A certain Fifty Shades of Grey has gotten the lion’s share of attention in the media and in popular culture, but did you know the human eye can in fact distinguish as many as 500 different shades of grey?
At Precision Vision, we are obsessed with shades of grey – but in a healthy way that truly benefits the lives of millions
Fifty Shades… well, still too many. But, 15 shades of grey, just about right: that’s the sweet-spot in one of the tests we make.
The Pelli-Robson Contrast Sensitivity Chart™ is recognized as the Gold Standard for research and clinical trials to determine threshold contrast sensitivity and subtle changes in CS. This threshold CS test uses fixed letter sizes and starts with high contrast black letters followed by 15 steps of grey in lighter and lighter shades. Each step follows a logarithmic progression right down to contrast levels that even the most sensitive people cannot see.
The Mars Letter Contrast Sensitivity Test was the first test similar to the Pelli-Robson test for near distance testing and is very popular. Today the P-R Charts are available in a small size for use at near. Precision Vision can also now supply standard-size charts that are made to be trans-illuminated in an ETDRS Illuminator Cabinet™.
Would you believe that only one shade of grey could have a huge impact on a patient’s life, a patient’s family and an eye care professional’s diagnosis? It’s true. The Colenbrander Mixed Contrast Test™ is that tool. In a single presentation a patient is shown an eye chart in varying letter sizes that has high contrast black letters, symbols or sentences on one side next to grey low contrast letters, symbols or sentences at 20% Weber (10% Michelson).
This contrast acuity test provides uniform distance and illumination in high and low contrast and the test takes only a minute or two to get results. Normally sighted people will lose one or two lines in acuity when going from the black to the grey but some people will lose several lines or not see the grey side at all. We have many stories of this chart helping patients who were told they were fine when tested only with high contrast charts yet they didn’t see well in activities of daily living and had eight lines of loss on the LC side. We also have many doctors who have told us this chart should be in every practice including those performing laser refractive procedures.
We love shades of grey, we’ve been excited about our shades of grey for many years. We commit a tremendous amount of resources to the development and manufacturing of the world’s most trusted tests for contrast sensitivity and other test categories.
Precision Vision is all about printing the ‘unprintable.’ We take tremendous pride in creating the highest quality vision screening and testing products available with unparalleled accuracy. We are able to print and measure sensitivities to all the shades of grey – even those many can’t see.