This is the most used device in hospitals nowadays.
Each division on the scale corresponds to an indentation of 1/20 mm on the cornea.
The design theory is to use the pointer to press the cornea and then indirectly get the intraocular pressure.
Schiotz type. All the parts contacting the cornea are stainless steel which is anti-acid and does no harm to tissues.
The instrument is safe, reliable, applicable and convenient.