This document provides an overview of an online human eye lab covering the senses, receptors, structures of the eye like the retina, cornea, iris, lens, and blind spot. It describes exercises using an eye model to demonstrate how the eye focuses light and the effects of different lens shapes and eye lengths on vision. Learners use the model to find their own blind spot and correct near-sightedness by trying different corrective lenses. The document includes images and videos to enhance understanding of eye anatomy and function.

1. Human Eye Lab
BIOL 1408
Online Lab
Summer I 2018

2. Senses
● Our senses are critical to survival
○ Recognise food or danger
● Every sense requires specific receptors

3. Receptors
● Receptors are sensitive to a specific stimulus
○ 1 type of receptor can only sense one type of stimulus
○ E.g. Vision receptors are sensitive to light
○ E.g. Skin cannot see or taste
○ E.g. Taste buds cannot hear
● Receptors send signals (messages) to the brain.

4. The Eyes: Exercise 1
VIDEO LINK: How the Eye Works
● Light receptors in the eye form a layer
known as the Retina.
● The retina sends signals to the brain
(through the Optic Nerve), and then the
brain must interpret the signals

5. The Eyes
● Unfortunately, the area where the optic nerve merges with the retina creates a
blind spot.
○ We cannot see light that hits the optic nerve, therefore it is known as the
blind spot
● Find your blind spot! VIDEO: Online Eye Test

6. Another fun trick for your senses...
● Roll up a sheet of paper (pretend it’s a pirate’s spyglass) and hold it up to
your left eye.
● Hold your right hand in front of your right eye.
● With both eyes open, look into the distance and the side of your right hand
touching the paper roll, slowly move your right hand toward the end of the
paper roll.
Make a hole in your
hand!

7. Eye Models: Exercise 2
We will use an eye box model to demonstrate and observe the structures and
funtions of the vertebrate eye.

8. Cornea
Position of Iris
behind the
Cornea
Lens
Eye Ball

9. Front glass represents the Cornea
Opening is the pupil,
surrounded by the iris. The
iris is the pigmented part of
the eye.
Metal container represents
the Eye Ball.
Front view

10. Top View
Pupil and Iris Lens
Retina
Anterior
Chamber
(filled with
water)
Posterior
Chamber
(filled with
water)

11. Retina
(arrow on
Fovea)
Retina (arrow
on Blind Spot)
Yellow arrow
shows path of light

12. Compare the Eye box model to an Anatomic eye model.

13. Iris and Pupil
● Constricts to limit light entering eye.
● Dilates to allow more light into eye.

14. Lenses

15. Lens Shapes - Focus Light
A higher number indicates more curvature.

16. Lens Shapes - Focus Light

17. Turn on the light box and test out different lenses.
● Eye model has been set up
with the retina in the normal
position, the normal sized
pupil, and the light box a
standard 33 cm from the
cornea.
● Determine which lens
produces the clearest image
on the fovea of the retina..
● The following images show the
results from various lenses.
● Record your results in Table 1.

18. Diopter numbers
(+) indicates a Convergent lens
(-) indicates a divergent lens

20. ● Now that you have determined the
correct lens to give the clearest image,
look at the front of the eye model.
● Notice the image visible on the cornea.

21. ● Now look at the image on the
retina.
● Look at the location of the arrow
and the dot.
● Compare the image visible on the
retina to the image you saw on
the cornea.
● How are the images different?
What causes this difference?

22. Exercise 3
● Eye box model with retina in normal
position, normal pupil size, and light
box a standard 33 cm from cornea.
● Anterior and Posterior chambers full
of water

23. ● 2-3 cups of water
removed
● Remember water
represents the liquid or
humors of the eye.

24. ● 2-3 cups of water removed
● What happens to the image?

25. The Importance of the Lens
● Water has been replaced but the lens
was removed.
● What happened to the image?

26. Eyeball shape
● Eye model showing normal
position of the retina.
● Not too long.
● Not to short.

27. ● Eye model showing normal
position of the retina too far
back.
● Eye is too long.

28. Can the patient focus better when the light is near or far?

29. Light Source at 70 cm

30. Time to play Doctor (Optometrist)!
● Let’s fix the patient’s Nearsightedness
with corrective lenses.
● We will leave the internal structures of
the eye alone and try different
corrective lenses on the outside of the
eye.
● Find the lens that gives our patient the
clearest image.
● Record results in Table 2.

33. ● Eye model showing normal
position of the retina too far
forward..
● Eye is too short.

34. Note: The image on the retina is larger, but
is it in focus?

37. Pupil Size
Normal Pupil

40. Limitations of the Eye Model

41. Using the eye model to
demonstrate the blind spot