Types of Blindness

Blindness is the condition of complete or total loss of vision with inability to distinguish the darkness from bright light either in one eye or both the eyes.

Types of Blindness

• Color Blindness - It means the inability to recognize the color or distinguish some of the colors. Color vision is very important in day to day activities. Abnormal color vision can be dangerous while driving a car because the person cannot recognize and distinguish the different colors of the signal.
  Color blindness is caused by -
  • Congenital cause (Hereditary) - The color blindness is present from the birth and is incurable. It can be partial blindness or total blindness.
    Partial Blindness means cannot recognize green, red or blue color. The partial blindness for green color is very common and known as Green Blindness.
    Total Blindness means a person cannot recognize any color and sees everything grey.
  • Acquired cause - The color blindness can be acquired due to eye diseases like diabetes, cataract, glaucoma, and vitamin deficiencies, old age or side-effects of some medicines.

• Day Blindness- It means the vision is poor in bright light but better in dim light. It is also called as Hemeralopia.
  Normally retina has two types of cells called as rods and cons. These cells are light sensitive and hence they are stimulated by light. Rod receptor cells function in dark light and enable to see at night while cone receptors works well in bright light and enable to see in bright light. In day blindness, a person has the degeneration in cone receptors.

• Night Blindness - It means that the vision is poor in dim light but better in bright light. Hence such people cannot move freely in dark light and collides frequently to an object. It is also called as Nyctalopia. It can be due to hereditary or acquired.
  The acquired cause can be due to degeneration of the rods cells in retina. Also due to vitamin A deficiency, liver diseases like cirrhosis of liver.
                

How to diagnose Blindness?

• Visual Acuity Test - It helps to measure the vision and eyesight. An eye chart is placed and the patient needs to see the chart which allows to check the vision.
• Peripheral or vision field test - It helps to know how much area of vision does the patient able to see that is whether entire or some limited part of area. It is done at both the eyes at the same time.
• Color Vision Test -
  1) Lantern test - Edridge - Green Lantern is used . It is the old lantern test helps to detect the color blindness whether hereditary or acquired.
  
  

          2) Pseudochromatic chart - This chart consists of colored plates in which bold numbers are shown in   dots of various colors and of same size. A normal person can read the chart and identify the numbers easily while a color blind person unable to identify it.

Treatment for the blindness

• There is no cure for the hereditary type of blindness.
• Depending on the cause the acquire blindness can be corrected to some extend. For example the blindness is due to vitamin deficiency or due to some medication then either by giving those required vitamins or stopping the current medication can solve the problem.
• Special devices like eyeglasses or lenses available to correct the color vision but these will not be completely helpful.
• Always consult the ophthalmologist for any kind of blindness treatment.