Why glaucoma is called the silent thief of sight
Glaucoma usually takes side vision first, without pain. Here is why it goes unnoticed, who is at risk, and how it's found.
Glaucoma care in St. Cloud, Florida
Glaucoma takes sight from the edges in. Finding it early keeps it there.
Dr. M. Ali Tawfik Alyouzbaki, MD is an ophthalmologist whose practice centers on glaucoma: finding it before you notice it, lowering eye pressure in the way that suits your life, and protecting your field of vision for the long run.
Prefer email? Write to [email protected]
Vision loss usually starts in side vision, often on the side nearest the nose.[1]
Full field. Each dot marks a point checked in a standard 24-2 visual field test.Early loss. A patch above center, toward the nose, fades first. The other eye and the brain fill the gap, so most people notice nothing.Moderate loss. Arcs of the field are missing. People start to miss a step, a curb or a car on one side.Advanced loss. Only a small central island is left. Treatment can protect what remains, but lost vision doesn't come back.
Simplified illustration. In real life, missing areas aren't seen as haze or darkness. The brain fills them in, which is why early glaucoma goes unnoticed.
Written by Dr. M. Ali Tawfik Alyouzbaki, MD, OphthalmologistLast updated Sources citedEditorial policy
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Why it's called the silent thief of sight
Open-angle glaucoma, the most common type in the United States, usually has no pain and no early symptoms.[1] It damages the optic nerve slowly, and it's often advanced by the time people notice.[2]
It is also linked to more falls, depression and lower quality of life.[3]
- 2.7 million
- U.S. adults aged 40 and older had glaucoma in 2010[3]
- 5.5 million
- expected to have it by 2050
- 50%
- about half of people with glaucoma don't know they have it
Who is at higher risk
- Age
- Over 60[1]
- Background
- Black or Hispanic/Latino adults over 40; Asian adults are also at higher risk[3]
- Family
- A parent, brother or sister with glaucoma
- Eye pressure
- Higher than average pressure, even with healthy nerves[4]
- Cornea
- A thinner cornea, or low corneal hysteresis[5]
- Health
- Diabetes, and long-term steroid use in any form[3]
Common beliefs, checked
Myths and facts
Myth: If my eye pressure is normal, I can't have glaucoma.
Fact: Glaucoma can damage the optic nerve at normal pressure. This is called normal-tension glaucoma, and it's why the nerve and the visual field are checked, not just the pressure.[6]
Myth: I'd notice if I were losing vision.
Fact: Usually not. About half of people with glaucoma don't know they have it, because early loss is at the edges and the brain fills in the gaps.[3]
Myth: Glaucoma means eye drops for life.
Fact: Not always. In the LiGHT trial, about 74% of people treated first with SLT laser needed no drops to stay at their target pressure three years later.[7]
Myth: High eye pressure means I'll go blind.
Fact: Most people with high pressure but healthy nerves don't develop glaucoma within five years. In a large trial, 9.5% did without treatment and 4.4% did with pressure-lowering drops.[4]
Myth: Surgery can bring back vision that glaucoma took.
Fact: It can't. Every glaucoma treatment works by protecting the nerve that's left. That's why finding it early matters so much.[1]
Myth: Once my pressure is controlled, I can skip checkups.
Fact: Glaucoma can still progress at a controlled pressure. Regular visual fields and nerve scans are how progression is caught and treatment is adjusted.[5]
How glaucoma is found
No single number makes the diagnosis. Glaucoma is confirmed by putting five kinds of measurement together, then repeating them over time.[5]
Eye pressure
Tonometry
Measures intraocular pressure (IOP) in millimeters of mercury. Pressure varies through the day, so one reading is never the whole story.
Drainage angle
Gonioscopy
A special contact lens lets the doctor look at the angle where fluid drains. It separates open-angle from angle-closure disease.
Nerve layers
OCT
Optical coherence tomography scans the optic nerve fiber layer and the ganglion cells near the center. It can show thinning before you notice any loss.
Side vision
Visual field
You press a button when you see a small light. The map shows which parts of your field are working, and how that changes over time.
Cornea
Pachymetry and hysteresis
Corneal thickness changes how pressure readings should be read. Corneal hysteresis, a measure of how the cornea absorbs force, is now a recognized risk factor.
