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How Are You Seeing In The Dark

Most of us see better while driving during the day than at night.  There are a number of eye issues that could affect our night vision.

First and foremost, nearsighted people, especially if they are mildly under corrected in the prescription, will have “night myopia”.  This is a fancy way of saying; I need to get closer to signs to see them when I drive at night.   Night myopia is due to an optical effect when the pupil gets larger and when is there less ability to focus on distant objects.

Cataracts are one of the main potential factors causing people to complain of poorer night vision.   As the human lens changes from transparent to translucent, or even opaque, our contrast sensitivity and clarity of vision is reduced.

There are other ocular reasons for poorer night vision yet one of the newer recognized causes is a problem at the macula.  We know that macular degeneration is the number one cause of poor vision collectively in the United States population.  Its related to genetics, ultraviolent light absorption and can be made worse by smoking, cardiovascular disease, and other environmental effects.

We evaluate every patient at every eye health and vision exam for any signs of changes at the macula.  It is always good news to tell someone, you do not have any macula changes and certainly no macular degeneration.  New evidence however suggests that the structural changes we are looking for may not be the first and earliest changes when a patient starts to develop macular problems.

The earliest change, you guessed it, is a decrease in night vision or adaptation to light in the dark.  We are excited about a test we have added over the last year called, dark adaptation.  It is a simple test, only takes less than 10 minutes, and is covered by most insurances.  It’s a “functional” test not a “structural” test.  Therefore, it can give us an indication of whether the photo receptors (rods & cones) are potentially affected by early changes underneath the macula.

It has been found that a certain lipid buildup at the lower levels of the macula can inhibit oxygen and other vital nutrients in the sub macular area.  This buildup which is imperceptible with our current technology of structure analysis can have the earliest affects on how the macula functions in response to a flash of light.   Therefore, we’ve added this as a protocol test for patients that have had any changes in their night vision over the age of 60 and for patients that have a strong family history of macular degeneration or other night vision issues.  It helps us differentiate early macular changes from other causes such as cataracts or uncorrected nearsightedness.

What do we do if we diagnosis that the function is starting to be affected at the macula?  First, we follow patients on a more frequent level.  The sooner we start to see changes at the macula the better we can treat and protect the macula.  Secondly, if we know that function is starting to be affected, even before the patient notices any changes, we can institute the best medical therapy we have. This may include supplemental nutritionals to improve the protective layer of the macula.  It also may include obtaining a genetic test (vis swab of the cheek) to see what genetic factors a patient has individually inherited.

Understanding the new functional testing for early macular changes is more important than just being able to tell you your macula “looks normal”.  Combining structure and function, much like we do when we evaluate cataracts and glaucoma, is a new part of advanced macular analysis.  If you have any changes in your night vision that you’ve experienced over the last 5-10 years, let us know so that we can obtain a dark adaptation test to rule out any early potential macula changes that could lead to macular degeneration.