Vision Flashcards
normal vision
Emmetropia
Does not refract the rays enough for close vision (lens is not round enough or eyeball is too short)
hyperopia
Refracts the rays too much for far vision (lens is too round or eyeball too long
myopia
Change in the concentrations of rhodopsin and other photochemicals (higher concentrations make eyes more sensitive); takes minutes to hours for a many thousand fold difference.
Bleeching
What are the four types of light-dark adaptations?
Bleaching
Change in pupil size
Switchover
Neural adaptation
True or False? When the ciliary muscle is relaxed, the lens is in an oval shape ideal for far vision
True
True or False? When the ciliary muscle is contracted, it forces the lens into a round shape which has more refractory power and is better for close vision.
True
The ______ retina is for black and white vision. It is more sensitive and better for night vision
peripheral
The _____ is for color vision. It has better clarity and is better for daytime vision. It has more cones, more tightly packed, a better cone to ganglia cell ratio, and less light obstruction
macula or central portion
The Macula has better acuity than the peripheral retina because it has:
Less convergence Higher receptor density Greater percentage of cones Thinner cones Lateral inhibition
Horizontal, bipolar and amacrine cells are important for maintaining visual contrast by the means of ______. They enhance borders by inhibiting the area around the point of excitation
lateral inhibition
Light decomposes Rhodopsin leading to less ______ and _____
Na+ influx; hyperpolarization
True or False? Lateral geniculate segregates input from 2 visual fields, and sends information to layer IV of the cortex which sends it to other layers where it truly converges onto single cells
True
The iris sphincter muscle contracts in response to more light and thus constricts the pupil to decrease the amount of light entering eye.
Miosis
The iris radial muscle contracts in response to less light and thus dilates the pupil to increase the amount of light entering the eye
Mydriasis
