The Biro Schiotz Tonometer is used to measure and monitor intraocular pressure in the eye. Portable for emergency readings. Durable design U.S. Certification by AAO specifications. Includes 4 weights. Plunger retractor optional.

Schiotz Tonometers are used to measure and monitor intraocular pressure in the eye. The Schiotz tonometer has a free floating barrel with a footplate. The footplate radius is greater than that of the cornea when resting on it, allowing the instrument to slightly flatten the cornea. At the center of the footplate there is a hole through which a plunger protrudes. The plunger assembly can be loaded with additional weights so that its total weight varies from 5.5 grams in its unloaded state to 7.5 or 15 grams.

The movement of the plunger as it indents the cornea amplifies a mechanical pointer that reads over a scale at the top the instrument. The scale reading is converted into an approximate value of millimeters of mercury by use of a graph or conversion chart.

For more detail: http://www.guldenophthalmics.com/ccp7/index.php?app=ecom&ns=prodshow&ref=Shiotz_Tonometer&sid=20w120nu003z63117423gi3986s82zv2