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Non-Contacting Optical Pachymeter


Lein Applied Diagnostics has developed an innovative optical technology that makes high precision, non-contacting measurements on many items for both medical and industrial applications.

The confocal optical technology is based on scanning a tight focus of light through the medium under test and collecting the return signal. The unique feature of Lein’s technology is that we have taken a component from the telecoms industry, called a bi-di, and used this as the core of our systems. The advantage of this technology is that it is compact, low cost, robust and as it uses light it doesn’t need to contact the item under test. This is particularly valuable for medical applications.


The finished product will be a rechargeable standalone unit somewhat smaller than the prototype shown with its own screen and will connect to an app to provide enhanced information to the operator or uploaded into the cloud.

The i-Scan™ pachymeter itself contains a number of core elements:
  • The confocal measurement channel
  • An alignment channel to enable the operator to view the patient’s eye and the meter’s internal alignment features
  • An illumination ring that projects the alignment feature onto the patient’s cornea
  • A camera that can be enabled to collect images of the eye
  • A trigger to start the measurement
  • Audible feedback to tell the operator when a good scan has been collected
  • Automatic data capture and device stop after start.
It is built into a small case that is convenient for an operator to use without the need for a chinrest stage.
There is the option to place the meter in a holder on a slip-lamp chinrest stage.


Some of Lein’s key developments over the last couple of years have been in the areas of accuracy, precision, measurement time and ease of use.

The new i-Scan™ pachymeter demonstrates the following features:
  • Non-contacting. The meter uses an optical technique that doesn’t touch the eye
  • Handheld. The meter is compact and easy to move around. It can be used handheld or in a slitlamp chinrest cradle
  • Easy to use. A new operator can become proficient with just a few minute’s training
  • Comfortable. Both for the operator and the patient. There are no bright lights and the meter has a generous, 25 mm working distance
  • Fast. The meter can be aligned to the eye and data collected in around 10 seconds
  • Accurate. Tests comparing the new meter to a gold standard pachymeter show just a couple of micrometres variation
  • Repeatable. The standard error is typically 2 – 3 µm.

The specifications of the meter are:
  • Corneal thickness range: 200 µm to 900 µm
  • Display resolution: 0.1 µm
  • Laser safety: Class 1 laser product
  • Wavelength: 1310 nm and therefore invisible to patient
  • Software: Lein’s dedicated graphical user interface.

The meter has been designed to be fast and convenient to use.

First the meter must be aligned to the patient’s eye using the following steps:
  • Hold i-Scan™ in one hand, supporting its front with the forefinger and thumb of the other
  • Hold i-Scan™ around 2 cm from the patient’s eye and rest a few fingers on their forehead
  • Look into the meter, keeping your eye around 5 cm from the viewfinder
  • Adjust the alignment until you can see the patient’s pupil and iris and a white ring reflected from the cornea
  • Align the white reflection ring with the centre static display ring by moving the meter left/right, up/down.
Once familiar with the meter it takes an operator just a few seconds to align the meter to the eye.

Once aligned the following procedure is followed to make a measurement:
  • Press and release the trigger to start the meter scanning
  • Maintain the alignment of the white reflection ring with the centre static display ring
  • Alter the size of the reflection ring very slightly by moving the meter closer to/further from the eye and move the meter left/right and up/down until the circles are concentric and you hear a “ping” sound from the laptop. This ping confirms a good scan
  • Maintain alignment where you hear the audible feedback until you have captured all the required scans
  • Once all scans have been captured the device will stop automatically.
It generally takes just a few seconds to collect the data.

The corneal thickness results are displayed on the screen along with their standard deviation and the detail of the scans themselves.
Lein Applied Diagnostics Ltd reserves the right to update and improve this specification without prior notice

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