The iTrace vs. The NIDEK/Marco OPD III

At first glance, the iTrace from Tracey Technologies and the OPD III from NIDEK/Marco Ophthalmic (US-only) may appear to have similar attributes. Both devices offer the same suite of tools: a combined autorefractor, pupillometer, keratometer, wavefront aberrometer, and corneal topographer. So how can you determine which visual scanner will better suit your practice, the iTrace or the OPD? The answer starts with an analysis of how these tools capture data about a patient’s vision.





The iTrace’s diagnostic aberrometry uses proprietary ocular Ray Tracing technology, which sends 256 consecutive beams of light into the eye one at a time and measures where each lands on the retina. The resulting pattern is measured to record aberrations, producing an exact simulation of how light functions when it enters the eye during the process of vision. This is the most accurate replication of ocular function, and the most accurate objective refraction possible.
The OPD III uses dynamic skiascopy, which sends a slit of light beams into the eye and measures aberrations as a function of the beams that bounce back out of the eye. Dynamic skiascopy has a “fatal flaw” — the fact that it has to interpolate results around a 2 mm blind spot in the center of the measurement field. [1] In cataract patients with smaller-than-average pupils, the central 2 mm is essential and guessing it makes overall data unreliable and difficult to use as a basis for critical decisions about patient care.


In addition, because the area of measurement is limited with OPD-Scan technology, it misses “skewed rays” — returning beams of light that don’t bounce back in the measurement area. A study published in the journal Eye found that this may cause the OPS-Scan technology to miss higher order aberrations (tetrafoil, pentafoil, and hexafoil) [2], factors that can make a difference in the way vision correction should be planned for a patient. The problem with the OPD III is in the data it doesn’t see.

In Practical Terms: The iTrace vs The OPD III

In addition to the core differences in the technology used to scan patients, the following are key differences in the functionality and outputs available with the iTrace and the OPD III


When used as part of a surgical consult, a visual analysis should generate the most complete information about a patient’s vision, allowing doctors to have a better understanding of the source of visual errors and make better choices about vision correction.
iTrace Dysfunctional Lens Index

The iTrace Dysfunctional Lens Index

Both the iTrace and the OPD are designed to give doctors insight into the cornea and the lens. To further distinguish true visual function between the cornea and the lens, the iTrace generates a quantitative value that enables doctors to track vision loss over time, called the Dysfunctional Lens Index (DLI).

Doctors can track movement on a ten-point DLI scale with changes in a patient’s vision and make an informed decision on the right time to recommend a lens replacement procedure like cataract surgery or refractive lens exchange (RLE).

Toric IOL Planning

Both the iTrace and OPD generate an image of the eye used for planning the positioning of a toric lens, using values generated by respective methods of aberrometry and overlays of Angle Kappa and Angle Alpha. However, toric IOL placement is an area where precision is essential. Given the propensity for measurement error in internal aberrations with dynamic sciascopy, leading practitioners around the globe prefer the iTrace’s use of propriety ray tracing technology.
Toric IOL Planning


The iTrace is the only device that can measure accurately through artificial lenses. That means that after a lens replacement procedure, the iTrace can be used to validate surgical results or explore surgical surprises. If a patient isn’t satisfied with their vision after surgery, an iTrace scan is an invaluable tool for your practice.
iTrace Toric Check

The iTrace Toric Check

You can use the iTrace to verify the placement of a toric IOL and determine if any additional rotation is needed to further improve vision. If you want to do a post-surgical confirmation of a toric IOL’s placement with the OPD III, you’ll have to dilate the patient, and the results will be similar to an examination done with a slit lamp.

The iTrace generates a precise visual depiction of a toric IOL placement compared to the optimal axis location. It provides the patient’s current refraction and the exact degree of rotation it will take to get to the best outcome for a patient, guaranteeing the best possible results from toric lens surgery. All of this can be done without ever dilating a patient’s eyes!

Ready to Learn More
About the iTrace Advantage?

Integrate the iTrace easily into your current IT environment and patient databases. Unlike the OPD III, which functions exclusively in conjunction with an on-board computer, you can pull up the iTrace display on any networked computer in your exam lane.

More importantly, when you purchase an iTrace, you’re getting the benefit of a team dedicated to customer support. At Tracey Technologies, our team is dedicated to your success using the iTrace — and we’ll make sure that you have the resources you need to better serve your patients and grow your practice!

To learn more about using the iTrace in your practice, schedule a demo, call or email us today!