| The PASCAL® Dynamic Contour Tonometer is a revolutionary new digital tonometer that provides a direct trans-corneal measurement of intra-ocular pressure (IOP), and is sensitive enough to detect the ocular pulse amplitude (OPA) due to the patient’s heartbeat.
Using the principle of contour matching instead of applanation, the PASCAL® eliminates the systematic errors inherent in all previous tonometers, such as the influence of corneal thickness and rigidity.
Accurate and convenient to use, the PASCAL® meets the eye care professional’s need for conclusive, reliable and objective IOP measurements. It is quickly being adopted as a new standard for precision tonometry.
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Distinctive features of the PASCAL® Dynamic Contour Tonometer: - Slitlamp-mounted - same easy operation as the familiar applanation tonometer.
- Disposable tip prevents contamination and potential infection - safe and convenient.
- Direct measurement of pressure - no systematic errors from force-to-pressure conversion.
- Numerical display of result - avoids operator bias and reading errors.
- Self-calibrating - no mechanical calibration required.
- Battery operated - no cabling.
- Transparent tip provides for visual control of corneal interface.
- All functions are accessed with the unique Blue Knob - easy, single button operation.
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Clinical Benefits
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.
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The PASCAL Dynamic Contour Tonometer (DCT) is a third-generation, digital, contact tonometer for ophthalmological applications. The slitlamp-mounted device furnishes a numeric output of intra-ocular pressure (IOP) and of ocular pulse amplitude (OPA) upon touching the cornea for a few seconds. It measures pulsatile IOP directly and continuously (dynamically). |
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How the Dynamic Contour Tonometer works
PASCAL uses a solid-state pressure sensor, built into the center of a contoured, concave tip surface, to directly measure IOP when the tip is applied to the corneal surface. The contour surface has been calculated to generate minimum distortion of the cornea and to direct all forces acting within the cornea to the pressure sensor surface. The device can be mounted on any slitlamp, and is advanced towards the patient's eye by using the slitlamp's joystick. The sensing tip is mounted on an actuator which provides a precisely controlled appositional force. |
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The pressure detected by the sensor is digitized and stored in the device's memory. A built-in microprocessor determines the intra-ocular pressure (IOP) and its pulsatile fluctuations (ocular pulse amplitude, OPA) caused by cardiac activity. IOP and OPA are displayed as numeric values on an LCD display.
The part of the tip touching the eye is protected by a single-use disposable cover. The unit is battery-operated. |
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Results from Evaluation Studies
On normal corneae of healthy patients, with a corneal thickness (CCT) in the range 500 to 550 microns, good agreement with standard applanation tonometers was found. Over a wider range of CCT (450 to 630 mmHg), GAT revealed a linear dependence on CCT (slope: 0.25mmHg/10µm), while DCT was not correlated with CCT (zero slope). (Kanngiesser H, Robert VCA, ARVO Poster No. B276, 2002). No difference in IOP readings taken before and after LASIK surgery was found (whereas applanation tonometers produce false low readings upon surgical modification of the cornea). (Kaufmann C, Bachmann LM, Thiel MA, IOVS 2003, 44: 3790). Excellent correspondence of IOP measurements taken with the PASCAL device and manometric, intra-cameral pressure measurement has been demonstrated. Measurements on a cadaver eye model were found to be invariant to changes in CCT, whereas GAT and pneumatonometry exhibited a linear dependence on CCT. (Kniestedt C, Nee MT, Stamper RL ARVO posters No. B464, B480; ARVO 2003). |
Technical Data
- Class IIa medical device. CE Marked. FDA 510(k) cleared.
- Device mounts on tonometer bracket or accessory footplate of slitlamp.
- Dimensions: Housing: 170 mm (H) x 88 mm (W) x 40 mm (D); overall height including actuator: 180 mm.
- Weight: ca. 210 grams
- Display of results: backlit LCD 58 x 24 mm (2.2' by 1')
- Detection range: IOP 5 - 200 mmHg; OPA >1.0 mmHg (numerical precision ±0.2 mmHg)
- Analog/digital conversion: 100 Hz sampling rate; 12 bit resolution.
- Recording time: ca. 3 secs up to 180 secs.
- Calibration: self-calibrating; automatic compensation of atmospheric pressure. Optional test Kit is available for checking tonometer calibration and performance.
- Appositional force: 1 gram
- SensorTip diameter: 7 mm (pressure sensor: 1.2 mm)
- Contact surface: concave, shaped to match corneal contour.
- Cleaning/sterilization: SensorTip is protected from direct eye contact by sterile, single-use SensorCap covers.
- Power: battery-operated (3V battery pack).
