anatomy and physiology of eye

1. ChapterChapter :9:9
AnatomyAnatomy andand
PhysiologyPhysiology ofof EyeEye
Presented by: Prof.Mirza Anwar BaigPresented by: Prof.Mirza Anwar Baig
Anjuman-I-Islam's Kalsekar Technical CampusAnjuman-I-Islam's Kalsekar Technical Campus
School of Pharmacy,New Pavel,NaviSchool of Pharmacy,New Pavel,Navi
Mumbai,MaharashtraMumbai,Maharashtra
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2. Overview
• The eye is supplied by the optic nerve (2nd cranial
nerve).
• It is almost spherical in shape and is about 2.5 cm in
• diameter.
• It is possible to see with only one eye but three-
dimensional vision is impaired when only one eye is
used, especially in relation to the judgement of
distance.

3. Acessory structures of eye:

4. Acessory organs of eye:

5. Secretion of lacrimal fluid:

6. Functions
• The fluid that fills the conjunctival sac consists of
tears and the oily secretion of tarsal glands and is
spread over the cornea by blinking.
• The functions of this mixture of fluids include:
1. Washing away irritating materials, e.g. dust, grit
2. The bacteriocidal enzyme lysozyme prevents
microbial infection
3. Oiliness delays evaporation and prevents drying
of the conjunctiva
4. Nourishment of the cornea.

7. Structure of eye:

8. Anatomical features:
1. Sclera
• The sclera, or white of the eye.
• It consists of a firm fibrous membrane that maintains the shape of
the eye and gives attachment to the extraocular or extrinsic muscles
of the eye.
2. Cornea
• Light rays pass through the cornea to reach the retina.
• The cornea is convex anteriorly.
• Involved in refracting or bending light rays to focus them on the
retina.
3. Choroid
• The choroid lines the posterior five-sixths of the inner surface of the
sclera.
• Very rich in blood vessels and is deep chocolate brown in colour.
• Light enters the eye through the pupil, stimulates the nerve endings
in the retina and is then absorbed by the choroid.

9. 4. Ciliary body
• Consisting of ciliary muscle (smooth muscle fibres) and secretory
epithelial cells.
• Contraction and relaxation of the ciliary muscle changes the
thickness of the lens which bends, or refracts light rays entering the
eye to focus them on the retina.
• The epithelial cells secrete aqueous fluid into the anterior segment of
the eye, i.e. the space between the lens and the cornea (anterior and
posterior chambers).
• The ciliary body is supplied by parasympathetic branches of the
oculomotor nerve (3rd cranial nerve).
• Stimulation causes contraction of the smooth muscle and
accommodation of the eye.
5. Iris:
• visible coloured part of the eye.
• It is a circular body composed of pigment cells and two layers of
smooth muscle fibres, one circular and the other radiating. In the
centre there is an aperture called the pupil.
• The iris is supplied by parasympathetic and sympathetic nerves.
Parasympathetic stimulation constricts the pupil and sympathetic
stimulation dilates it

10. Contraction and relaxation of circular and radial
muscles:

11. Retina:
1. Innermost layer,extremely delicate structure and is especially
adapted for stimulation by light rays.
2. It is composed of several layers of nerve cell bodies and their
axons, lying on a pigmented layer of epithelial cells which
attach it to the choroid.
3. The layer highly sensitive to light is the layer of sensory
receptor cells: rods and cones.
4. Near the centre of the posterior part is the macula lutea, or
yellow spot.
5. In the centre of the area there is a little depression called
the fovea centralis, consisting of only cone-shaped cells.
6. Towards the anterior part of the retina there are fewer
cone- than rod-shaped cells.
7. The rods and cones contain photosensitive pigments that convert
light rays into nerve impulses.
8. The small area of retina where the optic nerve leaves the eye is
the optic disc or blind spot. It has no light-sensitive cells.

12. Interior of the eye:
1. The anterior segment of the eye, i.e. the space between
the cornea and the lens, is incompletely divided into
anterior and posterior chambers by the iris .
2. Both chambers contain a clear aqueous fluid (humour)
secreted into the posterior chamber by ciliary glands.
3. It circulates in front of the lens, through the pupil into
the anterior chamber and returns to the venous
circulation through the scleral venous sinus (canal of
Schlemm) in the angle between the iris and cornea.
4. There is continuous production and drainage but the
intraocular pressure remains fairly constant between 1.3
and 2.6 kPa (10 to 20 mmHg).
5. An increase in this pressure causes glaucoma. Aqueous
fluid supplies nutrients and removes waste from the
transparent structures in the front of the eye that have
no blood supply, i.e. the cornea, lens and lens capsule.

13. Physiology of vision

14. Structure of retina:

15. Structure of retina:

16. The cyclical bleaching and regeneration of
photopigment

17. Light and dark adaptation