Dr. Rizwana Khan

Cataracts

Cataracts - what are they?

Your eye works a lot like a camera. Light rays focus through your lens onto the retina, a layer of light-sensitive cells at the back of the eye. Similar to photographic film, the retina allows the image to be “seen” by the brain.

Over time, the lens of our eye can become cloudy, preventing light rays from passing clearly through the lens. The loss of transparency may be so mild that vision is barely affected, or it can be so severe that no shapes or movements are seen—only light and dark. When the lens becomes cloudy enough to obstruct vision to any significant degree, it is called a cataract. Spectacles or contact lenses can usually correct slight refractive errors caused by early cataracts, but they cannot sharpen your vision if a severe cataract is present.

The most common cause of cataracts is aging. Other causes include trauma, medications such as steroids, systemic diseases such as diabetes, and prolonged exposure to ultraviolet light. Occasionally, babies are born with a cataract.

Cataracts typically develop slowly and progressively, causing a gradual and painless decrease in vision. Other changes you might experience include blurry vision; glare, particularly at night; frequent changes in your eyeglass prescription; a decrease in colour intensity; a yellowing of images; and in rare cases, double vision.
As the eye’s natural lens gets harder, farsighted (presbyopic) people, who have difficulty focusing up close, can experience improved near vision and become less dependent on reading glasses. However, nearsighted (myopic) people become more nearsighted, causing a worsening in their distance vision. Some kinds of cataracts affect distance vision more than reading vision. Others affect reading vision more than distance vision.

Reducing your exposure to ultraviolet light by wearing a wide-brimmed hat and sunglasses may reduce your risk for developing a cataract, but once one has developed, there is no cure except to have the cataract surgically removed.

With a routine, outpatient surgical procedure, an ophthalmologist can remove the cataract, making either a small incision (phacoemulsification) or a larger incision (extracapsular extraction). Usually, a synthetic intraocular lens (IOL) is inserted at the time of cataract extraction to replace the focusing power of the natural lens. IOLs can be monovision (fixed-focus for a preset distance) or Multifocal, which allows focused vision at many distances. The time to have cataract surgery is when the cataract is affecting your vision enough to interfere with your normal lifestyle.

Cataract surgery is a very successful operation. One and a half million people have this procedure every year in the United States, and 95% have a successful result. As with any surgical procedure, complications can occur during or after surgery, and some are severe enough to limit vision. But in most cases, vision, as well as quality of life, improves.

IOL - Intraocular Lens

An intraocular lens (IOL) is a tiny, lightweight, clear plastic or silicone disc placed in the eye during cataract surgery. An IOL replaces the focusing power of the eye’s natural lens.

Your eye’s natural lens plays an important role in focusing images on the retina.

When a cataract develops, the lens loses its clarity. Light rays cannot focus clearly, and the image you see is blurry. Spectacles or contact lenses usually can correct slight refractive errors caused by early cataracts, but they cannot sharpen your vision if an advanced cataract is present.

The only treatment for cataract is to remove the eye’s natural lens and replace it with an Intraocular lens. This procedure is most commonly carried out via small incision cataract surgery. Mostly this surgery is carried out as a day case procedure under commonly local anaesthetic.

The surgeon makes a few small incisions close to the edge of the cornea and then inserts a small, ultrasound instrument to break up the center of the eye’s natural lens. The lens is then vacuumed out through one of the incisions. The surgeon folds and inserts the IOL through the same incision. These incisions are usually self-sealing often requiring no stitches.

The intraocular lenses implanted offer many advantages. Unlike contact lenses, which must be removed, cleaned, and reinserted, the IOL remains in the eye after surgery.

The rapid evolution of IOL designs, materials, and implant techniques has made them a safe and practical way to restore normal vision after cataract surgery.

The most common type of IOL is the monofocal or fixed-focus IOL. The monofocal lens helps you attain clearer vision at one distance. Note that Spectacles or contact lenses are still required in order for you to see clearly at all ranges of distance.

Another type of IOL is the multifocal IOL. The multifocal lens has several rings of different powers built into the lens. The part of the ring you look through will determine if you can see clearly at far, near, or intermediate distances. These lenses offer spectacle independence for most of patients daily activities.

Risks associated with implanting IOLs include overcorrection or under-correction, infection, increased floaters, retinal detachment, dislocation of the implant, halos, glare, dry eye, decreased contrast sensitivity, clouding of a portion of the IOL, and loss of vision.

If you are going to have cataract surgery, you and your ophthalmologist should discuss which IOL may be best for your vision needs.

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