Eye Stuff (56b - 65b) Flashcards
Includes eye pathologies
Between which two layers of the eye is the retinal pigment epithelium located?
Between photoreceptos and the choroid
What are some of the common causes of cataract?
- Lens fibers lose transparency
- Usually age related
- May be caused by steroids
- Results in posterior subcapsular cataract
What are the symptoms of cataract?
- Improved near vision
- Worse:
- Glare
- Far vision
- Night vision
- Changes in color
Describe the symptoms/signs of retinal vein occlusion
- Sudden, painless, visual field defect + loss of vision
- Will see hemorrhages (not blanching) on eye exam
What are the consequences of damage to burst neurons?
Cannot generate saccadic eye movements
Visual acuity of _____ or worse is classified as legal blindness
Best corrected visual acuity of 20/200 or worse is classified as legal blindness
- Someone with 20/200 vision that can be corrected (with glasses) is not legally blind (in terms of disability elligibility)
How would you inhibit accomodation to get an accurate measurement of a patient’s refractive power?
Cycloplegic refraction - stops the ciliary muscle from contracting and accomodating
Important especially in younger patients who are really good at accomodating (suspect especially if pupils are always constricted and/or they look a bit cross-eyed; due to synkinetic reflex during accomodation)
A patient’s fundus exam looks like this
What lifesytle interventions would you suggest?
These are drusen, indicative of age-related macular degeneration
- Stop smoking
- Take vitamins! AREDS 1 or AREDS 2
- Eat green leafy vegetables
Note: Anti-VEGF treatment begins when AMD has progresssed to exudative stage
When retinal ganglion cells are damaged, will rod vision, cone vision, or both be affected?
Both!
- The rod and cone pathways converge on the RGCs
- The rod pathway “piggybacks” onto the cone pathway
(RGCs may be damaged in glaucoma or neurodegenerative disease)
What is “disparity” as it applies to vision?
Slightly different views seen by the right eye and the left eye
- The brain uses these differences to make calculations about depth - this is stereopsis
What two features of primate vision does the midget system support?
High accuity
Red/green color opponency
Until what age is eye patching useful to treat amblyopia?
9-10 years old
Scotomas that are “homonymous but noncongruent” indicates what kind of damage to the lateral geniculate nucleus?
Damage to some but not all layers
Which area of the brain is involved in visual memory, learning, and recognition?
Temporal lobe
Vs. parietal lobe, which is responsible for attention/awareness of objects in the visual field
A patient presents with ptosis and diplopia that is worse in the evening, and not always present.
They note that sometimes they have trouble getting words out, and they are choking on food more often when eating.
When you apply ice to the patient’s face the ptosis improves
What is your leading diagnosis? How would you confirm?
Myasthenia gravis
Confirm using tensilon test
What is the differential for leukocoria in an infant?
- Cataract
- Coloboma
- Retinoblastoma
- Most concerning
What test is used to see if a patinet’s eyes are in alignment?
Light reflex
How would damage to the 6th nerve nucleus present?
Bilateral loss of abduction
wouldn’t be able to communicate through the medial fasciculus longitudinus to the other eye’s CN 3 nucleus to move the other eye, so both eyes don’t move
What changes to the retina occur with diabetic retinopathy?
How will this affect vision?
- Loss of pericytes and endothelial cells
- Basement membrane thickening
- Decompensated endothelial function
- Leakage and microvascular occlusion
- -> Retinal hypoxia
- -> Expresssion of molecules
- -> Breakdown of retina/blood barrier
- Can lead to neovascularizaiton (in proliferative DR)
If a rod cell catches some light, does it become hyperpolarized or depolarized?
How does this fit into the visual pathway?
If a rod cell catches some light, it becomes hyperpolarized
- Rod cells are very sensitive to single photons, even in really dim light
- This means they can help support the cone pathway / allow us to deduce what is going on when there isn’t a lot of light
- The hyperpolarized rod cell is turned OFF
- Allows amacrine (A2) cells to send activating signal to ON bipolar cells
- “Helloooo we see some light!”
