Test 2: Visual CC Flashcards
**Presbyopia **
- Lens elasticity decreases with age= accomodation decreases= flatter lens.
- Near point recedes= people hold what they’re reading further and further away.
- One of the beauties of aging.
Glaucoma- Know what causes it, what glaucoma does to vision, and the symptoms
- Blocked outflow of fluid through canal of Schlemm. Pressure on the entire eyeball= damage to retina and optic nerve.
- Vision is BLURRED but not dimmed. Normal light gets to the retina but they have fewer photoreceptors= blurriness
- Peripheral vision is lost first and proceeds towards middle
Open angle glaucoma
- = angle between iris and cornea is normal and cause is unknown.
- accounts for 95% of cases.
Closed angle glaucoma
angle between iris and cornea is smaller and causes the blocked outflow
This amount of pressure will cause optic nerve damage
>20mm Hg
Pupillary light reflex
Light shined in one eye causes constriction of both pupils
**cataracts- know what it is and some possible causes. treatment? **
Proteins are constantly growing and being turned over in the lens. If the proteins aren’t turned over then the lens thickens and gets cloudy and opaque.
Causes: rubella (congenital), UV light, diabetes, radiation therapy, some drugs
Treatment: replace the lens
Uveitis
Inflammation of uvea (iris, ciliary body and choroid)= VASCULAR part of eye
Usually from eye injury
Retinal detachment
- What is it and how is treated
- chances of recovery
- boys vs girls
- things that can cause it?
- Neural retina tears away from pigment epithelium. Must be repaired surgically to avoid damage because neural retina will die without the blood supply (considered a medical emergency)
- RECOVERY IS DEPENDENT ON TIME (how quickly surgery is done) AND LOCATION (of detachemnt)
- males>females
- can be from trauma, surgery, genetics, etc.
Patient: recent trauma to the head, seeing flashes of light and specks floating.
DDx?
Detached retina from trauma. Fluid pulled apart the neural and pigmented epithelium. Must be treated ASAP.
- Is color blindness a real thing?
- Why is it more common in males?
- *Technically NO. *Loss of a cone color is “better thought of as color confusion”. The ability to **distinguish **colors is impaired.
- M-cone (absorbs green) and L-cone (red) are on the x-chromosome.
- Inability to detect RED
- Inability to detect **GREEN. **
- No red= PROTANOPIA
- No green=** DEUTERANOPIA**
**DEUTER= **two, green is the combination of two colors
PRO= professional, also “slang for prostitute”. I wasn’t allowed to wear red as a kid because it was too “prostitute like”.
What can blind people (striate cortical lesions) still detect? How?
Can have a puillary light refelx in the blind eye. **Normal circadian rhythm. **
Melanopsin-containing ganglion cells-Intrinsic light sensitivity- they will respond to light (even if rods and cones don’t) and send that info to the hypothalamus. They are also connected to the suprachiasmitic and pretectal nuclei.
Pathway of “blind sight”
Retina–> superior colliculus –> pulvinar –> posterior parietal cortex = tracking and orientation
Random shape floaty thing in your visual field.
What is it called? What causes it?
- Scotoma
- lesion of the retina or optic nerve.
- Causes: toxins, retinal hemorrhage, trauma, tumors.
Damage to right optic nerve. Which eyes have direct and consensual pupillary light reflexes?
Right eye (nerve damaged)= consensual light reflex
Left eye (normal)= direct light reflex (pretty sure it loses consensual because Rt eye cant process stuff?)
Hemifields
nasal and temporal
Monocular zone
crescent zone seen by only one eye
Papilledema
- **What is it? **
- **Sx? **
- **What is it usually a good sign for? **
- Block of axoplasmic flow (often from high ICP) causes swelling of the optic nerve head (= papilledema).
- Can cause partial/complete visual loss.
- increased ICP (intracranial pressure)
You’re playing catch with someone who sucks. They say they don’t see the ball moving
Akinetopsia= can’t see movement
Lesion to dorsal stream V5- involved in speed, motion and direction.
What’s involved in positioning of objects?
Parietal and occipital gyri.
Scotoma
- Randomly shaped region (bilateral or unilateral) of vision loss or reduction.
- It can be any shape
- LESION TO RETINA OR OPTIC NERVE from toxins, trauma hemorrhage
- Light in damaged eye: no consensual response in good eye, no direct response in bad eye
- light in good eye- normal response in both eyes
Congruous deficit
Visual field loss of one eye is the same as the other eye. More common when lesions are closer to visual cortex
Incongruous Lesion
More common in anterior lesions. Two eye visual fields are not the same.
Line of Gennarie
Myelinated fibers in layer 4b of Area 17= geniculocalacrine input
Macular sparing
Caudal visual cortex also supplied by MCA collaterals, so occlusion of calacrine from PCA won’t wipe it out
What can cause loss of **binocular vision? **
- LGN axons compete for parts area Area 17 during critical period of development. If visual input is weakened from one eye (congenital cataracts, strabismus or ambylopia) LGN from one eye fails
- Most of layer IV stellate cells get input from ONE eye only= loss of stereopsis (3Dness)
Achromotopsia
- Loss of color recognition without loss of object recognition due to **localized damage to certain part of association cortex. **
- NOT THE SAME AS COLOR BLINDNESS
Difficulty/inability to judge which object is closer.
Damage to magnocellular pathway especially in parietal association cortex. “where stream”