Spotlight on Technology & Technique

Pupil Diagnostics Go Digital

By Samantha Stahl, Assistant Editor

Way back in the 19th century, a little thing called pupil defect testing began. Since then, despite the leaps and bounds ophthalmic technology has made, not much has been done to improve this subjective test. Relying on the swinging flashlight test to detect a Marcus Gunn pupil isn't particularly conclusive. The RAPDx from Konan Medical updates pupil testing for the 21st century with a high-definition, infrared, machine-vision system that offers a more reliable test for neuro-pupillary dysfunction.

Objective Testing

“The swinging light test is difficult to do in clinic,” says glaucoma specialist Theodore Krupin, MD, of Chicago. “The patient has to be dark-adapted and the clinician has to have skill. Also confounding are dark irises against dark pupils in a dark room. It's a test that we're doing, but not doing well. It's not standardized and completely subjective.”

With RAPDx, he says, all of those problems are taken care of. The test is conducted in a dark room. The patient places his face onto the instrument, which shines light individually into the left and right eyes. The pupil size and timing data between the two eyes is then compared to present the physician with a value representing the difference between the two eyes. “This is simple and quantified, a big change from what we have done prior,” he says.

“The technicians can easily administer this test for us, and provide back an objective, documented report that is significantly more detailed than the best human observer. All of our technicians also do the swinging light test, and I can tell you there's a real difference in the quality of the results,” notes Dr. Krupin.

Rather than using only white light, the instrument also uses different colored stimuli and patterns to stimulate the eye in the area of the macula and non-macular areas. He says that those with AMD in one eye have shown the biggest response to the test, and he has only encountered one patient with AMD who didn't have a positive response.

“As a screening test, it's very sensitive and really picks up on a lot,” he says. “An abnormal response can be related to many pathologies, but the RAPDx device tells you there's something wrong with the patient.” While the swinging light test can't make a diagnosis, Dr. Krupin notes that the most important thing is to flag a patient who needs further or closer examination to gather more data.

Patients with glaucoma who have a different extent of damage in each eye will cause a swinging light positive test. He has found that only about 15% of ocular hypertension patients have an abnormal response. “Even though we're calling them hypertensives, we're more concerned that there's a defect between the eyes that could be on the way to glaucoma. This is incredibly valuable new information.”

Dr. Krupin hopes that with expanded use, the instrument will act as a way to protect against progression of disease. “In looking for progression, the RAPDx device may detect defects earlier than nerve fiber layer or visual fields,” he says. “This may be able to pick up on when the pathology is getting worse.”

Beneficial Features

While the first RAPDx model Dr. Krupin used struggled with getting a response from small pupils, Konan has since put in cameras that can detect smaller pupil sizes. The device cannot be used with patients who have had glaucoma surgery because of the effect on the iris — a testament, he says, to the device's superb sensitivity.

The RAPDx presents monocular stimuli to digitally test for pupillary defects.

Because the instrument doesn't rely on the patients doing anything beyond keeping their eyes open, he says that the RAPDx device is very patient friendly. Automated blink detection minimizes error — if the patient blinks at any time during the recording, the machine reschedules that portion to the end of the test. Dr. Krupin also appreciates that the test is quick — within a few minutes he has results.

Included are Konan's cloud services, which the company says allows scalable test processing and archiving, web-enabled service and support, and QR linked patient information.

“It's an unbelievably good device,” says Dr. Krupin. “This gives you a lot of information in a short period of time.” OM

For more information, visit www.RAPDx.com.