When the light rays focus well on the retinal surface, we see clearly. When they focus a little in front of the retina, or behind it, we notice blurriness.
The lens is flexible and in normal, clear vision, tiny muscles change the convexity/concavity of its shape to allow us to focus well at all distances. The lens is composed of water and protein arranged so as to keep it very translucent, allowing the light to pass through to the retina unimpeded.
As We Age
The lens gradually changes as we age. The arrangement of protein and water changes so that some of the protein clumps together, creating a slight blockage to the light rays. This is a cataract. Cataracts start small, growing very slowly, and causing the light rays to scatter as they pass through it. This makes them unable to focus on the retina and we experience blurriness and over-brightness. If left untreated for long enough, the cataract can extend throughout the lens, causing loss of vision.
The earlier a cataract is diagnosed and treated, the better we can retain our vision.
Three kinds of cataracts
• Nuclear cataracts – begin to form in the center of the lens, spreading outwards, caused by aging of the lens
• Cortical cataracts – begin to form at the edge of the lens and extends inwards, often caused by diabetes
• Subcapsular cataracts – begin to form at the back of the lens, and most often diagnosed in diabetics, people on high doses of steroids, those with retinitis pigmentosa, or with severe farsightedness.
Causes of cataracts
Research is ongoing as to causes. We don’t know yet why aging should cause a cataract to form or what other factors might contribute to its formation.
Some studies have pointed to ultraviolet light, so that some eye doctors suggest we wear sunglasses and a shady hat to protect our eyes
Other studies suggest cosmic radiation as a contributing cause, as it seems that airline pilots more often develop cataracts
People with diabetes experience eye changes caused by impaired blood circulation. But they also more often get cataracts, as do people on steroids, tranquilizers and diuretics. It’s unknown as yet whether the medical conditions or the drugs are contributing more to cataracts.
Other studies have pointed to:
• Excess salt
• Heavy use of alcohol
Symptoms of cataracts
With all three types of cataracts, the symptoms are mild at first. You may notice them only in one eye.
• Blurriness or cloudiness
• Diminished brightness of color
• Glare from light sources, especially at night
The symptoms slowly increase over time. But deteriorating vision need not be an accompaniment to aging. A good eye doctor will be able to determine which type of cataract you have and advise you about cataract surgery.
This is the most often-performed out-patient surgery in the U.S. and almost all people who have it achieve excellent vision.
• Your eye surgeon will examine your eyes to determine the right power for the intraocular lens (IOL) he’ll implant for you. The IOL is made of lightweight plastic.
• A local anesthetic is given and a relaxing medication (only some patients).
• Using a microscope, the surgeon makes a tiny incision.
• Ultrasound may be used to first break up the natural lens so it can be removed more easily, or sometimes it’s removed as is. The lens’s rear membrane (posterior capsule) is left intact.
• The IOL is gently inserted and the incision closed. Dissolvable stitches may be used.
• Afterwards, your surgeon will give you an eye shield and you can go home the same day.
In some cases, the posterior capsule becomes cloudy after cataract surgery. This makes your vision blurry again, but it can be treated with a laser. The eye surgeon makes a small opening in the capsule to allow light to reach the retina as it should.