Diffraction in glaucomatic eye

1. DIFFRACTION IN
GlAUCOMATIC
EYE
GROUP 3

4. GLAUOCOMA
•Glaucoma is a group of eye disorders.
•Intra ocular pressure of eye increases in
glaucoma.
•It causes blindness by harming the optic nerve,
the large nerve that is responsible for vision.
•It can occur at any age but is more common in
older adults.

5. MAIN TWO TYPES OF GALUCOMA
➢Open-angle Glaucoma
➢Acute Glaucoma (Closed-angle Glaucoma)

6. OPEN-ANGLE GLAUCOMA
• Most people who have open-angle glaucoma feel
fine.
• And do not notice a change in their vision at first
• Because the initial loss of vision is of side or
peripheral vision.
• And the visual acuity or sharpness of vision is
maintained until late in the disease.

8. CLOSED-ANGLE GALUCOMA
• The mechanism of open-angle glaucoma is believed
to be slow exit of aqueous humor through the
trabecular meshwork.
• In closed-angle glaucoma the iris blocks the
trabecular meshwork.
•Diagnosis is by a dilated eye examination.
• Often, the optic nerve shows an abnormal amount of
cupping.

10. ❖Severe eye pain.
❖Nausea and vomiting (accompanying
the severe eye pain)
❖A haziness in the cornea
❖Blurred vision.
❖Halos around lights.
❖Reddening of the eye.
SYMPTOMS OF CLOSED-ANGLE GALUCOMA

12. GLAUCOMATIC EYE NORMAL EYE

13. THE PATHOLOGICAL DIFFRACTION HALOS
• The coloured halos associated with glaucoma are
due to diffraction phenomenon
• It is caused by corneal edema occurring in the
states of raised tension
➢Corneal collagen is arranged in sheets of fibrils called lamellae that are
arranged orthogonally throughout the stroma

15. • Because of increased tension subepithelial droplets
will be formed in the cornea
• These have different optical properties from the
medium in which they lie.
• As light travels through this it suffers diffraction

16. HOW DO WE SEE HALOS RINGS AROUND LIGHT

17. • Normally people may see halos rings around sun

18. •One or more diffuse concentric rings of light around
the Sun or Moon called is as halos rings
•formed by diffraction of light as it moves through
water droplets in the atmosphere
•In glaucomatous eye the diffracting body will be
inside the eye
•That is referred as subepithelial droplets.

19. WHAT IS THE PHENOMENON OF DIFFRACTION
• Diffraction refers to various phenomenon that occurs
when a wave encounters an obstacle or a slit.
• It is define as the bending of waves around the corners
of an obstacle or through an aperture.
• Waves enter to the region of geometrical shadow of the
obstacle / aperture.

21. Diffraction effects
• Diffraction caused by the wave nature of light.
• Diffraction is the spreading of light as it passes
through an aperture or passes by the edge of an
object.
• Diffraction effects are depended on the size of the
aperture or object.

22. THE CONDITIONS FOR DIFFRACTION
• The effect is only noticed when the gap is of a similar
size to the wavelength of the wave.
• Too large a gap compared to the wavelength, and the
waves pass through without much change.
• Not shown is that too small a gap and the waves
cannot get through.

23. •Simple experiment show that the greatest
diffraction is given by a narrower slit or longer
wavelength of light used.
•It can be shown that angle of the first minimum
(dark region) is given by the following formula
•Sin θ=λ/d
•where λ is the wavelength in metres and d is
the slit width in metres

25. A SINGLE SLIT DIFFRACTION
• A simple diffraction pattern can be observed if a light
source is looked at through a narrow single slit.
• The fringe pattern is a series of alternate bright and
dark fringes with each fringe parallel to the slit.
• The central fringe is much brighter than the others
and twice the width.

27. DIFFRACTION GRATING
• A big problem with single & double slit experiments are
that the fringes are very dim
• because not enough light gets through.
• And also there is a big region where constructive
interference can take place.
• A better pattern can be obtained using a diffraction grating
• In any particular direction, only those waves of a given
wavelength will be conserved, all the rest being destroyed
because of interference with one another

28. The diffraction grating with a monochromatic light source produces a
series of bright sharp maxima
symmetrically arranged about a central bright fringe.
The central bright maximum is called the zero
order maximum: the first maxima, either to the right or left, the first
order maxima and so on. If white
light is used, then a mini-spectrum of colours is observed in each
diffracted beam