EXAM 1 - Week 1 to 3 Flashcards
What occurs when RPE starts to disengrate?
Photoreceptors cannot recycle, thus dying off
What is photopic vision?
Where cones predominatly function
What gives the retina its duplex property?
Rods and Cones
What is mesopic?
Combination of cones and rods function
What is scotopic?
Where rods predominantly function
Where is the opsin found in rods and cones?
In the outer segment
What photoreceptor sheds its discs
Rods
What is the maximum absorption (not sensitivity) of rod wavelength?
Around 500nm - Green color
Note: Rods are most sensitive to Violet color
What is sensitivity of cone wavelenght?
S-420 - Blue
M-530 - Blue - Green
L - 560 -Yellow - Green
What is the Rod sensitivity in nm?
498
What is the physiological dark adapt time?
35 minutes
How many photons can a rod be stimulated for vision to occur?
100’s of rods
How many photons are needed to stimulate a rod?
1 photon
In order by wavelength, put the photoreceptor in order.
Blue, Rod, Green and Red
True or False, you can detect one photon of light.
False. You personally cannot but your rod can
Is there an area where there are no photoreceptors?
Yes, the optic disc
What do we have more of rods or cones in the eye?
Rods
Where is the peak of cones?
Outside the fovea, 20 to 30 degrees
What is predominantly found in the fovea?
L and M cones
What is more dominant between L and M cones?
Varies. From 1 to 1 or 16 to 1 (M to L)
What is Dr. Cameron’s research with Zebra fish being conducted?
AMD
What is the lowest threshold for a Cone response, in regards to Dark Adaptation?
10 minutes
When do rods start functioning in regards to Dark Adaptation and when is the threshold met?
Don’t start till 10 minutes and 20 minutes after there is a threshold
What is the photochromatic interval?
Difference between rod plateau and cone plateau interval
At 35 minutes, what is the sensitivity of the human eye in dark adaption?
100,000 times more
What are the 5 areas where Dark Adaption can be effected?
Light Intensity - Brighter the room, the longer it takes to recover
Light Duration
Wavelength - What wavelength are rods sensitve to (Violet)
Location
Rhodopsin regeneration - slower regeneration and takes a while
What are the 4 sub-titles for the parting the curve graph?
Note: background must be red and stimulus is green
1 - Dark Light
2 - Square Root Law
3 - Weber’s law - slope will be the same for scoptic and photopic
4 - Saturation
What is a quanta in the nervous system?
1 packet of a neurotransmitter
You pt. a rod monochromat, has asked for advice regarding tinted lenses. You should advise a darkly tinted lens of which color?
Red lenses
What color as a background will activate both rods and cones for light adaptation?
Green will be the background and Yellow be the test spot
Where does neural nose occur for rods?
Dark light
Where is the threshold start to pass the neural noise area?
square root law
where is traditional vision occurring?
Weber’s law - Most of this occurs here
Where is saturation occurring?
Saturation
How many ganglion cells will 10 rods connect to?
1 ganglion cell
How many cones will connect to a ganglion cell?
5 cones
What is Ricco’s law?
Looking at spatial summation, its the AREA you look at.
What happens when a threshold has been achieved?
An action potential occurs
What is the type of summation that is rated over time?
Temporal Summation
Note: If you see a flash within 100ms, you will only see one flash in the Scotopic
Note: If you see any flash over 10m/s, you will see more than one flash
What is the stiles crawford effect?
Light has to strike a cone perpendicularly, while for rods it doesn’t matter.
What is the sclera largely consist of?
Collagen
How much refraction power does the cornea provide?
2/3 of refractive power entering the eye (40D)
What happens to the lens when you would like to increase the power of the lens?
Decrease the curvature of anterior lens surface
What part of photoreceptors does adaption for transmitting the neural signal?
Innermost PR cells
What type of photopigment is located in Rods and Cones?
Rods - Rhodopsin
Cones - Opsin
Where are rods located the most?
Outside of the fovea.
How many discs is a rod made of?
600 to 1000
Note: Disc membrane is seperate from the plasma membrane of the cell except at the base
When do rods shed?
During the day, specifically the evening
What is the name of the specialized terminal of a rod?
Spherule
Where are cones predominantly located?
20 to 30 degrees outside the fovea.
True or False. The plasma membrane of the photoreceptor is Continous with the disc membrane of the Cone.
True
Where are the cell bodies of bipolar cells, HC, AC, Interplexiform cells and Mueller cells located in the retina?
