Cataract

Cataract

A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light.

 The natural lens sits behind the colored part of the eye (iris) in the area of the pupil, and cannot be directly seen with the naked eye unless it becomes extremely cloudy. The lens plays a crucial role in focusing unimpeded light on the retina at the back of the eye. The retina transforms light to a neurologic signal that the brain interprets as vision. Significant cataracts block and distort light passing through the lens, causing visual symptoms and complaints.

Early in the development of age-related cataract the power of the lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colours. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated. The condition usually affects both eyes, but almost always one eye is affected earlier than the other.

 Many people are in fact unaware that they have cataracts because the changes in their vision have been so gradual.

When people develop cataracts, they begin to have difficulty doing activities they need to do for daily living or for enjoyment. Some of the most common complaints include difficulty driving at night, reading, participating in sports such as golfing, or traveling to unfamiliar areas; these are all activities for which clear vision is essential.

Cataracts are very common, affecting roughly 60% of people over the age of 60, and over 1.5 million cataract surgeries are performed in the United States each year.



Causes of Cataract

Cataracts develop for a variety of reasons, including :

. Long-term exposure to ultraviolet light

. Exposure to radiation

. Secondary effects of diseases such as diabetes, hypertension 

. Advanced age, or trauma (possibly much earlier)

. The use of certain medications, such as oral, topical, or inhaled steroids. Other medications that are more weakly associated with cataracts include the long-term use of statins and phenothiazines.

. Exposure to microwave radiation .

. Atopic or allergic conditions are also known to quicken the progression of cataracts, especially in children.

 They are usually a result of denaturation of lens protein. Genetic factors are often a cause of congenital cataracts and positive family history may also play a role in predisposing someone to cataracts at an earlier age, a phenomenon of "anticipation" in pre-senile cataracts. Cataracts may also be produced by eye injury or physical trauma.



Classification of cataract

1.  Age-related cataract

A. Senile Cataract   ( an initial opacity in the lens, subsequent swelling of the lens and final shrinkage with complete loss of transparency in eldery)

a.Cortical Senile Cataract   ( opacities are most visible in the outside of the lens which is called the lens cortex)

·         Immature senile cataract (IMSC): partially opaque lens, disc view hazy

·         Mature senile cataract (MSC): Completely opaque lens, no disc view

·         Hypermature senile cataract (HMSC): Liquefied cortical matter: Morgagnian cataract

b. Senile Nuclear Cataract   ( the central portion of the lens is most affected, which is the most common situation)

·   Cataracta brunescens

·   cataracta nigra

·   cataracta rubra

B. Congenital cataract      ( Cataracts that occur at birth or present very early in life during the first year of life )

·         Sutural cataract

·         Lamellar cataract

·         Zonular cataract

·         Total cataract

These cataracts require prompt surgical correction or they may prevent the vision in the affected eye from developing normally.

2. Secondary cataract

Slit lamp photo of anterior capsular opacification visible a few months after implantation of Intraocular lens in eye, magnified view

·         Drug-induced cataract (e.g. corticosteroids)

      3. Traumatic cataract

·         Blunt trauma (capsule usually intact)

·         Penetrating trauma (capsular rupture & leakage of lens material—calls for an emergency surgery for extraction of lens and leaked material to minimize further damage)

There is an even more specific change that occasionally happens, when the opacity develops immediately next to the lens capsule, either by the anterior, or more commonly the posterior, portion of the capsule; these are called subcapsular cataracts. Unlike most cataracts, posterior subcapsular cataracts can develop rather quickly and affect vision more suddenly than either nuclear or cortical cataracts.

People who have a higher risk of developig this form of cataract are:  people with diabetes, high farsightedness, retinitis pigmentosa or those taking high doses of steroids.

symptoms

Each type of cataract has its own symptoms. With a nuclear cataract you may notice an improvement in your near vision. This is called 'second sight'. However when the cataract gets worse this will disappear.
A subcapsular cataract may not give any symptoms in the beginning, but only in a later stage when it is more developed.

 Symptoms of a cataract

·    Cloudy or blurry vision.

·    Colors seem faded.

·    Glare. Headlights, lamps, or sunlight may appear too bright. A halo may appear around lights.

·    Poor night vision.

·    Double vision or multiple images in one eye. (This symptom may clear as the cataract gets larger.)

·    Frequent prescription changes in your eyeglasses or contact lenses.

·    These symptoms also can be a sign of other eye problems. If you have any of these symptoms, check with your eye care professional.

At first, the amount of tinting may be small and may not cause a vision problem. Over time, increased tinting may make it more difficult to read and perform other routine activities. This gradual change in the amount of tinting does however not affect the sharpness of the image transmitted to the retina.

In advanced lens discoloration the ability to identify blues and purples is decreased. Black is seen instead of purple or blue.

Treatment of Cataract

A diet high in antioxidants, such as beta-carotene (vitamin A), selenium and vitamins C and E, may forestall cataract development. Meanwhile, eating a lot of salt may increase your risk.Eating high amounts of meat increase the risk of Cataract too. 

   The study examined the dietary surveys filled out by 27,670 self-reported nondiabetic people aged 40 or over and monitored their medical records to see if and when cataracts developed. Strong correlations showed up between cataract risk and diet type.

The risk was greatest for high meat eaters (who ate more than 3.5 ounces of meat each day), and it decreased from one group to the next, in this order: moderate meat eaters, low meat eaters, fish eaters (people who eat fish but no other meat), vegetarians and vegans. In fact, the risk for vegans was roughly 40 percent lower than for the high meat eaters.

          

 you should only consider surgery when your cataracts have progressed so far that they seriously impair your vision.

Cataract surgery

 is very successful in restoring vision. In fact, it is the most frequently performed surgery in the United States, with more than 3 million Americans undergoing cataract surgery each year. Nine out of 10 people who have cataract surgery regain very good vision, somewhere between 20/20 and 20/40.

During surgery, the surgeon will remove your clouded lens and in most cases replace it with a clear, plastic intraocular lens (IOL).

New IOLs are being developed all the time to make the surgery less complicated for surgeons and the lenses more helpful to patients. Presbyopia-correcting IOLs potentially help you see at all distances, not just one. Another new type of IOL blocks both ultraviolet and blue light rays, which research indicates may damage the retina.

Risks of surgery

Some common problems can occur after surgery. These may include increased pressure, blurring from swelling, inflammation (pain, redness, swelling), and sometimes bleeding. More rare and serious problems include infection, loss of vision, or light flashes. If you experience increasing pain or a worsening of vision after surgery, you should contact your eye doctor. With prompt medical attention, almost all problems can be treated successfully.

Cataract surgery slightly increases your risk of retinal detachment. Other eye disorders, such as high myopia (nearsightedness), can further increase your risk of retinal detachment after cataract surgery.

Sometimes the eye tissue that encloses the IOL becomes cloudy after the operation and may blur your vision. This condition, called an after-cataract, can develop months or years after cataract surgery.