Full Review Flashcards
During gestation, when does the eye form?
Between 1st and 4th months of gestation
What forms during gestation weeks 3-4?
Eye fields
Optic vesicle
What forms during gestation weeks 5-6?
Optic cup
Lens vesicle
Choroid fissure
Hyaloid artery
What forms during gestation weeks 7-8?
Cornea
Anterior chamber
Lens
Retina
What forms during gestation weeks 8-10?
Eyelids
What forms during gestation weeks 9-15?
Iris
Ciliary body
The eye fields form from a population of what cells?
Cells from the anterior neural plate
In humans, when do the frontal eye fields begin to form?
Around 17 days
Where do the eyefields start to form?
In the prosencephalon
As the eyefields get pushed forward, what begins to occur?
Folding, bringing the eyefields together
After folding of the eyefields, what beings to form?
Optic groove
Eye fields are invaginating and forming a sulcus
How long does it take for the neural folds to meet at the top?
25 days
What structure forms the optic vesicle?
Optic groove
When the neuroectoderm and the surface ectoderm come in close contact (around day 25), what happens?
The optic groove begins to push itself out (evaginates), creating the optic vessicles
Neuroectoderm coming in contact with surface ectoderm induces what?
Lens placode
What does the lens come from?
Surface ectoderm
True or false: formation of the optic vesicle occurs at the same time as induction of the lens placode.
True
When the lens placode is induced, does it begin on the outside, or the inside?
Outside
How does the lens get inside the eye?
Lens placode and and optic vessicle invaginate
When the lens vesicle invaginates with the optic vesicle, what forms?
A bi-fold
When the optic vesicle invaginates, what is formed?
Optic cup
When the lens placode invaginates, what is formed?
Lens vesicle
As the optic vesicle and cup form, what is occurring to the optic stalk?
Also ingavinating
Where the optic stalk invaginates, what is created?
Choroid fissure
What grows within the choroid fissure?
Hyaloid artery
What feeds the lens vesicle during formation?
Hyaloid artery
What surrounds the back of the lens?
Hyaloid artery
What is the role of the posterior lens fiber?
Obliterate the lens cavity
When does the cornea differentiate?
After the differentiation of the lens and retina - around one month
What serve as the scaffolding for creating the iris?
Iridopupilary membranes
When do we first see something that actually resembles an eye?
After one month
When do the pupilary membranes usually go away?
After birth
What happens if the pupilary membranes persist after birth?
They may fix the pupil, and make it so it can’t change size
What keeps the lens nice and smooth?
Crystallines
During development, is the cornea clear or opaque?
Opaque
What cells form the outer corneal epithelium?
Surface ectoderm
What cells form the inner portions of the cornea?
Neural Crest Cells
All of the structures of the eye, with the exception of _____, come from the ectoderms.
Hyaloid artery
Inner layer of the cornea
During weeks 7-8, what is occuring in the retina?
There is a gap between RPE and neural retina. Neural retina begins to differentiate into the 10 total cell types
When the eyelid first is formed, is there a fissure?
Nope. It is just one structure
During what trimester do the eyelids un-fuse?
3rd trimester
From what tissues does the iris form?
Optic cup tissues
The folding of the “rim” of the optic cup forms what two structures?
Iris
Ciliary processes
What are the two principle pathways from progenitor cell to retinal cell?
Ganglion cell pathway
Cone/horizontal cell pathway
What cells can arise from the ganglion cell pathway?
Ganglion cells
Amacrine cells
Rods
Bipolar cells
What cells can arise from the cone pathway?
Cones Horiztonal cells Muller glial cells Rods Bipolar cells
Both the ganglion and cone cell pathways may differentiate into what?
Bipolar cells
Rods
Which retinal cell types migrate more than the others?
Bipolar cells
Rods
Which cells are “born” at about the same time?
Amacrine
Cone
Ganglion
Horizontal
Which cell type begins to form after the amacrine, cone, ganglion, and horizontal cells are formed?
Rods
What retinal cell type is born after rods?
Bipolar cells
What is the last retinal cell type born?