Inner Nuclear Layer
What is the % of Small midget GC’s in the eye?
80%
What is the % of Large Parasol GC’s in the eye?
10%
How many degrees away is the optic disc away from the fixation point?
15 degrees
What is the primary target for the optic tract?
LGN
Which layers receive input from the ipsilateral eye?
2, 3, 5
How many layers are there for the ventral Magnocellular layer?
2
How many layers are there for the dorsal Parvocellular layer?
4
Which cortical area do LGN synapse?
V1 or Broadmann Area 17
Which PR is more prone to being more hypersensitive?
Rods.
Note: rods are more sensitive to light
What is the photoreceptor in order by wavelength smallest to Largest?
S, Rod, M, and L
What is the visual acuity in the Scotopic system?
20/200
When phagocytosis of discs doesn’t occur, what damaging disease can occur?
Retinitis Pigmentosa
How many molecules of rhodopsin molecules are contained in a rod?
10,000
What wavelength region are most likely to be absorbed by rhodopsin?
507nm
True or False. A lower threshold = high sensitivity
True
What is the photochromatic interval?
Pt. dark adapts and where both PR’s regenerate
What is the Purkinje Shift?
Lighting conditions that change from scotopic to photopic
Note: 507nm to 555nm
In regards to Dark Adaption, how would light effect your ability to dark adapt?
Dim light: cause dark adaption faster
Bright light: cause dark adaption slower
In regards to Dark Adaption, How much time does it take a cone plateau duration?
10 minutes
In regards to wavelength, what color are humans sensitive to and that has a lower threshold, with a high sensitivity?
Violet
True or False. Ganglion cells are always spontaneously firing?
True
True or False. Amacrine cells are always firing?
False. Only when light has been stimulated, only then an action potential will be displayed.
What type of neuron displays action potentials?
Amarcine cells
Note: When light goes off, an action potential will get excited.
If a photoreceptor hyperpolarizes a horizontal cell synapsing on it will?
Hyperpolarize
During light adaption, when being outside on a sunny day, amount of light is increased by many thousands but the appearance ________ changes
Never
In regards to spatial summation, Under photopic conditions, what three visual contradictions manifest to maximize visual resolution at the expense of sensitivity?
Contrast, Visual Acuity and Visual Resolution
Note: Photopic system is poor under spatial summation but excellent under spatial resolution
What are the 2 types of GC cells?
M (parasol = Alpha) cells and P (midget = Beta) cells
What is the % of Parasol cells in the retina?
5% of all GC.
Note: They are transient, they will work quickly and die off quickly
What is the % of Midget cells in the retina?
90% of all GC
What is the time for scotopic temporal summation?
100 m/s
Note: within 100 m/s you will have 2 responses but higher than 100 will give you one
What GC does not require a PR but can receive light on their own?
Melonopsin Cells
What is the function of the super chiasm nucleus?
Rhythm maker to keep homeostasis.
What is the temporal summation in the photopic system?
10 m/s
In the photopic luminosity curve, how is the stimuli rated radiometrically and photometrically?
Radiometrically - equal
Photometrically - different
What is the basic unit of photometry?
lumen
Note: Luminous power is non-directional
What is the formula for lumens?
lumens = (luminous efficiency) (680 lumens/W)(W)
What does Abney’s law of additivity state?
Adding the values of each wavelength
What is luminance?
Light coming off a surface
Is there more convergence on a Alpha cell or Beta cell?
Alpha cell
What is illuminance?
Amount of light falling on a surface
What is the resting potential in front of the eye?
6 mV
What disease can an EOG find out?
Best’s disease
What is the arden ratio?
Ratio of light rise to the dark trough expressed as a %
What would be considered an abnormal Arden ratio?
165 to 180%
For an ERG, what does a Ganzfeld dome provide?
A sphere that illuminates the retina evenly
In regards to ERG components, which wave provides the largest ERG wave?
B wave - Mueller cells and On bipolar cells
When you see reduced Photopic and Scotopic ERG’s and reduced amplitude, what type of disease can be considered?
Retinitis Pigmentosa
If you a find a pt. with rod levels that are normal but the cones are lost but a little functional?
Cone Dystrophy
If you find a pt. with no scotopic system and photopic system is some what functional, what health issues do you think this individual has?
Complete CSNIB
A pt. is tested and you find the scotopic system is normal but there is no detectable flicker and NO functional photopic system, what issues does this pt. have?
