InSight #4: Sunglasses

Sunglasses are more than just a fashion statement:  wearing a good pair of shades is one of the most important things you can do for your eyes.  If your eyes are unprotected, UV rays can damage them, increasing your risk for eye disease later in life.  If you’re confused about mirror coatings, polarized lenses, lens colour, the difference between cheap and inexpensive sunglasses, read on to find out the answers!

Do darker sunglasses (that you can’t see my eyes through) protect from UV rays better than lenses that are lighter in colour?

• No.  Dark lenses don’t necessarily provide more UV protection than lighter shaded ones.  While darker-tinted lenses are appropriate for very bright conditions (or from people whose eyes are more sensitive to light), experts recommend medium-tinted lenses for day-to-day use.

Does it matter what lens colour I choose?

• Yes.  For the best colour perception, lenses should be grey, amber, brown, or green.  Green lenses are recommended for ordinary, day-to-day use as they offer good colour contrast and minimal colour distortion.  Red, orange, blue, or purple tints can cause colour distortion and let in too much light.

Do I need expensive sunglasses or are inexpensive ones just as good?

• You don’t need expensive shades.  Look for a label or tag indicating the level of UV protection.  A cheap pair of sunglasses offering a high UV protection is a safer bet than an expensive pair with low UV protection.

What percentage of UV protection should I look for in sunglasses?

• There are two kinds of UV rays:  UVA and UVB.  We recommend shades that block 99 to 100 per cent of UV radiation—and make sure that includes both UVA and UVB.  If you buy a pair of sunglasses that don’t block UV rays, you could be doing even more damage to your eyes.  Sunglasses that just shade your eyes without adequately blocking UV radiation can cause your pupils to dilate in the sun, allowing in more rays.

What is the best style of sunglasses to protect my eyes?

• Large-framed, close-fitting, wraparound shades offer the best protection.  The lenses should be big enough to shield your eyes from all angles (above, below, left, and right), and block light coming in around the frames.  If you wear shades while playing sports, make sure the lenses are made from shatter-resistant polycarbonate, not glass.

When should I wear my sunglasses?  What about children?

• You should wear them anytime you are outside—winter or summer—and experiencing sunlight or reflected light (for example from water or a ski hill).

Anyone who spends a great amount of time outside at work or play should be particularly alert.  Shades are also recommended for people who have had cataract surgery or who take certain medications, such as tranquilizers, sulfa drugs, or birth control pills, which can increase the sensitivity of your eyes to light.

Children who play outdoors should also wear sunglasses.  Children’s shades should be impact-resistant, with bendable frames and unbreakable, polycarbonate (not glass) lenses.  

With UV exposure, your risk of eye disease builds over time.  The more UV rays your eyes absorb over your lifetime, the greater your risk of conditions such as age-related macular degeneration (AMD) and cataracts later on.  Taking steps now can really pay off down the line.

What are polarized lenses for?

• This type of lens blocks glare caused by reflection from flat surfaces.  For this reason, they are recommended for driving, boating, fishing, skiing, or any other activity where there is a chance of glare from water, snow, or the ground.

What about photocromatic lenses that lighten or darken in response to UV light? Are they sufficient in bright conditions?

• Yes, they are sufficient for bright conditions. However, bear in mind that photocromatic lenses take a few minutes to lighten or darken when going from one light situation to another.

What about lenses that clip on to my existing glasses?  Do they work?

• Clip on sunglass lenses are worn over top of your prescription glasses.  While handy, clip-ons might not fully. 

InSight #3: Sun Protection

As people are increasingly becoming aware of the dangers of ultraviolet rays and are learning that overexposure the sunlight may do permanent damage to their eyes, the demand has grown dramatically for lenses that can protect eyes from UV light.

Short term exposure to UV unquestionably causes a temporary inflammation for the front of the eye, resulting in redness, itching, and a gritty feeling.  Of more concern, however, is the growing evidence of long term exposure to UV that can contribute to the formation of cataracts.  There is also some evidence that it might contribute to some retinal disorders.  Therefore, may optometrists are advocating UV-protecting glasses.

