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What's the difference between glaucoma and cataracts?

illustration of eye with glaucoma vs eye with cataracts

From the time we wake up to the moment we drift off to sleep, our eyes constantly take in information. Like the rest of our body, our eyes eventually tire, age and become susceptible to disease and other vision-related conditions.

Two of the most common vision-threatening conditions are glaucoma and cataracts. In fact, cataracts are the leading cause of blindness, with glaucoma a close runner-up. While many are aware these conditions exist, few people understand how they affect eyesight or how they differ.

To bring some clarity to the subject, here are the basics about cataracts and glaucoma, including differences, similarities and threats they pose to your vision if left untreated. 

What is glaucoma?

Glaucoma is damage to the optic nerve that connects the eye to the brain that's typically caused by excessive pressure in the eyes. 

Imagine your eyeball as a tiny beach ball. If you add too much air to the beach ball, the pressure puts it at a higher risk of popping. While glaucoma will not cause your eyeball to pop, having too much pressure in the eye can damage the optic nerve that relays visual information from the eye to the brain, causing vision loss.

The optic nerve sits at the back of the eye and works by transferring visual information from the retina to the part of the brain that processes visual images. When eye pressure gets too high, it begins to press on the optic nerve, making it harder for the optic nerve to do its job. 

The first noticeable symptom of glaucoma is darkening peripheral vision. The longer the condition goes undetected and untreated, the more damage it can do, eventually spreading across your entire field of vision and causing blindness.

What are cataracts?

Cataracts are characterized by a clouding of the lens of the eye, which is located directly behind the pupil.

The lens of the eye works in several ways that make vision possible. It focuses light onto the retina to create a clear picture to send to the brain via the optic nerve. The lens also enables the eye to change focus, which makes it possible to see distant and up-close objects.

Our eyes’ lenses are essentially made of water and strategically placed protein that allows light to filter through. As we get older, that protein starts to gather into little clumps — cataracts — that cloud the lens.

If left unaddressed, cataracts will continue to worsen, building into a larger, thicker cloud and eventually leading to blurred vision that's not correctable with glasses or contact lenses.

How are glaucoma and cataracts similar?

Glaucoma and cataracts both occur more frequently in older adults and impair vision, but the similarities pretty much end there. They are considered the two leading causes of blindness, but the ways in which they affect the eyes are quite different.

How are glaucoma and cataracts different?

Here are a few of the main differences between the two conditions:


  • No symptoms experienced until vision loss occurs.

  • Condition progresses rapidly once vision loss begins.

  • Eye pressure and optic nerve are affected.

  • Damage/loss to vision is permanent and cannot be restored.

  • Early diagnosis and treatment are essential to prevent permanent vision loss. 


  • Early symptoms consist of blurred or hazy vision and glare.

  • Condition progresses relatively slowly.

  • Affects the eye's crystalline lens.

  • Cataract surgery can restore lost vision. 

  • Immediate treatment is not required.

Another difference is how surgical procedures are performed to treat the conditions.

Cataract surgery involves removing the cloudy lens from the eye and replacing it with a clear intraocular lens (IOL).

Glaucoma surgery reduces eye pressure by enabling fluid (aqueous humor) that's continually produced inside the eye to drain from the eye more easily.

See your eye doctor

Because glaucoma usually has no symptoms until permanent vision loss has already occurred, it’s important to have regular eye exams so your optometrist or ophthalmologist can check your eye pressure and look for early signs of the disease.

And though vision loss from cataracts can be restored with surgery, as cataracts develop, they cause gradual vision changes that can affect your ability to drive safely before you are aware you're not seeing as clearly as you should.

Routine eye exams are essential to make sure you are seeing your best and not at risk of vision loss as you grow older.

WORRIED ABOUT GLAUCOMA OR CATARACTS? Find an eye doctor near you and schedule an appointment. SEE RELATED: Differences between macular degeneration and glaucoma?


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