diease

Cataract


Cataract overview and Definition

 Cataract is defined as the condition which result in clouding of the eyes. The person might feel difficult to view through the fogged eyes.

It makes them difficult to read and do other household activities


Epidemiology

cataract is common among the older individals.


Structure of Cataract

Types of cataract:

Nuclear cataracts:

It is also known as nuclear sclerotic cataract. It occurs in the center of the lens which is termed as nucleus. Over a period the lens gets hardens and turns yellow or brown. This might result in difficult vision and the halos are seen at night when bright objects are viewed.

Cortical cataracts:

This takes at the outside portion of the lens which is called as the cortex. They start as white wedges like triangles that point towards the center of the eye. As they develop they might result in the scatter of the light. The main symptom is glaring.this might result in haziness of the vision, fooging of the eye.

Posterior subcapsular cataracts:

These form just inside the back of your lens capsule, the part of your eye that surrounds the lens and holds it in place. They're directly in the path of light as it passes through the lens.

 

They're quicker to come on than other cataracts, and you may get symptoms within months. They affect your close-up vision and make it harder to see in bright light.

Anterior subcapsular:

This forms in front of the lens capsule.

Congenital cataracts:

This is present since birth. Some are linked to the genes and others might occur due to illness such as the mother affected by rubella during pregnancy.

Traumatic cataracts:

Any blunt trauma might result in swelling, thickening and whitening of the fibers of the lens. While the swelling and other conditions might resolve within time, but the whitening of the fibers preceded by configurational changes in protein.

Secondary:

Diabetes mellitus and intake of corticosteroids such as prednisone.

Lamellar pr zonular cataracts:

This cataract passess from parent to child. This might take fine white dots in the middle of the lens and might take the shape of the Y. the whole center portion might turn white.

Posterior polar cataracts

You get these on the back center of your lens, and they're often due to genes that are passed down through your family.

Anterior polar cataracts

They form on the front and center of your lens and look like small white dots. These cataracts typically cause any damage to the vision.

Christmas tree cataracts

They are called polychromatic cataracts. They shows shiny, colored crystals in your lens. They are most common in people who have a condition called myotonic dystrophy.

Brunescent cataracts

If nuclear cataract is left untreated it turns very hard and brown. This is called brunescent.

It makes it hard for you to tell colors apart, especially blues and purples. Surgery is difficult.


Pathophysiology

Lens is made of water and protein fibers. Opacity occurs when the proteins shows clumpsiness.

This result in ability of the lens to show reduced amount of refraction property resulting in reduced visual acuity.

Chemical modification of the lens makes it to look thicker and harder.

Another mechanism involves if glucose is present in excess it leads to the activation of the polyol pathway. This results in formation of the sorbitol ( a molecule obtained as a result when an enzyme glucose reductase reacts on the glucose). The deposition of the sorbitol occurs in the lens. This results in hyperosmotic effects leading to opening of aquaporins channel and influx of water though it resulting in the formation of the cataract.


Clinical signs & symptoms

Blurred vision

Vision that is cloudy, blurry,foggy and flimy

Sensitivity to bright sunlight,lamps and headlights

Glare (seeing a halo around the lights), especially when you drive at night with oncoming headlights

Prescription change sin glasses including sudden nearsightedness

Double vision

Need for brighter light to read

Difficulty seeing at night(poor night vision or Nyctalopia)

Alteration in seeing the colour change.


Differential Diagnosis

Visual acuity test:

This is a fancy way of saying "eye chart exam."  The physician might ask you to read the letters from the distance.

Slit-lamp exam:

 The physician uses a special microscope with a bright light and examine the different parts of your eye. They might examine at your cornea, the clear outer layer. They'll also examine the iris  the colored part of your eyeand the lens that sits behind it. The lens bends light as it enters your eye so you can see things clearly.

Retinal exam:

The physician drops in your eyes to widen your pupils, the dark spots in the middle that control how much light gets in. This lets them get a good look at the retina. The tissue around the back of your eyes and a better view of the cataract.


Prognosis

Most of the time surgery shows the better prognosis and restore the vision


Prevention

Have a regular eye examination

Quit smoking

Wear sunglasses

Have a regular checkup with other systemic illness

Avoid alcohol consumption.