There are several causes of blindness worldwide. Cataracts are one of the most treatable types of conditions which, without surgical intervention, cause blindness. (Learn More)

Cataract surgery removes the diseased lens from the eye and replaces it with an artificial lens, but most ophthalmologists will not move their patients immediately into cataract surgery when the condition is first diagnosed. (Learn More) Many people experience slowly worsening symptoms with cataracts, but can adjust light levels in their homes, along with prescription lenses like glasses, to manage the problem for years. However, once partial blindness impacts your ability to perform daily activities and puts your personal safety at risk, you will likely need cataract surgery. (Learn More)

We’ll help you learn more about what blindness is in the medical community, how cataracts lead to blindness, and what kind of timeline you can expect if you have cataracts or are at risk of developing them.


What Causes Blindness?  

Blindness colloquially means total vision loss, but the medical definition for the term is slightly different. For example, partial blindness refers to a loss of vision leading to extremely limited visual input; you may not see anything clearly, even with glasses or contact lenses, but you may be able to see colors or shapes. Complete blindness means that you do not see anything including light. Legally blind people have vision rated at 20/200 or worse, so they cannot see the “E” on the top of a standard eye chart.

While both partial and complete blindness can be congenital, meaning you may be born with this condition or it could begin in early childhood, this is also a condition that impacts many people in adulthood when they experience vision loss. There are several reasons you may lose your vision, including:

  • An accident or injury leading to eye trauma or loss.
  • Diseases like diabetes that can lead to nerve degeneration, including in the eye.
  • Macular degeneration.
  • Blocked blood vessels from a blood clot.
  • Lazy eye.
  • Complications from an eye surgery.
  • Eye-specific diseases like cataracts.

Although there are many causes of blindness that are not treatable, cataracts are one of the most common and most treatable issues that can lead to partial or complete blindness.

Why Do Cataracts Lead to Blindness?

Cataracts are a degenerative condition in the lens of the eye. Normally, a healthy lens refracts light through the pupil and onto the retina, so the image is transmitted to the brain. Changes to the shape of the lens can lead to refractive errors like nearsightedness, farsightedness, or astigmatism.

When cataracts develop, that means the proteins in the lens are breaking down. This may seem to be a refractive error at first because you may develop blurry vision or difficulty focusing on objects. However, your optometrist will be able to diagnose the issue and monitor the progress of cataracts.

Symptoms associated with cataracts include:

  • Blurry vision.
  • Foggy or “dusty” vision.
  • Yellowing of colors.
  • Sensitivity to light.
  • Seeing double.
  • Difficulty seeing well at night.
  • Needing more light to read or perform close tasks.

There are a few different types of cataracts that can lead to different visual changes.

  • Nuclear cataracts: These are first experienced as nearsightedness or a slight temporary improvement in up-close reading vision for people who are farsighted. Over time, the center of the lens will become cloudy or yellow/brown. The cataract itself forms in the center of the lens and spreads. This can lead to drastic changes in the ability to see light and color.
  • Cortical cataracts: In some ways, these are the opposite of nuclear cataracts, as they form at the edges of vision instead of at the center. They begin as whitish streaks or wedge-shaped opaque areas which point in, toward the center of the lens. If left untreated, these streaks will fill the vision.
  • Posterior subcapsular cataracts: These begin as a small, opaque area at the back of the lens, impacting how light filters to the retina. You will not get as much light in the eye, and your reading vision will be impacted. You may experience glows or halos around lights, especially at night. These often progress faster than other types of cataracts.
  • Congenital cataracts: These cataracts form in the lens of a developing fetus, are caused by trauma or disease in utero, or begin just after birth due to genetic risks. They do not always affect vision, but many parents will have them removed from their babies as soon as possible so the child can have the most normal possible vision.

Cataracts most often set in due to age, and they are likely to begin about age 40. They progress slowly, and many people do not need cataract surgery until they are 60 or older. There are several risk factors that increase the likelihood of developing cataracts, so you should consider making some lifestyle changes if you have a family history of this condition, are concerned about the condition, or have already developed early stage cataracts.

  • Get regular eye exams to follow changes in your vision and diagnose any diseases.
  • Quit smoking.
  • Drink alcohol moderately or not at all.
  • Wear sunglasses to protect against ultraviolet (UV) exposure.
  • Eat a healthy diet.
  • Manage other health problems like diabetes or heart disease.

Even with these lifestyle changes, your cataracts will progress over time. Eventually, you will need cataract surgery to prevent full blindness.

When Should I Expect to Need Cataract Surgery to Prevent Blindness?  

According to the Centers for Disease Control and Prevention (CDC), there are 20.5 million Americans ages 40 and older who have a cataract in one or both eyes. These cataracts are predominantly age-related. Millions more struggle with cataracts from trauma, disease, congenital issues, family history, or other problems that cause cataracts to form sooner.

By age 75, about half of all Americans have cataracts or a history of cataracts. About 6.1 million people, or 5.1 percent, have cataract surgery, in which the diseased lens is removed and replaced with an artificial lens. This is the simplest way to prevent blindness in people who have cataracts, but even after diagnosis of a cataract, you are not likely to be sent to surgery immediately.

It is difficult to predict how rapidly cataracts will develop, as this experience is different for everyone. Age-related cataracts often progress slowly, but this is not a fast rule. Your ophthalmologist will be able to make an educated guess about the progression of this disease based on your eye exams, what type of cataracts you have, and how the cataracts developed.

Once you receive a diagnosis of a cataract, it is important to stay in contact with your optometrist or ophthalmologist about symptoms, and get regular checkups. The speed of cataract development can change over time, so your ophthalmologist will adjust their prediction for when you may need surgery over time.

Additionally, cataracts typically develop in both eyes, but they will begin at different times and progress at different rates. Again, keeping up with regular eye exams and making lifestyle changes can slow the progression of cataracts so you can retain your vision as long as possible. However, there is no medically proven way to prevent cataracts, and they will progress over time after you develop them. Fortunately, cataract surgery is very effective at restoring most of your vision once your cataracts have progressed to the point of partial blindness. After a few weeks of recovery, you will be able to see most things clearly, so you can go back to driving, reading, and performing other tasks without a lot of corrective eye wear. You will likely still need a prescription of glasses or contact lens to improve the focus of your artificial lens.

References

Blindness and Vision Loss. (August 20, 2016). Medline Plus.

What Are Cataracts? (November 9, 2018). American Association of Ophthalmology (AAO).

About Cataracts. (September 2015). National Eye Institute (NEI).

Cataracts. (June 23, 2018). Mayo Clinic.

Cataracts: Common Eye Disorders. (September 29, 2015). Centers for Disease Control and Prevention (CDC).

Eye Diseases. (2015). American Association of Ophthalmology (AAO).

How Long Does It Take for Cataracts to Develop? (December 22, 2011). American Association of Ophthalmology (AAO).