Chat Highlights
Measuring Your Own Eye Pressure
September 19, 2001

Norma Devine, Editor

On Wednesday, September 19, 2001, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Measuring Your Own Eye Pressure." 

P:  Has anyone tried Bausch & Lomb's Proview™ to measure intraocular pressure at home? I understand it's available in the U. S. at Wal-Mart and other drug stores.

P:  I did, but I could not see a phosphene.

P:  I don't think I want a home tonometer.  It would make me crazy.

Moderator:  I don't think I want one, either.  I think if I had one I would use it and use it and use it.

P:  Is it uncomfortable to use?

P:   Not at all.  If you closed an eye and lightly and briefly touched a pencil eraser to the eyelid near the nose, that's about what you would feel.

P:  I only see my doctor every six weeks.  If my IOP (intraocular pressure) went up in the meantime, I would freak out.  

P:  Using just my fingers, digital tonometry, I found that my IOPs were accurate within 3 mm Hg.  

Moderator:  Yes, good old digital tonometry.  I use it to try to guess what my IOPs are before I go for an IOP check.

Moderator:  Here's Dr. Wilson.  Welcome, doctor.

Dr. Rick Wilson:  Thanks.  Hello, everyone.

Moderator:  Before we discuss the Proview™, the new home eye pressure monitor, can you tell us how to perform digital tonometry and if we should use it?

Dr. Rick Wilson:  Digital ocular compression is used on the closed eyelid, on the middle of the cornea, with the eye looking straight ahead.  You cannot just push with one finger on the eye or you will just be testing how easy it is to push the eye back into the orbit.  You must alternately push in, using the index fingers of both hands, side by side, to get an idea how easy it is to indent the eye.

Moderator:  I usually try to do that before my exams to see how close I can come.

Dr. Rick Wilson:  I feel it is fine to do it if you have glaucoma, especially after your doctor has checked the IOP so you have a benchmark. 

P:  Where on the eye are the fingers placed? 

Dr. Rick Wilson:  Look down and apply the pressure to the top of the eye, behind the cornea.

P:  If you have had a trabeculectomy, wouldn't that be right on a bleb? 

Dr. Rick Wilson:  It would be, and it's probably not a good idea if you have a bleb, unless it is done quite gently.

P:  My eyes are such a mess, and since I have to massage my left eye three times a day I don't think I should measure my own IOP, do you?

Dr. Rick Wilson:  Massage is really a misnomer.  I prefer "flushing."  What you should be doing is applying a steady pressure on the eye to force fluid under pressure out the fistula. If you are kneading the eye, I feel you may be adding unnecessary trauma to the eye.  I'm not sure any of you need home tonometry.  As the machines get better, we will need to reevaluate that.  The idea is very tempting, if the machine is accurate and using it doesn't cause patients to concentrate on the IOP testing to the detriment of the rest of their lives.

P:  When a trab is working in one eye, it is smaller than the other.  That is a way of comparing the two, but how can you tell the IOP is up in the eye that has not had a trab?

Dr. Rick Wilson:  Unless the IOP is way up, it would be difficult to tell.  

P:  I gently let the three fingers of one hand roll over the closed lid and I can feel the big ball shape.

Dr. Rick Wilson:  That's one way, but not the most accurate.  I would recommend the two-finger technique.

P:  I use the phosphene method with my finger.  How accurate would that be compared to the digital tonometry you describe?

Dr. Rick Wilson:  Since there is no gauge in your finger, I doubt if it would be that accurate, but you might be able to gauge a relative hardness from one day to another.

Moderator:  What do phosphenes have to do with eye pressure?  How are phosphenes used to determine IOP?

Dr. Rick Wilson:  I think phosphene refers to the electric- like discharge that the deformed retina emits as the wall of the eye is pushed in.  If the pressure is high in the eye, you have to push a lot harder to deform the wall of the eye to the point that the phosphene is seen.  On the Proview™ home eye pressure monitor, the pressure needed to see the phosphene is recorded on a sliding scale.

P:  When the eye hurts, then you know the pressure is up, right?

P:  I can tell when my IOP goes up.  It hurts.

