1. Vision Lab Review eye anatomy especially:
Path of light through eyeball
Cellular layers of retina
Intrinsic eye muscles
Blind spot and fovea centralis

2. Vision Process can be Divided into Three Steps
Light enters eye, is focused by lens onto retina
Photoreceptors transduce light energy into electrical signal

3. 3.
Electrical signals sent along neural pathways are processed in visual cortex

4. Pupils are dilated in response to the contraction of the
Radial ciliary muscle
Circular ciliary muscle
Radial iris muscle
Circular iris muscle
Both C) and D) apply c

5. Light Modification Pre-Retina
Amount of light is changed by altering pupil aperture from 1.5 – 8 mm
Pupillary constriction due to ?
Dilation ?
Pupillary reflex is consensual
Autonomic reflex you get contralateral response.

6. Fig. 10.28 Postganglionic sympathetic axon From superior In dim light
cervical
ganglion
Radially arranged smooth
muscle fibers of the iris
Circularly arranged
smooth muscle fibers of
the iris
In normal light
Pupil
Ciliary
ganglion
From
oculomotor
nerve
In bright light
Postganglionic
parasympathetic
axon

7. The Lens … … focuses light by changing its shape
Refraction: Light waves are bent, or refracted when they pass from one medium into another, due to different densities.

8. Fig 10.34 Fig. 10.34 Ciliary muscle fibers relaxed Suspensory
Copyright © McGraw-Hill Education. Permission required for reproduction or display.
Fig
Ciliary muscle
fibers relaxed
Suspensory
ligament taut
Lens thin
and focused
for distant
vision
(a)
Ciliary muscle
fibers contracted
Suspensory
ligament
relaxed
Lens thick
and focused
for close
vision
Fig 10.34
(b)

9. Accommodation: Light is focused (to keep objects in focus) by changing lens shape
Lens attached to ciliary muscle via suspensory ligament (= zonulas)
Ciliary muscle contracts
Lens bulges up

10. Vision Problems
Accommodation
Ability of eye to focus differentially on objects of near vision (< 6 m or 20 feet)
Fig 10-31

11. More Vision Problems Astigmatism: asymmetry of cornea / lens
Presbyopia: loss of accommodation

12. Testing for Astigmatism

14. Determine Near-Point of Accomodation

15. Testing Visual Acuity
Snellen chart

16. Fig. 10.35 Emmetropia (normal vision) Rays focus on retina
Copyright © McGraw-Hill Education. Permission required for reproduction or display.
Emmetropia (normal vision)
Rays focus on retina
No correction necessary
Hyperopia (farsightedness)
Rays focus behind retina
Convex lens corrects
farsightedness
(a)
(c)
Myopia (nearsightedness)
Rays focus in front of retina
Concave lens corrects
nearsightedness
Astigmatism
Rays do not focus
Uneven lens corrects
astigmatism
(b)
(d)

17. Visual Field and Binocular Vision
3 vs. 2 dimensional view