Portable Home Tonometry Basics: Why It Matters

First a few basics:

Glaucoma is the leading cause of permanent blindness in the world. Unlike cataracts (which is when the lens inside your eye turns cloudy), when you lose vision from glaucoma it cannot be regained. We often describe glaucoma as "the thief in the night" because it gradually causes loss of vision in the sides of your vision rather than the center. Since we do not use our peripheral side vision as actively as the central vision, a lot of damage can occur before we notice this missing vision - by then it is too late to save what is gone and we can only try to prevent further loss. This makes for a very sneaky loss of vision, hence the "thief in the night." We want to lock out this thief forever!

A big part of diagnosing glaucoma is determining the health of the optic nerve. The portion of the eye that is damaged in glaucoma is the nerve in the back of the eye. This is what connects the eye to the brain, where vision is interpreted. Your brain is kind of like what gets to watch the television and the optic nerves are the cables from the wall providing the Netflix, Hulu, and infinite other streaming options that have cute, little Baby Yoda's in them. 

Diagnosing glaucoma

These are the main factors a doctor looks at to make a diagnosis of glaucoma: (1) physical exam, (2) eye tests, (3) eye pressure

1. Physical exam of the eye and the structure of the optic nerve:

  • Doctors will look at every part of your eye, but the nerve inside your eye is what makes us want to figure out if someone has glaucoma. We decide by expert training and pattern recognition if the nerve looks abnormal in any way. Everyone comes in different shapes and sizes and so does your optic nerve! It can look very different from a "normal" nerve and still be normal, but if it looks any sort of unusual way then your doctor will take a few pictures and run a couple non-invasive (but annoying) tests. 

2. The tests!

  • Tests sound scary so it is important to highlight that these are more like an annoying video game than anything else. 
  • Visual Field: This is a side vision test. It is like a hearing test where they start loud and slowly lower it until you are guessing wrong on hearing a sound. In our case, rather than saying "Yes" to a sound you hear, you are clicking a button when you see a light flash. You do this while staring straight ahead. The machine then creates a map of where you saw everything and displays darkened areas where vision is missing. When vision is getting worse for a glaucoma patient, the doctor might check this test every month. For stable patients it can be as rare as every other year, though every 6 months is common.
  • Optic Nerve OCT: This is a scan of the optic nerve thickness. I like to tell patients that the nerve looks like a donut sitting on a table and we are looking at it from above. When the donut hole is large we have a skinny donut. If a patient's donut is skinny then it is more likely they have glaucoma, and if it is getting skinnier from visit to visit then something (usually glaucoma) is causing damage to the optic nerve. When the pressures are high at the same time it is almost always glaucoma causing this change. If the donut is not getting more skinny then the glaucoma is stable...or maybe you don't even have glaucoma! But keep in mind: if someone has seen your Visual Field or your OCT get worse at some point, then most doctors would recommend treatment to prevent vision loss with a better safe than sorry approach. I certainly would explain that same approach to any family member or loved one.

3. Eye pressure

The best for last! The eye pressure is both (1) a factor we use to help diagnose glaucoma, and is also (2) our only major number that we measure to determine if our treatments are effective. In other words we determine if our treatments work based solely on the eye pressure.  Basically, we can measure a lot of things (as you can tell!) to see if damage is occurring , but we prevent vision loss by lowering the pressure to a safe level and making sure it never (even at home) creeps up above certain maximums. In some people the maximum safe pressure might even on the low side in the normal range (10-21). Said another way: a pressure of 21 might be safe for one person's eyes, while another might need a pressure to always be below 14 to prevent vision loss. This makes for a very personalized treatment plan where technology like the iCare HOME is invaluable for preventing vision loss.

How much to treat?

If you have been diagnosed with glaucoma, we definitely want to leave your pressures lower than we found them. On the other hand, if one eye drop per day can get your pressure to a safe level then why would you want to take multiple types of eye drops multiple times per day? No thank you! Our goal is to protect vision, while minimizing the inconvenience and costs of treatment. Some have bothersome side effects (burning, dryness, redness), while others are more expensive up front (like a laser procedure) and last for a period of 2-5 years. Decisions on treatment plans are unquestionably best made between a patient and his or her eye doctor.

You may have noticed that eye doctors never really talk about when you can never worry about glaucoma. Instead, we focus on keeping a close eye on the health of your optic nerve by determining if a patient is high or low risk of getting worse over a certain period of time. Having glaucoma can be very stressful, but remember: it would be even worse to be losing vision and not know it. You can fight this and we can help!

If you have glaucoma or are a glaucoma suspect, or simply want to optimize your eye health, please visit our products page and learn more about our expert analysis of home eye pressure, as well as our industry leading warranty and pricing on the iCare Home. You are on a journey and we are here for you. 

TL;DR: (too long didn't read ;)

Glaucoma causes damage to your optic nerve, which damages "side-vision" over time (typically slowly, but sometimes quickly). Doctors check your eye pressure as much as they think is necessary but your time and their time is limited so they try to keep visits to a safe minimum. Home eye pressure testing solves this problem with the iCare Home so that you can take your own eye pressures. This results in better and more thorough data. Digital Glaucoma is on a mission to save as much vision as possible by taking that data and creating expert analysis to send to doctors so that the best treatment decisions can be made. Lowering eye pressure and making sure it (really) stays low (no matter where you are) is the name of the game. 


A few notes:

We mentioned above that side vision is lost. Really it can be the top or bottom vision as well and that is even more common, which is why "peripheral" vision loss is more accurate. Loss of side vision in particular limits your ability to be legal to drive in certain states so we do focus in on this description a bit more often, but loss of lower vision leads to more falls. And beyond that, we want to keep all the vision no matter what we use it for!


This post does not contain medical device nor is it intended to provide medical advice. Medical advice is between a patient and a doctor with whom they ahve established a relationship.

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