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Dr. Lloyd's blog has now been retired. We appreciate all the wisdom and support Dr. Lloyd has brought to the WebMD community throughout the years.

Tuesday, November 18, 2008

When Things Appear Clear but Different

Sometimes it can be very difficult for a person to describe something like a visual symptom.

“…it’s kinda green and it looks like it is on fire”

“…I see a repeat image but it begins 30 seconds afterwords”

“…think of it like a bright halo with a big upside-down X in the middle” (hey, isn’t an upside-down X still an X?)

Having practiced medicine for nearly 30 years I have witnessed many valiant attempts. Fortunately, most of the time, there is a nondangerous explanation to describe whatever the patient saw. On the other hand, specific symptoms are highly informative clues to the eye doctor.

“…my right eye just sees things differently than the left eye”. Such a disclosure may indicate a genuine problem.

Take a look at the top picture of colorful fall foliage. The vibrant colors jump out of the top photo. Imagine seeing that image with your left eye, but after covering the left eye the image in the right eye resembles the bottom picture. It’s still clear, the image is still crisp, but the colors appear washed-out. The medical term for this change is color desaturation. Acquired color desaturation often signals a problem in the affected eye or in the attached optic nerve. Here’s some comfort, a brain problem would not preferentially cause one-sided color desaturation.

Such a great disparity between the two eyes may not be noticed unless one eye is temporarily covered – like during an eye exam. There are some simple, painless clinic tests that can evaluate color desaturation complaints. Remember, the cause is likely inside the affected eyeball or its optic nerve. Cataract, for example, commonly causes this symptom and its presence is easy to confirm.

If the retina or optic nerve is the culprit then it is likely that other vision tests will be similarly abnormal. The penlight test of pupil behavior is a great example. A person with color desaturation due to an optic nerve problem like undiagnosed glaucoma will also demonstrate an abnormal pupil response to a swinging penlight test. On the other hand, if the pupils behave normally then the cause is localized to the eyeball and likely a fixable problem.

Here’s what you should know:

  • It’s a good idea to check the vision in each eye separately every so often
  • See your eye doctor if you sense color desaturation in one eye
  • Don’t give up if the first eye doctor cannot explain your unusual symptoms. Consider letting a second specialist listen to your story.

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Posted by: Bill Lloyd MD at 3:55 pm

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