Understanding Low Vision

Dr. Russel Lazarus, July 14, 2021

More than 1 billion people worldwide live with low vision.

If the best vision a person can achieve with medical treatment, surgical procedures, or prescription glasses is 20/70, they are considered to have ‘low vision.’

Vision loss can be caused by a variety of eye conditions and diseases, such as macular degeneration, cataracts, and glaucoma. The vast majority of patients who experience visual loss do not become totally blind, rather, they maintain some residual and usable vision.

Those who have low vision can benefit greatly from visual aids that maximize their eyesight as much as possible.

It’s critical to first understand how the eye works in order to comprehend blindness and other types of vision loss.

How the eye works

The eye is made up of four basic components that help it function:

  • Cornea and lens – found at the front of the eye; they focus light entering the eye, allowing an image to form on the retina.
  • Retina – also found at the back of the eye, the retina is a neural layer that detects color and light, and converts these into electrical signals.
  • Optic nerve – transmits electrical signals from the retina to the brain for interpretation, allowing a person to comprehend the information delivered by the eye.

Blindness or reduced vision can arise when one of these components is damaged or degenerate over time.

Understanding types of vision loss

Vision loss is a blanket term that describes the partial or total loss of vision. Some terms to describe the various types of vision loss include those below.

Low vision – when a person has a visual acuity of 20/70 or lower. Their vision can’t be improved, even with glasses or contact lenses.

Legally blind – when a person has vision of 20/200 or lower. If visual aids such as glasses can correct a person’s vision to better than 20/200, they aren’t considered legally blind.

Totally blind – when a person has a complete loss of functional sight.

Common sub-types of low vision are:

  • Loss of central vision – in the center of a person’s vision there are blind or dark spots.
  • Loss of peripheral vision – a person cannot see anything above/below eye level or to either side. However, their central vision is intact.
  • Blurred vision – objects, near and far, are out of focus.
  • Hazy vision – a person’s field of vision appears covered with a sheer curtain or film.
  • Night blindness – difficulty seeing in low-lit places or at night.

If you’ve noticed any changes in your vision, contact an eye doctor near you.

SEE RELATED: Guide to Low Vision Devices

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Eye conditions that cause vision loss

Early diagnosis and treatment can mean the difference between some vision loss and total or near-total blindness for many people. This is especially true for eye diseases, which sometimes don’t show symptoms until irreversible visual loss has occurred.

Common eye conditions and diseases that can cause vision loss, including blindness, include:


Cataracts cause the natural lens of the eye to become less transparent, resulting in cloudy or misty vision. During cataract surgery, the clouded lens is removed and is replaced with an artificial one.

If left untreated, cataracts can eventually cause blindness.


Glaucoma is a group of eye conditions that affect your peripheral vision and damage your optic nerve, usually due to a buildup of fluid and pressure in the eye.

Glaucoma is a lifelong condition for which there is no cure. Early detection and treatment can often help to reduce vision loss.

Macular degeneration

Macular degeneration occurs when the retina (the macula) begins to degenerate and compromise central vision; it’s frequently associated with aging.

The key to preventing vision loss is early detection and treatment. Anti-VEGF medications and laser eye surgery can often restore some lost vision, though there is no cure.

Diabetic retinopathy

Diabetic retinopathy (DR) is a complication of diabetes in which high blood sugar levels damage the blood vessels that nourish the retina. DR doesn’t have any visible symptoms in its early stages. The patient eventually develops eye pain, blurred vision and vision loss.

Patients must control their blood sugar, cholesterol, and blood pressure in order to prevent or manage diabetic retinopathy. Laser eye surgery, medication injections, and surgery to remove scar tissue or blood from the retina are all treatment options.

Low vision aids

A number of visual aids can help people with low vision or partial vision optimize their vision.

Accessible smartphone apps, e-readers, and a variety of other types of adaptive technology can aid people with any level of vision loss.

Your local eye doctor should be able to assess any low vision you  may have and provide you with low vision glasses, devices, and aids that can help improve your life by allowing you to do the activities you enjoy.

LEARN MORE:  Guide to Low Vision

If reduced vision is impacting your life, schedule an appointment with an eye doctor near you to have your vision assessed, a low vision aid might just change your life.