This document discusses blindness and low vision. It defines blindness as the inability to see due to injury, disease or congenital conditions. Low vision refers to vision loss that cannot be fully corrected with medical treatments or glasses. The document then discusses the legal and educational definitions of blindness, and how visual acuity is measured. It provides details about the anatomy and physiology of the human eye, and describes the types and causes of vision problems such as errors of refraction, eye muscle imbalances, and various eye diseases.

1. and
Blindness
LowVision

2. What is blindness?
The state or condition of being unable to see because of injury, disease,
or a congenital condition.

3. What is low vision?
Refers to vision loss that cannot be corrected by medical or surgical
treatments or conventional eyeglasses.

4. Two general definition of blindness
• That is based on measurement of visual acuity, field of vision, and peripheral
vision.
• is the ability to clearly distinguish forms or discriminate details at a specific distance.
LEGAL
DEFINITION
Visual Acuity

5. Snellen Chart
• 20/20 (normal vision)
• 20/70 (poor vision)
• 20/200 (poor that falls to
blindness)

6. • Refers to the area that normal eyes cover above,
below on both sides when looking at an object or
when gazing straight ahead. The field of normal
vision covers approximately a range of 180
degrees. When looking directly at an object , the
central field of vision is used.
Field of vision

7. Covers the outer ranges of the field vision.
A person may have poor central
vision but good peripheral vision.
Peripheral Vision

8. •Refers to the condition where visual acuity is 20/20 in the
better eye after the best possible correction with glasses or
contact lenses.
•Peripheral is limited to an area of 20 degrees or less from
normal 180- degree field.

9. • Not all legally blind persons are totally blind. In total
blindness the person is absolutely without the sight
but may have light and movement perception and
travel vision. The degree of blindness include light
perception, movement perception, and travel vision.
Although classified as blind , the person can still use
his or her residual vision.
EDUCATIONAL DEFINITION

10. Blind children use their sense of
touch to read Braille and train in
orientation and mobility to move
around and travel independently
Low vision children
learns to read
material in large
print.

11. The Process of Normal Vision

12. The sense of vision is a complex and intricate physiological. There are
three elements necessary for good vision to take place. These are a pair
of health, intact and efficiently functioning eyes with complete parts,
well-lighted objects and images and healthy brain.

13. Anatomy and Physiology of the
Human Eye
The eye is a complex part of the human body that no other
organism can equal.
There are five physiological or physical system in vision namely:
the protective structure, the refractive parts, the muscles, the
retina and the optic nerve, and the brain where vision takes place

14. The Protective Structure
These are the eye socket which contains the eyeball
where most of the parts of the eye are found. It
protects the sensitive mechanism for vision from
trauma, together with the bones of the checks and
forehead.
The tear ducts or lacrimation system protect the
eye by secreting fluid or tears that clean and keep
the eye moist. The eyelid moisten and cleans the
cornea through blinking. The eyebrows and
eyelashes catch foreign bodies that may enter the
eyes.
The protective structure surround the eye to protect it
from the harm.

15. The Refractive Parts
The refractive structure bend or refract
light rays so that the image of the objects
focuses on the retina.
These are the cornea is the curved
transparent membrane that protects
sensitive parts of the eye. It is the front
window of the eye that starts the process of
vision by bending the light rays into patterns
or images.

16. The aqueous humour is the watery liquid that
fills the front chamber of the eye to keep the
eyeball properly inflated.
The pupil is a circular hole in the center of the
colored iris. The pupil constrict or dilates to
regulate the amount of light entering the eye.
The lens is a transparent and elastic little
envelop of fluid suspended by tiny strong
muscle.

17. The Muscle
• The muscle function to coordinate and balance the movement of the
eyes. They turn, raise and lower the eyes in response to cranial or
brain nerve impulse.

18. The Retina
• The retina is a multilayered sheet of nerve tissues at the back of the eye.
The retina is the last part of the neural receptor system for vision. It
contains some one hundred thirty seven million light receptors called rods
and cones.
• The rods are responsible for night vision or for seeing objects and images
under of low illumination.

19. • the most sensitive part
of the retina is the
macula, at the center of
which lies the fovea, the
area that is vital to the
exact discrimination of
the details of an image
or object.

20. • The optic nerve is connected to the retina and conducts visual
images to the brain. The optic nerve is capable of transmitting
messages from the retina to the brain at a speed of three
hundred miles per hour.