Muller glial cells
What is the order of retinal cell birth?
- Amacrine, cone, ganglion, horizontal
- Rods
- Bipolar cells
- Muller glial cells
Which cells continue to be born after birth?
Amacrine, rods, bipolar, Muller cells
Which cells are largely born before birth?
Cones
Ganglion cells
Horizontal cells
What does the retina start as?
A mass fo progenitor cells
Where to the progenitor cells reside?
In the ciliary regions
What creates the optic nerve?
Axons of the ganglion cells
Where do the ganglion cells migrate to?
Thalamus
What cells are responsible for forming the barrier of the outer nuclear layer/outer plexiform layer?
Horizontal cells
Which retinal cell layer is one of the first specified?
Ganglion cell layer
Which cells “give a ride” to many of the migrating retinal cells?
Radial glial cells
Which cells start having the first neurotransmitter vesicles forming?
Horizontal and amacrine cells
Cones make contact with which cells first?
Horizontal cells
What forms the second synapses?
Off BP cells to cones
After off BP cells synapse to cones, what other synapses begin?
Ribbon synapses (on BP to cones)
Where do glutamate receptors appear first?
Off BP cells
Which cells have the strongest on response?
Amacrine cells
As the vision system develops, there are many connections being made all over the place. What must occur before it functions properly?
Pruning
What are the first responses that occur in the developing eye?
Excitatory - occurs in the dark
Center-surround organization of receptive fields is apparent as soon as ___ are detected.
Light responses
Turtles are initially ___. (anisotropic; isotropic)
Anisotropic
Dark-rearing mice until about 3 weeks after birth leads to an increase in the fraction of what?
Bistratified, On-Off ganglion cells in the retina
If you suture a kitten’s left eye, what happens in the cortex?
The ocular dominance columns will shift, so that there aren’t any cells for the left eye, and they all go to the right.
What happens if you suture a cat’s left eye closed 12 weeks after birth?
The response of cells is even in each ocular dominance column, but the number of cells is reduced.
If you suture both eyes closed at birth, what happens to the cells in the cortex?
There is a normal distribution of cells; ocular dominance columns are in tact, but they don’t work correctly. Many don’t work at all.
If you suture an eye during the critical period, but open it before the critical period ends, what will happen?
They affected eye will not recover
After suturing an eye during the critical period, what is the only way to recover brain function?
Reverse suturing before the critical period ends
What happens if you raise monkeys in darkness (binocular occlusion) from 2 weeks old up to 3-6 months?
Deterioration of the visual cortex - they behave as if they are blind, and never fully recover
After 1 year, what effect will reverse suturing have on a monkey?
No effect
When do babies begin to see clearly?
4-6 months
When do babies begin the “hand to mouth” movement?
8-12 months
How much accommodation do babies have at birth?
None - poor ciliary muscle control
What is a baby’s VA at birth?
20/600
At what age are babies capable of focusing an image on the retina, but it is still blurry?
2-3 months
At 2-3 months, why is the image still blurry for a baby?
The photoreceptors are still getting organized. Some cells are still being “born”
What VA is “expected” around 3 months?
20/200
Once photoreceptors are born, they still need to mature. What needs to occur?
Their outer segments still need to elongate
Why is a “newborn” photoreceptor less effective than a mature one?
The outer segments are short, so there is less surface area to catch photons
According to Ricco’s law, is the threshold area larger or smaller as an adult than as a child?
Larger as an adult
Compared to adult levels, in the 1st month, a baby is __ times less sensitive to light.
50
Compared to adult levels, in the 3rd month, a baby is __ times less sensitive to light.
10
Why are babies more attracted to bright colors?
They are less sensitive to light, so the brighter the color, the easier they can see it
During the first week of life, what wavelengths are babies missing?
Shorter wavelengths (they already have long wavelength cones)
Which of the cones is last to develop?
Blue cones
What contrast difference is a 1 month old able to discriminate?
5%
What contrast difference is a 2 month old able to discriminate?
0.5-0.75%
When do babies eyes begin to fixate, coordinate movement, and have some smooth tracking?
