Contact tonometry is similar to non-contact tonometry with the obvious difference- contact tonometry comes in direct contact with the eye.
In developing countries, contact tonometry poses a greater cultural issue. Dilation and numbing drops are not highly accepted, which turns people away from wanting to get tested for glaucoma. As discussed in the last post, glaucoma undiagnosed will cause irreversible blindness.
Like non-contact tonometers, contact tonometers are very expensive. Most are sold for close to $4,000. Non-portable ones are even more expensive.
So at this point you might be wondering, why would anyone need a contact tonometer over a non-contact tonometer? The largest draw to a contact tonometer is the accuracy. Non-contact tonometers are not nearly as accurate as contact ones.
Contact tonometers measure IOP by applying direct pressure onto the cornea. In order to come in direct contact with the eye dilation and numbing is required. This is not desirable in developing countries, but it is necessary for a contact tonometer to measure the IOP. Most tonometers are calibrated to measure in millimeters of Mercury (mmHg).