3-D view of visual field. What does visual sensitivity depend on? What’s the main thing that limits island?

Answer 5

• at the tip of the island is where macula is = 20/20 vision
• visual sensitivity depends on: age, attention level, refractive status, pupil size, media opacities, characteristics of stimulus
• main limiting factor = stimulus (e.g. elephant vs mosquito)

Question 6

List the 5 strategies for visual field testing

Answer 6

1 - confrontation
2 - amsler grid
3 - tangent screen
4 - goldmann perimeter
5 - humphrey perimeter aka automated perimetry

Question 7

Confrontation Visual Fields is one of 5 strategies to test visual field. It is inexpensive, fast and practical but it’s both examinee and examiner-dependent. What are some techniques employed in confrontation visual fields?

Answer 7

• examiner and examinee are arm-lengt away & situated at same height/level
• pt covers left eye with palm
• ask pt to see if s/he can see examiner’s face (tests central 10 degrees)
• finger counting
• finger moving (to test peripheral vision)
• red object
• hand moving (to test monocular vision)
• examiner’s palms (side by side close to midline)

Question 8

Confrontation visual fields are excellent in testing?

Answer 8

• central scotomas

- hemianopias when pt can only see one side of face.

Question 9

Amsler Grid involves a grid that is held at 14 inches away. Patient can monitor vision changes at home. What is amsler grid used to test?

Answer 9

• test central 10 degrees of visual field
• test one eye at a time
• ask pt to see if any parts of grid are blurred/distorted

Question 10

Tangent screen is not used as often. It’s manual kinetic. What does it test?

Answer 10

• test central 20 degrees of visual field

- examiner is at 1 meter away from patient and move objects on screen from periphery to central

Question 11

Goldmann perimeter (manual kinetic) can show what about the patient’s visual field?

Answer 11

• test entire visual field
• move object & pt can click on buzzer
• plot results on chart to evaluate visual field

Question 12

Explain the Humphrey:Automated Static visual field detector

Answer 12

• computer screen w/ printer
• standardized
• begins by plotting blind spot to monitor fixation & reliability
• click when pt sees object
• object is made brighter or dimmer (static perimetry)
• can check for false positives and false negatives

Question 13

These are some visual field defects; define them:
scotoma
arcuate
altitudinal
hemianopia
quadrantanopia

Answer 13

1- scotoma -a portion of visual field is missing
2 -arcuate - arc-like shape defect produced by retinal nerve fiber bundle damage
3 -altitudinal - superior or inferior defect that respects horizontal meridian
4 - hemianopsia - nasal or temporal defect that respects vertical meridian
5 - quadrantanopia - defect that affects one quarter of visual field

Question 14

retinal ganglion axons will converge to form optic nerve. There’s a vertical line that bissects fovea to delineate nasal-temporal demarcation as well as a horizontal raphe that divides retina into superior and inferior. List 2 examples of retina visual field defect that we talked about in class.

Answer 14

1- central scotoma due to macular generation, foveal lesion

2 - arcuate field defect due to glaucoma (damage to optic nerve due to build-up of pressure in eye)

Question 15

Problems with optic nerve can lead to problems with color vision, visual acuity, right afferent pupillary defect. List 3 examples of optic nerve visual field defect. Realize that nothing is pathognomonic.

Answer 15

1 - altitudinal defect
2 - central depression
3 - central scotoma

Question 16

Wilbrand’s knee

Answer 16

when inferonasal fibers cross at the chiasm will loop back into contralateral optic nerve sheath before returning to chiasm.

Question 17

T/F: macular fibers form a little chiasm within the chiasm, which is very impt bc then in order to block central vision, one needs to severe the chiasm

Answer 17

True

Question 18

What is the classical defect if one damages the optic chiasm?

Answer 18

bitemporal hemianopsia

-nasal fibers carrying temporal field are severed at the chiasm causing temporal field deficits.

Question 19

What happens when one damages the wilbrand’s knee in Right optic nerve?

Answer 19

Wilbrand’s knee contains inferonasal fibers conveying superiortemporal field of vision that after crossing the optic chiasm will loop back onto contralateral optic nerve sheath. If one damages the right wilbrand’s knee, then you will get JUNCTIONAL SYNDROME. The right field of vision is completely damaged, and a section of the left superior temporal field is lost.

Question 20

Lesions beyond the optic chiasm present as homonymous field defects. The more posterior the lesion, the more incongruous or congruous the defect?

Answer 20

congruous

Question 21

What’s the difference btw damage to injury to optic tract vs injury to LGN?

Answer 21

Optic tract contains retinal nerve fibers & pupillary fibers that will not synapse at the LGN but at the pre-tectal area. Therefore, damage to optic tract can result in injury to retinal nerve fibers + pupillary light fibers while injury to LGN only affects vision fibers.

Question 22

The LGN contains 6 layers and has an intricate retinotopic organization, which is why injury can only affect a sector of LGN, leading to a condition called ____________.

Answer 22

sectoranopia

Question 23

After synapsing at LGN, there are parietal and temporal radiations. What type of visual field do they carry?

Answer 23

temporal radiations carry superior field information

parietal radiations carry inferior field information

Question 24

What is meyer’s loop?

Answer 24

unlike the parietal radiations that go straight to calcarine fissure, terminating in the cuneate gyrus, the temporal radiations go forward, loop around, and then terminate at the lingual gyrus. This loop-around is called meyer’s loop.

Question 25

Anterior lesion of temporal radiations (of meyer's loop) leads to quadrantanopia. Explain the visual loss.

Answer 25

Temporal radiations carry superior field information. Therefore, lesion here will cause homonymous, incongruous superior right side of both eyes are affected.

Question 26

Posterior lesion of temporal radiations leads to what type of visual field loss?

Answer 26

Contralateral homonymous incomplete superior quadrantanopia; incomplete refers to the fact that some of inferior field of vision is lost as well (not respecting the horizontal meridian)

Question 27

Explain the pattern of field loss if there's a lesion in parietal optic radiations

Answer 27

Contralateral homonymous inferior quadrantanopia

Question 28

What percentage of visual cortex is devoted to central 10 degrees of vision?

Answer 28

about 50% which shows how impt the central 10 degrees of vision is.

Question 29

Lesions in occiptal lobe has what kind of sparing?

Answer 29

Macular sparing