ANP 1106 Lecture Notes - Lecture 31: Rhodopsin, Emmetropia, Opsin
29 Apr 2018
School
Department
Course
Professor
ANP1106 – Vision Problems
Vision Problems
- Emmetropia
o Normal vision, 20/20
- Myopia
o Good near vision (nearsighted) but poor far vision, image forms in
front of retina
o Due to eye being 4mm too deep
o Correction requires concave lenses
- Hyperopia
o Poor near vision (farsighted), image forms behind retina
o Due to eye being 4mm too shallow
o Correction requires convex lenses
- Astigmatism
o Due to unequal curvatures of lens/cornea
o Correction is both concave & convex lenses
- Presbyopia
o Accommodation is decreased due to loss of lens elasticity
o Occurs during ages 10-50
- Cataracts
o This is an opacity of the lens which clouds and blocks vision
Vision Photoreceptors, Cones
- Photoreceptors found in retina detect light
- Photoreceptors made of:
o Outer segment – light receiving area, contains visual pigment
molecules in discs
o Inner segment – metabolic area
o *Connected by stalk
- Visible spectrum detected by blue (420), green (530), red (560) cones which
reach max sensitivity at different wavelengths
- Red-Green Perception Test
o Most common color blindness is the difficulty in distinguishing red
and green due to defective X chromosome (called achromatopsia)
Vision Rhodopsin Cycle
- Visual pigment is made of 2 molecules
o 1) Retinal
▪ Photosensitive – binds to opsin in dark, dissolves from it in
light
o 2) Opsin
▪ Scotopsin – rods
▪ Photopsins – cones to detect colors red, blue, green
- Steps
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Myopia: good near vision (nearsighted) but poor far vision, image forms in front of retina, due to eye being 4mm too deep, correction requires concave lenses. Hyperopia: poor near vision (farsighted), image forms behind retina, due to eye being 4mm too shallow, correction requires convex lenses. Astigmatism: due to unequal curvatures of lens/cornea, correction is both concave & convex lenses. Presbyopia: accommodation is decreased due to loss of lens elasticity, occurs during ages 10-50. Cataracts: this is an opacity of the lens which clouds and blocks vision. Photoreceptors made of: outer segment light receiving area, contains visual pigment, inner segment metabolic area, *connected by stalk molecules in discs. Visible spectrum detected by blue (420), green (530), red (560) cones which reach max sensitivity at different wavelengths. Red-green perception test: most common color blindness is the difficulty in distinguishing red and green due to defective x chromosome (called achromatopsia)
