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Cataract

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Overview of cataract

As people grow older the natural eye lens become opaque leading to blurred vision.

It is called cataract. It is one of the leading causes of visual disability and preventable blindness.1 As the world’s population ages, cataract-induced visual dysfunction and blindness is on the rise. Genetic as well as environmental factors contribute to its development.2,3 It can occur in one or both eyes. It gradually develops over a long period of time and the loss of vision is gradual and painless, hence people do not realize till late that they have a cataract. Therefore, it is important to have regular eye check-ups especially after the age of 60 years.

The burden of cataract blindness is a major challenge for all developing countries.4 The blindness control efforts have been successful in arresting the increasing prevalence of blindness in India and there is hope that the goals of the ‘Vision 2020 right to sight’ initiative can be achieved if there is strong political will and prioritized action.5

During 1981 to 1982 India performed around 0.5 million cataract surgeries, and this increased to 4.8 million in 2006 with 90% intraocular lens acceptance.

Development of Cataract

The lens is a clear part of the eye, which is made mostly of water and protein. It consists of three layers: the outer layer (capsule), the middle layer (cortex) and the inner layer (nucleus). It lies behind the iris and the pupil and focuses the light on the retina. In the older people the protein molecule on the lens clumps together and the lens become cloudy. It is usually start as a small, opaque spot and slowly grow larger. This cloudiness blocks the light reaching the retina, causing vision problems, which is called cataract. Vision is not usually affected until a large area of the lens becomes cloudy. Besides age related, there are less common types of cataract where lens become cloddy even in children and young people.

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Types of cataract

Cataract is classified into three different types, depending upon the part of the lens affected.

Nuclear cataract:

It is the most common cataract seen. This cataract forms in the nucleus, the center of the lens, and is due to natural aging changes and is usually visible.

Cortical cataract:

It forms in the cortex of the lens, beginning with whitish streaks that extend to the front of the lens. These cataracts are commonly seen in diabetic patients.

Subcapsular cataract:

This begins at the back of the lens. People with diabetes, high farsightedness, or those taking high doses of steroids may develop a sub-capsular cataract.

A study in 2007 showed the cumulative incidence of nuclear cataract was 29.7%; cortical cataract, 22.9%; posterior sub capsular cataract (PSC), 8.4%.7

Age-related cataracts are the most common type. Other less common types of cataracts like are:

Secondary cataract:

Cataracts can occur after some of the eye surgery, such as glaucoma. They are sometimes even linked to steroid use.

Traumatic cataract:

Cataracts can develop after an eye injury, some years later.

Congenital cataract:

Some babies are born with cataracts or develop them in childhood, often in both eyes.

Radiation cataract:

Cataracts can develop after exposure to some types of radiation.

Symptoms of cataract

Cataracts are generally painless gradually developing condition. The most common symptoms are:

  • Blurred or hazy vision
  • Light sensitivity
  • Halos around lights
  • Impaired night vision
  • Yellowing or fading of color vision
  • Double vision
  • Frequent change in spectacle prescriptions

Risk factors for cataract

The biggest risk factor for cataracts is aging. Other risk factors are

  • Diabetes
  • Family history of cataracts
  • Smoking
  • UV exposure and
  • Eye trauma

Additionally, some cataracts are congenital, meaning they are present since birth.

Diagnosis and Tests for cataract

Torch light examination can diagnose cataract. Iris shadow on the lens is seen as a milky white opacity.

Ophthalmoscopy:

The lens media appears hazy.

General examination:

To find out the conditions like diabetes or hypertension.

Detailed dilated eye examination

Detailed dilated eye examination including direct and indirect ophthalmoscopy can be done to confirm the condition.

A-scan ultrasonography

To determine the axial length of the eye and intraocular lens (IOL) power.

Complete blood investigation

Complete blood investigation including bleeding time and clotting time.

Treatment of cataract

Cataract is a progressive disease and treatment is essentially removal of lens followed by IOL or spectacles. Till date nowhere in the world an anti-cataract drug is approved for cataract. However, agents with unproven efficacy are available in some developing countries. Such agents might come up in the future, which help in delaying the onset and progression of cataract formation in humans.1

What is the Optimum Time to do Surgery?