Your first glaucoma visit usually includes most of these. Some are repeated at the next visit to set a reliable baseline. What happens at an evaluation
Open-angle glaucoma treatment, step by step
Every step aims at the same thing: a pressure low enough to protect your optic nerve. Most people move up only if the target isn't met or the field keeps changing.
Angle-closure disease follows a different path, starting with laser iridotomy or lens surgery. Read about angle closure
- Step 1
Agree on a target pressure
Based on your nerve, field and risk, a target is set that should slow or stop damage. Lowering pressure by about a quarter cut progression in a landmark trial.[8]
- Step 2
Start with laser or drops
Selective laser trabeculoplasty (SLT) is now endorsed as a first-line option alongside drops. Many people stay at this step for years.[5]
- Step 3
Adjust or combine medicines
If the target isn't met or the field changes, drops are added or switched, or SLT is repeated.
- Step 4
Consider MIGS
Small drainage procedures, often done at the same time as cataract surgery, for mild to moderate glaucoma.
- Step 5
Traditional surgery
Trabeculectomy or a tube shunt creates a new drainage path when pressure needs to come down further.
Your first-visit checklist
These help make the first appointment useful.
- All your eye drops, in their bottles, or a list with doses and times
- Glasses, and contact lens details if you wear them
- Past visual field printouts and OCT reports, if you have them
- A list of all medicines, including steroid inhalers, creams or pills
- Family history: who had glaucoma, and at what age
- A driver, in case your pupils are dilated
Quick answers
It depends on your age and risk. People over 60, Black or Hispanic/Latino adults over 40, and anyone with a family history of glaucoma are at higher risk and should ask how often they need a dilated eye exam.[1]
No. Pressure checks use numbing drops. The visual field test takes several minutes per eye and asks you to click when you see a light. OCT is a quick scan with no contact.
Often, yes. Plan for blurry near vision and light sensitivity for a few hours, and consider bringing a driver.
No, but it can usually be controlled. Treatment can't reverse damage, but starting early can stop further loss.[1]
From the articles
SLT laser or eye drops first? What the LiGHT trial found
A large trial compared starting glaucoma treatment with a quick office laser versus daily drops. The results changed guidelines.
Narrow angles: when a laser helps, and when it's an emergency
What a narrow drainage angle means, what the ZAP and EAGLE trials found, and the warning signs of an acute attack.
High eye pressure without glaucoma: what ocular hypertension means
High pressure doesn't always lead to glaucoma, and glaucoma can happen at normal pressure. What the big trials show.
Sources and references
- National Eye Institute. Glaucoma. National Institutes of Health. View source (opens in a new tab)
- Centers for Disease Control and Prevention. About common eye disorders and diseases. Vision and Eye Health. View source (opens in a new tab)
- Centers for Disease Control and Prevention. Announcement: Glaucoma Awareness Month, January 2016. MMWR Morb Mortal Wkly Rep. 2016;65(1):12. View source (opens in a new tab)
- Kass MA, Heuer DK, Higginbotham EJ, et al. The Ocular Hypertension Treatment Study: a randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002;120(6):701-713. View source (opens in a new tab)
- Gedde SJ, Bowden EC, Challa P, et al; American Academy of Ophthalmology Preferred Practice Pattern Glaucoma Committee. Primary Open-Angle Glaucoma Preferred Practice Pattern. Ophthalmology. 2026;133(4):P1-P103. doi:10.1016/j.ophtha.2025.12.029 View source (opens in a new tab)
- Glaucoma Research Foundation. Types of glaucoma. View source (opens in a new tab)
- Gazzard G, Konstantakopoulou E, Garway-Heath D, et al; LiGHT Trial Study Group. Selective laser trabeculoplasty versus eye drops for first-line treatment of ocular hypertension and glaucoma (LiGHT): a multicentre randomised controlled trial. Lancet. 2019;393(10180):1505-1516. View source (opens in a new tab)
- Heijl A, Leske MC, Bengtsson B, et al; Early Manifest Glaucoma Trial Group. Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial. Arch Ophthalmol. 2002;120(10):1268-1279. View source (opens in a new tab)
Book a glaucoma visit
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