Eye Diseases What is Cataract?

Human eye has a natural lens which is normally transparent and forms a clear image of the outside world in the eye. When this lens develops haziness or opacity, the sight is decreased or may be completely lost - this is called cataract.


What causes Cataract?

When a cataract forms, there is a change in the chemical composition of the lens, but scientists are not clear about what causes these chemical changes. The most common form of cataract is related to aging, although this type can occur around the age of 50 or even earlier. Cataracts also may be associated with diabetes, other systemic diseases, drugs, and eye injuries. Sometimes babies are born with congenital cataracts or develop them during the early years of life.

What are the Symptoms of Cataract?

Cataracts usually develop gradually, without pain, redness, or watering in the eye. The most important symptom of cataract is a decrease in vision or eye sight for distance & or near objects. Other features can be decreased vision in bright or low light, decreased contrast, glare, altered color appreciation, seeing many images of one object, rapid changes in the number or power of glasses, or rarely pain, redness and watering. Affected persons may have a feeling of having a film over the eyes and may blink frequently in an effort to see well. In advanced cases there is complete loss of sight and pupil becomes pearly white in color. However, none of these symptoms are seen exclusively in cataract. Some cataracts never progress to the point where they seriously impair vision, whereas others eventually block most or all vision in the affected eye. The effect of a cataract on vision depends on several things like - its size, its density and its location within the lens. In certain types of cataract, night driving becomes harder because the cloudy part of the lens scatters the light from on-coming headlights, making these lights appear double or dazzling. Also, the person with a cataract may have trouble finding the right amount of light for reading or close work.

What should one do?

The first thing a person must do on experiencing any of these symptoms is to consult an eye surgeon (Ophthalmologist) giving details of ones symptoms and getting ones eyes thoroughly examined. Answers to the following questions should be sought -

• Do I have cataract ?
• Do I have any other eye disease ?
• What is the cause of cataract in my eye ?
• What are the treatment modalities available ?
• What treatment would be most suitable for me ?
• What is the expected outcome of the treatment or surgery in my case ?
• What are the risks involved and possible complications ?
• How long can I wait before I get operated ?
• What does the surgery involve in terms of time and expenditure ?

Once it is decided that the patient has cataract the treatment is essentially surgical, the only question that arises is when? The decision is patient's - whenever the patient feels his vision has decreased to a level where he finds it difficult to carry on his routine daily activities he can get operated (no longer is it required for the cataract to become mature). However, in certain cases where there are associated complications or potential risk of complications, an early (even urgent) operation may be required - where the advice of consulting eye surgeon should be followed.

How is Cataract Operated?

The contemporary standard procedures done to remove cataract and restore vision are -

1. Extra-capsular Cataract Extraction (ECCE) with Intra-ocular Lens (IOL) Implantation.
2. Phacoemulsification with Foldable Intraocular Lens (IOL) implantation
   (No-Stitch Surgery).

ECCE with IOL implantation is the conventional procedure. It involves making an incision (about 6-8 mm) at the edge of cornea (junction of black with the white of the eye in the upper part) followed by making an opening in the capsule of the lens. Through these openings the nucleus (hard portion) of the lens is expressed and cortex (soft portion) of the lens is sucked out. IOL is inserted and positioned either inside the capsular bag or over the capsule (if the capsular support is deficient then IOL is positioned in the anterior chamber or may not be implanted at all).The incision is then sutured (stitched) using micro-fine suture material. In most cases these sutures are not required to be removed.

In Phacoemulsification the incision is much smaller self sealing (about 3 mm) and the nucleus of the lens is converted to a pulp using high frequency ultrasound sound waves and sucked out. Then a foldable IOL is inserted through this small incision and positioned into capsular bag. The main advantages of this operation are early rehabilitation and decreased occurrence of high astigmatism (cylindrical power in glasses). All these operations are done under local (or topical) anesthesia which makes the eye and surrounding area numb and senseless, and the patient although conscious does not feel any pain or discomfort. General anesthesia, which has its own risks, is used only in children and uncooperative patients.

What is an Intra-Ocular Lens (IOL)?

Intra-ocular Lenses (IOL) are small (5-7 mm) lenses made of Silicone, Acrylic or PMMA, and are implanted inside the eye in place of natural lens. The greatest advantage of IOL is a clear wide field of vision and the fact that the patient does not have to constantly wear thick glasses. However, glasses with low power may be still be required. The reason being that unlike natural lens the IOL has a fixed power (estimated by doing pre-operative Ultrasound Biometry) which is usually adjusted such that the mid-range or routine viewing distances are seen clearly, and for distances closer or further low powered glasses may still be needed.. The IOL stays in the eye lifelong and usually does not create and problem or discomfort to the patient.

"Have realistic expectations" - The surgical technique and the quality of the IOL are not the only factors that decide the result of cataract surgery; but also the condition of the eye otherwise, the cornea, the retina and the presence of systemic diseases like diabetes, hypertension, asthma, infections, etc. Though the overall results are excellent with restoration of good vision, yet it is not possible to duplicate nature's gift of vision.