Generally, the surgery is not required as soon as cataract is developed at same time, surgery should not be delayed till very late stage, as the chances of complication is more in that situation. Subjective feeling of the patient is also important. Generally the surgery is done when the patient feel difficulty in performing his day-to-day work like driving, work and his/her favorite hobby etc. Surgery is advised when there is any noticeable deterioration in eyesight.

The choice of surgery in the urban settings today is phacoemulsification with foldable lenses.4 Earlier, it was extra capsular extraction of lens and now it is used in selected situations.

Cataract Surgeries

Phacoemulsification or Phaco

A small incision is made on the side of the cornea, (limbus) in the manner of Z and a tiny probe is inserted into the eye. This emits ultrasound waves that soften and break the lens so that it can be removed by suction. Then, foldable lens is placed in that position and the flap is replaced without any suture. It is also called ‘small incision cataract surgery’. Today most of the cataract surgeries are done by this method.8

Extracapsular Surgery

Here a long incision is made on the side of the cornea, and the lens is removed as one piece. The remaining parts are removed by suction. Once cloudy lens is removed, often it is replaced by an artificial lens called an intraocular lens (IOL). An IOL is a clear, plastic lens that requires no care and becomes a permanent part of the eye. Some may not have an IOL because of the other eye disease or some problems during surgery. For these patients, a soft contact lens or glasses that provide high magnification may be suggested.8

Preoperative Medications

Prophylactic antibiotic capsules/tablets.

Prophylactic antibiotic eye drops.

Tab. Anxit 0.25 mg, a night before surgery.

Topical mydriatic eye drops for the dilatation of the pupil.

After the Surgery

Most of the patients notice an instant improvement in sight, although complete healing may take several months. Antibiotic and steroid combination eye drops are to be used for up to two months after surgery. Most of them go home on the same day of the surgery, and will probably be able to carry on with normal daily activities, but do think about the following:

Avoid rubbing the eye; better to wear an eye shield if the person is a restless sleeper.

Do not lift any heavy things, and avoid strenuous exercise and swimming.

If it is windy, take care of your eyes.

Take care of washing the hair; avoid getting soapy water in the eye.

Avoid wearing eye make-up until complete recovery.

Possible Problems

Operative procedure for cataract is one of the most successful operations. An unforeseen serious complication occurs in less than 2% of patients. Thickening of the lens casing the part of the eye that holds the lens in place is among the most common and easily correctable complications. This is treated by laser treatment.3

Prevention of Cataract

Cataract is a natural age-related process and cannot be prevented. There are certain measures, which can reduce the risk of its development or can slow down its progression:

By reducing exposure to UVB radiation wearing sunglasses and a hat with a brim and avoiding direct UV exposure.

By smoking cessation.

A good nutritious diet including green leafy vegetables, fruits and other foods with antioxidants can help reduce the risk of age-related cataract.

The National Eye Institute suggests that if one with the age of 60 years you should have an eye exam at least every 2 years.8 Widespread surgical services capable of delivering good vision rehabilitation accessible to all in need can help reducing disability and blindness.3 Appropriate treatment at appropriate time can save the eye sight.

References

1.Gupta SK, Joshi S, Velpandian T, Awor L, Prakash J. An update on pharmacological prospectives for prevention and development of cataract. Indian J Pharmacol. 1997; 29: 3-10.

2.Khandekar R, Sudhan A, Jain BK, Shrivastav K, Sachan R. Pediatric cataract and surgery outcomes in Central India: A hospital based study. Indian J Med Sci 2007; 61: 15-22.

3.Brian G, Taylor H. Cataract blindness - challenges for the 21st century. Bull World Health Organ. 2001; 79. 3.

4.Srinivasan A; Aravind H; Syeda STB. Curr Opin Ophthalmol. 2008; 19(1): 60–65.

5.Murthy GV, Gupta SK, Bachani D, Jose R, John N. Current estimates of blindness in India. Br J Ophthalmol. 2005; 89(3): 257–260.

6.Wilson ME, Thakur SKJ. Paediatric cataract blindness in the developing world: Surgical techniques and intraocular lenses in the new millennium. Br J Ophthalmol. 2003; 87: 14–19.

7.Klein BE, Klein R, Lee KE, Gangnon RE. Incidence of age-related cataract over a 15-year Interval: The Beaver Dam Eye Study. Ophthalmology. 2007.

8.National Eye Institute, USA. The National Institutes of Health (NIH). 2007;

Written by: healthplus24.com team

Date last updated: December 29, 2014