- Signal that there is some light to RGCs
- Allows us to make some sense of what is going on
- But no color vision and decreased acutiy because the cone cells aren’t signaling as much/providing as much invo to ON bioplar cells
Although somehow cones are insensitive to light? If the above is WAY off base please lmk so I can attempt to pass this exam :o
A patient presents with flashes and floaters
What are the most likely causes?
How do you differentiate?
Retinal dettachment
Posterior vitreous detachment vs. Retinal detachment
- Retinal detachment will be accompanied by a curtain/veil loss in vision
- This is an emergency! Call the ophthamologist!
- PVD is less serious and typically doesn’t present with vision loss
- Normal as we age
What systemic conditions are associated with retinal artery occlusion?
- Hypertension
- Diabetes
- Hypercholosterolemia
These, plus hypercoagulable state are the conditions also associated with retinal vein occlusion
How might a posterior communicating aneurysm present?
3rd nerve palsy - eye dilated, will be in the “down and out” position
MUST evaluate for Pcomm aneurysm to prevent subarachnoid hemorrhage
In myopia:
- Light is focused [anteroir/posterior] to the retina
- The eye is [over/under] powered
- May be because the eye is too [long/short] or the cornea is too [steep/flat]
- Correct with a [converging/diverging] lens
In myopia:
- Light is focused anterior to the retina
- The eye is over powered
- May be because the eye is too long or the cornea is too steep
- Correct with a diverging lens
What defines wet/exudative age-related macular degeneration?
Neovascularization
- Irregularities caused by drusen promote angiogenesis
- Leads to bleeding (toxic to the retina) and fibrosis
- Wet AMD = end-stage
Picture = drusen
Flattening the cornea would fix [myopia/hyperopia]
Steepening the corena would fix [myopia/hyperopia]
Flattening the cornea would fix myopia
Steepening the corena would fix hyperopia
What is Adie’s pupil?
How does it present?
Acute, idiopathic, postganglionic ciliary nerve dysfunction
-> pupil cannot constrict
What is the definition of glaucoma?
Visual field defects due to optic nerve damage
Typically associated with high intraocular pressure
Postganglionic neurons that control pupillary dilation are located in the [location]
Postganglionic neurons that control pupillary dilation are located in the superior cervical ganglion
- Arousal
- -> IML: Sends preganglionic sympathetics
- -> Superior cervical ganglion: sends postganglionic sympathetics
- -> Pupil dilator
The choroidal circulation is under [autonomic/metabolic] control
The retinal circulation is under [autonomic/metabolic] control
The choroidal circulation is under autonomic control
The retinal circulation is under metabolic control
What prevents vascular growth in the retina?
Soluble VEGF receptors
- Bind VEGF and prevent it from initiating angiogenesis
- Basically, these receptors sequester VEGF o prevent it from having any effect
A right “pie in the sky” visual field defect results from damage to what structure?
Left Meyer’s loop (temporal) lesion
List the steps in the phototransduction cascade
(Staring with light hitting a rod cell)
*Remember, there is amplification at each step*
- Photon absorption converts 11-cis-retinal to all-trans retinal
- Rhodopsin is activated
- Activates transducin via GPCR
- PDE synthesized
- Converts cGMP to 5’-GMP
- Decreased cGMP -> closing of Na+ channel
- Cell hyperpolarization
- Rod cell is turned off
- Allows amacrine cells to activate ON bipolar cells, which signal to RGCs
- Basically, this pathway is more sensitive in low light. It helps signal to RGCs so we put an image together, even when we’re not getting a lot from the cone pathway
Preganglionic neurons that control pupillary dilation are located in the [location]
Preganglionic neurons that control pupillary dilation are located in the interomediolateral cell column (IML)
- Arousal
- -> IML: Sends preganglionic sympathetics
- -> Superior cervical ganglion: sends postganglionic sympathetics
- -> Pupil dilator
What is the limiting factor in our visual acuity?
Cone spacing in the fovea