Ideally, your doctor would recommend a lens that blocks 100% of the UV rays below 390 nanometers in wavelength.  Realistically speaking though, even some of the good materials might transmit 1 or 2%.  This level of UV protection can be found in both dark and clear lenses, prescription and nonprescription lenses.  

Shopping for Sunglasses

To judge the quality of non-prescription sunglasses, first check to see if your eyes are visible through them. If they are, then the glasses aren’t dark enough.  The lenses should screen out 75-90% of the light.  (This test won’t work with light-sensitive lenses like transitions or photo-gray because they are nearly clear indoors).
Next, hold the glasses at arm’s length and look through them at a straight line, like the edge of a door. Slowly move the lens across that line.  If the straight edge distorts, sways, curves or moves, the lens is not optically acceptable.  It’s hard enough to squint in the sun all day and yet have your body relaxed enough to play well and concentrate on a set of tennis or a round of golf.  You are looking for distortion-free sunglasses.  
Check to be sure that the lens tint is not darker in one area than another and that one lens is not darker than the other. Finally, check the frame, the hang-tag or the case for the level of UV protection.  The closer you get to 100%, the better.

Another question you might ask your eye doctor is whether it is necessary to wear sunglasses in the winter.  Even though the sun’s rays may feel less intense during the winter, they are still strong enough to worry about eye damage, including snow blindness.  New snow can reflect up to 80% of UV rays, according to the World Health Organization, while normal ground surfaces and bodies of water tend to reflect less than 10%.  The numbers for beach sand and sea foam are estimated at 15% and 25%.

In addition, what if you’re wearing contact lenses that have UV protection?  Because such lenses can decrease the amount of UV rays the enter the cornea and affect the eye structures beneath, this is a good idea.  However, you still need to wear sunglasses over contacts because UV rays will still affect the eye tissue that is not covered by the contact lenses.  Your eyes will be more comfortable too, with the light and glare reduction that sunglasses provide.

Sun Gazing

If you gaze at the sun for longer than a minute, sun gazing can literally burn a hole in the retina.  In the early stages, the retinal tissue swells and the retinal pigment is destroyed.  Several months after the exposure, a small gray lesion will appear in the center of the macula.  After several weeks, the lesion fades and is replaced by a tiny hole.  Since the very center of the macula, the fovea, is responsible for sharp vision, acuity may drop to 20/200 following sun gazing.  Symptoms generally develop a few hours after exposure.  An aching feeling develops over the eyes and there may be a vision defect in the central field.  The individual may also experience wavy vision and colour defects.  

Sun gazing can inflict serious damage to sensitive retinal tissues which will result in a severe loss of vision.  There is always an increase in this problem following an eclipse.  Be careful!!  It is important that proper glasses be used and that you never stare directly at the sun!

InSight #2: Macular Degeneration

Macular degeneration, often called AMD or ARMD (age-related macular degeneration) affects an estimated one million Canadians and is most common in people over 50.   Vision loss from macular degeneration is a growing problem because of an aging population.  AMD can be devastating, but with proper support sufferers can livesatisfying and independent lives.

AMD occurs with degeneration of the macula, which is the part of the retina responsible for the sharp, central vision needed to read or drive.  Because the macula primarily is affected in AMD, central vision loss may occur.

Dry Macular Degeneration
(non-neovascular)

• Dry AMD is more common and occurs because the tissue beneath the retina thins as we age.  It progresses over a matter of years.
• Dry AMD is diagnosed when yellowish spots (know as drusen) begin to accumulate typically around the macula from deposits or debris from deteriorating tissue.  Gradual central visual loss may occur, but it is not as severe as wet AMD.

Wet Macular Degeneration
(neovascular)

Dry AMD progresses to this more advanced and damaging form of the eye disease in about 10 percent of cases.  With wet AMD, new blood vessels grow beneath the retina and leak blood and fluid.  This leakage causes permanent damage to light-sensitive retinal cells which die off and create blind spots in central vision.