21. The Brain
• Vision takes place in the occipital lobe of the brain located at the
back of the head. The occipital lobe is the one of the four lobe of the
brain that are named for the major skull bones that covers them.
• Audition or hearing takes place in the temporal lobe found behind
the forehead. The parietal lobe at the top of the head towards the
rear processes body sensation.

22. • The frontal lobe is a part of the cerebral cortex in the cerebrum or
forebrain which is the largest part of the brain that governs the highest
functions associated with conscious activities and intelligence.

23. How vision takes place?
The basic function of the eye is to collect visual information in the form
of mechanical energy from the environment through psychological
process called sensation.
During the process of vision, the stimuli are converted into electro
chemical form or nerve impulse through the process called
transduction.

24. • The optic nerve conveys the nerve impulse to the
occipital lobe of the brain where perception takes place
• There are three conditions for vision to take place, first
the eye are stimulated by light rays in the form of
mechanical energy; second, the light rays are reflected
from objects in the visual field, lastly the mechanical
energy is converted into nerve impulses which the brain
processes into visual images.

25. Types and Causes of Problem of Vision
The inability of the eyes to function efficiently may be traced to:
1. Errors of refraction
 After the light rays enter the cornea, aqueous humour and pupil and the
lens fail to refract or bend the light rays to focus on the central part of
the retina. In hyperopia or farsightedness ,the lens fail to focus the
light rays from near objects on the retina. Myopia or Nearsighted, the
opposite take place. In astigmatism, the cornea which normally forms
a portion of a spherical lens is deformed, the refraction of the light rays
becomes faulty and blurred vision results.

27. 2. Imbalance of the eye muscles
 When the muscles of both eyes
do not work together in a coordinated way.
3. Disease of the eye
 Cataract- is caused by clouding of the
lens which results the progressive blurring
of vision and eventually blindness occurs.

28.  Diabetic retinopathy- occurs when
diabetes mellitus interferes with the
flow of blood to the retina causing it to
degenerate.
 Disease of the cornea- injuries and
infection due to accidents and malnutrition scar
the cornea which shoes as a whitish spread.
Cornea scar is commonly called “pilak”

29.  Disease of the retina(retinal disease)- the most sensitive part of the
visual mechanism ,can be congenital or present at birth. Many of the
disease are due to prenatal causes, that is, they occur during
pregnancy.
 Coloboma- is a degenerative disease in
which the central and or peripheral areas
of the retina are not completely formed .
This result to impairment of the visual field
and the central visual acuity and blindness.

30.  Retinitis Pigmentosa- is a heredity
condition that result in the degeneration
of the retina. The field of vision becomes
narrow and eventually results to blindness.
 Glaucoma- is a condition in which
there is excessive pressure in the eye.

31. 4. Trauma or accidents
Retinal detachment (dizziness, severe
headache and blurring)

32. Rubella or German Measles
• Rubella is a mild disease in most people.
• The danger is that pregnant women who come in contact
with someone with rubella especially during first three
months of pregnancy risk having rubella baby
• Rubella is responsible for 95% of deaf and blind babies.

33. • These problem can prevented by immunizing all girls aged between 10
and 16 years with the rubella vaccine.
• Since February 1989, rubella had been added to the measles/mumps
vaccine to make the 3 in 1 measles/mumps/rubella vaccine.

34. Symptoms
• Rubella is usually a mild
illness with a rash and fever.
• A mild headache,
accompanied by a slight fever
and swollen lymph glands of
the neck may appear about
two days before rash.
• The rash appears as blotchy
brownish-red spot on the face
and neck.

35. • An attack lasts from two to five days and may be accompanied by
mild catarrh and fleeting pains in the hands and feet.
• Rubella is sometimes mistaken for the more serious ordinary measles
or other viral infections.

36. How it spread?
• The virus is present in an infected person's nose and mouth
• It spread to others though droplet infection in cough, and sneeze, by
direct kissing, by handkerchief, towels, beddings, eating and drinking
utensil and other items.

37. • Incubation period is from 14 to 23 days.
• The contagious period is from one week before to as long as four days
after the rashes appears when an infected person can pass on thaw
disease

38. Who should be
immunized?
• All children aged between 12 and
15 months should be immunized
with the measles/mumps/ rubella
vaccine.
• Girls aged between 10 and 16
years old should be immunized
with rubella vaccine.
• Women who are planning to
become pregnant, it is wise to
discuss the need for
immunization with her doctor.

39. •Rubella immunization should NOT be given to: women
who already pregnant; women who may become
pregnant within 3 months of receiving the vaccine;
people suffering from fevers and serious disease
•Before immunization, the doctor must be told about
anychronoc illness, infections or allergies.