All blindness is not the same. Visual loss varies largely when it comes to how individuals actually experience it. Vision loss can present as slight impairment to the total absence of sight. While it can impact daily life significantly, vision impairment is a reality for over 2 billion people globally, according to the World Health Organization (WHO),
Blindness vs. Low Vision
While “blindness” may be commonly thought of as a complete lack of vision, the reality is that most people with moderate vision loss can see varying levels of light, shapes, shadows, or even some residual sight. The difference between Blindness and Low Vision is determined by something called visual acuity.
Visual acuity is the measurement of how clear an individual’s vision is from a certain distance. This measurement is used to determine levels of vision loss. In the US, Legal Blindness is when an individual has a central visual acuity of 20/200 or worse in the better-seeing eye. The next level of higher visual acuity is considered Low Vision.
Levels of Vision Loss
When it comes to vision loss, there are varying degrees of condition. Below are the different terms used to describe the type or level of vision loss:
- Total Blindness – When there is an absence of light perception, it is referred to as Total Blindness. Individuals experiencing Total Blindness cannot see light, shadows, or anything else.
- Legal Blindness – When vision is seriously damaged, but not completely missing, it’s considered to be Legal Blindness as measured by central visual acuity. In the US, less than 20/200 visual acuity in the visually-superior eye with the best correctional aid (like glasses or contact lenses), or has a visual field of 20 degrees or less in the visually-superior eye.
- Low Vision – Low vision is one step higher than Legal Blindness, with the visual acuity category of moderate or severe. While Low Vision is not considered “Legally Blind,” vision cannot be fully corrected by visual aids such as glasses, contacts, or surgery.
- Cortical Blindness – When the brain’s visual processing center (occipital cortex) is impaired, this is referred to as Cortical Blindness. While there is no damage to the actual eye, complete or partial vision loss can result.
- Color Blindness – When vision loss results in the inability to tell certain colors apart like yellow, red, blue, or green, it’s referred to as Color Blindness. Even less common is Total Color Blindness, or Color Vision Deficiency, where individuals can only see through shades of gray.
- Night Blindness (Nyctalopia) – Night Blindness is when individuals have trouble seeing in low-light environments — like at night — and is caused by a retinal cell disorder.
Causes of Blindness
Looking at the larger scope, vision loss can happen in one of two ways: at birth (Congenital Blindness) or after birth (Acquired Blindness).
Occurring at birth or shortly after is referred to as Congenital Blindness, which is usually caused by genetics, infection, issues with development, or other prenatal factors.
When vision loss occurs after birth, it’s called Acquired Blindness, and can be the result of an illness, injury, or other medical conditions. Vision loss can happen suddenly or gradually over time. Some diseases that cause progressive blindness include age-related macular degeneration, diabetic retinopathy, or cataracts left untreated.
Vision Rehabilitation
Navigating visual impairment is never easy, but there are options. While vision loss can dramatically impact an individual’s quality of life, mental health, confidence, safety, and independence, Vision Rehabilitation and related programs and services provide tremendous hope for people living with blindness and low vision.