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the transparent, semi-rigid disc that sits behind the iris.


why the lens full name is the crystalline lens

When we’re young, this lens is crystal-clear (which is why its full name is the crystalline lens). But as you discovered in your reading, the lens will start to turn yellow, brown, or cloudy in most people when they’re older.

This happens because the lens absorbs the harmful ultraviolet (UV) light that enters the eye throughout a person’s life. In addition, the chemistry of the lens changes over time. Eventually, the combination of UV absorption and normal aging causes the lens to become less transparent and more opaque.


medical conditions that can cause cataracts to form at a fairly young age.

diabetics and
smokers tend to get cataracts early.
(Even children can develop cataracts as a result of diabetes. The term for this is juvenile diabetic cataracts.) People who take lots of steroid medications are also at elevated risk for early cataracts,
and preliminary research hints that other medications can have this effect as well.


There’s growing evidence that a diet rich in what can protect against cataracts

There’s growing evidence that a diet rich in antioxidants—nutrients that help protect the body against damage by destructive molecules called free radicals—can reduce the risk of cataracts. These nutrients include vitamins A, C, and E, zinc, lutein, and copper. Also, some studies suggest that eating lots of fish, which contains omega-3 fatty acids, can lower your cataract risk. This is yet another reason to choose healthy foods!


congenital cataract

when a child is born with cataracts


leading cause of severe vision loss in the united states



Why is glaucoma a "sneaky disease"

because it doesn’t have any obvious early symptoms. As a result, it’s often fairly difficult for people to know they have glaucoma unless they get an eye examination.


congenital glaucoma.

being born with glaucoma


angle-closure glaucoma

angle-closure glaucoma, pressure builds up inside the inner eye. This damages the optic nerve, because fluid can’t drain out of the eye.


normal tension or open angle glaucoma,

normal tension or open angle glaucoma, damage occurs to the optic nerve even though eye pressure is normal or even low.


what part of a persons vision with glaucoma affected?

As glaucoma progresses, a person’s peripheral (side) vision becomes more and more reduced. Eventually, the person develops advanced tunnel vision. However, the central portion of the vision remains intact. Here’s an illustration showing the vision impairment of a person with advanced glaucoma:


what to reccomend to people with glaucoma

Since glaucoma primarily affects peripheral vision, you’ll want to recommend glasses that enhance people’s ability to see to the sides. Your patients or customers should avoid thick-rimmed frames, and the frame parts that hook over the ears (called the temples) should be as thin as possible.

You’ll also want to recommend an antireflective lens coating to improve overall vision, especially at night. And be sure to suggest sunglasses to help people with glaucoma preserve the vision they have left. They certainly won’t want to develop a cataract in addition to having glaucoma! The eye medications that doctors use to treat glaucoma will often cause patients’ eyes to become red, so you might want to recommend a very light lens tint for cosmetic reasons.


two forms of macular degeneration:

wet and dry


treatments for macular degineration

Doctors can intervene surgically to slow or stop the progression of the wet type, although they can’t restore the vision that’s already been lost. The dry type, as you read, progresses much more slowly than the wet type and isn’t treatable.


Amsler grid,

one test used to measure the progression of macular degeneration.


what to reccomend to people with macular degeneration

When you’re assisting people with macular degeneration, you’ll notice that most of them have prescriptions with very high magnification. This is so we can enhance their peripheral vision as much as possible, helping to make up for their poor central vision.

As a result, these people’s lenses tend to be very thick and heavy. So instead of recommending a very large frame, you’ll want to recommend a thinner (but sturdy) frame and thinner lens materials. This will draw attention away from the thickness of their lenses.

Certain antireflective lens coatings can also help people with macular degeneration see a bit better. And, as always, you’ll want to persuade people with this condition to wear sunglasses in order to protect their remaining vision.


part of vision affected by macular degineration

the central vision is affected by macular degineration Even people with severe macular degeneration don’t become totally blind, because they still have useful peripheral vision. But because we rely heavily on our central vision for driving, reading, watching TV, and even socializing with other people, living with macular degeneration is a huge challenge.


what to reccomend to people with diabieties

If you work in a low-vision clinic, you’re likely to see many patients with partial vision loss due to diabetes. These patients typically wear magnifying lenses that are quite thick. You can help them select thinner lenses and frames that draw attention away from the lenses. Your role may also include helping these patients use telescopic lenses and other high-tech vision aids.

And as you’ve learned, patients with any eye condition that affects the retina and lens will want to protect their remaining eyesight. So you’ll want to make sure that patients with diabetes-related eye conditions have UV protection in their regular lenses and also wear sunglasses with UV protection when they go outdoors.


diabetic retinopathy,

When diabetes is uncontrolled the blood vessels in the retina can leak. may cause blind spots to develop like


Other vision problems that can result from diabetes

early cataracts and glaucoma