3 months
What develops that allows a baby to track smoothly?
Myelination of the axons, allowing signals to travel faster
What is an important component of recognition for a baby?
High contrast
Ex. hairlines, edges of faces
By _ months, fixation occurs.
2 months
When do babies begin to mimic smiles?
2 months
What visual developments are occurring around ages 4-6 months?
Acuity
Color
Movement
Recognition
What is a baby’s VA at 4 months?
20/100
When do babies begin to see blue hues?
Around 4 months
When does real tracking and hand-eye coordination begin to occur?
4 months
At what age will a baby hesitate when presented with false depth cues? (baby checkerboard drop-off experiment)
4-6 months
At age 4-6 months, saccades and pursuits may occur at a rate of ___.
200-250 milliseconds
What is the difference between a baby’s saccades/pursuits and an adult’s?
There is a lag in initiation
When do babies begin to recognize strangers and faces?
6 months
What change is facilitating the development of saccades, facial recognition and the like?
Neuronal branching
What causes the brain to grow and branch?
Extrinsic factors - retina sending more info to the brain
At what age is the optic nerve myelinated?
4-5 months (but still not fully functional yet)
When do babies start associated and using different depth cues?
8-12 months
When does VA improve to 20/30?
8months-1 year
If a child is going to be an emmetrope, when will they see 20/20?
Abot 36 months
What aspects of vision development are fast?
Color
Visuomotor
What aspects of vision development are slow?
Acuity
Coordination
Does a baby have stereo at birth?
Nope
When does stereo begin to emerge?
3-4 months
When is adult level stereo reached?
6 months
Most visual systems have kicked in around 6 months, except for which 4 things?
Grating acuity
Color vision
Vernier acuity
Contrast sensitivity
What does grating acuity test?
Resolution acuity
What is another name for Vernier acuity?
Hyperacuity
What are the 3 ways to assess resolution acuity?
Visual evoked potential (VEP) Optokinetic Nystagmus (OKN) Preferential looking (PL)
What is the most rudimentary way of assessing resolution acuity?
OKN
What must occur in order to get a measurement with OKN?
Must be able to resolve the bars. If not, it just looks gray, and no fixation will occur.
Why is OKN the most rudimentary?
You don’t need any V1 processing to get a reading. It is controlled by the region that controls oculomotor response
If a stimulus is received using a VEP, where will a response be elicited?
Primary visual cortex
What does a VEP recording look like 7 days after birth?
Nearly a flat line
When do you start to see a VEP response in babies?
Around 1 month
At what age does a VEP response look adult-like?
About 6 months
When using the VEP method, when does a baby “see” 20/20?
6-8 months
At one month, what should the FPL visual acuity and the Snellen equivalent be?
1 cycle/degree
20/600
At three months, what should the FPL visual acuity and the Snellen equivalent be?
3 cycles/degree
20/200
At six months, what should the FPL visual acuity and the Snellen equivalent be?
6 cycles/degree
20/100
At twelve months, what should the FPL visual acuity and the Snellen equivalent be?
12 cycles/degree
20/50
At 3-5 years, what should the FPL visual acuity and the Snellen equivalent be?
30 cycles/degree
20/20
What is the best card for VA in infants? It is really expensive…
Teller Acuity Card
What are the three preferential looking cards that can be used for infants?
Teller Acuity
Cardiff Acuity
Lea Grating Paddles
What does the Cardiff Acuity test for?
Contrast
When does forced choice preferential looking reach adult levels?
5-6 years
What are the limiting factors for VA development in infants?
Foveal cone immaturity
Incomplete myelination of the optic pathway
Cortical immaturity
When does the “macular dip” begin to be seen?
At birth
How long after birth does it take for the cones to be fully developed?
About 45 months
What happens in the central retina at about 16 weeks post natal?
4-8 fold increase in cone density
Volume and density of synapses dramatically ___ after birth.
Increase
When do foveal cones reach adult length?
4 years
When does foveal cone density reach adult level?
45 months
How long does it take for complete myelination of the optic pathway to occur?