Wet AMD falls into two categories:

• Classic:  When blood vessel growth and scarring have very clear, delineated outlines observable beneath the retina, this type of wet AMD is known as classic choroidal neovascularization (CNV), and usually produces more severe vision loss. 
• Occult:  New blood vessel growth beneath the retina is not as pronounced, and leakage is less evident in the occult CNV form of wet macular degeneration, which typically produces less severe vision loss.

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Normal VIsion

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Vision With Macular Degeneration

Controllable Risk Factors
Smoking: This is a major risk factor.  A British study found about 25% of AMD cases causing severe vision loss to be directly associated  with smoking.  Another study showed that people living with a smoker doubled their chances of developing AMD.

Over exposure to the sun : Wear a hat when outside and sunglasses with at least 98% UV protection.

High Blood Pressure

Obesity and Inactivity:  Overweight patients with AMD had more than double the risk of developing advanced forms of the disease compared with people of normal body weight.  In the same study, those who performed vigorous activity at least three times weekly reduced their risk of developing advanced AMD, compared with inactive patients.  Make sure you maintain a low-fat diet and a healthy weight. 

Drug Side Effects  Some cases of AMD can be induced from the side effects of toxic drugs.  Make sure to tell your eye doctor if you are taking any medications or drugs for other conditions you may have.

Symptoms

• Blurred or fuzzy vision
• Straight lines that appear wavy or crooked
• Decreased contrast or colour sensitivity
• Difficulty seeing at a distance
• A small but growing blind spot in the center of vision

More Information

 If you would like more information on diabetic retinopathy, talk to your eyecare professional or check out the following online resources available to you. 

• CNIB
  • www.cnib.ca
• Canadian Opthalmological Society
  • www.eyesite.ca
• Canadian Association of Optometrists
  • www.opto.ca

InSight #1: Diabetic Retinopathy

What is it?

Diabetic Retinopathy is an eye condition where elevated blood sugar levels cause blood vessels in the eye to swell and leak into the retina. 

Without treatment, it can result in uncorrectable vision loss or even blindness.  However, with regular, comprehensive eye exams by your eye doctor, it can be detected early and treated.

Symptoms

In the early stages of Diabetic Retinopathy, there are often no symptoms and your vision still may not be affected.

People with proliferative retinopathy or macular edema may experience vision loss when blood from leaking blood vessels blocks the field of vision.  However, at this stage, if is still possible to have no noticeable symptoms, or for symptoms to occur suddenly with no apparent warning.

That is why it is so crucial for people living with diabetes to see their eye doctor regularly for comprehensive eye exams.  The earlier diabetic retinopathy is detected, the better the chance that it can be effectively treated and further vision loss prevented.

Visit your eye doctor without delay if you notice:

· Dark spots in your visual field.

· Blurred, distorted, or double vision.

· Large “floaters” - specks in the form of dots, circles, lines, or cobwebs that move across your field of vision.

Prevention & Risk Factors

Everyone with diabetes is at a risk of developing diabetic retinopathy, but there are certain factors the increase this risk.  Some of these factors of can be controlled of course, but others cannot.

Uncontrollable Risk Factors:

· Type of diabetes:  People with Type 1 diabetes are more likely to experience vision loss sooner.

· Ethnicity:  Aboriginal Canadians are three to five times more likely than the general population to develop Type 2 diabetes, placing them at a much higher risk of developing vision problems related to diabetes.

Controllable Risk Factors:

· High blood sugar:  Target ranges for blood sugar levels are dependant upon age, medical condition, and other risk factors.  Ask you doctor what your levels should be.

· Smoking:  Smoking increases your risk of vision loss when you have diabetes.  It also increases blood pressure and blood sugar levels, making it harder to control your diabetes.

· High blood pressure and cholesterol:  If you have diabetes and high blood pressure and/or high lipid (fat) levels, you are more likely to develop diabetic retinopathy.

More Information

 If you would like more information on diabetic retinopathy, talk to your eyecare professional or check out the following online resources available to you. 

• CNIB
  • www.cnib.ca
• Canadian Opthalmological Society
  • www.eyesite.ca
• Canadian Association of Optometrists
  • www.opto.ca