FEDERAL EMPLOYEE'S
HEALTH AWARENESS FORUM

Glaucoma - A Patient's Treatment, Symptoms, & Concerns

• Part V The Beat Goes On

• Continue to Part VI (The Beat Foes On)

• Return to Beginning of Series

• Download Parts I-VIII (Word Document)

The PASCAL DCT, Fluctuating IOP, and OCT Scans

Continuation from Part IV of this series. My wife Mary was diagnosed with Glaucoma about 10 years ago. This section of our Health Awareness Forum follows Mary’s case from its inception in 1995 to present day treatment. These articles document the many issues we encountered with diagnosis and treatment over the years. Parts I through VI of this series discuss Mary’s Glaucoma diagnosis, treatments and surgeries, and summary of our findings. They also present treatment options and things to consider if you are diagnosed with this disease. 

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The Beat Goes On.... and On............ and On.................. Part V
A Glaucoma Patient’s Perspective and Observations 

The PASCAL DCT, Fluctuating IOP, and OCT Scans

Mary advised the doctor on her next visit that she didn't take the second medication that she was prescribed. She was concerned that the medication would cause her IOP to spike as it did in the past when on two medications. While at the office, Mary's IOP pressure was measured three times and again with widely varying results. The first check was R14/L14, the second check 5 minutes later was R20/L21 and the Doctor's measurement 30 minutes later was R23/L26. We advised the doctor that Mary's IOP was measuring R16/L18 (corrected) with her Proview monitor at home and only varying + or - 1 mmHg morning to night. Mary was suppose to have a series of tests taken that day but because of all of the confusion they were rescheduled for a later date. We knew that something wasn't right and discussed this with the doctor before leaving, again expressing our concerns about the accuracy of the Goldmann Tonometer. The doctor annotated in Mary's records that he would be the only one to measure her pressure on her return visit.

That week I researched alternate IOP measuring devices and looked for cases online that discussed wildly fluctuating Goldmann IOP measurements. Much to our surprise we discovered that a new IOP measuring device called the Pascal Dynamic Contour Tonometer (DCT) was available and had been since 2003 in the United States.  The device literature states, "Unlike applanation tonometers, which are influenced by corneal thickness and other characteristics of the cornea and hence may produce misleading estimates of IOP, a contour tonometer provides an accurate direct measurement of true IOP which is independent of inter-individual variations in corneal properties."  I immediately checked for relevant case studies and found many that confirmed the units diagnostic benefits over the Goldmann and other applanation tonometers. I searched for doctors offices that were using the device and discovered that Mary's doctor had the only one available in the Pittsburgh area. I emailed him and he agreed to use the Pascal to check her IOP next visit.

The wildly fluctuating IOP still needed to be explained and I asked Dr. Elliot M. Kirstein, OD, FAAO from Cincinnati, Ohio about my wife's IOP variations. Dr. Kirstein is the U.S. Research Coordinator for the Ziemer Ophthalmic Systems, AG. He suggested what we suspected for some time now and said, "changes like this are common with people who tighten up temporarily causing the IOP to spike. When they relax and breath a little, it drops. By the way, in the aforementioned case, the lower pressure would be the most believable one."  We now had confirmation from several sources on what we had been saying for years. My wife's IOP is directly affected by her "White Coat Blood Pressure."  Anytime she gets near a doctor her blood pressure elevates substantially.

On the follow-up visit, Mary's doctor checked her eyes with the new PASCAL (DCT) unit, the Goldmann Tonometer (GAT) and Mary took a Proview reading. The readings were as follows:

We calculate a new Proview correction factor for her doctor's GAT readings and another taking into consideration Mary's thicker corneas. Basically, if you use a Proview IOP Monitor at home I suggest having the doctor take your IOP readings. Take the Proview reading just before the doctor takes the GAT reading. In the case above Mary's Proview correction factors would be as follows:

Right Eye (Correction factor)

(GAT) 21 - (Proview) 16 = 5

Left Eye (Correction Factor)

(GAT) 23 - (Proview) 17 = 6

Now when Mary takes her readings we will add 5 to the right eye and 6 to the left eye Proview readings to track the doctor's GAT (unadjusted) readings next visit.

