When a patient has difficulty with contrast sensitivity, then we start thinking about strategies that we can do to help them out.

The importance of lighting that is Direct and Contained

One of the easiest things has to do with appropriate task lighting. So if the patient's trying to read something, then we would like task lighting. That is what we call direct and contained. So something that's going to come kind of over the shoulder and project directly onto the material that they're trying to read, not a traditional lamp where the light is going to escape out of the top of the shade and underneath and cast shadows on whatever it is they're trying to see. If we can get an enhancement in the contrast, then we almost get a magnification bump. So it becomes easier for the patient to see even though the size hasn't changed. So that is why lighting is one of the big things that we talk about with patients that have difficulties with contrast.
Learn more about lighting for low vision.

How Digital Magnification Devices can Improve Contrast

There are also types of magnification devices, particularly digital devices, such as CCTVs, that will allow an individual to change contrast as well as magnify the image. So they may be able to change something that is blue ink or red ink into a black ink on a white background appearance. Or they can do reverse contrast, which is white writing on a black background.

Understanding Glare Sensitivity

When we talk about glare sensitivity, there are two types of glare sensitivity. One of those is what we call disability glare. And then there's just comfort glare.

Disability glare is what we've all experienced, if we're say, driving through a tunnel, and you're in the dark, and then you emerge into the sunlight and is literally blinding to you in those moments. It can also be things for these patients like flickering light through trees. So you're driving down the interstate and the sunlight flickering through the trees as you go along. And it becomes blinding to them that basically washes out the vision to where you can't see well.

Discomfort glare sensitivity is going to be where the glare is just uncomfortable. So these are usually the people that are going to prefer wearing a hat or a sun visor or sunglasses all the time, even if they're indoors.

What I recommend for glare sensitivity

Thankfully, we have certain absorptive filters that are really excellent at helping with both discomfort and disability glare sensitivity. These absorptive filters essentially filter out certain wavelengths of light and allow other wavelengths through and then we can control the transmission of the light. So we can allow more or less light to come through. So let's say we have somebody who's really glare sensitive, then we might put them in a dark gray filter, where they're not going to get much light out at all. Whereas somebody who has a little bit of indoor glare sensitivity, then we might use something like a plum filter, where they can still see really well when they're inside. Indoors they can see all the detail and contrast they need but they eliminate the glare from specific things such as glare coming in from the sunlight in the windows.

What works best for people who had a concussion and are experiencing glare sensitivity?

Glare sensitivity is also really common to see in the traumatic brain injury population. Topaz filters are an example of one that is often preferred in this population. These patients may wear these filters indoors outdoors or both. Topaz is going to help cut the particular glare that these patients are experiencing.

Glare when driving at night

Another time that glare can be an issue is going to be at nighttime driving. So we talk about night driving, of course, we lose what's called the peripheral lock. During the daytime when we're driving around, we can see what's directly in front of us. But we also have a lot of peripheral visual information as well. When it becomes dark at night, we lose that peripheral or side vision, we don't have any input there, what we have is just what is directly in front of us. This can become particularly disorienting for patients when they're driving at night especially when they have headlights coming toward them. For glare from night time driving most patients will wear filters that are specially made for that. This filter is a light yellow filter that has an anti reflective coating on it. This can be very beneficial because it helps them not to be as affected by the glare of oncoming headlights or street lights and things like that. These filters make it so the patient does not get as much of the starburst and halo effect when they are driving.

What is color blindness? Is it the same as contrast sensitivity?

Color blindness is extremely common, affecting 8% of men and .5% of women. While both color blindness and contrast sensitivity impact the way a person see’s colors, they have different causes and are not known to be correlated to one another.

There are two types of cells in the retina that receive light, those are rods and cones. Rods are going to be more for dim lighting situations. And cones are going to be more densely populated in the center of your vision and they're going to be responsible for your color vision. We have red cones, green cones, and blue cones. Most commonly when we talk about color blindness, this is going to be difficulty in seeing red or green. And on some occasions people will have difficulty with blue as well. Most commonly colorblindness is a congenital condition, meaning it's something that you're born with. In some instances, we can also have an acquired color deficiency and that would be something more associated with pathology, things like macular degeneration, optic nerve diseases, glaucoma, other things like that.

Schedule an appointment for an eye exam for night blindness at our renowned optometry clinic in Hixson, serving patients from the surrounding areas including Chattanooga, Cleveland, and Middle Valley. Call (423) 321-8233 or fill out this form to make an appointment today.
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