Eye Physiology Flashcards
What is refraction?
The bending of light when it passes from one optical medium to another
What is accommodation?
When we can focus on far off or near objects by changing how much we bend the light rays
How does a sharp image form on the retina?
- Light waves from an object bend at the cornea
- They then bend some more at the lens to form a clear image on the retina
Which parts of the eye are the best benders of light?
- The cornea is the most powerful bender of light
- The lens has the capacity to change its bending power
What three things happen during accomodation?
- Lens changes shape (becomes thicker and more spherical)
- Pupil constricts
- Eyes converge
How does the lens thicken?
- Ciliary muscle contracts making the ciliary body bulge
- The space in the midle decreases
- Suspensory ligaments become lax
- Lens is no longer under stretch
- Lens becomes thicker
What is the nerve innervation to the ciliary body?
Parasympathetic
How does pupilliary constriction occur?
- The sphincter pupillae is a concentric muscle around the border of the pupil which constricts the pupil
- It gets parasympathetic innervation
What is convergence?
When an object is up close in order to focus, our eyes have to turn in to look at the object
Which muscles are used to converge the eyes?
Medial rectus (CrN III) on both sides
What is phototransduction?
The conversion of light energy to an electrochemical response by the photoreceptors (rods and cons)
Name the visual pigments found in rods and cones
- Rhodopsin (found in rods)
- Opsins S, M and L (found in cones)
What role does vitamin A play in the visual pigment?
Visual pigment regeneration
Describe the visual pathway
- All fibres from the eye pass through the optic nerve to the optic chiasma
- At the optic chiasma the medial/nasal fibres cross to the opposite side
- Fibres from the optic tract synapse at the LGB of the thalamus
- From here the optic radiation passes from behind the internal capsule to reach the primary visual cortex in the occipital lobe
