Poor Contrast Sensitivity
Bioptic Driving in Rain or Fog
Decreased Contrast in Rain and Fog: A related problem is the reduced contrast sensitivity in rain and fog. Yellow filters often help contrast perception in these conditions. Bioptic drivers learn early the safe range of their visual environment. Most avoid bad weather situations.
Traffic Lights and Bright Background Light: A traffic light can be difficult to view from a distance when overwhelmed by a bright sky. The human eye attempts to adapt to see the traffic light, but is overwhelmed by the brighter background light. Sun filters are helpful.
The Special Case of Achromatopsia / Cone Dystrophies
Some patients will experience much more debilitating glare due to their condition. In Achromatopsia and other cone dystrophies, patients suffer debilitating glare. It occurs due to the lack or impairment of the cone cells. New technology in the form of the Optical Coherence Tomography (OCT) allows us to verify the loss of cone cells in the fovea, the center of the macula where only cones should be found.
The cone cells have chemicals that work and are stable in bright light. Without cones cells, these patients must rely on the rod cells. Rod cells contain 
a chemical that is not stable in bright light, but works well in low light levels. These patients find their vision is washed out in bright lighting. Only by reducing light levels to a dark enough level that the rod chemicals are stable can the patient function well in daylight.
Various filters, dark sun lenses and hats have been used by these patients, but have not fully controlled the glare problems of these patients making it more difficult to take the next step of bioptic driving. However, recent 
advancements in the fitting soft contact lenses and the useof red selective filters allows us to help most achromatopsia patients function better in bright lights inside and out.
Our practice has worked extensively with these selective filtered contact lenses on patients from across the United States. These special red or dark amber filter contacts are custom prescribed in different levels of darkness in and different sizes of the filtered portion. They have revolutionized care for Achromatopsia patients and op
ened the possibility for more of these patients to be considered for bioptic driving
In Achromatopsia and other Cone Dystrophies,even after we apply the red central contact lens, we can attach an additional small dense red filter to the base sunglass to enhance the patient’s ability to see the red stoplight.