Optics: Entoptic Phenomenon

Question 1

Entoptic images are…

Answer 1

Visual sensations that arise from within the eye itself

Question 2

Entoptic images are __________ as they are only see by the person whose eye it is

Answer 2

Subjective

Question 3

Most Entoptic images are benign but are important to…

Answer 3

Understand their causes and include them in patients reports

Question 4

Not all entoptic images arise from characteristic of the optics of the eye, some arise from…

Answer 4

Higher neuronal processes

Question 5

Small surface changes across the cornea can redirect light ___________ the _______________

Answer 5

Outside the retinal image

Question 6

Refractive entoptic effects:

Answer 6

-tear film
-corneal corrugations
-shadows
-white blood cells
-blue field entoptoscopy

Question 7

Entoptic effects in the tear film:

Answer 7

-Eye blinks causing a horizontal ridge of tears that are left momentarily when the lids came together.
-report a shadow effect seen as horizontal striation

Question 8

Corneal corrugations of entoptic images:

Answer 8

-Squeezing lids tightly cause shadow streaks or monocular diplopia and decreased VA
-can last for more than an hour in some cases

Question 9

Entoptic phenomenon from shadows:

Answer 9

-Small bright light source close to the eye produces an out-of-focus patch of light on the retina where shadows of objects are formed

Question 10

Entoptic phenomenon from shadows:

Answer 10

-Small bright light source close to the eye produces an out-of-focus patch of light on the retina where shadows of objects are formed

Question 11

Types of shadows:

Answer 11

-ocular opacities
-purkinje tree

Question 12

What factors can cause pt to see shadows?

Answer 12

-corneal scars
-lens opacities
-IO foreign bodies
-floaters

Question 13

The effect of shadows will be strongest for opacities ___________ to the retina because….

Answer 13

Closer, closer objects are more apt to project an umbra

Question 14

Anterior opacities may…

Answer 14

Not be seen at all

Question 15

Astoroid hyalosis in an ________opacity

Answer 15

Anterior

Question 16

Astoroid hyalosis for doctor looking in

Answer 16

Look bright and make view of fundus difficult due to glare

Question 17

Astoroid hyalosis for patients looking from retinal side

Answer 17

Look darker and they may not be aware of them

Question 18

Purkinje tree

Answer 18

Shadows of retinal blood vessels cast out due to the vessels being in front of the photoreceptors

Question 19

Purkinje tree is normally not seen but a small bright light can reveal them as a…

Answer 19

Branched pattern around fovea

Question 20

In purkinje vascular test, a patient with a good. Functions macular should be able to see what when the light source is moves?

Answer 20

A negative image of his or her retinal vessels

Question 21

Entoptic perimetry is a method of measuring…

Answer 21

Entoptic phenomenon

Question 22

Entoptic perimetry is used for:

Answer 22

-retinal capillary detail
-fovea a vascular zone
-macular blood flow
-diabetic retinopathy
-AMD

Question 23

When looking at a blue bright background such as the sky a person may see…

Answer 23

Bright spots moving along curved lines

Question 24

The phenomenon of the blue filed occurs because:

Answer 24

-blue light is absorbed by rbc but not by wbc which creates a gap in the blood column that appear as bright dots

Question 25

Movement of the dots on the blue background are synchronized with…

Answer 25

Your heartbeat

Question 26

Diffraction effects for entoptic phenomenon:

Answer 26

-colored halos -asterisms

Question 27

Colored halos are caused by

Answer 27

Corneal edema

Question 28

Corneal edema increases…

Answer 28

Increase IOP that forces water into cornea producing water clefts that act as refractive particles

Question 29

Patients may report colored halos around small bright light during…

Answer 29

Episodes of acute glaucoma

Question 30

Colored halos can also be caused by…

Answer 30

Swimming in chlorinated pool and over wear of contact lenses

Question 31

Asterisms

Answer 31

-Small bright object against dark background that have spikes -assumed to be due to diffraction of the suture lines of lens

Question 32

Pressure phosphates of entoptic phenomenon:

Answer 32

-digital pressure -moores lightening streaks

Question 33

Digital pressure applied to eyelid with eye closed can cause a…

Answer 33

Bright spot seen in the visual field on the opposite side of the

Question 34

Why does bright light occur with pressure?

Answer 34

Pressure directly activates the retinal cells and the field reversal due to optical crossed projection

Question 35

Moores lightening streaks

Answer 35

-vitreous liquefies with ages causing the points of remaining adherence between vitreous and retina to tug during eye movements -produces pressure phosphernes that appear as lightening streaks

Question 36

When a patient is seeing moores lightening streaks then you should…

Answer 36

Check carefullat for the possibility of retinal detachments

Question 37

Effects of entoptic phenomenon due to xanthophyll:

Answer 37

-Maxwell’s spot -haidinger’s brush

Question 38

Maxwells spot

Answer 38

Blue filter placed in front of eye as you view and bright background as a dark disc appears in the macular area

Question 39

Haidinger’s brush

Answer 39

If one looks at a uniform white background through a Polaroid filter, a small yellow hourglass figure appears centered on fixation point

Question 40

Haidinger’s brush is due to…

Answer 40

Birefringence induced by xanthophyll

Question 41

Electrical phosphenes and entoptic phenomenon:

Answer 41

-blue arcs on the retina

Question 42

Blue arcs of the retina:

Answer 42

Red patch of light is projected against a dim background and blue arcs will be seen following direction of optic nerve fibers

Question 43

Blue arc on the retina effect is due to:

Answer 43

An electrical short circuit between the axons from ganglion cells under the red stimulus and ganglion cells encountered along the path of the axons