2 years
Why is Vernier acuity called hyperacuity?
It is 10 times better than grating acuity
Which is worse at birth, Vernier acuity or grating acuity?
Vernier acuity
At what age does Vernier acuity surpass grating acuity?
4 months
When does Vernier acuity reach adult levels?
6-8 years
Which ethnicity has the highest incidence of myopia?
Asian (18.5%)
What ethnicities have the lowest prevalence of myopia?
African Americans
Whites
What ethnicities have the highest prevalence of astigmatism?
Asians and hispanics
What are the risk factors for myopia progression?
Age Family Hx Amount of near work Gender (female>male) Race
When do ocularmotor functions reach adult levels?
3-6 months
When does accommodation reach adult levels?
3-4 months
When do convergence and fusion reach adult levels?
22 weeks
When does stereopsis reach adult levels?
6 months
Define amblyopia.
A condition in which the best corrected visual acuity is poorer than 20/20 in the absence of any obvious structural anomalies or ocular disease
Amblyopia is a Dx of ___.
Inclusion
What are the 3 amblyogenic factors?
Srabismus
Anisometropia
Image deprivation
What are the five aspects of visual function affected by amblyopia?
Reduced contrast sensitivity and visual resolution
Increased sensitivity to contour interaction effects (crowding)
Abnormal spatial distortions and uncertainty
Unsteady and inaccurate monocular fixation
Inaccurate accommodative response
What is isometropic amblyopia?
When both eyes have a similar, high refractive error
At how many diopters of cyl do you worry about anisometropia?
> 1.50
At how many diopters of cyl do you worry about isometropia?
> 2.50
At how many diopters of plus do you worry about anisometropia?
> 1.00
At how many dioptes of plus do you worry about isometropia?
> 5.00
At how many diopters of minus do you worry about anisometropia?
> 3.00
At how many diopters of minus do you worry about isometropia?
> 8.00
For amblyogenic strabismus to occur, what conditions must be met?
Constant strab
Unilateral strab
Onset before ate 8
What would be the expected VAs for a child that had their binocular congenital cataracts removed around 4-6 months of age?
20/50
With monocular form deprivation, where would you expect to see changes in the brain?
Cortex and LGN will both have morphological changes
What would be the expected VA for a child having had their monocular congenital cataract removed at about age 4-6 months?
20/400
When must a monocular congenital cataract be removed to still be able to recover VA up to 20/40?
2 months
What accounts for more than 90% of all amblyopia?
Strab
Aniso
Which type of amblyopia doesn’t show any contrast sensitivity loss?
Strabismis
Anisometropic amblyopes have contrast sensitivity loss at ___ spatial frequencies.
High
What three things may hyperopic isometropic amblyopia cause?
Accommodative esotropia Normal vision (if accommodates well) Bilateral refractive amblyopia if the child maintains binocularity by underaccommodating
What induced meridional amblyopia?
High astigmatism - usually bilateral
Why does WTR astigmatism cause less meridional amblyopia?
Pt. can squint to “fix” the blur
When is the peak of emmitropization?
Around age 6
When are the fastest changes occurring in the visual system?
Around age 2
What is the normal progression rate of myopia?
-0.50 per year
In strabismic amblyopia, where is VA loss the greatest?
At the fovea
Also shows nasal/temporal asymmetry
What is the definition of crowding?
The recognition of a given character is degraded by the presence of neighboring characters
What factors affect the degree of crowding?
Separation between the characters
Character size
Location in the visual field
What mainly causes the amblyopic reading deficit?
Increased crowding effect
Describe fixation for anisometropic amblyopes.
Central and unsteady
Describe fixation for strabismic amblyopes.
Eccentric and unsteady.
How can fixation be measured in strabismic amblyopia?
Maxwell spot/Hadinger’s brush
Visuoscopy
Accommodation is __ secondary to amblyopia.
Reduced
What accommodative issues arise in amplyopic persons?
Reduced accommodation
Inaccurate and unsteady accommodation
Affect ability to do sustained reading and fine visual tasks
At what age do vehicle accidents increase and why?
