Saturday, November 1, 2014

Cataract and Cataract Surgery FAQs

In my line of work, I get asked lots of questions about cataracts, quite simply because they are one of the most common causes of blurred vision as one gets older.

Here goes:

1. What are cataracts? Are they a growth in the eye?

Cataracts are not growths.  One of the parts of the eye, called the lens, undergoes ageing processes over the years. A lens, like a camera or spectacle lens, needs to transmit and focus light and therefore needs to be transparent. Unfortunately age causes many lenses to become hazy and this blocks vision, much like trying to look through a dirty window.

2. How do I know if I have cataracts?

The main problem with cataracts is blurred vision. Of course, there are many other causes of blurred vision, such as shortsightedness or astigmatism. Therefore, if vision is blurry, try wearing spectacles first and see if the vision is cleared up.

If so, the problem is probably just spectacle power, or perhaps the cataracts are very mild. Significant cataracts will cause blurred vision even if spectacles are worn. Generally speaking, if vision cannot be made clear with glasses, one should visit the eye doctor to make sure there are no serious eye problems.

3. How does it feel like to have cataracts?

This is related to the prior question. Although we may think that cataracts are just a hazy lens and are the same, in fact there are a few types of cataracts that affect vision in slightly different ways. For example, vision can be clearer under certain conditions, or sometimes patients get double or triple vision.

A yellow nuclear sclerotic cataract
A yellow nuclear sclerotic cataract
One type of cataract causes the lens to become yellowish (above). This is called 'nuclear sclerosis', and the eye also becomes more and more shortsighted. Patients with this type of cataract may need to increase their shortsighted spectacle power several times a year. On the other hand, long sighted people may find their spectacle power getting less and less, and near vision getting better and better! This is sometimes called second sight.

Another type of cataract causes glare. This means that a person can see reasonably well in the dark, but when there is a bright light shining from in front, vision undergoes a 'white out', ie everything turns bright white and vision suddenly becomes very blurry. This happens with a cataract called a 'posterior subcapsular' cataract.

A very dense, white cataract
If cataracts are neglected for a long time, they can turn white (regardless of which type they originally were). White cataracts are more dangerous than other types, because they sometimes absorb water and swell. A swollen lens can physically block the drainage angle of the eye, or leak proteins which also block the drainage angle. This causes a sharp spike of eye pressure, leading to a type of glaucoma and eye pain. This is the only situation where cataracts are associated with eye pain.

4. What causes cataracts?

As mentioned, most cataracts are due to age related changes in the eye. Proteins break down, clump together, sometimes water is even absorbed into the lens causing to swell.

Besides age, there are other less common causes of cataracts. Certain medicines such as steroid eyedrops or tablets, if taken in high doses for too long a time, can cause cataracts to develop. Diabetes, which results in too much sugar in the blood, also cause cataracts to develop earlier, especially if the blood sugar levels are not controlled properly and become very high for a lot of the time. Cigarette smoking is well known to be associated with earlier cataract development as well. Finally, bad injuries to the eye, such as a direct punch or a hit in the eye can also cause a cataract to develop.

5. How can I prevent cataracts, or can I slow down their progression?

Firstly, any risk factors such as diabetes or cigarette smoking should be addressed. Modifying these risk factors will have the biggest impact on slowing cataract progression.

Secondly, eat a healthy diet full of antioxidants. In general, it is better to get these naturally from green leafy vegetables and colourful fruits, rather than supplements. However, certain nutrients may only be obtainable in large quantities in supplements.

Studies of big groups of people suggest that eating more fruits and vegetables can delay cataract development, but nothing conclusive so far can be said for individual nutrient supplements such as vitamin C.

6. How are cataracts treated?

Cataracts are treated with surgery to remove them, and at the same operation they are replaced by lens implants made of a special acrylic material.

Cataract surgery is carried out under local anaesthesia, and is painless. The hazy lens material is broken up with ultrasound, and then removed through a very small incision about 2mm long. The lens implant can then be folded and injected into the eye through this very small opening.

Recovery is very quick, with most patients seeing very well even on the day after surgery.

Sometimes patients ask me if they should wait until after their holiday to have surgery. I tell them that if time permits, to do it before, as they will enjoy the view so much more!

7. What are the latest advances in cataract surgery?

The most important developments in cataract surgery have to do with how spectacles can be avoided after surgery. Yes, no matter how high the spectacle power before surgery, most of the time spectacle wear can be avoided after surgery. How is that possible?

Focusing of light in the eye depends on the cornea, the lens, and how long the eyeball is. The shape of the cornea can be changed (in LASIK), and the lens power can be changed (in cataract surgery) to reduce or eliminate spectacle power.

A normal spherical Tecnis (AMO) lens
A Toric Tecnis (AMO) lens. Note the dots arranged in a line at the sides of the lens. This allow the surgeon to place the lens in exactly the right position to reduce or eliminate astigmatism after surgery
The Tecnis Symfony (AMO) lens. This is a multifocal lens that is also available in a toric version (right) so it can be used in most patients

Nowadays, lens implants also come in 'toric' versions to correct astigmatism, and there are also 'multifocal' lenses that give good near and far vision to avoid reading glasses after cataract surgery. 

For patients who would like clear far and near vision without glasses, and have astigmatism, there are even multifocal+toric lens implants.

Multifocal lens implants can give halos around lights at night, however, this has been minimised with newer extended depth of focus (EDOF) implants like the Tecnis Symfony (above).

Laser cataract surgery

Some surgeons are now using a type of laser to help to do certain steps of the surgery. They call this bladeless cataract surgery, much like how LASIK became 'bladeless' LASIK.

Unfortunately, using this laser to help with surgery makes the surgery much more expensive and also can result in problems that probably would not have happened if the surgery had been done with conventional phacoemulsification surgery. In the article above, 1/3 of patients had conjunctival haemorrhage, and 1/5 had anterior capsular tags. In 1/3 of patients, the pupil became smaller, making the surgery more difficult for the surgeon and increasing the risk of other complications.

Although this technology may become better with time, and surgeons will become more experienced with using it, currently this is an example of how a 'latest advance' is not necessarily better and in fact has become a kind of marketing tool.

Below is an exchange in the local newspapers in 2013, where the Singapore Academy of Medicine published a response in the Straits Times to counter certain unfounded claims put forth by proponents of the laser cataract surgery procedure:

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