An innovative digital tonometer by Diaton offers non-invasive IOP measurement.

Just as there are several modalities for measuring IOP today, there are also many variables that can negatively impact those measurements. Corneas that are abnormally thin or thick, corneas that are crooked or rigid, corneal hysteresis or keratoconus, edema or erosions, and scaring caused by surgery or injury — all these dynamics will complicate glaucoma screening due to the involvement of the cornea in IOP readings. Another type of tonometer, however, has been allowing physicians more flexibility when taking IOP measurements because it works independently of the cornea.

The Diaton, a digital tonometer manufactured by New York-based DevelopAll Inc. (formerly BiCOM), works by placing the device over the upper eyelid, above the limbus, to obtain more accurate results, especially among patients in whom IOP is otherwise difficult to measure. “Many corneas are not typical,” says Roman Iospa, chief executive officer at DevelopAll Inc. “We’re offering a more accurate way of measuring IOP, avoiding influence of corneal variability.”

CHARACTERISTICS AND APPLICATIONS

A transpalpebral, transscleral instrument approved by the FDA, the Diaton requires no anesthesia or sterilization. With a pen-like feel, it is handheld and easily portable. Patients can have their measurements conducted without removing their contact or scleral lenses. The tonometer requires no consumables, such as replacement tips or covers, no calibration, and there’s no need for pachymetry or to adjust for central corneal thickness. As a non-invasive tool, it carries no risk of scratching the cornea or spreading infection through the device itself — an important consideration given raised awareness for public health best practices related to the spread of viruses such as COVID, influenza and respiratory syncytial virus.

Coming out of the coronavirus pandemic, “Patients today are more likely to understand the entry points to infection, with the eye being one of them,” says Mr. Iospa. “During the pandemic, there was a push against conducting puff and contact tonometry, and our product has proven to be safer. A combination of no puff and no contact with the eye ensures the lowest possible risk of viral transmission.”

According to Emil William Chynn, MD, MBA, FACS, medical director at Park Avenue Laser Vision, New York City, the device has also been especially useful among patients where standard direct applanation tonometry is difficult or not viable, such as among pediatric patients, those with strong blink reflexes, those who have undergone refractive surgery or in the presence of certain corneal pathology. “Using this instrument is also the only option when there’s hardware in the cornea, such as with a keratoprosthesis, because everything else is based on contact with the cornea,” Dr. Chynn says.

Measuring IOP in immobilized patients is also possible because the measurements can be recorded with patients in either a sitting or supine position. Patients diagnosed with chronic conjunctivitis or corneal dimness after penetrating keratoplastics, keratoprosthesis, high degree of ametropia or astigmatism will also benefit from utilizing the device. Measuring IOP immediately after LASIK, LASEK or photorefractive keratectomy is also accurate with this tonometer. In addition, no anesthesia is used nor latex disposables, avoiding the possibility of allergy to either.

TONOMETER TECHNIQUE

Equipped with a lightweight, surgical-grade stainless steel tip that extends slowly from the device when it is held vertically above the patient’s eye, the tonometer captures measurements by resting onto the eyelid as it is lowered. With the patient seated and their head tilted, the clinician pulls the eyelid back to clear the lid of the cornea. The tip is then placed onto the eyelid behind the lashes. When the patient is comfortable, the clinician presses down once with the tip then lifts the device and tilts it back to re-register the tip. A digital screen displays a measurement within seconds. This process is repeated three times in order to record an average reading.

As Mr. Iospa explains, the tonometer functions based on Newton’s second law of motion, which states that the acceleration of an object is dependent upon the net force acting upon the object and the mass of the object. “We drop the tip onto the eyelid, measure the speed of the rebound and convert that into an IOP,” he says. The tip can be cleaned with an alcohol swab after use.

Certain habits need to be cultivated to avoid errors, notes Mr. Iospa. “The most likely error is allowing the eyelid to slide back to the cornea when the reading is taken,” he says. “That will result in an artificially low result because the device is calibrated for the eyelid and the sclera.” Another problem would be to not hold the device completely vertical. “The device beeps to guide the user into proper positioning,” Mr. Iospa explains.

CLINIC PROTOCOL

A longtime user of the tonometer, Mark Latina, MD, an associate clinical professor, Tufts University School of Medicine and inventor of selective laser trabeculoplasty, says integrating the device is an easy transition for any practice. “The learning curve is not as steep as with other devices because you don’t have to applanate,” he says. “You just need to palpate the lid, and once that technique is confirmed it’s a very reproducible device. Techs can use it and record the information while the physician is seeing other patients. And the company offers online support, so the clinic doesn’t have to conduct its own training with staff.”

What stands out most, however, is the product’s efficiency and its ability to reduce the length of examinations, Dr. Latina says. “Techs can conduct the eye pressure measurement before the patient is seen by the physician. And there are no tonometer tips to replace or other parts. Another huge plus is that you don’t need a slit lamp.”

Despite being available on the market for about 10 years, it’s these types of attributes that have continued to generate more interest in the device, according to Mr. Iospa.

“There’s a ‘wow’ factor that we are seeing with this tonometer, and we are receiving a lot of interest,” he says. “Consistency with IOP measurements is very important, and this device is helping physicians to find that consistency.” OM