Physiology of Vision Flashcards
Fibrous outer layer
Sclera and Cornea
Vascular middle layer
Iris, ciliary body, choroid
Neural inner layer
Retina
Aqueous humor is needed because…
It gives nutrients to the lens and cornea
It creates refractive power to the eye
What is the image formation based on?
The combined refractive power of the cornea, aqueous humor, lens and vitreous body
What is the main function of the lens?
To provide a refractive power that can be adjusted
Convex or concave lens?
Convex lens
Distant vision, ciliary muscle…
Relaxes
The accommodation reflex definition
A reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in vergence, lens shape and pupil size (accommodation).
The Accommodation Reflex pathway
Information from the light on each retina is taken to the occipital lobe via the optic nerve and optic radiation (after a synapse in the lateral geniculate body of the posterior thalamus), where it is interpreted as vision. The peristriate area 19 interprets accommodation, and sends signals via the Edinger-Westphal nucleus and the 3rd cranial nerve to the ciliary muscle, the medial rectus muscle and (via parasympathetic fibres) the sphincter pupillae muscle
Power of the eye
1/focal length
Layers of Retina
- Pigmented epithelium
- Photoreceptor layer
- Outer nuclear layer - cell bodies of rods & cones
- Outer plexiform layer - axons of rods & cones
- Inner nuclear layer - cell bodies of horizontal and bipolar cells
- Inner plexiform layer - axons, bipolar, amacrine, ganglion cells dendrites
- Ganglion cell layer - cell bodies
- Optic nerve layer - long axons of ganglion cells = optic nerve
Müller cells function
- Long glial cells
- Stretch almost the entire length of the retina
- Function to maintain extracellular environment
- Regulating K+
- Remobe debris
- Uptake of neurotransmitters
Properties of Rods
Function to detect light. More amount of rhodopsin than cones makes them more sensitive to light. They have vision in darkness, but low acuity = how clear you can see the image, because many rods synapse on each bipolar cell
Properties of Cones
Participates in color vision. Primarily located in the macula. Have high acuity due to one to one synapse with bipolar cells, especially in the fovea of the macula. Cones for red, blue and green colors.
