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Cataract

What is cataract?

Cataract is clouding of the clear lens of the eye, which lies behind the eye aperture known as the pupil. This clouding can be slight to complete opacity causing obstruction in passage of light leading to decrease in the vision.

 

 

The lens of the eye performs the function of focusing the images of what we see on the retina, a light sensitive layer located at the back of the eye. These images are than converted into electrical signals and carried by the optic nerve to the brain, enabling us to perceive the image. Hence, any obstruction in the path of the light till it reaches the retina, like a clouded lens leads to blurry image and decrease in vision.

What are the causes of cataract?

Cataracts are commonly related to aging process. In young age, the lens is clear and able to change shape for accurate focusing, but as we age the proteins in the lens break down making it rigid and cloudy.

 

 

There are many causes of non- age related cataract which accelerates the break drown of lens proteins. These includes:-

1.Diabetes

2.Inflammatory lesions of the parts of the eye like iritis, uveitis

3.Any blunt or penetrating trauma to the eye

4.Prolonged sun exposure, Ionizing radiation, Xrays, UV rays

5.Disorders like atopic dermatitis, hyperparathyroidism and hypothyroidism

6.Smoking and tobacco use

7.Family history of cataract

8.Various genetic diseases:
  a.Downs Syndrome
  b.Galactosemia
  c.Myotonic dystrophy
  d.Wilsons disease
  e.Homocystinuria

9.Infections which affects the baby when in the womb (congenital infections) like
  a.Cytomegalovirus
  b.Herpes
  c.Rubella
  d.Toxoplasmosis
  e.Syphilis

10.Various medications like
   a.Corticosteroids
   b.Haloperidol

However, in many cases the cause of cataract is unknown

What are the types of cataract?

There are various ways to classify cataracts depending on their location within the lens, by causes etc.

The lens is made of three parts and can be compared to a fruit. The outermost layer which acts like the skin of the lens is known as the capsule. The innermost layer, like the seed of the fruit is known as the nucleus and the middle fleshy layer is known as the cortex.

1.Nuclear cataract- In these type opacities seen within the nucleus of the lens and are commonly seen in age related cataracts 
2.Cortical cataract- It is characterised by spoke like opacities extending from the periphery of the lens towards the centre affecting the cortex.
3.Subcapsular cataract – When opacities are seen near the capsule it is termed subscapular. This subtype is commonly seen in diabetic individuals or those taking high doses of oral corticosteroids.

These cataracts can be further classified depending on the location of the opacity through the lens – anterior, posterior etc.
Congenital cataracts are those in which lens opacities are observed from the birth and commonly seen in genetic disorders or any intrauterine infections while age related cataracts are termed as senile cataracts.

If the whole lens is opaque the cataract is termed mature and the lens appears as milky white obstructing complete vision in that eye. Any cataract which is not completely opaque are termed immature cataract.

 

 

Do I have cataract? (Signs and symptoms)

Cataract develops slowly and painlessly and is not a tumour and not contagious. It may affect one eye or gradually both eyes. The vision gets affected only when the cataract has involved large portion of lens. In the initial stages no symptoms may be noted.

When the lens opacity is large enough you may notice blurring of vision as if looking through a frosted, cloudy glass. You may experience excessive glaring from the oncoming headlights while driving. The sunlight may appear too bright. Halos may be seen around objects.

Contrast sensitivity is lost and colours appear dull, there are problems seeing shape against a background.

In some individuals there can be improvement in near vision, termed second sight. Unfortunately, this effect is short lived and eyesight worsens as cataract matures.

What tests are needed to be done?

A standard eye exam and a slit lamp examination is all that is needed to diagnose cataracts. Some may require further workup if secondary causes of cataracts are suspected.

How is cataract treated?

For many people in initial stages use of bifocal spectacles, better lighting, magnifying glasses, sunglasses to reduce glare can help.

But for these in whom vision is deteriorating and daily activities of life are hampered the cataract surgery is to be considered.

Cataract surgery is simple and relatively painless procedure where the clouded lens is taken out and replaced with an artificial intraocular lens. You get admitted in the morning for the surgery and can get discharged by the end of the day. This surgery can be performed whenever you feel like and is not an emergency surgery unless the cataract has matured to such an extent that the lens content seeps out into the eye causing inflammation and glaucoma.

Will surgery cure me completely?

Complete 20/20 vision cannot be guaranteed if there is associated other eye disorders like macular degeneration, glaucoma, retinopathy.

How do I prevent cataract?

Even though cataract is an age related process, various preventive measures can help slow down the progress of cataracts. This includes:

1.Use of sunglasses with UV filter
2.Quitting smoking
3.Tight sugar control in diabetic
4.Regular eye checkup

References:

•Common Causes of Vision Loss in Elderly Patients - July 1999 - American Academy of Family Physicians". Aafp.org. 1999-07-01. Retrieved 2011-11-22.

•eMedicine - Cataract, Senile : Article by Vicente Victor D Ocampo. From eMedicine The Continually Updated Clinical Reference