Patient guide
Glaucoma: the eye disease you cannot feel
Glaucoma is usually slow and silent, and nothing on this page is urgent. One form is not: sudden eye pain with a red eye, blurred vision with rainbow halos around lights, or eye pain with headache and nausea needs treatment within hours. Call (609) 246-0236. If the office is closed, or you cannot reach us, go to a hospital emergency room — most have an ophthalmologist on call.
Glaucoma is damage to the optic nerve, the cable that carries what the eye sees to the brain. It usually happens slowly, over years, and it takes side vision first, which the brain is very good at not noticing. By the time most people would notice anything, a good deal of nerve has gone, and it does not grow back.
That is why glaucoma is found by testing rather than by symptoms, and why about half of the roughly three million Americans who have it do not know. This guide explains who is at risk, what the tests measure, and what treatment involves when it is needed.
What glaucoma is
The eye makes a clear fluid that circulates inside the front of it and drains out through a mesh where the iris meets the cornea. The balance between how much is made and how easily it drains sets the eye pressure. In most glaucoma, the drain works less well, the pressure runs higher than the nerve can tolerate, and nerve fibers die off at the back of the eye.
Pressure is the part we can measure and treat, but it is not the whole story. Some people have pressures above the usual range for decades and never develop damage. Others develop glaucoma with pressures that look normal. The diagnosis rests on the nerve and on the vision it is producing, not on the pressure reading alone.
Two main kinds
- Open-angle glaucoma, by far the most common in the United States. The drain is open but works poorly. No symptoms until late. This is the kind the rest of this guide is about.
- Angle-closure glaucoma, where the iris physically blocks the drain. It can be slow and silent too, or it can close suddenly, which is the painful emergency described at the top of this page. People with narrow angles are identified at an exam and are often offered a preventive laser.
Who is at higher risk
- Age. Risk rises steadily after 40 and sharply after 60.
- Family history. A parent, brother or sister with glaucoma raises your risk several times over. This is the single most useful thing to tell us.
- Ancestry. People of African descent develop open-angle glaucoma more often, younger, and more severely. Risk is also higher in people of Hispanic descent as they age, and angle-closure is more common in people of East Asian descent.
- Higher eye pressure on a previous exam.
- A thin cornea, measured at an exam, which both lowers the pressure reading and marks a nerve more easily damaged.
- Strong nearsightedness.
- Long-term steroid use, including inhalers, nasal sprays and creams used near the eyes, in people who respond to them with a pressure rise.
- A previous eye injury.
- Diabetes and low blood pressure, more modestly.
None of these means you have glaucoma. They mean the tests below are worth doing regularly, and that a change on them is taken seriously.
How it is found: what the tests measure
No single test diagnoses glaucoma. Each looks at a different part of the problem, and together, repeated over time, they show whether the nerve is stable or losing fibers. All of them are done in this office.
- Eye pressure
- Measured here without the puff of air. It varies through the day, so a single reading is a snapshot, and readings at different times of day are useful.
- Corneal thickness
- A quick measurement that calibrates the pressure reading and is itself a risk factor.
- The drainage angle
- Viewed with a special lens to see whether it is open or narrow. This decides which kind of glaucoma is in question and whether a preventive laser is worth discussing.
- The optic nerve
- Examined directly and photographed, so this year can be compared with last.
- Nerve scan (OCT)
- Measures the thickness of the nerve fiber layer to a few thousandths of a millimeter and compares it with people your age and with your own earlier scans. It can show thinning years before a field test changes.
- Visual field test
- Maps your side vision, one eye at a time, by having you press a button when you see a small light. It shows what the nerve is actually delivering. It improves with practice, so an odd first result is repeated before anything is concluded.
Between a normal exam and definite glaucoma there is a middle ground called glaucoma suspect: something looks different enough to watch closely without yet being damage. Many people live in that category for years and never progress.
