The PASCAL is a computerized pressure sensor. It can measure only what it sees at any given moment. Measuring IOP at 100 times per second, it will record actual momentary IOP fluctuations in addition to the IOP pulse curve.  Valsalva, lid squeezing or digital pressure are artifacts, which may cause artificially high values. This is more common with initial readings. A great asset of the PASCAL is that it is difficult to render a false negative. Artificially low readings tend to occur with excess tear film. In this situation, most or the entire view of the probe would fill with tear. If this occurs, give the patient an additional drop of anaesthetic, wait a minute, carefully dry the probe and retake the measurement. Excess lacrimation tends to decrease with generous anesthesia.

Because excellent glaucoma management is so closely linked to precise and reliable IOP control, repeat measurements are suggested to rule out artifacts and to build confidence in repeatable reported values. The PASCAL's digital readout also includes a reading quality or "Q" value. The range of values is between 1 and 5, where 1 is the most reliable. Repeat measurements are suggested even with excellent Q values. Most importantly, when the PASCAL is on the eye, count at least 5 heart beats before removing it. Longer measurements give the computer more data, which, understandably, will significantly improve accuracy and repeatability.
While the skills required to perform DCT are similar to GAT, a few points should be reviewed. Doctors often forget the importance of proper patient positioning for slit lamp procedures. The PASCALworks best when the patient's chin is resting solidly in the chin rest and their forehead is firmly pressed against the slit lamp forehead band. It is generally helpful to have the patient rest their hands on the slit lamp hand rests. Doing so will cause the patients mass to move forward and head to be more stable.

While these practices may seem elementary, following through with them makes DCT as well as other slit lamp procedures much easier for patients and doctors. As with Goldmann, lids can be carefully restrained as long as there is no pressure applied to the globe.

The PASCAL is not influenced by variation in corneal elasticity or CCT. Therefore, knowledge of a patient's CCT is not, in any way, needed to determine dynamic contour IOP. There is no CCT correction required for dynamic contour IOP.

But, independently of IOP, CCT has been recognized as a likely independent risk factor within glaucoma. Additionally, it has been incorporated into the standard of care for the management of glaucoma as well as LASIK, corneal disease and contact lens fitting.

Use CCT to refine your assessment of your patient's glaucoma risk; not to try and correct the systematic error in a Goldmann IOP estimate.

We are not aware of any IOP measurement up to 200 mmHg in humans under normal conditions. However, provoked transient IOPs, for example during LASIK procedures, may reach pressures in the range of 100 mmHg and more.
In production, we test our devices with a known pressure ramp that covers the range from 5 to 200 mmHg. The extreme linearity of our sensor permits extends over such a wide range and exemplifies the high performance criteria we apply to PASCAL. Limiting the pressure range of the device would not improve its performance in other areas and would therefore not be of any benefit to the user. (06/06/2005)

Actually, pressures below 5mmHg can be measured; but the accuracy of such low measurements may be questionable. The firmware in the PASCAL tonometer is set to a pressure threshold of 5mmHg. Below the threshold, the device will record data, but the feedback audio will be deactivated. Therefore, the PASCAL will measure and store normally, but since you do not hear anything, it seems as if nothing is happening. Proceed normally, and you should get a double beep when you lift the tip off the eye, and the result should appear on the LCD as usual.

In firmware #4.1, a "low OPA" mode has been added to facilitate measuring low IOPs and / or low OPA values.

The IOP value displayed corresponds to the average of a few minimum points on the ocular pulse curve. This value might be termed "diastolic IOP” as it corresponds to the minimum pressure to which internal structures are subjected during the cardiac cycle.

PASCAL IOP measurements are not influenced by corneal thickness and other variations in corneal properties. Therefore, no correction should be applied to your readings.

The Cantilever is in correct position if you hear an uninterrupted oscillating sound synchronous with the patient’s heartbeat.
If the Cantilever excursion is too small, the oscillating sound will be broken and discontinuous. (This is the most common error in user technique, particularly if the user has been trained to take Goldmann applanation tonometry readings where minimal corneal contact pressure is preferable.)
If the Cantilever excursion is too great, you will hear alerting beeps.

You may be just barely touching the patient's eye, without sufficiently deflecting the Cantilever (see also previous question). Move closer to the eye until you hear an un-interrupted, oscillating sound.

The PASCAL software routine requires a minimum of three full, undisturbed heartbeat cycles for computing IOP and OPA reliably. To get a reliable result with an acceptable Q score (Q = 3 or better), count at least five cycles of the sound wave before pulling off the eye. If you have difficulty getting acceptable quality data, taking a longer measurement is usually the most promising approach.

PASCAL #4.1 firmware features the capability to select a desired level of Quality (Q value). When the desired Q has been reached, the system will play an audio signal indicated that you may terminate the measurement. You will notice that setting the desired Q to 1 or 2 will produce mor consistent results but will require longer contact times.

You may be touching the eye before the LCD display screen has initially illuminated following activation of the PASCAL with the Blue Knob. During activation, the PASCAL performs a self-test and sets the current pressure reading to zero. If the SENSORTIP is already in contact with the eye at this point, no further pressure increase will be detected and no sound will be heard. Nevertheless, the PASCAL is acquiring data, and after the Interrupt Maneuver the software will usually be able to retrieve the correct IOP value from the data.

Yes. Upon initialization, each printer is assigned to its PASCAL unit, and once this has happened, each PASCAL will only talk to its assigned printer. To initialize the printing function of your PASCAL and to assign a specific printer to it, all other printers present must remain switched off during the initialization procedure.

Yes. The printer will print the results of all PASCAL units to which has been assigned, provided they are within range. Each printout will contain the serial number of the PASCAL unit which has sent that specific data set. Printing to the same printer from several devices may create a risk of data confusion. Therefore, be careful to properly identify each printout.

The PASCAL may be fitted onto almost any commercial slitlamp, either on a "swing arm" or n the pivot post of the slitlamp. Depending on your type of slitlamp, the tonometer may be fitted in lieu of a pre-existing Goldmann tonometer (using the same attachment device and screws), or for alternate use of either tonometer. Your distributor will propose a solution, either based on existing stadard attachment kits, or a custom solution.

The PASCAL's firmware performs several internal checks and calibrates the pressor sensor to current atmospheric pressure before each measurement. The pressor sensor is extremely stable, and a deviation of its factory-set calibrtation is extremely unlikely. If you obtain a suspicious reading from your PASCAL, please try first to repeat the measurement. You also might try to do a measurement on an eye you have measured before, to check whether you can repeat the previously obtained value.
Also, a Test Kit is available (you may purchase the kit from your distributor; or your distributor may perfrom a calibration check as a service for you). Should the performance test indeed reveal a deviation from the correct calibration value, your PASCAL should be returned to the factory for re-calibration.

The first curve you get is the complete ocular pressure curve. It shows the entire data collected, from the moment when you switched the PASCAL on, until the device shuts down after it has detected that you have lifted the PASCAL off the patient's eye. (The time axis runs from top to bottom on the printend paper strip; the pressure axis runs from left to right). The second graph is an expansion of the first. It zooms in on the range of pressure data that the PASCAL microprocessor has acutally selected for calculating IOP and OPA as well as the quality score Q. Looking at this expansion, you should see that the average of the several minima seen in the curve corresponds to the IOP value calculated and displayed by PASCAL. And the average of the several maxima, minus the average of the minima, will correspond the the OPA value found by PASCAL.