Understanding Blindness: Things to Keep in Mind

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A 2022 study found that India is home to approximately 5 million blind people and 70 million visually impaired people. Read on to know the causes, symptoms, risk factors, diagnosis, and treatment of blindness and visual impairment.

What is blindness? What is a visual impairment?

Strictly speaking, blindness refers to the inability to perceive light. However, in general terms, we refer to blindness as the loss of vision. In contrast, visual impairment refers to a decrease in vision that cannot be corrected by traditional methods such as spectacles.

What is visual acuity?

Visual acuity measures how well you’re able to see objects. It is usually measured by asking you to read an eye chart from a certain distance. Visual acuity is typically 20/20, which means that you are able to make out details that should normally be visible from 20 feet away. As an example, if your vision is ’20/40,’ it means you need to be as close as 20 feet to see what a normal person can see at 40 feet. According to the WHO, blindness can be defined as a visual acuity of less than 3/60.

What are the types of blindness?

Although there is no fixed classification, some types of blindness include:

  • Complete blindness: There is a complete loss of vision. A person is not able to even perceive light
  • Partial blindness: You have limited vision but you’re still able to make out certain details
  • Legal blindness: In this case, your visual acuity is less than 1/60 in the better eye
  • Social blindness: The visual acuity is between 3/60 to 1/60
  • Economic blindness: Visual acuity is between 6/60 to 3/60
Understanding Blindness

What is colour blindness?

Normally, the human eye can perceive and appreciate the three colour ranges – red, blue, and green due to the presence of ‘cones’, which are colour receptors present in the eye. They are of three types – red-sensitive, blue-sensitive and green-sensitive. In colour blindness, the eye has trouble distinguishing between the different colours. In most cases, people are unable to completely see or appreciate the colours; in very rare cases, people cannot see any colour at all.

What are the causes of blindness?

The leading causes of blindness include:

  • Cataract
  • Glaucoma
  • Age-related macular degeneration
  • Diabetic retinopathy
  • Corneal scarring
  • Infections
  • Prolonged, untreated refractory errors
  • Childhood blindness

What are the causes of childhood blindness?

Childhood blindness is especially common in developing countries like India. Some causes contributing to childhood blindness include:

  • Vitamin A deficiency
  • Infections like measles, conjunctivitis, etc.
  • Congenital cataract
  • Congenital glaucoma
  • Retinopathy of prematurity, a condition that occurs in premature babies due to the development of abnormal blood vessels in the eye

What are the symptoms of blindness?

In case of complete blindness, you won’t even be able to perceive light. In partial blindness, symptoms can include:

  • Blurring of vision
  • Pain in the eyes
  • Presence of floaters or black spots
  • Inability to distinguish colours and shapes
  • Inability to see at night
  • Extreme sensitivity to light

What are the symptoms of blindness in children?

Symptoms in children are slightly different compared to adults. These include:

  • Difference in the size of the pupils
  • Difference in the colour of the pupil (it appears white instead of black)
  • Bumping into walls, furniture, and objects
  • Inability to focus the eyes
  • Side-to-side movement of the eyes (nystagmus)
  • Not following an object or a person with their eyes, or not making proper eye contact
  • Rubbing the eyes frequently
  • Squinting
  • Having trouble seeing at night
  • Eyes that are turned inwards

What are the risk factors for visual impairment and blindness?

The most common risk factors for visual impairment and blindness include:

  • Uncontrolled diabetes
  • Family history of eye conditions like glaucoma
  • Uncorrected refractory errors like myopia (short-sightedness), hypermetropia (long-sightedness) etc.
  • Deficiency of vitamin A
  • Premature birth (in babies)
  • Uncorrected strabismus (‘crossed eyes’)
  • Uncorrected amblyopia (‘lazy eye’)

How is blindness diagnosed?

Your doctor will take a detailed history of your symptoms and perform a thorough eye examination. This includes:

  • Visual acuity: This involves reading an eye chart from a particular distance
  • Visual field testing: This is to check your field of vision. Cover one eye and look straight ahead while your doctor stands in your peripheral vision, holding up his fingers, and asks you how many you can see
  • Tonometry: This is commonly employed for glaucoma and is used to check your eye pressure
  • Slit-lamp examination: This involves using a microscope with a bright light in order to examine your eyes
  • Other eye tests include an electroretinogram, an electrooculogram, etc.
  • In case of diabetes, infections, etc., your doctor may ask to check your blood glucose, HbA1c, and serum immunology

What is the treatment for blindness?

Depending on the cause, the treatment for blindness will vary:

  • Medications: For infections, glaucoma, or vitamin A deficiency, you are put on antibiotics or antiviral drugs, eye-pressure lowering agents, and vitamin A supplements, respectively
  • Surgery: In case of cataracts, corneal scarring, or trauma to the eye, your doctor prescribes the corresponding surgery
  • For diabetic retinopathy, your doctor will ask you to bring your blood glucose levels under control, prescribe medications, and, in severe cases, ask you to undergo surgery
  • Transplant: In severe cases, your doctor will prescribe a corneal or retinal transplant in the case of a damaged cornea or retina, respectively

Is blindness preventable?

You can certainly reduce your chances of visual impairment and blindness by:

  • Undergoing regular eye check-ups
  • Getting the right treatment for your refractive errors (corrective specs, lenses, or surgery)
  • Keeping your blood glucose levels in check to prevent diabetes-related complications
  • Eating a well-balanced, nutritious diet to prevent any kind of deficiencies or ensuring you take proper supplements
  • Reducing exposure to direct sunlight by wearing protective eye gear
Dr. Aditi

Dr. Aditi

An MBBS and a medical reviewer with a penchant for healthcare articles and blogs. Read her contributions and writings about various healthcare topics.

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