The human eye is one of the most intricate and delicate parts of the body. We know this without even thinking about it. Think of your reflexes and how quickly you can instinctively blink to protect your eyes from a perceived threat, such as a foreign object or an extremely bright light. Sight is a valuable sense to our survival, and we are hard-wired to preserve it.
But even our well-honed reflexes can’t protect us from every threat to our precious sight. Some threats to our vision encroach from within. For these threats, we rely on trained medical professionals to examine our eyes using instruments and expertise that aren’t available to us. Tonometers are one such instrument, and the ability to read them and act on their results is an example of that expertise. In this look at the purpose and importance of tonometry, we’ll further explore this device and its relevance to your continued gift of sight.
Tonometry begins deep in your cranium with a part of the body it cannot reach. We are speaking of the optic nerve, a forked nerve that runs from the eyes to the brain. Think about your television and how a cable transfers information to present the picture on your screen. The optic nerve is the coaxial cable of your mind; the nerve transmits information to your brain so you may see and interpret what your eyes pick up. However, the optic nerve, like the rest of our nervous system, does not take damage well. The body cannot repair damage to the nerve, and such damage results in the loss of sight, whether this leads to loss of peripheral vision or complete and irreversible vision loss.
What, then, might damage the optic nerve? Rare causes include severe inflammation and tumors that press upon the nerve. By far, the most common cause of damage to the optic nerve comes from an abundance of fluid pressure within the eye. The eye contains aqueous humor, a fluid that lubricates and nourishes the eye. Aqueous humor must maintain a certain level of pressure to keep the eyeball in shape and in place. But when the fluid cannot properly drain and recirculate, the pressure rises to unhealthy levels and presses upon the optic nerve, gradually causing damage.
The tonometer, from the Greek for “pressure measurement,” does exactly what those morphemes would suggest—it measures the pressure of fluid in the eye. A tonometer does this by pressing a highly calibrated instrument against the surface of the eye and recording the resistance it encounters. High pressure indicates that your eye could be damaging its own nerve. A lack of intervention would certainly lead to a lack of sight over time. Doctors may try to resolve the insufficient drainage with medication or surgery, but this would not be possible without the valuable insight that the tonometer lends, further attesting to tonometry’s purpose and importance. Just as ophthalmologists rely upon the tonometer, they too rely on ophthalmic equipment providers to keep this vital instrument sanitary and accessible to a variety of patients.