The human eye has three layers: the outer layer includes the cornea and sclera, the middle layer contains the iris, choroid, and ciliary body, and the inner layer hosts the retina, rods, cones, and fovea. Light enters through the cornea and pupil, and the lens focuses it onto the retina where photoreceptors convert it into nerve signals sent to the brain via the optic nerve. The ability of the lens to change shape allows for accommodation and clear vision at both near and far distances.

1. SENSE ORGAN
LIFE SCIENCES
UNIT 1
THE HUMAN EYE

2. PHOTORECEPTORS
Humans have a stereoscopic vision
(Dharmedra, 2018)
The eye is situated in the orbital cavity
and supplied by the optic nerve.
It is spherical in shape and can view an
object from a different angle.
Figure 1

3. STRUCTURE OF THE EYE
• The main parts of the eye are found n 3 layers:
• 1. Outer layers = cornea and sclera
• 2. Middle layer = iris, choroid and ciliary body
• 3. Inner layer = rods-cones, retina and fovea

4. Figure 2

5. OTHER IMPORTANT PARTS
Lens = attach to the suspensory ligaments
Humors = aqueous humor and vitreous humor – transmit
light rays and support the eyeball
Optic nerve = transmits impulses to the brain
NB: The human eye reacts to light and pressure
(Khinza,2018)

6. OUTER LAYER,
STRUCTURE AND
FUNCTION
The sclera: white outer
layer, protects and
supports eyeball
Cornea: front
transparent part of the
eye, refracts light rays
Conjunctiva: front
transparent membrane,
provides moisture for
the surface

7. MIDDLE LAYER,
STRUCTURE AND
FUNCTIONS
Pupil: black hoe in the
middle of the eye,
admits light into the eye
Choroid: 2nd pigmented
layer, absorbs stray light
and contains blood
vessels for nutrients
and oxygen
Iris: colored part,
regulates the size of the
pupil and regulate light
entrance
Lens: transparent
biconvex, refract and
focuses light on the
retina

8. NNER LAYER,
STRUCTURE AND
FUNCTION
Retina: contains
photoreceptors,
cones and rods
Rods: make
black and white
vision possible
Cones: make
color vision
possible
Fovea: best
image possible

9. FIGURE 3
•Blind sport: nerevs
and vessels leave the
eyeball, if light was
to be directed to this
area no image can
be visible
(Bishnoi,2014)

10. THE TWO CAVITIES ARE SEPARATED BY THE
LENS AND CILIARY BODY
Aqueous humor: watery substance filling the anterior cavity
Vitreous humor: jelly like substance filling the posterior cavity
Ciliary body: produces the aqueous humor

12. SUMMARY ON
HOW THE EYE
WORKS
•Light rays coming from
an object enter the eye
through the cornea,
proceed through the pupil
then to the eye lens
which converts light rays
and produce an image.

13. ACCOMODATION
•The ability of the lens to
change shape to allow
the eye to focus on far
and near objects

14. NEAR VISION AND DISTANCE VISION
NEAR DISTANCE
Ciliary muscles contract Ciliary muscles relax
Suspensory ligaments relax suspensory ligaments pull tight
Lens become more convex lens becomes less convex

15. ASTIGMATISM
A visual disorder that is
caused by an uneven
cornea or lens
It can be corrected by
wearing lens that is
unevenly corrected to help
the uneven cornea

16. REFERENCES
AWAN, M., 2013. SLIDESHARE. [ONLINE]
AVAILABLE AT:
HTTPS://WWW.SLIDESHARE.NET/MARIAHAWAN/STRUCTURE-AND-
FUNCTION-OF-EYE
[ACCESSED 22 08 2021].
AVAILABLE AT: HTTPS://WWW.SLIDESHARE.NET/ASHOKBISHNOI1/EYE-
ANATOMY-AKKI
[ACCESSED 22 08 2021].
IRSHAD, K., 2018. SLIDESHARE. [ONLINE]
AVAILABLE AT:
HTTPS://WWW.SLIDESHARE.NET/KINZAKHAN32/STRUCTURE-AND-
FUNCTION-OF-THE-EYE?FROM_ACTION=SAVE
[ACCESSED 22 08 2021].
P, D., 2018. SLIDESHARE. [ONLINE]
AVAILABLE AT:
HTTPS://WWW.SLIDESHARE.NET/PATELDHARMENDRA4/THE-HUMAN-EYE-
AMATOMY
[ACCESSED 21 08 2021].

17. LINKS
FIGURE 1.
HTTPS://WWW.GOOGLE.COM/URL?SA=I&URL=HTTPS%3A%2F%2FWWW.VECTEEZY.COM%2FVECTOR-
ART%2F1783903-DIAGRAM-OF-HUMAN-EYE-ANATOMY-WITH-LABEL&PSIG=AOVVAW33EC_YE6QPKPH-
DM0P7KDG&UST=1629662183988000&SOURCE=IMAGES&CD=VFE&VED=0CASQJRXQFWOTCNDHTPXYWVI
CFQAAAAADAAAAABAI
FIGURE 2.
HTTP://WWW.GOOGLE.COM/URL?SA=I&RCT=J&Q=&ESRC=S&FRM=1&SOURCE=IMAGES&CD=&CAD=RJA&
DOCID=PVGXFFLO6PUW3M&TBNID=ZQKOYYXVWXCYAM:&VED=0CAUQJRW&URL=HTTP://WWW.APPSYCH
OLOGY.COM/BOOK/BIOLOGICAL/VISION.HTM&EI=9WZHUSA9EC7I4AOG-
IGABG&PSIG=AFQJCNHPLS8LEUNZOSQOO2HGU9L5GAPWDQ&UST=1382176846628571
FIGURE 3.
HTTPS://WWW.GOOGLE.COM/URL?SA=I&URL=HTTPS%3A%2F%2FMAMMOTHMEMORY.NET%2FBIOLOGY%
2FORGANS-AND-SYSTEMS%2FTHE-EYE%2FBLIND-
SPOT.HTML&PSIG=AOVVAW38XHR0SAD01S5OPTWTTWYT&UST=1629750194124000&SOURCE=IMAGES&C
D=VFE&VED=0CAWQJHXQFWOTCOCQ_OC6XFICFQAAAAADAAAAABAD
SLIDE SHARE
DHTTPS://DRIVE.GOOGLE.COM/DRIVE/FOLDERS/1SMKICW0OIH3XVJ2DPIT9JV36UB1FPPKT?USP
=SHARINGRIVE LINK.