Central Vision Loss
Central vision loss can be devastating – it may be much harder to do everyday activities, such as reading a book, driving a car, or even recognizing faces. Vision loss is usually the result of damage to the eye, either from an injury or from a disease. A number of conditions can cause vision loss, including some of the most common eye conditions in North America today.
About 12 million people in the United States experience visual impairment, many of which are affected by central vision loss. Early detection and prompt treatment of central vision loss can effectively limit disease progression and help people continue the activities of daily life that they enjoy. Fortunately, assistive technology exists to help the visually impaired improve their sight enough to lead full and productive lives.
What is Central Vision Loss?
Central vision is the field of view in the center of your vision as you look straight ahead. It is different from peripheral vision, which is what you see to the left and right as you look straight ahead. One’s visual field encompasses everything that one can see, including in the periphery.
- Central vision is different from the peripheral field, which is what one can see on the left and the right when looking straight ahead
- Central vision makes up only 3% of a person’s total visual field
- Central vision is essential for determining object details and estimating distances
Changes in The Visual Field
The loss of central vision can affect visual acuity, which is the ability to discern shapes and details in one’s vision. Those who lose central vision often feel like they are missing fine details or seeing blurred spots in the center of their visual field. As the underlying disease and the damage it causes progress, the blurred spots will eventually turn into dark or “blank” spots. Losing central vision is the result of damage to specific tissues and structures within the eye, which can originate from multiple causes, including:
- Macular Degeneration
Signs and Symptoms
Vision is a complex human experience made possible by intricate structures and systems within the eye. Here is a guide as to how we develop vision:
- The center of the eye consists of a pupil whose diameter is determined by the iris (the coloured area of one’s eye).
- Light enters the pupil through the clear surface of the eyeball, known as the cornea.
- Light rays move past the cornea, are bent by a lens, and focused onto the retina
- The retina contains photosensitive cells (rods and cones) that detect light.
- Rods are used to create night vision
- Cones are used to create color vision and acuity
- The retina then transmits visual signals through electrical impulses passed through the optic nerve to the brain,
- The final image of vision is perceived in the brain upon receipt of visual signals
Central vision loss is typically the result of damage to the macula, a small area in the middle of the retina that provides sharp, clear central vision. Some diseases affect only the macula, while others damage other parts of the retina too.
- The macula is densely packed with photoreceptor cells.
- The macula is responsible for our central vision.
- The macula is important to color vision and discerning details in the field of vision
- The macula is just 5mm in diameter.
Note that different diseases of the eye affect different ocular structures. Damage to the macula is most commonly associated with experiencing central vision loss.
Age-Related Macular Degeneration
AMD is a degenerative disease that causes a decline in the functioning of the eye, specifically due to damage of the macula.
- AMD is a leading cause of loss of vision in adults over the age of 50
- AMD is characterized by degenerative changes, including thinning of the macula
- Macular thinning results in a loss of vision in the central field and decreased visual acuity
- Central vision loss can be observed in one or both eyes depending on the extent of damage
Glaucoma is a group of eye conditions that damages the optic nerve. The most common risk factor for developing glaucoma is increased pressure inside the eyeball. Glaucoma produces characteristic visual field changes:
- In the early stages, only peripheral vision is typically affected
- Advanced stages of Glaucoma eventually affect central vision, and can lead to significant vision loss in both eyes
- Glaucoma can also lead to complete blindness
Macular edema is characterized by the development of fluid filled pockets inside the macular region. This fluid is derived from damaged and/or leaky blood vessels in the central retinal region. Pooling up of the macula with this fluid disturbs its normal function. Pooled fluid in the macula causes swelling that distorts vision by creating blurry images and disrupting the vividness of color perception.
For the macula to perform its function effectively, it must lie flat. Macular pucker refers to bulges and wrinkles on the surface of the macula that can lead to:
Because of its wide-reaching effects and complications, diabetes is one of today’s leading public health concerns. It is characterized by an increased blood sugar level, which inadvertently can damage vessels in the retina. Here’s how Diabetic Retinopathy (DR) progresses:
- In the early stages, DR causes blurring of vision, floaters in the field of vision, and changes in the perception of colors
- If left untreated, DR can progress to permanent central vision loss
Cataracts are common causes of vision loss characterized by the development of opacities on the eye’s lens that prevent light from falling onto the retina.
- Cataracts cause vision to appear cloudy and fuzzy
- People with cataracts may become sensitive to glare and struggle to form a sharp image
- Cataracts have the potential to affect the entire field of vision
- Cataracts are often associated with macular degeneration
- Cataracts can be reversed through surgery
Holes and tears can develop in the macula to cause central vision loss. These holes lead to direct impairment of the central vision as objects will appear blurry, distorted, or wavy.
- The holes can grow to create a dark or blind spot in the central visual field
- Holes are not known to affect peripheral vision
Diagnosis of central vision loss is made after testing by an eye doctor to determine abnormalities in the central visual field. A common test used is the Amsler Grid, where graph paper with a dot in the centre is presented to the patient. The lines around the dot will appear straight to people with healthy eyes, whereas the lines will appear distorted and/or wavy to people experiencing central vision loss.
Treatment for central vision loss involves addressing the underlying cause(s).
- For central vision loss due to wet AMD, anti-VEGF therapy is used. This involves injecting a medication called anti-VEGF periodically directly into the eye to slow vision loss.
- Diabetic Retinopathy causing central vision loss can be treated by improving blood sugar levels. More severe cases may require laser surgery intervention.
- Macular Edema is treated with steroids to reduce inflammation and restore central vision.
- Macular holes may heal on their own, but often require surgery to repair.
- For Cataracts and Puckers, surgical repair is necessary to restore central vision.