Friends
After a bit of a summer hiatus, I am sharing another installment in my “Living With Blindness” series. I hope you will find this information both interesting and helpful. Please share it with your friends and family who may be challenged with vision issues.
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At age 33, I was diagnosed with a retinal degenerative disease called retinitis pigmentosa, also known as RP. It’s a complicated disease that causes progressive vision loss and affects both peripheral and central vision. Because RP attacks the retina, it is helpful to understand more about how the retina works. This isn’t meant to be a physiology lecture., It is simply my attempt to explain some difficult concepts in layman’s terms with the hope that you can better understand the disease. Let’s start by taking a closer look at the retina.
What is the retina?
The retina is a thin layer of cells located at the very back of the eye. The retina is the critical layer that allows the eye to receive light and convert it to electrical impulses. These electrical impulses are transmitted from the eye to the brain along the optic nerve. The brain then converts the electrical impulses into images. These images are essentially what we see as we look around us. Healthy vision depends on a healthy retina with properly functioning light receptors, also called photoreceptors.
What is central vision?
Photoreceptors are scattered all across the retina, with a thick cluster of cells in the central area called the macula. The photoreceptors in the macula are called cones. These cone cells are responsible for our central vision. Central vision is essential for reading, color vision and fine motor tasks like threading a needle. Central vision allows us to look directly at an object across the room and see its detail and distinguish its color.
What is peripheral vision?
The photoreceptors scattered across the retina outside the macula are referred to as rods. These rod cells are responsible for peripheral vision. Our peripheral vision senses what is below or above us, as well as what is to our left or right.
Can you give me an example?
Pretend you are standing in a garden looking at a beautiful yellow rose. It is your central vision that helps you notice the yellow color. Your central vision allows you to distinguish the fine details of each rose petal as well as the green leaves surrounding the bloom. Yet, while you are staring at the flower, you are still aware of the garden all around you. You can tell there is a tree to your right. You can pick up the blue sky overhead and the mulch on the ground below. You can see the tree, the sky, and the mulch all without ever moving your eyes from the magnificent yellow rose. You are seeing the sky, tree and mulch with your peripheral vision.
What about contrast?
Peripheral vision is also responsible for helping us to
distinguish contrast. A good example of this concept is to consider climbing a set of brick steps. While all the steps are made of the same red brick color, you are able to see where one step ends and another begins. You can see the faint shadow separating the steps. The contrast between the steps helps you differentiate where one step ends and another begins. The rod cells in the retina provide this ability to distinguish contrast.
What about adjusting to changes in lighting?
Our ability to adapt to changes in lighting is also controlled by our rod cells in the retina. When we leave a dark room and step into bright light, these photoreceptors help our eyes adjust to the sudden change in lighting.
How does RP affect vision?
While RP can present in a variety of ways, it most often attacks the rods in the peripheral area of the retina first. As the rod cells die, vision is lost in that area of the retina. As more and more of these photoreceptors are lost, the person loses more and more of their visual field.
The term, visual field, refers to the entire scope of what a person can see. For instance, as you look around the room, you see everything present in the room. A person with visual field loss sees the room around them, but there are missing or distorted sections of the room. It’s as if portions of the picture are missing.
RP commonly causes night blindness, limiting the person’s ability to function in the dark or low lighting situations. Loss of night vision is an early sign of RP. Another symptom of the disease is loss of the ability to determine contrast, and depth perception is also impacted.
Want more information?
For more detailed technical information on the disease process as well as updates on the clinical research regarding treatment options, check out The FoundationFighting Blindness at www.blindness.org
For excellent video and podcast offerings on coping with progressive vision loss, explore the resources at hadley.edu: https://hadleyhelps.org/
For real-life insights into the journey through progressive vision loss, check out my inspirational memoir, “Rough Places Smooth: Moments In A Journey Through Blindness” by Anita Peden Sherer. Now available on Amazon in paperback or Kindle ebook.
-APS 9/26/2024
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NOTE: these posts and references are intended to share helpful information and personal insights about coping with progressive vision loss. This content is not intended to replace appropriate medical advice. For specific concerns related to your personal vision, please consult your doctor.
Want to read more of Anita’s story?
GRAB A COPY OF
Rough Places Smooth:
Moments in a Journey Through Blindness
by Anita Peden Sherer
NOW AVAILABLE ON AMAZON
AS PAPERBACK AND KINDLE EBOOK!
Faith Beyond Sight 