White coat hypertension (or white coat syndrome) is a widely recognized blood pressure phenomenon. However, white coat ocular hypertension is not yet recognized by the medical community. One of the first reports of white coat ocular hypertension was published Tuesday, April 24, 2007 here on my blog in an article titled White Coat Syndrome for Eye Pressure.
Today's article represents a follow up to that first report. The purpose of this experiment was to determine if my intraocular pressure is again different when measured in the doctors office compared to when measured at home.
I define white coat ocular hypertension as a situation where patients exhibit elevated eye pressure (intraocular pressure) in the doctor's office but lower eye pressure at home (or in similar situations where they are comfortable). Patients with white coat ocular hypertension will often experience elevated eye pressure under stressful situations other than the physician's office. My data reported below and in the first report of white coat ocular hypertension fit this definition well.
I used a Reichert AT555 non-contact tonometer (AT555) to measure my intraocular pressure at home prior to going to the doctor's office. I took the AT555 tonometer with me to the doctors office and set it up in the room adjacent to the exam room the doctor would be using to measure my intraocular pressure with a Goldman contact tonometer. In the first experiment both my doctor and I were aware of the results of each intraocular pressure measurement immediately and my doctor oversaw my AT555 tonometer measurements (which I performed just as I do at home). In the current experiment, during the period the intraocular pressure values were obtained, I was not aware of any of the intraocular pressure values; my doctor was not aware of the values from the AT555 tonometer. I performed the AT555 tonometer measurements like I do at home without the supervision of the doctor. The doctor did, however, read the Goldman values himself because no one else on his staff was qualified to assist. The AT555 values are completely free of any bias, but we can't say the same thing about the GAT measurements. However, the fact that the GAT values are in close agreement to the AT555 values indicates operator bias is probably not an important factor in these results.
We obtained three Goldman intraocular pressure values for each eye between 3:37 PM and 4:45 PM. We obtained six averaged intraocular pressure values for each eye with the AT555 between 3:32 PM and 4:55 PM in the doctor's office. Each averaged AT555 intraocular pressure value is the average of three individual IOP readings. I also obtained intraocular pressure values the same way with the same AT555 before and after the doctor visit.
The results show that my intraocular pressure was 14.7 mmHg OD (right eye) at home before the doctor's visit. My intraocular pressure reached 21 mmHg by Goldman and 20.3 mmHg by AT555 during the doctor's visit. Back at home my intraocular pressure (OD) returned to 15.0 mmHg quickly and over the next three hours it further declined to 13.3 mmHg.
In my left eye the change was much less pronounced. My eye pressure was 12.0 at home before the doctor's visit. It reached 15.0 mmHg by Goldman in the doctor's office and it returned to 11.3 as soon as I was back at home.
Additional data are shown in the table below, with tonometers and times noted.
|Dr. P Office||15:32||13.7||18.3||AT555 Reichert|
|Dr. P Office||15:37||15.0||19.0||Goldman contact method|
|Dr. P Office||15:39||12.3||18.7||AT555 Reichert|
|Dr. P Office||15:42||14.0||19.0||Goldman contact method|
|Dr. P Office||15:52||13.0||18.0||AT555 Reichert|
|Dr. P Office||16:23||13.3||20.0||AT555 Reichert|
|Dr. P Office||16:45||15.0||21.0||Goldman contact method|
|Dr. P Office||16:47||12.0||18.7||AT555 Reichert|
|Dr. P Office||16:55||13.7||20.3||AT555 Reichert|
The above values were obtained on 25-May-2007.
Clearly, going to the doctor's office is correlated with elevated intraocular pressure values for me. My right eye has greater optic nerve damage and the data above indicate that my right eye also responds more strongly to the stress of the doctor's office.
We speculate that over time, as I repeat this experiment, the psychological factors that produce white coat ocular hypertension might begin to recede. Comparing the current results to the prior results for my left eye indicates that this might be the case. Further replications of the experiment will help clarify that.
However, there is a potential confounding factor I recognized in the current experiment. The anticipation of going to the doctor's office began affecting my intraocular pressure before I actually arrived at the doctor's office. The planning involved in preparing for this experiment put me in a frame of mind that produced a slight elevation in the intraocular pressure in my right eye long before I actually arrived in the doctor's office. (I noticed the effect in the morning almost as soon as I got up.) Specifically, my eye pressure was approximately 1 to 2 mmHg higher at home before the doctor's office than what was expected. Note that my intraocular pressure was 14.7 OD at 3:00 PM at home. The data to support my statement that my intraocular pressure was elevated before the doctor's visit are not included in this report, but you can view my latest eye pressure report here to get a feel for my normal values on a day without stress. You'll see that a value of 11.5 to 13.5 would be within the normal range and that the actual value of 14.7 is unusual. Given that I have recorded 28,000 intraocular pressure values over the last 300+ days, I can perform very nice statistical analyses. However, even without reporting any detailed analysis it is clear that the current data are consistent with white coat ocular hypertension syndrome.
Going beyond the current data, my personal experience indicates that the doctor's demeanor contributes to the magnitude of the intraocular pressure elevation. In March I had my eye pressure checked in the same office (even in the same chair) by two different doctors. The first doctor took a detailed medical history and asked me a lot of questions. She was very terse. The second doctor just came in to check my intraocular pressure and she was much more low key and friendly. I felt more relaxed with her. My eye pressure was about 5 mmHg lower with the second doctor. There was about 20 minutes between measurements. This example wasn't carried out as an experiment, so it is harder to draw conclusions, but I do feel this observation is valid.