Ch 3 - Vision Flashcards
The 3 layers of the eye
Outer layer = Fibrous
Middle layer = Vascular
Inner layer = Neural
Components of the outer layer of eye
Cornea & it’s epithelium
Conjuctiva
Sclera
Components of the middle layer of eye
Choroid
Iris
Components of the inner layer of eye
Retina
Blind Spot
Part of the retina
Anatomically called the optic disc which is the head of the optic nerve
It contains no receptors
Macula
The central point of the retina
Has the highest visual acuity
Fovea
Depression of macula where light is focused
Rods
- low thresholds
- sensitive to low-intensity light
- low visual acuity (sharpness/clarity/distinctness) due to arrangement of many rods synapsing w/ bipolar cells
- increased in periphery of retina
- function well in darkness (black & white vision)
Cones
- high threshold
- sensitive to high-intensity light
- high visual acuity due to arrangement of one cone to one bipolar cell
- increased in macula
- function well in daylight; color vision/photopic vision
These cells are the final retinal link of the visual pathway
Ganglionic cells
Outer Photoreceptors Segments
- contain rhodopsin which is a light-sensitive pigment
- rods contain stacks of free-floating double-membrane discs containing large amounts of rhodopsin
- cones contain cone-shaped in-foldings of surface membrane and have less rhodopsin
- the inner segment produces the photo pigment & the outer segment stores the photo pigment
Inner Photoreceptors Segments
- contain mitochondria & other organelles
- synthesized rhodopsin
- the inner segment produces the photo pigment & the outer segment stores the photo pigment
Do we SEE by excitation or inhibition?
Inhibition
Visual Pathway from Optic Nerve
Optic Nerve -> Optic chiasm -> Optic tract
Optic nerve is before the crossing, chasm is where it crosses, tract is after the crossing
Ipsilateral blindness
The lesion is on the same side as the blindness; occurs at the optic nerve
Bitemporal hemanopia
The lesion is at the level of the optic chiasm. You lose temporal eye fields (the lateral/peripheral views) leaving you w/ tunnel vision
Binasal hemanopia
You cannot see in the middle. You lose both nasal fields. Can only see in the periphery.
Contralateral hemanopia
The lesion is in the optic tract & it effects the same sides of both eyes. Ex: if you lose blindness in left half of your left eye, your losing blindness in the left half of your right eye
