Unraveling the Human Eye: Anatomy and Functions

1. UNIT-IIAnatomy and physiology of eye: Review Presented By : HezilReemaBarboza

2. Learning objectives • At the end of class learner will be able to : • explain the parts of eye • describe the function of eye

3. THE HUMANEYE

4. Anatomyof the Human Eye

5. Layers of theEye • Sclera: outer white layer; maintains shape of eye; muscles attached control eyemovement • Choroid: contains bloodvessels

6. Sclera

7. Chambers & Fluids ofEye Liquids(humour): • gives shape toeye • Help refract lightrays

8. Regulating Amount ofLight • Iris • Pupil

9. contractedpupil dilatedpupil

10. Focusing LightRays • Cornea • Lens • Ciliarymuscle

11. Focusing LightRays • Light rays from distant objects enter theeye • parallel to oneanother • Light rays from close objectsdiverge.

12. NearbyObjects DistantObjects

13. Accommodations Changing the shape of theeye lens to keep objects infocus

14. Retina • Opticnerve • Opticdisc • Maculalutea • Foveacentralis ImageProduction

15. Retina • At the back of theeye • Consist of 2 types of light-sensitive cells: rods andcones • Converts light signal into an electrical signal that is transmitted to the brain through the opticnerve

16. Rods andCones • rod cells: lightsensors • 120million • Functions in less intenselight • Used in peripheral vision • Responsible for nightvision • Detects black, white and shades ofgrey • cone cells: detectscolour • 7million • Highest concentration at foveacentralis • Functions best in brightlight • Perceives finedetails • 3 types of cone cells, each sensitive to one of the three primary additive colours: red, green, andblue

17. MaculaLutea • Small yellowish area of the retina near the optic disc (“yellowspot”) • Area that provides the most acute vision (clearvision) • When the gaze is fixed on any object, the centre of the macula, the centre of the lens, and the object are in a straight line http://www.britannica.com/EBchecked/topic/355512/macula-lutea

18. Fovea Centralis (CentralFovea) • A pit in the centreof the maculalutea • Contains no rodcells • Has high concentration of conecells • Recall: cones are associated withcolour vision and perception of finedetail • No blood vesselsto interfere withvision • Provides sharp detailed vision (e.g. needed during reading, driving etc.) http://www.britannica.com/EBchecked/topic/355512/macula-lutea

19. OpticNerve • Nerve cells that transmit message from light-sensitive cells in retina to thebrain

20. Activity: The reappearingdot • Draw an X on a pieceofpaper. Then drawa dot 6 cm to the right of theX. • Cover your left eye with your lefthand. • Hold the paper with your right hand at arms lengthaway. • Focus your right eye on the X but keep the dot in your peripheral vision. • Slowly move the paper towards your face and notice when the dot “disappears” and “reappears”.

21. BlindSpot • Optic disc:where the optic nerves converge and exit theeye • No light-sensitive cells to detectlight rays • Results in a break in the visual field, known as a blind spot

23. Right Eye Fovea Centralis Blind spot

24. Producing anImage The converging lens produces an inverted image which the brain interprets as beingupright

25. Producing anImage • Cells on retina trigger a nerveimpulse • Nerve cells sends an electrical signal to the brain via the opticnerve

26. Summary Understanding of anatomy and physiology of eye enables the students to learn about the eye disorders.

27. Evaluation: • What are the parts of eye? • What is the function of eye?

28. References • SmeltzerSC, Bare BG, Hinkle JL, Cheever KH. Text book of medical surgical nursing. 11th ed. New Delhi: WoltersKluwerPvt Ltd; 2009. • Lewis, Dirkson, Heitkemper,Bucher. Lewis's Medical Surgical Nursing. India: Elsevier;2011.