Panel reaches consensus on IOP

September 1, 2007

Singapore-A group of leading authorities on IOP has issued a consensus document on the topic that aims to optimize care of patients with glaucoma. Conducted under the auspices of the World Glaucoma Association (WGA), the work was released at the World Glaucoma Congress (WGC) here and represents the fourth published consensus from the WGA.

Singapore-A group of leading authorities on IOP has issued a consensus document on the topic that aims to optimize care of patients with glaucoma. Conducted under the auspices of the World Glaucoma Association (WGA), the work was released at the World Glaucoma Congress (WGC) here and represents the fourth published consensus from the WGA.

“IOP is our only modifiable risk factor for glaucoma and is vital to all aspects of glaucoma diagnosis and treatment,” said Robert N. Weinreb, MD. “Measurement of IOP is straightforward, but interpretation of the data is not simple and has been limited by what methods have been available for measuring IOP and the limited number of determinations that can be obtained in clinical practice.”

Dr. Weinreb is past president of the WGA, chairman of the WGA Consensus Committee, and director of the Hamilton Glaucoma Center and the Distinguished Professor of Ophthalmology at the University of California, San Diego. Dr. Weinreb’s co-chairs for the IOP consensus project are James Brandt, MD, University of California, Davis; Ted Garway-Heath, MD, Moorfields Eye Hospital, London; and Makoto Araie, MD, University of Tokyo.

“Emerging information has led to reconsideration of many existing concepts about IOP and its evaluation,” Dr. Weinreb said. “The WGA consensus frames a current view on IOP from an international panel of experts and puts forth recommendations on how it can best be used to minimize glaucoma progression, prevent vision loss, and preserve quality of life.”

More than 120 authorities from around the world collaborated to develop the consensus on IOP. They were organized into committees to address topics that covered basic science, epidemiology, measurement techniques and interpretation, IOP variation, IOP as a risk factor, clinical trials, and target IOP. In a series of sessions conducted via the Internet over several months, each committee met to review relevant information and then produced a preliminary document.

“Our goal in producing the consensus was to be as comprehensive as possible,” Dr. Weinreb said.

A thorough process

The initial documents were circulated to the members of each group and to each of the 70 member societies of the WGA to solicit comments. In Fort Lauderdale, FL, prior to the annual meeting of the Association for Research in Vision and Ophthalmology in May, each consensus committee presented its report at a meeting. All member societies of the WGA were invited to be represented at that program. Following a day of discussion, a consensus panel reviewed the reports and the feedback. Revised reports were generated and sent to the member societies for final feedback. Based on the input received, the final IOP consensus was created and published during the WGC.

A consensus promulgation meeting also was held during the WGC, at which all 70 glaucoma-society members were represented. Each society was provided with a slide set and copies of the IOP consensus and prepared to disseminate the consensus information and educate its ophthalmologist members. The IOP consensus book is published by Kugler Publications and also is available for purchase.

The IOP consensus is designed to be user-friendly, making it a useful tool for practitioners, Dr. Weinreb told Ophthalmology Times. The consensus is an important resource, and some of the points reached by the consensus committees highlight discrepancies with prevailing opinion, he added.

For example, the basic science section includes language stating that uveoscleral outflow makes up 25% to 57% of total outflow in young, healthy humans and decreases with age, he said.

“Many textbooks still say that uveoscleral outflow contributes only 10% to total outflow,” Dr. Weinreb said. “The significantly higher proportion suggested by available evidence has important implications for glaucoma treatment.”

The section on IOP measurement emphasizes the importance of central corneal thickness and compares newer technologies for IOP measurement with the standard Goldmann applanation technique, he said.

“From comparisons of different tonometers in the same population, it was concluded that there was insufficient evidence to recommend any method of measurement at the current time as being superior to Goldmann applanation tonometry,” Dr. Weinreb said. “However, these new methods are being investigated extensively, and such a view will be reassessed in the future.”

Another important point of the IOP measurement section is its discussion of the importance of calibrating the Goldmann tonometer, he said.

“That is a necessary practice that even the vast majority of experts who attended the consensus meeting in Florida were not doing routinely,” Dr. Weinreb added.

Regarding IOP as a risk factor, the group found strong evidence to support the idea that higher mean IOP is a significant risk factor for glaucoma development and progression. They also found, however, that insufficient evidence exists to support ideas that 24-hour IOP fluctuation or longer-term IOP variations (over periods of more than 24 hours) affect the risk of disease development or worsening.

“This information is important because the concept of IOP fluctuation as a risk factor has been popularized widely,” Dr. Weinreb said. “Further study is needed.”

Other highlights

The epidemiology section of the consensus document, chaired by Anne Louise Coleman, MD, PhD, includes language pointing out that studies using similar methodologies to measure IOP in multiple racial groups generally have not been performed. Therefore, direct comparisons of potential racial-ethnic differences cannot be made.

“The available data indicate that IOP is lower in Asians than in persons of African or European descent, but sufficient direct comparative studies have not been done,” Dr. Weinreb said.

The clinical trials section, chaired by Felipe Medeiros, MD, discusses protocols for IOP measurement and reporting and emphasizes the importance of obtaining at least two post-screening IOP measurements on at least two different days for calculating a baseline IOP prior to randomization.

That methodology has not been followed routinely in clinical trials, Dr. Weinreb noted.

The target IOP section, chaired by Henry Jampel, MD, also emphasizes that a target IOP should be estimated and recorded in such a way that it is accessible on subsequent patient visits. Additionally, the report indicates that the target IOP requires periodic reevaluation.

Following a meeting in San Diego, the WGA issued its first consensus document regarding the diagnosis of glaucoma in November 2003.

In April 2005, it released a consensus document on open-angle glaucoma surgery. That report was followed in May 2006 by a consensus on angle closure and angle-closure glaucoma.

Updating the information in those publications is an ongoing project for the WGA Consensus Committee, Dr. Weinreb concluded.OT