Techniques to enhance contrast

	Written by Janis Winters, O.D., a member of the AOA's Vision Rehabilitation Committee.

When I examine adult patients who have significant vision complaints that are inconsistent with visual acuity and other examination findings, I find it helpful to consider contrast sensitivity loss as a causative factor. I often think of the analogy that low spatial frequency contrast loss is like viewing the world through a plastic bag. Contrast sensitivity issues have been associated with reduced reading performance, ambulation mobility, driving, face recognition and tasks of daily living. I have examined patients with contrast sensitivity loss due to a variety of ocular conditions. In addition, I see patients whose contrast has declined as they have aged either due to reduced retinal illumination or neurologic function.

So, what can be done to help these patients?

Lighting

Contrast issues can make people more sensitive to reductions in lighting. So, first and foremost, I ask the patient about their use of lighting. If they have issues with reading, what is the lighting like in the area where they read? Patients often rely upon ceiling fixtures or traditional lamps for lighting.

I typically recommend task lighting for reading or near activities. Task lighting can effectively illuminate near objects in part due to inverse square law. The inverse square law dictates that a light closer to an object provides more intense illumination. In addition, the light can be positioned to optimize illumination while limiting glare.

In the kitchen or bathroom, I recommend using the maximum wattage/number of bulbs in ceiling fixtures. Under-the-counter lighting also can be installed. Areas around stairs and hallways can be hazardous and can have inadequate lighting. Again, ensuring appropriate wattage bulbs are used is important. Motion detectors can be used to ensure the light is always on when someone is present.

Filters

Many patients may notice filters help in improving contrast. Filter colors and percentage transmission that are helpful can vary. Yellow, rose, orange and brown are often used. Percent transmission of the filters and filter color can vary. I trial in office to determine the specific filter color and transmission percentage that is best and make specific recommendations.

Reading

Books, newspapers and magazines have different contrast levels. It is important to educate patients about the differences and recommend materials with best contrast (i.e., white paper and black ink). Sometimes low-contrast materials can be photocopied to enhance contrast.  Similarly, when patients are writing or reading handwritten notes, black ink and white paper is preferable for best contrast.

Electronic devices have controls that allow contrast to be enhanced. I often advise those with contrast issues to put contrast settings on televisions as they prefer. Electronic devices such as smartphones, tablet devices or e-readers may have settings included that allow text to be viewed with enhanced contrast or reverse polarity (black background with white letters).

Overall, it is important to specifically assess the activity the patient is having issues with as well as their environment. There may be relatively simple changes that can be made to improve vision function, which will allow patients to comfortably perform desired activities.

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Written by Janis Winters, O.D., a member of the AOA's Vision Rehabilitation Committee.

Disclaimer: The information contained in this article represents the opinion of the author and not the AOA. These are not clinical practice guidelines, nor has the evidence been peer reviewed. There are additional aspects to this topic that may not be presented, or considered, based on the specifics of the case.