Transparencies vs. “real world” vision – there is a difference. Are you testing accurately?


The vision test equipment you’re using might not reflect how well your patients are seeing out in the “real world.”

In daily life – in their houses, walking around town – people see using reflective light. Here a light wave hits an object and much of it bounces back to the eye. (Darker colors like black are absorbed – thus color gradations and shadows are formed.) The reflected light wave maintains the same frequency as a directly incoming wave. Similar to seeing one’s image in a high-quality mirror, the resulting image is very accurate to the original in terms of color and other factors.

However, many vision screening instruments incorporate transparencies to test functional vision. Here objects are illuminated from behind, and light refracts through the transparency film – no matter how thin – to reach the eye. The degree to which the material slows down the light determines the angle of refraction – amount the light wave bends.

Additionally, the eyes adjust differently to backlit objects than they do to objects viewed under “regular” (reflective) conditions. That’s why heavy computer users can experience a significant degree of eye strain, and sometimes seek specialized vision care products – like monitor shields) and vision therapy programs.

Unless your patients sit in front of a computer screen during 100 percent of their waking hours, they see the world primarily through reflective light. Which leads to the question: Shouldn’t you be testing their vision through the same means?

Background research taken from