Rod Monochromat
Which test would you conduct if you would like to find out how much progression has occurred in Glaucoma Progression?
mfERG
With VEP, what changes and stays the same, WAVELENGTH OR LATENCY?
W - does not change
L - changes
NOTE: VEP tests the brain stimulation
What is the positive peak for VEP?
P100
Note: there are 2 negative peaks, N75 and N135
CHAN ET. AL found what 2 distinct issues with the ERG test and VEP test?
ERG - Reduced
VEP - Reduced Amplitude but Increased Latency
Which region of the retina do Bipolar cells synapse to ganglion cells?
IPL
Which region of the retina do PR’s synapse to Horizontal cells?
OPL
True or False. PR’s create a action potential.
False. They create a GRADED POTENTIAL
What major chemical mechanism is used when recreating rods?
Recoverin
What is rhodopsin made of?
Hint: Think of two compounds
Opsin and chromophore
What is the name, when PR’s are connected to HC’s?
Sign-Conserving synapse
What occurs to PR’s, Glutemate and Bipolar cells, when dark conditions are present?
PR’s - Depolarize
Glutamate - Increase release
BC’s - Excited
What occurs to PR’s, Glutemate and Bipolar cells, when Light conditions are present?
PR’s - Hyperpolarize
Glutamate - Decrease release
BC’s - Inhibited
Do BC’s provide an action potential?
No
Do AC’s provide an action potential?
Yes
Do GC’s provide an action potential?
Yes
What protein does transducin activate?
Phosphodieserase
Do HC’s provide and action potential?
No
What type of cone bipolar cell has an increased spatial summation and decreased spatial resolution?
S cone
In light, what happens to Calcium channels?
Close
In Dark, what happens to Calcium channels?
Open
As an individual reaches the presbyopia stage, what usually occurs to the crystalline lens?
Lens becomes opaque and Cataracts form
What usually gives the retina its reddish color?
Choroid and RPE
Note: Retina is transient
True or False. Albino individuals, there choroid can be seen, via fundus photo.
True
You have a pt. whose OPL and INL are splitting, what health problem can this be?
Degenerative Retinoschisis
A pt. shows profound signs of a feathery like tuft and has 20/20 vision. What could be the white like issue?
Myelinated nerve fibers
Your pt. complains of a vision lost in certain areas of their visual field. You conduct your tests and diagnose a cherry red spot and you believe what major vasculature vessel is effected?
Central Retinal Artery
Most of UVC absorption occurs at what structure of the eye?
Cornea
Most of UVA and UVB absorption occurs at what structure of the eye?
Crystalline lens
In the absence of phagocytosis, what debilitating disease can occur to the visual system?
Retinitis Pigmentosa
Rods that shed their discs accumulate and thus overpowering the retina and killing off many rods
True or False. Rod Monochromats can get it anytime during their lifetime.
False. It is congenital.
What is perimetry?
Visual field test
What is static perimetry and Kinetic perimetry?
Static - pt. pushes button when a stimulus occurs
Kinetic - stimulus remains constant but the stimulus is moved around
When the plots for perimetry are connected, what type of diagnoses test is this called?
Isopter
In perimetry, what is the most commonly used unit?
Apostilb (asb)
Note: Visual field test gives you result of 10 will equal 1000asb. However, when 21 is given, which is poor number compared to 10, will give you an asb of 79.4
What is worst, UVA or UVB?
UVA - it penetrates the dermis and can cause melanoma
Note: UVB - can penetrate the epidermis and can cause wrinkles and possibly melanoma
What type of colored lens will help in the aid of protecting from UVB and UVA radiation?
Yellow - long pass filter, which blocks blue light
What diagnostic test will detect Best’s Disease?
EOG
What is the benefit of mfERG, compared to ERG?
mfERG - can do an entire scan of the retina, where as ERG must be specific
To find outer retinal diseases, what test can be preformed?
ERG
You have a pt. that is non-responsive and you would like to find their ability to contrast sensitivity and maybe even get their VA. What diagnotic test would you preform?
VEP - Use this test, when you get pts. who act like that you don’t exist!!!!
Note: It is crucial pt. look at a fixating chart
Damage to the choriocappilaris and Bruch’s membrane , can lead to what debalitating disease which occupies the fovea?
ARMD - Either wet (leaky blood) or dry (no vascular hemmoraging)
When a person lives in the Northwest or in Canada, they generally don’t get enough light. What disorder can occur and what is a new measure to correct this?
Disorder: SAD
Measure: Give them light
