Types of Cataract Surgery

chillibreeze writer — Jayita Ganguly

WHAT IS CATARACT?

The word cataract arouses worry, fear, doubt, queries and myths in the mind of patients or their families. The human eye has a natural lens, which is normally transparent, and forms a clear image of the outside world on the retina. Any clouding or haziness of this lens is called cataract.

AETIOLOGY

Cataract may develop at any age - right from birth to old age. It is commonly seen in the elderly, after the age of 60, as a normal aging process. It may also be seen in the young due to:
-ocular diseases like uveites
-systemic diseases like diabetes
-trauma
-radiation
-infections and a host of other causes.

SYMPTOMS

1) Decrease in vision for distant and/or near objects
2) Decreased vision in bright or low light
3) Decreased contrast
4) Altered color perception
5) Seeing many images of one object
6) Rapid change in number or power of glasses

Once a person experiences any of these symptoms, a thorough examination by an ophthalmologist is highly advisable. Once a cataract is diagnosed, the treatment is essentially surgical. The only question is WHEN?

WHEN TO GO IN FOR SURGERY?

The decision to get operated lies entirely with the patient. Whenever the patient feels this impaired vision interferes with routine daily activities, surgery can be undertaken. However in certain cases where there are associated complications or a potential risk of complications, an early or even an urgent surgery may be required. Then the advice of the consulting surgeon must be followed.

TREATMENT MODALITIES

Cataracts have been one of the greatest beneficiaries from advances in technology. Now the surgery is a simple out patient procedure. The stay at an ambulatory surgery centre is a few hours and recovery time after surgery is dramatically reduced. Most people enjoy good vision with minimal dependence on corrective eyewear.

EVOLUTION OF CATARACT SURGERY

1) INTRACAPSULAR CATARACT EXTRACTION - A few years ago, the accepted method of cataract surgery was to open the anterior chamber of the eye and pluck out the lens known as intracapsular cataract extraction. This required the cataract to be ripe or firm enough for the surgeon to be able to grasp. So the patient had to wait for the cataract to mature, which led to a situation of minimum visibility. This method is hardly practiced now.

2) EXTRACAPSULAR CATARACT EXTRACTION - This method requires making a large incision 10-12 mm in length and several sutures have to be placed. It differs from intracapsular cataract extraction in that the posterior capsule of the lens is left intact. Only the anterior capsule is removed and through that opening the cataractous lens.

3) SMALL INCISION CATARACT SURGERY - This procedure involves a small self sealing incision. The shape of the incision creates a flap that takes advantage of the intraocular pressure to seal it shut.

3A) MANUAL SMALL INCISION CATARACT SURGERY (manual SICS) - Self sealing small incision cataract surgery offers several advantages in a developing country like India because a large chunk of preventable blindness is due to cataract. SICS offers a low cost solution with the advantages of early visual rehabilitation, lower chance of surgical astigmatism and better uncorrected visual acuity. A 5-6mm incision is required and a non foldable lens is used.

3B) PHACOEMULSIFICATION- This uses a small incision, about 3.2mm in size (smaller than manual SICS) but is machine dependent. It is a technique where a small probe is inserted into the capsular membrane surrounding the cataractous lens. Ultrasound is used to break up or emulsify the hard core, nucleus, of the lens into tiny pieces, which can be removed through the tip of the probe. Then a foldable intraocular lens is injected through the small incision and positioned into the capsular bag.

The advantages of suture-less small incision cataract surgery over conventional cataract surgery are many.

1) Faster recovery of good vision.
2) Faster return to normal activities.
3) Return within hours of procedure.
4) Reduces the chances of surgically induced astigmatism or ruptured sutures.
5) Shorter surgery time
6) Ability to stop surgery at any point in the procedure.
7) Less discomfort after surgery.

Not every surgery can be performed as a "no stitch" procedure. The decision to place a suture is made by the surgeon, but the number of sutures is much less compared to conventional cataract surgery.

INTRAOCULAR LENSES (IOL) - which are implanted in to the eye in place of natural lenses are small(5-7mm)lenses made of soft polymer (silicone or acrylic). Previously, polymethylmethacrylate was used as lens material. Advances have brought the use of silicon acrylate which is a soft material.

TYPES OF IOL-They may be foldable or non-foldable. They may be

1) Fixed focus monofocal-used in majority of cases. They provide quality distance vision. But they require reading glasses.

2) Multifocal-The lenses are made of multiple concentric rings that focus for near and distant vision simultaneously and the brain decides which image to ignore. As the whole lens is not devoted to the generation of each image, the quality of the vision is inevitably reduced compared to a standard monofocal lens and the risk of haloes and glare at night exists.

3) Accommodating monofocal lens - The IOL implants flexibility allows it to move inside the eye in response to the focusing action of muscles of the eye. It achieves good distance and intermediate (computer vision) without glasses. About half of these patients do not require glasses for most reading tasks and the other half generally use weak plus glasses for reading tasks.

Cataract surgery in the vast majority of cases is safe, effective and successful with over 98% achieving satisfactory vision. But as with any surgery, complications can occur. However, serious problems are not very common and most can be treated successfully.

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Jayita writes for chillibreeze.

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