Tonometer and Its Application

Tonometer is a boon to medical optics as it helps detect glaucoma at very early stages. It measures the pressure inside the eyes to detect if the glaucoma treatment is going well or not. Glaucoma refers to the group of eye diseases that can cause partial or complete blindness over time. In such diseases, the nerve that connects the eye and the brain gets damaged due to excess pressure. As described earlier, it determines the pressure with absolute accuracy, thus, helping greatly in the treatment. Tonometry is the procedure performed by an eye specialist using tonometers to determine the pressure of the eyes. Let’s study the uses of tonometer and types of tonometry in brief.

Tonometer

Hjalmar Schiotz, in the early 1900s, designed and introduced the first clinically helpful tonometer, which was extremely simple to use with high precision. The model got high acceptance. Due to the invention, the knowledge of glaucoma and its effect on the eyes increased greatly. Later in the 1950s, Goldmann adjusted ocular rigidity in the tonometer. The modern electronic and non-contact tonometers still obey the principles of Goldmann and Schiotz.

The test performed for determining the eye pressure (intraocular pressure) using this instrument is the tonometry. The test is essential for people facing blurry visions (especially those over the age of 40 or 60). If the disease (glaucoma) remains untreated, it can cause complete blindness. Glaucoma increases the pressure inside the eye, which eventually harms the optic nerve leading to vision loss. As mostly the symptoms of this disease remain unnoticed, the tonometry test is necessary in case of any abnormal changes in eye vision.

Who should go for a Tonometry Test?

The people with the following symptoms must visit their eye specialist to get a tonometry test:

• Sharp eye pain
• Loss of vision or blurry vision
• Cloudy vision around the lights.
• My eyes are getting red.

According to the American Academy of Ophthalmology (AAO), the people who are at high risk of glaucoma and should have a tonometry test are as follows:

• People of age 40 or above have an increased risk of developing glaucoma.
• If a person has a family history of this disease, they are more likely to have it.
• Facing issues like myopia and hypermetropia. 
• Having some other chronic eye infections or injuries in the eye.
• A person with diabetes is more likely to catch such other diseases.
• Other reasons include abnormal blood circulation, high blood pressure etc.

How is Tonometry Performed

Tonometry is performed by using the tonometers in three primary ways. These three primary ways for the detection of eye pressure are as follows:

Method 1

This method gives the most accurate results, and it measures the required force to flatten an area of the eye’s cornea. You will not feel any discomfort as to this determination. The surface is numbed using specific eye drops. Now, a strip of paper (stained with orange dye) remains suspended near the side of the eye under observation. Rest your forehead and chin on a slit lamp and keep your head still. The eye specialist will continuously move this lamp until the tonometer reaches the eye’s cornea. The specialist will use blue light to make the range dye glow green. Now, he will examine the eye on this slit-lamp, and the dial adjustment will give the pressure reading.

Method 2

The second method involves a device held in hand, just like a pen. The eyes are numbed with eye drops, just like in the previous case. This pen-like device will reach the cornea and instantly record the eye’s pressure.

Method 3

Method 3, or the air puff method, is a non-contact method for determining eye pressure. This method involves resting the chin on an examining device. The specialist will reflect a tiny light beam (off of your cornea) into a detector. During this procedure, the air puff slightly flattens the cornea. This flattening depends upon the eye pressure. Now, the light beam will move to another spot on the detector. The pressure on the eye will depend upon how far the light beam will move. This test is most preferable as it involves no-touching with proper accuracy. 

Normal and Abnormal Eye Pressure

If the test performed by the tonometer turns out normal, then the person shall not have glaucoma. As described by Glaucoma Research Foundation, 12 50 22 mm Hg is the normal eye pressure. If the tonometry reading comes above 20-22 mm Hg, then the person shall have glaucoma or pre-glaucoma. Now, the doctor will perform additional tests to confirm the results.

Conclusion

Glaucoma is a severe eye disease responsible for blindness in several people above 60. A tonometer is an instrument in medical optics that determines the pressure on the eye. The pressure tends to remain high for patients with glaucoma. People with blurry vision, redness in the eye or cloudy vision must visit their eye specialist for their eye check-up. There are three basic methods of performing tonometry. The tonometry has a great significance as it gives the result with high accuracy, and the disease can be treated early. Moreover, if the disease remains untreated, it can cause complete blindness.