Treatment, when it is needed
Every proven treatment works the same way: by lowering the eye pressure, which slows or stops the loss of nerve fibers. Lowering it enough, early enough, is what protects vision. In the largest trial of people with raised pressure and healthy nerves, treatment roughly halved the number who went on to develop glaucoma over five years.
- Eye drops, usually one drop once a day to start. They work only when used every day, for life, which is the hard part of glaucoma treatment and the thing most worth being honest about at the visit if it is not happening.
- Laser to the drain (SLT). A painless office procedure, performed by an ophthalmologist, that improves outflow. A large UK trial found it at least as good as drops as a first treatment, with most patients needing no drops at all for several years afterwards. It can be repeated.
- Surgery, for glaucoma that keeps progressing despite drops and laser. Several operations exist, from small stents placed during cataract surgery to procedures that create a new drainage route.
What treatment cannot do is restore vision already lost. That is the whole case for finding it early, when there is almost nothing to restore.
Living with it
- Keep the visits. Glaucoma is managed by comparison. Each set of tests only means something next to the last one.
- Tell your family. First-degree relatives should have their pressure, nerve and angle checked at a routine exam and say why.
- Tell us about steroids prescribed by anyone, in any form.
- Driving is usually unaffected until glaucoma is advanced, because the side vision loss is gradual and both eyes compensate. It is checked at your visits.
- Exercise is good for it. Regular aerobic exercise modestly lowers pressure. Positions that put the head well below the heart for long periods, such as some yoga inversions, raise it and are worth mentioning if you do them often.
Common questions
My pressure was normal. Does that mean I do not have glaucoma?
Not on its own. A meaningful share of people with glaucoma have a pressure in the normal range at any single reading, and pressure also changes through the day. The nerve scan and the visual field are what rule it in or out, which is why both are part of an exam here rather than add-ons.
Is glaucoma hereditary?
Strongly. Having a parent or sibling with it raises your risk several-fold. If you have been diagnosed, the most useful thing you can do for your family is to tell them to be examined and to say why.
Can I feel my eye pressure?
No. Even pressures well above normal cause no sensation in open-angle glaucoma. Pain from pressure happens only in a sudden angle-closure attack, which is the emergency described at the top of this page.
Will I go blind?
Very few people who are found early and treated consistently lose useful vision. Blindness from glaucoma happens mainly in people diagnosed late, or who stop treatment. The two things in your control are keeping the visits and using the drops.
Does marijuana treat glaucoma?
It lowers eye pressure for three or four hours, which would mean dosing around the clock to protect the nerve. No eye care or glaucoma society recommends it, and the approved treatments work better with fewer effects on the rest of you.
Does glaucoma testing go through my vision plan or my medical insurance?
Testing and monitoring for glaucoma or a glaucoma suspect is a medical visit and goes through your medical insurance, even though you are seeing an optometrist. Medicare covers a yearly glaucoma test for people at higher risk. Vision plans cover routine eye exams and eyewear; medical plans cover conditions. Many patients carry both and are not sure which applies. Vision plan or medical insurance explains the difference, and a call with your plan details before you book sorts it out beforehand rather than afterwards.
Book an exam
Pressure, the drainage angle, nerve scans and visual field testing are part of an examination here, and glaucoma suspects are followed in this office. If you have a family history and have not been checked, or it has been more than two years, book an exam.
Book an exam Call (609) 246-0236
Khoury Eye Care, Hamilton Mall, 4403 Black Horse Pike, Mays Landing.
Sources
The figures and recommendations on this page come from the following. Ask at your visit if you would like a copy of any of them.
- American Academy of Ophthalmology. Primary Open-Angle Glaucoma Preferred Practice Pattern. 2020.
- 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. Archives of Ophthalmology. 2002;120(6):701-713.
- Gazzard G, Konstantakopoulou E, Garway-Heath D, et al. 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.
- Tham YC, Li X, Wong TY, et al. Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. Ophthalmology. 2014;121(11):2081-2090.
- National Eye Institute. Glaucoma: facts and statistics. nei.nih.gov.