Vision Flashcards
Scotopic vision
Monochromatic vision produced through the rods in low light.
Photopic vision
Chromatic vision produced through the rods in low light.
Dark current
Continous inflow of Na+ and Ca++ into rods and cones in dark through cGMP-regulated channels, causing hypopolarization and glutamate release.
Hemidecussation
Partial crossing of optic fibers in the chiasma opticum ensuring that information collected from the same part of the visual field by the two retinas is analyzed in the same hemisphere.
Optical illusion
Distortion of visual perception at the cortical level caused by previous experiences.
Sclera
The outermost, white layer of the eyeball.
Cornea
Frontal, transparent part of the sclera with the highest refracting power.
Conjuntiva
Very sensitive epithelial membrane covering the sclera and cornea lining the inside of the eyelids.
Iris
Circular, pigmented membrane behind the cornea, perforated by the pupil; its contraction regulates the amount of light passing into the eye.
Choroid
The middle, vascularised layer of the eyeball, including the iris and the ciliary body (ciliary muscles).
Fovea centralis
A depression in the center of the macula of the retina, the area of the most acute vision, where only cones are present.
Blind spot (optic disc)
The spot on the retina, where the axons of the ganglion cells and blood vessels penetrate the wall of the eyeball; no receptor cells are found here.
Musculus ciliaris
The lens is attached to the ciliary body (ciliary muscles) in the eye, it’s contraction is needed for accommodation.
Glaucoma
Eye disease caused by an excessive intraocular pressure
due to a disturbance in the production and reabsorption of the aqueous humor.
Cataract
Eye disease caused by an opacity of the lens.
Presbiopia
In elederly people the lens looses it’s flexibility, thus accommodation is no longer possible for short distancesM corrected by reading glasses.
Cis-retinal
Organic compound derived from vitamin A;
Transducin
G-protein in rods and cones, activated by the photopigment during light detection.
Rhodopsin
Photopigment of the rods.
Opsin
Protein part of the photopigment.
Horizontal cell
Inhibitory interneuron in the retina connecting receptor cells.
Amacrin cell
Interneuron in the retina establishing horizontal connections mostly close to the ganglion cells.
Melanopsin
Photopigment contained by the W ganglion cells.
M ganglion cell
Ganglion cell projecting to the magnocellular layer of the corpus geniculatum laterale.
P ganglion cell
Ganglion cell projecting to the parvocellular layer of the corpus geniculatum laterale.
Colour blindness
Disturbance of colour vision caused in most cases by a mutation in the gene coding
for the photopigments; the most common form is red/gren colour blindness.
