4.        Meniscometry: OSDx® measures the Radius of Curvature (RoC) of the lower tear meniscus (LTM) by reflectometry. The operating principle is measurement of the reflection image of a known sized object and using concave mirror formulae to calculate the RoC. Note that RoC is not tear meniscus height (TMH) – the latter can only be measured using anterior segment OCT. However, RoC has got good correlation with TMH and can be used interchangeably. Unit of measurement is millimetres.
   1.         Switch to Meniscometry mode. Selecting the Meniscometry mode automatically switches the illumination to infrared (you will not be able to see any illumination coming on). Click on the start camera button to start the test.
   2.         Position the two parallel red line markers on the area of the meniscus you want to measure. Keep the meniscus vertically in the middle of the red marking lines. OSDx® takes readings automatically and freezes a valid reading and stops the camera. To retake the reading click the start camera button again. Reading will not be frozen unless quality parameters are met

 

 

3.         A running graph of the acquired data is displayed above the image and gives an indication of the quality of the data acquired. The graphical pattern should be one of the two types displayed below (single central hump well above the baseline or a double hump well above the baseline). The red gate lines will demonstrate whether the correct portion has been measured. Also, note the SD, which must be below 0.05 for a data to be accepted. 20 readings are taken from 20 consecutive frames for SD to be calculated.