FOUNDATIONS OF VISION
Visual Impairments
Most of the time, your eyes do an amazing job. But if you have found Chadwick Optical, chances are something about your vision isn’t working quite right and you want to understand why. Let’s break down the different ways things can go wrong in the visual system, what they look like, and what can help.
Where the First Problems Begin
Your cornea and lens work together to focus the world’s light onto your retina. Ideally, this creates a perfectly sharp image. If they don’t do that well, you need glasses or contacts to compensate. That extra lens brings the light into perfect focus on your retina.
The Lens and Age
After age 40, your lens naturally stiffens. You might notice you see fine far away, but now you need reading glasses, or you are blurry at a distance and need help up close. This is a normal condition called presbyopia.
Later in life (typically 60s–70s), the lens can become cloudy, which is known as a cataract. A surgeon can remove the old, cloudy lens and replace it with an artificial intraocular lens (IOL). This replacement can often fix your prescription, potentially removing the need for glasses afterward.
When the Pathway is Damaged
Once a clear image lands on your retina, it travels through a network of pathways to your visual cortex where your brain actually “sees”. If this pathway is damaged, such as by a stroke, vision can be affected. About 1 in 3 stroke survivors experience homonymous hemianopia, which is losing vision on one side.
How Retinal Damage Works
The retina covers a huge field—about 180–190 degrees of your visual world. If a piece of your retina is damaged, that patch of vision disappears. However, vision loss doesn't usually look like a black hole; instead, your brain quietly edits the gap away, similar to your natural blind spot.
Test Your Blind Spot
Try this to find your physiological blind spot—the spot where your optic nerve enters the retina:
- Close your left eye.
- Look at the left dot on the image below with your right eye.
- Move closer or farther until the right dot vanishes.
You’ve just found your physiological blind spot—the spot where your optic nerve enters the retina. You don’t see it in daily life because your brain quietly fills it in.
The Problem With Field Loss
When someone has conditions like hemianopia, diabetic retinopathy, retinitis pigmentosa, or glaucoma, they lose parts of their visual field, but the brain quietly hides it. Individuals may bump into things or miss obstacles without seeing a distinct "hole" in their vision. This makes these conditions frustrating to live with and tricky to detect early without proper testing.
Brain Injury and Vision
Concussions and other brain injuries are another significant source of visual impairment. After a concussion, people often struggle with migraines, light sensitivity, or feeling visually "off". Unlike cataracts, there is no simple test that pinpoints exactly where the system is breaking down. Fortunately, vision therapy and specialized lenses can help retrain the visual system after a brain injury.
The Bottom Line
From aging eyes to strokes to brain injuries, vision loss isn’t always obvious, but it can deeply affect daily life. There are solutions available, from advanced lenses to field expansion aids and therapy. You don’t have to face visual impairment alone.
Are you struggling with a visual impairment that standard eye exams can't seem to explain?
Send your questions to our "Ask Chadwick" video series here.