Spotlight on Technology & Technique

Monitoring Glaucoma With Motion Pictures

By Leslie Goldberg, Associate Editor

Ophthalmologists have many sophisticated tools that aid them in assessing glaucoma patients — automated perimetry, GDx, OCT, nerve fiber layer analyzers — but, for some tasks, the most commonly used tools are their own two eyes.

When performing structural assessment of glaucomatous progression, "for years the standard has been photographs, usually stereo photographs, of the optic nerve," explains New York's Nathan Radcliffe, of Weill Cornell Medical College and New York Presbyterian Hospital.

"Clinicians reference and compare old photos to new to look for progression," he says. "The nice thing about this technique is that standard photographs are routinely obtained for a variety of diagnoses, are available for many of our patients and are transferrable from one practice to another. A lot of historical data can be gained through photos." However, identifying the often-subtle changes between serial fundus images can be a challenge, even for the best clinicians.

Dr. Radcliffe believes that the new MatchedFlicker software application (from EyeIC of Narberth, Pa.) is the next evolutionary step in the ability to compare photos. It monitors onset and progression of glaucoma through change detection in time-series retinal photos. MatchedFlicker's technologies convert two photographs into a "movie" that flickers back and forth, allowing users to view change more easily as motion.

The software takes digital photos and automatically aligns them at a subpixel level using a computer algorithm. Users select images to compare and the computer program automatically aligns, resizes, rotates and adjusts them to provide a movie. The software does not alter the color of the photos, nor does it distort specific features or regions of the photograph.

"The software makes it possible to track small changes, such as the progression of peripapillary atrophy, which are often difficult to see in a side-by-side photo comparison," says Dr. Radcliffe.¹

Figure 1. A screen shot from the MatchedFlicker program. The upper left image demonstrates the original image taken in 2001. The lower left image represents a follow-up photo from 2004. On the right is the follow-up image matched with the baseline image. Both white-lined annotations demonstrate progression.

Physician Feedback

Dr. Radcliffe says that overlaying the images makes differences impossible to miss. "With this software, you can look at all the aspects of the optic nerve. You can look at disc hemorrhage, nerve fiber layer changes, at the cup, etc. You are able to evaluate all these different features of glaucoma with Flicker, whereas with OCT and HRT, you can only evaluate certain aspects of the optic nerve," adds Dr. Radcliffe.

With MatchedFlicker, doctors can mark areas of concern and save them within a Flicker file, and may highlight regions of change in printout.

"It is simple to use but you have to be able to recognize parallax," explains Dr. Radcliffe. "Users may see apparent change that does not represent real change. You need to recognize if one image is taken perfectly centered and the other is off center. Once you learn to identify and recognize parallax, your interpretation of the images becomes very accurate."

The bottom line, concludes Dr. Radcliffe, "is that this is a tool that helps physicians do a better job at looking at the optic nerve." OM

To view a MatchedFlicker movie, please read this article online at www.ophthalmologymanagement.com.

For more information on EyeIC's MatchedFlicker, visit www.eyeic.com.

Dr. Radcliffe uses MatchedFlicker in his research but has no financial interest to disclose.

Reference

1. Vanderbeek BL, Smith SD, Radcliffe NM. Comparing the detection and agreement of parapapillary atrophy progression using digital optic disk photographs and alternation flicker. Graefes Arch Clin Exp Ophthalmol. 2010 Apr 15.