What causes Cataracts?
Cataract Types and Effects

I often get asked "What causes cataracts?" For most people the answer is AGE. The lens of the eye ages due to accumulation of years. Causes of cataracts also include UV radiation, medications and illness. In the same way that some people's skin ages faster or slower, there are variations in the age at which cataract occurs. Most people in Australia are into their late 50s to 60s when cataract is diagnosed.

Senile cataract is not a term generally used anymore. It used to refer to cataract that was a result of aging rather than a disease or trauma etc. These days, they are classified by their location in the lens. Each location actually has some differences in symptoms and effects. This is apart from the fact that no-one likes being called senile!

What Causes Cataracts: Nuclear Cataract

This is the most common type in my experience. It is the result of the natural aging processes in the eye. The oldest, innermost sections of the lens gradually turn yellower with age. At this point it is called nuclear sclerosis. Your clarity of vision may not be affected at all.

With more time, the transparency of the lens decreases enough to affect your vision. This is when it is a clinically significant cataract. Your Optometrist won't mention it until this point - it is not worth calling it a cataract until it is interfering with vision. So, if your vision is still 20/20 you have nothing to worry about. Your lenses will gradually age as you do. Good diet and exercise, not smoking and wearing sunglasses and a hat outside are the main things we can do to delay the onset of cataracts.

The Nuclear type will frequently affect the clarity of your distance vision before worsening your near vision. Changes to the structure of the lens can cause your glasses prescription to change, typically getting more short-sighted.

(Although, some companies have homeopathic preparations (cataract eye drops) that claim to be able to slow down or reverse the affects of aging on the lens. I have not been able to find any published clinical trials on these yet)

Cortical Cataract

This cataract type occurs in the outer layers of the lens (the Cortex). It features spoke-like or radial opacities in the lens periphery that don't affect vision much until they impinge on the central pupil zone. This type can make your vision change more rapidly, depending on the location of the spokes. You can also get double vision if you're unlucky!

What causes cataracts to present as one type or another? Just lucky, I guess. Aging causes both nuclear and cortical types, often at the same time, as well.

Posterior Subcapsular Cataract

As you can see in the name, this type occurs just inside the capsule that holds the lens in place and it is in the back of the lens. Unfortunately, the majority of light passing into the eye has to go through this point, so a tiny opacity can really affect your vision!

Most commonly, this type is the result of prolonged use of Corticosteroids and some other medications. The higher the dose and the longer the course of treatment, the more likely you are to develop some opacity here. By reducing the dose and duration of treatment, the production of cataract can be reduced. Damage that is already done cannot be reversed.

People who are on these medications should be monitored by their Optometrist and General Practitioner or Specialist at least every six months. This type may also occur in diabetes, trauma or radiation.

Congenital Cataract

These are opacities in the embryonic lens, so they end up in the inner layers of the lens. There is very little effect on vision if these are small. If a child is born with a large enough cataract that it prevents them having clear vision, it must be removed early or they will not be able to develop vision in that eye. What causes these cataracts varies but the important ones are diseases during gestation (such as Rubella) or a metabolic disorder.

Other causes of cataract:

• Blunt or penetrating trauma
• x-ray radiation
• Electrocution
• Copper or iron particle left in the lens from penetrating injury
• Intra-Ocular inflammation
• Diabetes

Read Cataract Eye Surgery for a helpful discussion of when to have cataract surgery and when to leave well enough alone....