Software uses trend, event analyses to measure progression

San Diego—The newest version of proprietary software (Guided Progression Analysis, Carl Zeiss Meditec) to measure the progression of glaucoma combines event and trend analyses and permits faster and more quantitative evaluation of progressive change in visual field, said Donald L. Budenz, MD, MPH, professor of ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine.

“And it builds in this concept of needing to confirm progression not only on just a single field but on two fields,” he added.

Dr. Budenz advised clinical correlation, however.

“Not everything that appears like progression on visual fields is going to be glaucoma, so one needs to rule out other factors…to explain progression on [the software],” he said.

Use of the software requires a particular, newer perimeter (Humphrey Field Analyzer II-i, Carl Zeiss Meditec), Dr. Budenz said. The program “adjusts for the reduced hill of vision in many of our elderly patients who develop cataract, and it works with the old threshold fields from the early and mid 1990s and the newer [Swedish interactive threshold algorithm] fields from the late 1990s,” he said.

The software was developed based on parameters for change used in the Early Manifest Glaucoma Treatment study, Dr. Budenz said. The new program determines change at specific points by comparing information from the pattern deviation plot instead of information from the total deviation plot as used in glaucoma change probability software. In theory, he said, this ability eliminates the confounding factor of change caused by diffuse depression of the visual field, which can occur in eyes with cataract, for instance.

The new software’s trend analysis capability “plots a new [visual field] index against a patient’s age and shows the rate of change thus far and then provides a prediction of future loss if the patient’s course is not changed,” Dr. Budenz said.

“Unlike mean deviation, it weighs central points more than peripheral points…and plots the age of the patient on the x axis rather than time,” he added.

The resulting graph can be helpful in explaining progression to patients, Dr. Budenz said.