Cataracts is the Most Common Cause of Reversible Visual Loss in People Over 40

June is National Cataract Awareness Month.  Cataracts are the most common cause of reversible visual loss in people over 40, and are the leading cause of blindness in the world. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. Though very common, and an increasingly important issue, cataracts remain somewhat of a mystery to many; it is thus that I present some answers to some of the common questions posed to me in the office.

What is a cataract?

A cataract is defined as a clouding of the natural crystalline lens of the eye.  The lens, which is about the size of a lentil, lies behind the iris (the circular colored part of your eye), and is the main focusing element of the eye.  It is composed mostly of protein fibers and water, and is clear in its ideal state so as to allow light to focus on the retina in the back of the eye.  (see fig 1) As we age, the natural composition of the lens starts to change, and causes the lens to be less clear.

Are there different types of cataracts?

Yes, there are several different subcategories, based on where the cloudiness of the lens is most notable. A nuclear sclerosis cataract is the most common type associated with aging. As we get older, the central fibers in the natural lens harden and yellow.  A subcapsular cataract is when the clouding occurs primarily on the posterior or anterior surface of the natural lens.  A cortical cataract is a spoking of the lens, and is associated with wedge-like opacities in the material surrounding the center of the lens. (See Figs. 2 and 3.)

You mentioned age. Are there other causes and risk factors?

While age is indeed the number one cause of cataract formation, there are a number of other risk factors which can lead to generalized, or focal, clouding of the lens.  Nuclear cataracts are also associated with ultraviolet light exposure, cigarette smoking, poor nutrition, and diabetes. Prior trauma, including any type of intraocular surgery (including LASIK or other refractive surgeries), can also greatly speed the formation of any type of cataract. Posterior subcapsular cataracts generally occur in younger patients, especially those with Type 1 Diabetes. Chronic use of corticosteroids in any form, be it on the skin, in eye drops, or orally are also classically associated with this type of cataract. Previous intraocular inflammation (iritis, uveitis), previous radiation to the eye or surrounding tissue, and  trauma can also lead to this type of early-forming cataract. Lastly, cortical cataracts are also linked to diabetes, as well as ultraviolet light exposure and smoking.

How do I know if I have a cataract? What are the signs I should be aware of?

The signs and symptoms vary a bit with the type of cataract that one has, but all cataracts lead to a degradation of one’s best corrected vision.  In other words, changing your glasses or contacts, however frequently, no longer seems to work to sharpen up your vision. Generally, people note a progressive loss in vision, and may even experience dramatic shifts in the power of their glasses or contacts, depending on the way the cataract is growing. In fact, there is even an interesting phenomenon known as “second sight”, in which one’s vision shifts so dramatically that reading glasses are no longer needed. (This does tend to be only a transient benefit, but is enjoyable by many who have worn reading glasses since they turned 40!)

Other signs may include doubling of vision through one eye, due to the distortion of the light rays as they enter the eye through a cloudy lens. (See Fig. 4.) People with very yellow lenses may also note changes in their perception of color and hue saturation, and may also need much more light to read than before. In addition, people with capsular cataracts may find their reading vision is much worse than their distance vision, due to the central clouding of the lens.  Glare, halos, and worsening vision in bright light are also very common complaints of people with maturing cataracts.  (See Fig. 5.)

What, if anything, can I do to prevent cataract formation?

To some degree, developing a cataract is like getting wrinkles or laugh lines; we are going to get some naturally as we age, but the amount we get may be influenced by how we take care of ourselves.

My first three recommendations are sunglasses, sunglasses, sunglasses! We know that ultraviolet light is a bad player in skin diseases, and the eye is no exception when it comes to its vulnerability. Get yourself a good pair of sunglasses, and not off a street vendor, no matter how tempting the bargain is; there is no guarantee in UV protection in these ubiquitous glasses, and even if they shield your eyes, UV rays may still be getting through.

Next, cease and desist all cigarette smoking, not just for your general health, but also due to the link to cataract formation, as well as other important eye diseases like macular degeneration.  Eat a well-balanced diet with green vegetables, in light of the role that nutrition can play in the aging process. Last, but not least, be proactive and see your ophthalmologist for a thorough eye exam, to look for and rule out all potential causes of visual loss.

What should I do if I’ve been told I have a cataract?

First, do NOT panic. Again, a cataract is part of the normal aging process, and just having some changes in the natural lens of your eye is no cause for alarm, or to sign yourself up for surgery the next day. A good refraction with an ophthalmologist or optometrist can often do wonders to improve your vision significantly, as will using better light for reading. When you can no longer do the things you enjoy, be it playing tennis or reading, then you will know that you are ready for cataract surgery.


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