We still believe that Mary's actual eye pressure is lower because of her thicker corneas and due to the fact that at home her pressure reads lower. The Proview tracks the IOP increase when she is in the doctor's office. In this case her IOP in the right eye would be the GAT reading -1 or 20 and the left eye with a cornea thickness of 592 would be a - 3.5 or 19.5. This seems to us to make more sense because the eyes are much more balanced with the R 20/ L 19.5 reading. We use the Duke University Eye Center's IOP Correctional Values Chart that is identical to the chart the article on the referenced web site.

To calculate a Proview correction factor for Mary's thicker corneas  

Right Eye (Correction factor for Cornea thickness of 561 microns)

(GAT) 21 - 1 = 20 - (Proview) 16 = 4

Left Eye (Correction Factor Cornea thickness of 592 microns)

(GAT) 23 - 3.5 = 19.5 - (Proview) 17 = 2.5

To compensate for cornea thickness Mary will add 4 to her right eye Proview reading and 2.5 to the left eye Proview reading to track the doctor's GAT readings adjusted for thicker corneas.

I believe a more accurate way to calculate the correction factor is to do a ratio that you can use as a multiplier. For example. We know that the Proview reading of 16 in Mary's right eye equals an adjusted GAT reading of 20. When you divide 20 by 16 you get a multiplication factor of 1.25. This is another way to correct the Proview. When Mary's right eye Proview pressure read 14 the next day at home her actual pressure would be 14 x 1.25 or 17.5 mmHg. You can see there is a difference of .5 between using a standard + 4 or the multiplication factor of 1.25.  Her left eye multiplication factor would be 19.5 divided by 17 or 1.15. 

It would be beneficial if Bausch and Lomb developed a digital Proview monitor that you could enter the correction factors in and then read the actual IOP direct. It could be easily done with today's technology. It really doesn't matter which you use, the multiplication factor or just add the points as described above. What matters is that you can track your IOP at home!!! Quite a benefit and this alone was a tremendous relief for my wife. IOP readings are relative at best and as you see in this series the readings seldom repeat with the GAT and we have found GAT readings very erratic. All Mary and I care about is that we can track with some certainty what's going on with her pressure at home. With the Proview we know from experience that Mary is able to measure and track her IOP fluctuations at home and the readings correlate to office visits if you calculate in the correction factors. We are curious to see if the PASCAL DCT will be more reliable and accurate. 

Mary was then scheduled for a visual field test. The test showed no eye sight loss in the left eye and only a very small amount of loss in the right eye where the schisis was detected several years ago. The Medical Center's visual field test equipment incorporates an internal error detection system that insures reliable results. If the patient moves their eyes or field of vision from center during the checks the equipment detects this and tracks the errors. If more than 4 errors are detected the test is invalid and must be repeated. Actually, her doctor was insistent that the test was done right. Mary had to repeat this test 4 times to obtain acceptable results.

The doctor explained that the test went well and we talked about our concerns. Basically, we still feel Mary is primarily ocular hypertensive and she desired to get off medications if at all possible. Previous OCT scans of the optic nerve were good except in the area where the schisis is formed on the optic nerve in the right eye. The doctor indicated that Mary had a very unusual case that hasn't been documented before and he is going to do a paper on the subject that could help others with this disease. He scheduled a battery of tests including a Spectral OCT, GDX, HRT and regular OCT laser scan. Mary spent a total of 6 hours in the office completing the exams and the doctor advised us that he was going to review the tests and get back to us. Mary was advised to come back in six months. We knew from the minute he said to come back in 6 months that he too was confident that Mary's apparent higher pressure was not the problem it was originally thought to be. This is the first time in years that she hasn't been at the eye doctor every two months or so.

The initial cursory review of the new tests along with the pressure readings, and visual field tests, gave us hope for the first time in years that we were making progress and getting answers. The doctor and his staff at the medical facility in Pittsburgh were very thorough and professional during her visits.

Continue to Part VI (Conclusion and Summary)

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