Sudden or progressive vision loss can be confusing, frustrating, and frightening. In some cases, vision loss is a normal part of getting older, but in others, vision loss may be related to a more dangerous underlying condition. 

Recognizing the early signs and symptoms of low vision is crucial to early diagnosis and treatment. In this article, Ability Central answers the following frequently asked questions about vision loss:

• How common is low vision?
• What are the common symptoms of low vision?
• What are the primary causes of low vision?
• How is low vision diagnosed?

What are the common symptoms of low vision?

Low vision is defined as the loss of sight that is not correctible with prescription eyeglasses, contact lenses, or surgery. It may include:

• Blind spots
• Poor night vision
• Problems with glare
• Night blindness, or the inability to see in poorly lit areas or at night
• Blurry vision
• Hazy vision, when vision seems covered with fuzz or film

According to the American Optometric Association, there are two categories of low vision:

• "Partially sighted" refers to people with visual acuity between 20/70 and 20/200 with conventional prescription lenses.
• "Legally blind" refers to people with visual acuity no better than 20/200 with conventional correction, or people who have a restricted field of vision less than 20 degrees wide. 

How common is low vision?

According to the Centers for Disease Control and Prevention (CDC), vision disability is one of the top 10 disabilities among adults 18 years and older and one of the most prevalent disabling conditions among children. Approximately 12 million people aged 40 years and over in the United States have vision impairment, including:

• 1 million who are blind
• 3 million who have vision impairment after correction, and
• 8 million who have vision impairment due to uncorrected refractive error.

What are the primary causes of low vision?

The American Optometric Association (AOA) defines nine primary causes of low vision:

• Macular degeneration is a disorder that affects the retina, causing blurred vision. It can cause difficulty reading and, for some, a blurry or blind spot in the center of the vision area.
• Cataracts are a clouding of part or all of the lenses inside the eye. When that clouding interferes with light reaching the retina at the back of the eye, there can be a general loss of vision.
• Glaucoma causes damage to the optic nerve. The first signs of damage are defects in side (peripheral) vision and difficulty with night vision.
• Diabetic retinopathy can cause day-to-day changes in their vision and, over time, may severely damage the retina.
• Retinitis pigmentosa is an inherited disease whose first symptom, night blindness, usually begins in childhood or adolescents. It gradually destroys night vision, severely reduces side vision, and may result in total vision impairment.
• Amblyopia is when the visual system fails to develop normally during childhood. The blurry vision that results is not easily corrected with regular glasses or contact lenses alone.
• Retinopathy of prematurity (ROP) occurs in infants born prematurely. It is caused by the high oxygen levels in incubators during the critical neonatal period.
• Retinal detachment is when the retina separates from its underlying layer. It can cause total vision impairment in the affected eye.
• Acquired (traumatic) brain injury is caused by a head injury or stroke. Signs and symptoms can include reduced vision, blurred vision, eye misalignment, poor judgment of depth, glare sensitivity, difficulty reading, double vision, headaches, dizziness, and balance problems.

How is low vision diagnosed?

An eye exam by your eye care specialist can diagnose low vision. The tests the eye doctor will perform include the use of lighting, magnifiers, and special charts to help test visual acuity, depth perception, and visual field.

If you have additional questions, see our complete library of low-vision information, including:

• Low vision signs and symptoms
• What to do after receiving a diagnosis
• Support available for low vision