Driving at night – What should I know?

Courtesy of Johnathon, Flickr Creative Commons

Courtesy of Johnathon, Flickr Creative Commons

One of the most common questions patients ask is how to improve their night vision. In fact, many elderly patients have given up night driving all together.

So, what is it about night driving that makes it so hard? Well certainly, our visual abilities are dependent on light. With reduced lighting comes a variety of limiting factors like reduced visual acuity, poor color vision, decreased depth perception, and impaired peripheral vision. All of these factors combine to make accidents 3x more likely at night.

So, how do we reduce our chances of an accident?

1) It is imperative that your vision is corrected to its maximum potential. A complete eye examination will not only check the best prescription for you – it can also detect potential problems that affect night vision like dry eye, cataracts and macular degeneration, all of which occur with greater frequency with age. Additionally, if you are prescribed glasses at your visit, make sure to obtain lenses with an anti-reflective coating. This coating will reduce glare dramatically and has been shown to improve reaction time.

2) Make sure your windows and headlights are perfectly clean. Every time I clean my windows at a gas station I wonder why I didn’t do it earlier. This advice goes for your glasses too. Even a perfect prescription can be worthless if your glasses are dirty or scratched.

3) Finally, it is important to know your limits. If you have real concerns about night driving there is nothing wrong with asking for a ride, catching a cab or public transportation or just ordering in. Until next time, be safe on the road!

 ~Dr. David Ardaya, OD
California Optometric Association
http://eyehelp.org
http://www.coavision.org

Color blindness – the causes and the effects

When we think of someone being color blind, we may think that he sees the world in black and white, or shades of gray.  But that is extremely rare.  In fact, almost 8% of men have some form of color vision deficiency where certain colors are more difficult to distinguish, or do not appear as vivid as other colors.  (Perhaps that explains the questionable wardrobe choices my husband sometimes makes.)

What causes it?

Most cases of color vision deficiency are inherited and passed down from the mom.  The photoreceptors in the retina responsible for color are called cones.  Each cone is sensitive to a certain color, in particular, red, green or blue.  If a person has inherited a recessive gene that causes one or more of the cones to be absent or to not function properly, then he will have abnormal color perception.

Photo courtesy of entirelysubjective on Flickr

Photo courtesy of entirelysubjective on Flickr

Some cases of color vision deficiency are acquired later in life as a result of a disease.  More common causative diseases are glaucoma, macular degeneration, and diabetes.  If you notice a change in your color vision, make sure to be evaluated by your optometrist. For eyecare providers, we tend to distinguish color vision deficiency into two broad categories.  Red-green and blue-yellow.  Red-green is inherited and the most common deficiency.  Those with this defect can still see red and green, but the colors are more difficult to distinguish and they may not appear as vivid as to the normal eye.  For example, red and green signal lights may look the same.  One may appear brighter but the lights may both look white.  (For this reason, I’m not a fan of the horizontal traffic lights in some smaller towns.)  Most people who have color vision deficiency have a mild form and are not disabled by this condition.

The other form of color deficiency is blue-yellow where patients have a difficult time distinguishing blue from green or yellow from violet.  This is less common and is usually caused by certain eye diseases.  Unfortunately, for many of these patients, color deficiency is just one visual problem among others.  These patients may also suffer from dimming of vision or distortion of vision.  Often times, bright lighting is helpful for these patients, and occasionally tinted lenses. 

How can I help someone that’s color deficient?

Of course, a comprehensive eye examination is important to rule out any causes of color vision deficiency other than genetics.  This also helps to determine the severity.  Most color deficient individuals carry on like normal without it interfering with their daily lives.  A helpful tip would be to not use the colors red and green as markers because the two colors may appear very similar.  Blue and red will be easier to distinguish.  Unfortunately, those with color vision deficiency should avoid careers that require distinguishing color differences such as airplane pilots, paint mixer, interior designer, etc.

Recently, new developments in tinted lenses have been able to allow some color vision deficient patients be able to see colors they have never seen before.  Sounds promising!

~Cindy P. Wang, OD, FAAO
California Optometric Association
http://www.coavision.org