Many factors must be considered when measuring glaucoma progression

June 29, 2008

Ophthalmologists should assess disease progression in patients with established and suspected glaucoma, should confirm with repeat testing any visual function loss that is seen, should remember that structural measurements have variability, and should consider using structural and functional testing together to detect disease progression, said Robert Weinreb, MD. The distinguished professor of ophthalmology and director, Hamilton Glaucoma Center, University of California in San Diego, LaJolla, CA, concluded a course about detecting progression in glaucoma by highlighting points made in the preceding presentations.

Ophthalmologists should assess disease progression in patients with established and suspected glaucoma, should confirm withrepeat testing any visual function loss that is seen, should remember that structural measurements have variability, andshould consider using structural and functional testing together to detect disease progression, said Robert Weinreb, MD.

Thedistinguished professor of ophthalmology and director, Hamilton Glaucoma Center, University of California in San Diego,La Jolla, CA, concluded a course about detecting progression in glaucoma by highlighting points made in the precedingpresentations.

Ophthalmologists should assess disease progression not only in cases of established disease but also in patients in whomglaucoma is suspected, Dr. Weinreb said.

"Progression is both the change from normal to abnormal or the change from abnormal to more abnormal," he added.It's also important to confirm loss of visual function, Dr. Weinreb said.

"If you have a functional test [result] that changes, it's not sufficient to accept that change," he said. "It's necessary torepeat the test and confirm that the visual function test has changed."

Dr. Weinreb also reminded attendees about variability in structural measurements.

"We've all been told that visual function testing has a disadvantage because it's subjective and that structural testing isimportant because it's objective," he said. "One should never forget that structural testing, just like functional testing,has variability."

Ophthalmologists should determine whether the change being measured is greater or less than the variability of the testingmethod, Dr. Weinreb said.

"Very often, this can be done by comparing change with change over time with a healthy group of individuals," he said.Structural and functional testing can be used together to detect the progression of glaucoma, Dr. Weinreb said.

"In the case of healthy eyes, we use structural and functional testing to detect any change that might indicate the presenceof glaucoma," he said.

Textbooks traditionally have characterized glaucoma as both a structural and a functional change that correspond to oneother, Dr. Weinreb said.

"We know from numerous studies . . . that many of these technologies have results that don't necessarily correspond to eachother," he said. "So you can say that these technologies are complementary.

"In the case of looking for a glaucoma diagnosis, what we can look for is not what is written in the textbooks, which iscorresponding functional and structural loss, but we can look for individuals who have healthy visual function [and] who havea confirmed change in visual function. Even in the absence of structural change that is detectable, these patients can alsobe considered to have glaucoma," Dr. Weinreb said.

Conversely, he added, in patients with a healthy structural appearance in whom structural change-from healthy tounhealthy-can be confirmed, "even in the absence of a change in visual function or an abnormality in visual function, with aconfirmed change in structure, we can diagnose glaucoma," he said.

A parallel situation can exist for patients in whom glaucoma already has been diagnosed, Dr. Weinreb said.

"We don't necessarily need to look for both structural and functional change to be convinced that the patient has [disease]progression," he said. "In the case of a patient who has existing glaucoma in which we see a change in the visual function .. . we might say that [the condition of a] patient has progressed even though the structure has remained stable.

"Conversely," he said, "in the patient who has a stable function, if we can confirm a structural change in the optic disc orthe retinal nerve fiber layer, whether it be from a hand-held lens or at the slit-lamp, with photographs using scanning laserophthalmoscopy or optical coherence tomography, we can say, 'This patient has progressive change as well.' "