Age 75 - slower response time
A smaller pupil causes people to be less tolerable to what?
Glare
With age, the smaller pupil causes problems adapting to what?
Changing light conditions
Elapsed time for glare recovery increases starting at what age?
60
The yellowing of the lens with age causes problems seeing which colors?
Short wavelength - blue, green, violet
What things help people with yellowed lenses to perceive color more accurately?
Using full spectrum hallogen or fluorescent bulbs
Yellowing of the lens may also cause a decrease in what?
Depth perception cues - contrast recognition problems
Whit is one of the first apparent aging changes in the retina?
Overall thinning
What things cause retinal thinning with age?
Loss of neuronal cells
Shortening of the outer segments
What is usually the only real aging change in the fovea?
Change in the cones
Where are cones lost the quickest due to age? The slowest?
Quickest in the periphery
Slowest in the fovea
What are the two pigments found in RPE?
Melanin
Lipofuscin
What is the origin of lipofuscin?
Phagocytized PR outersegments
Which pigment increases the most with age: Lipofuscin or melanolipofuscin?
Melanolipofuscin (MLF)
Lipofuscin may be a causative agent for what?
AMD
Where does drusen form?
Between RPE and Bruch’s membrane
Which type of drusen is a normal biproduct of age?
Hard drusen
When does color vision really start to go downhill?
Ages 65-90 - have a 50/50 shot at failing a D15 test
Stereo begins to decline at what age?
About 60
What factors contribute to a loss of contrast sensitivity around age 65?
Senile myosis
Nuclear sclerosis
When does useful field of view drop off the most?
70-80
Why isn’t aging a disease?
It isn’t fully treatable
What is the most widely used aging strategy?
Replenishing
What are the 4 aging strategies?
Wishful thinking
Fixing
Replenishing
Strengthening
What are the four major age-related eye diseases?
Glaucoma
Cataracts
AMD
Diabetic retinopathy
What is the major problem that arises from diabetes?
Diseased blood vessels
What leads to a risk of developing diseases like diabetic retinopathy and glaucoma?
Blood vessels not function correctly, making it so that nutrients cannot reach the retina
What are the 3 stages of diabetic retinopathy?
Background diabetic retinopathy
Diabetic macular edema
Proliferative diabetic retinopathy
What occurs in diabetic retinopathy?
Blood vessels get blocked and cause small hemorrhages in the retina
New blood vessels are poor, and can lead to microaneurysms and leak
Which type of glaucoma can lead to rapid vision loss?
Acute glaucoma
What are the 4 types of glaucoma?
Chronic open-angle
Acute closed angle
Low-tension
Congenital
What is the most common cause of blindness in the United States?
AMD
Which form of AMD is less serious?
Dry - more common (90% of cases)
What occurs in wet AMD?
Neovascularization with blood leakage
Which AMD causes faster vision loss?
Wet AMD
Which gene is more associated with wet AMD?
CFH
Which gene is more associated with dry AMD?
HTRA1
People with both alleles had an increased chance of __% to get AMD by age 65.
47%
AMD generally affects whom?
Caucasian males ove age 50
Smokers
What treatments are there for dry AMD?
None
What treatments are there for wet AMD?
Anti-VDGF (avastin, lucentis..)
Implantable telescope
Laser photocoagulation
Visudyne therapy
What is the cause of cataracts?
Sclerosis of the lens
What things increase the risk of cataracts?
Any Smoking
Heavy Alcohol use
What is the cause of Fuch’s dystrophy?
Deterioration of endothelial cells, leading to poor water drainage
What does Fuch’s usually cause?
Swelling and shape change of the cornea
Why do patients with Fuch’s usually wake up with blurry vision?
When the eyes are closed, the water cannot evaporate
What might you do to treat early Fuch’s?
Salt-water eye drops to dry the eye
Blow hot air on cornea
Sof-bandage CL for corneal blisters
What is the treatment for severe Fuch’s?
Corneal transplant
What is the first thing patients will notice if their RPE is dying?
Glare
