Eye disorders And diseases

Human eye is a sense organ , which reacts to light in every circumstances. It allows vision , conscious light perception including colour differentiation. Each eye constantly adjust the amount of light it lets in, focuses on object near & far, and produce continuous images that are instantly transmitted through optic nerve to the brain. The orbit is the bony cavity that contains the eyeball, muscles, nerves and vessels as well as the structure that produce and drain tears. 

    Main parts of human eye
  • Cornea
    Outer most layer of eye
  • Pupil
    The circular opening in the center of eye that acts as a gateway for light
  • Eye iris
    It is typically referred to as eye color which is in the middle layer.
  • Lens
    Lens is behind the iris and pupil
  • Retina
    Inner most layer of eyeball which has light sensitive cells and nerve endings.

Problems of eye
1. Nystagmus
Nystagmus Is an in voluntary rapid and repetitive movement of eyes – either horizontal (side to side) or vertical (up and down)
Nystagmus usually happens from diseases affecting the inner ear balance mechanisms or the back part of the brain. Pendular nystagmus can result from brain disease such as multiple sclerosis, but can be a congenital problem as well. 
Congenital or inherited nystagmus is not topically associated with serious medical conditions. But acquired nystagmus may be sign of a serious medical condition and it causes severe head trauma, toxicity, stroke, inflammatory diseases or other conditions which affected the brain. The most common cause of acquired nystagmus is certain drugs or medicines , excessive alcohol and any sedative medicines.
2. Diplopia

It is double vision, Causes a person to see two images of a single object.                   

Two types of double vision
Monocular – the double vision is present in only one eye.
Binocular – double vision is present in both eyes


  • Nerve or muscle damage in the eye cause double vision
  • Changes in thyroid function can affect the external muscles that control the eye
  • Stroke or transient is  chemic attack causes for double vision
  • Aneurysm, that is bulge in a blood vessel, can press on the nerve of the eye muscle.
  • Convergence – it is the condition, that eyes do not work together correctly.
  • Diabetes mellitus   
  • Myasthenia gravis
  • Brain tumor and cencess
  • Multiple sclerosis
  • Black eye- an injury can cause blood and fluid to collect around the eye.
  • Head injury

Causes of monocular double vision

  • Severe astigmatism
  • Corneal shape changes
  • Cataract
  • Dry eye
  • Pterygium – raised, fleshy growth on the clear tissues that cover your eyelids and eyeballs. This growth is not cancerous.

Causes of binocular double vision

  • Nerve damage
  • Diabetes
  • Cranial nerve palsy
  • Myasthenia gravis – this is an auto immune disorder which affects communication between nerves and muscles throughout your body. In the eyes, this can cause rapid fatigue
  • Graves diseases:-This disorder is the result of an overactive thyroid. About 30% people with this condition experience some type of vision problem.
  • Strabismus (crossed eye):-Common causes of double in children .

3.Cross eye
Crossed eyes occur either due to nerve damage or when the muscle around your eyes don’t work together because some are weaker a different visual message from each eye, it ignores the signals coming  from your weaker eye. Crossed eyes are common in children. Often the underlying cause is unknown. But it can also occur later in life.

  • Physical disorders
  • Eye injuries
  • Cerebral palsy or stroke


It is clouding of the normally clear lens of your eyes. For people who have cataracts, seeing through cloudy lenses is a bit like looking through a frosty or fogged-up window 

Types cataracts 

  • Nuclear sclerotic cataract
  • Cortical cataracts
  • Posterior subcapsular cataract
5.Myopia (Short sight/ near sightedness)
A condition in which close object appear clearly , but far ones don’t 


  • It occurs when the eyeball is too long
  • When the cornea or lens being too curved for the length of the eyeball.
  • It can be corrected by wearing artificial lenses 
6. Keratoconus
Keratoconus also called conical cornea. A condition in which the clear tissue on the front of eye(cornea) bulges outward. With keratoconus , the clear , dome shaped tissue that covers the eye (cornea) thins and bulges outward into a cone shape. It’s cause is unknown.


First appear during puberty or the late lenses and include blurred vision and sensitivity to light and glare 


The weakening of the corneal tissue that leads to keratoconus may be due to an imbalance of enzymes within the cornea