Traditional tonometers are mainly divided into two types: indentation and applanation.
1. Indentation type: a certain weight of intraocular pressure measuring rod is used to depress the cornea into a depression. Under the condition that the weight of the tonometer remains unchanged, the deeper the indentation, the lower the intraocular pressure, and the measured value is affected by the hardness of the eyeball wall Influence. Schiotz tonometer falls into this category.
2. Flattening type: flattening the convex surface of the cornea with a certain force without sinking, the eyeball volume changes very little, so it is less affected by the hardness of the eyeball wall.
According to the flattened area or pressure of the cornea, it can be divided into two types.
1. One type is fixed applanation and integrable, depending on the amount of force required to flatten the area, the smaller the required force, the lower the intraocular pressure, such as the Goldmann applanation tonometer;
2. The other is a fixed pressure (the weight of the tonometer does not change) to look at the applanation area, the larger the applanation area, the lower the intraocular pressure, such as the Maklakov applanation tonometer.