Moderator:  If my IOP is real high, it hurts to even come close to touching my eye. 

Dr. Rick Wilson:  If the pressure changes quickly, it hurts.  If the IOP goes up slowly, the IOP can be in the 50s and the sensation will be one of glare.

P:  So if my left eye (the worst one) suddenly becomes sensitive to glare, does that mean my IOP could be up?  

Dr. Rick Wilson:  Probably not.  Patients who complain of unusual glare usually have IOPs in the 50s.

P:  A neuro-ophthalmologist told me he thinks that if patients can measure their IOP at home, they will be calling their doctors in the middle of the night if they find their IOP elevated.

Dr. Rick Wilson:  I've often given out my home phone number, and can only remember one or two times I regretted doing that.  Few have abused that trust.  I feel that I would rather have the patients worrying less. 

Moderator:  Dr. Rick, I had your phone number when I was post-op.  Thanks!  

P:  How much is "normal" diurnal variation?

Dr. Rick Wilson:  Normal diurnal variation is 3 to 4 mm Hg.  In glaucoma patients without medication it varies, on average, 9 mm Hg. 

P:   Is that variation of 9 mm Hg because of sporadic compliance or total non-medication (the disease process) in the case of glaucoma patients?  

Dr. Rick Wilson:  That 9 mm Hg of diurnal curve is because all of us make more fluid at one time of the day than another, depending upon our innate hormonal cycle.  Glaucoma patients lack an overflow capacity and the pressure backs up.

P:  Do you know whether, during Dr. Moster's testing of the Proview™ eye pressure monitor at Wills, it has recorded IOP's above 22 mm Hg?  

Dr. Rick Wilson:  I don't know.  It was suspicious when it seemed every doctor in the room who tried it when I did had an IOP of 15 to 16 mm Hg.

P:  Wouldn't 24-hour pressure monitoring be useful?  I am usually very tense when my IOP is being measured in the doctor's office. 

Dr. Rick Wilson:  Yes, it can be useful. 

P:  I usually go to my doctor at the end of the day, because I don't have to wait so long.  Is it better to go at different times of the day for IOP measurements?

Dr. Rick Wilson:  Yes, it is.  Also, more people have higher IOPs in the early morning than later in the day.  The wait in my office is always near zero for the first few patients of the day, before the emergencies and problems build up.

P:  In the past you have mentioned a "moving van" full of documentation was needed for FDA approval of medicines.  Does that also apply to medical devices like the Proview™?

Dr. Rick Wilson:  Probably only a large truck-load of documentation is needed. 

P:  I understand that, even with medication, the diurnal variation of IOP is wider with exfoliative glaucoma.  Is that correct?

Dr. Rick Wilson:  The diurnal variation in exfoliative glaucoma can be wider, but not nearly as much as in pigmentary glaucoma.

P:  In what instances might a home eye pressure monitor, such as the Proview™, be useful for glaucoma patients?

Dr. Rick Wilson:  If the patient is getting worse in spite of what seem to be well-controlled IOPs, then home tonometry makes a lot of sense, if the device is accurate.  I need more experience with the Proview™.

P:  The Valsalva maneuver has been shown to raise IOP by as much as 10 mm Hg.  Any idea how long this effect would last?

Dr. Rick Wilson:  For less than a minute, I would guess.  As soon as the Valsalva (holding one's breath and bearing down on the diaphragm) stops, the eye would start to drain easily again.

P:  How do you define a pressure "spike," and approximately how long do spikes last?

Dr. Rick Wilson:  It's a loose term meaning an acute rise in IOP, usually of 7 to 8 mm Hg or more and fairly short-lived.

Moderator:  Thanks for your help, Dr. Rick.  

Dr. Rick Wilson:  You're welcome.  Goodnight, everyone!

Moderator:  Dr. McNamara, a retina specialist, will be joining us for a chat in November.

End of highlights for September 19, 2001.

Click to read an article about the new phosphene eye pressure monitor by Dr. Moster.

On September 26, Dr. Werner discussed "Your Blood Pressure and Glaucoma" in the Chat room. Click here for highlights of that meeting.

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