That dang air puff
A lot of people are scared to visit the eye doctor because of the air puff test. What is it? Is it absolutely necessary? Can you avoid it?
The air puff test is what people commonly call the non-contact tonometry (NCT) test. It is used to determine the pressure inside the eye, also known as the intraocular pressure (IOP). Knowing a patient’s IOP is the most important tool that optometrists have to screen for glaucoma. An IOP that’s elevated to an unsafe rage feels very similar to most types of high blood pressure – that is you feel just fine. By the time you begin to notice symptoms it is too late. Consequently it’s important for your doctor to check your IOP at least annually.
I can hear you saying, “Come on doc. That test is horrible!” I totally agree with you. The NCT machine blows a measured amount of air at the eye which deflects the cornea a bit. Infrared sensors measure the corneal deflection and correlate it to the pressure inside the eye. When one puts it that way it doesn’t sound too bad. In fact it works extremely well on a research lab bench. In the real world…well…not so much. Our eyes have a great natural reflex that protects them when something comes close or contacts the eyelashes. That’s why people blink and get nervous about the air puff. In fact, patients typically blink and clench their eyes so much during NCT that the IOP reading frequently is nowhere near the true value. I’m the worst at this. Do NCT on me, and I become as fussy as a toddler without his nap and snack. I dislike doing NCT on patients and having it done on me so much that we don’t even have this machine at Park Slope Eye. It’s a really dated technology.
Fortunately there are alternatives. A very common and extremely accurate way to measure the IOP is Goldmann tonometry (aka the blue light test). With this test, patients get a yellow eye drop that makes the eye glow when exposed to a blue light. The doctor steers an illuminated prism very close to the eye. When the doctor looks in his microscope, the IOP is correlated to the degree that the prism bends the light. This method is considered the gold standard of IOP measurement. It is painless but still scares many patients.
At Park Slope Eye we have an even better way to determine patients’ IOP. We have a special device from Helsinki, Finland that gives just as accurate IOP readings as Goldmann tonometry. A very tiny wand bounces off the tears and the device measures the force at which it returns. It’s very fast, painless, and requires no drops. A few seconds after I explain it to patients, the machine has already measured the IOP three times in each eye! We are one of the few offices in New York that actually has this technology. Ask a friend who comes to Park Slope Eye what they think about it. Stop by the office if you don’t know anyone who is a patient here. I’d love to demo it for you (and make you some coffee)!
Spencer Ritenour, O.D.