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The GALILEI™ Dual Scheimpflug Analyzer
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| The GALILEI™ Dual Scheimpflug Analyzer is a high precision optical system for corneal topography and three dimensional analysis of the anterior eye segment, based on a Revolving Dual Channel Scheimpflug Camera and a Placido Disk.
GALILEI™ combines the advantages of two technologies: Placido imaging furnishes high accuracy curvature data, while Scheimpflug imaging is optimal for precise elevation data.
GALILEI™ incorporates several important diagnostic modalities. Combining them in a single device not only saves office space and investment cost; it also lays the basis for obtaining consistent, combined diagnostic information from a single set of merged measurement data.
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GALILEI integrated functionalities:
- High Resolution Scheimpflug images
- Pachymetry
- Corneal and Lens topography
- 3D Anterior chamber analysis
- Crystalline Lens thickness
- Corneal and lens densitometry
- Pupillometry
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Technical Features
Dual Scheimpflug Imaging
Merging of Placido and Scheimpflug data
Although the resolution of Scheimpflug images is high
enough to deliver accurate profile data, it is insufficient
to calculate central corneal power (curvature data)
with acceptable accuracy. GALILEI™ overcomes this
limitation by merging Placido and Scheimpflug data,
acquired simultaneously by the two techniques, into
a comprehensive single data set. This is essential
for obtaining highest accuracy for both elevation and
curvature data across the entire cornea.
Near/Far Fixation Target
The GALILEI™ Dual Scheimpflug Analyzer features
an adjustable near/far fixation target that allows the
examination of the anterior chamber, crystalline lens, and
any intraocular lenses at different accommodation states.
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The Optical Scheimpflug Condition
Scheimpflug imaging differs from conventional
techniques in that the object plane, lens plane,
and image plane are not parallel to each other,
but intersect in a common straight line. The
major advantage of the Scheimpflug geometry
is that a wide depth of focus is achieved.
The Scheimpflug principle has been applied in
ophthalmology to obtain optical sections of the
entire anterior segment of the eye, from the
anterior surface of the cornea to the posterior
surface of the lens. This type of imaging
allows assessment of anterior and posterior
corneal topography, anterior chamber depth,
as well as anterior and posterior topography of
the lens.
Dual Scheimpflug Imaging
The principle advantage of Dual Scheimpflug
imaging is that corresponding corneal thickness
data from each view can simply be averaged
to compensate for unintentional misalignment,
which results in a corrected measurement
value at the corresponding location. The dual
Scheimpflug imaging principle is independent
of inclined surfaces, and thus allows accurate
pachymetry without knowledge of the actual
decentration of the slit from the apex. Living
human eyes are always in motion even under
perfect fixating conditions, and scanning
takes time. Therefore, the rotational device
axis may become decentered from the aligned
apex position during the course of the
rotational scan acquisition. In this situation,
the projected slits impinge upon the anterior
surface of the cornea inclined, resulting in
two apparent slit images deviated from each
other in thickness. The reciprocal relationship
of the dual views allows simple averaging of
the corresponding thickness values to correct
the values at each of the slit positions. The
dual Scheimpflug system has only to take
into account decentration and allocate each
averaged thickness and posterior height
value to its proper location, whereas single
Scheimpflug systems additionally have to make
estimations on the variable surface inclination
for calculating correct thicknesses or posterior
heights.
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Technical Data
System Dimensions
- Dimensions (HxDxW) of
optics module
507 x 301 x 293 mm (20 x 12 x 11.5”)
- Dimension (HxDxW) of
system with table
1235–1435 mm (H) x 612 mm (D) x 930 mm (W)
(49–57” x 24” x 37”)
- Weight of optics module 11 kgs (24 lbs)
- Weight of complete
system with table
- Power requirement
110–120 VAC, 50–60 Hz, fused 8A
220–230 VAC, 50–60 Hz, fused 6.3A
System Characteristics
- Measuring principle
Rotational scan of Dual Scheimpflug slit images,
merged with Placido Disk images
- Scheimpflug camera: 1000 x 1000 pixel CCD
- Top view camera 1024 x 786 pixel CCD
- Placido disk 20 monochrome rings, 200 mm diameter
- Observation illumination Infrared LED 810 nm
- Slit illumination Blue LED light (UV free), 470 nm
System Dimensions
- No. of Scheimpflug
images per scan
typically 15–60 (settable by user)
- No. of measured data points per scan > 122’000
- Time for a full scan 1–2 secs
- Total area covered 14 mm diameter
Data Processing and System Control
- Computer Dual Core Processor
- Operating System Windows XP Professional
- Storage Capacity 2 GB RAM; 240 GB Hard Disk
- Monitor 17” LCD monitor, 1280 x 1024 pixel
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