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As understanding of the multifaceted nature of glaucoma continues to grow, the steps practitioners need to take to monitor progression of the disease evolve. Key steps to take to monitor progression include confirming with repeat testing any visual function loss, remembering that structural measurements have variability, and using structural and functional testing together.
Hong Kong-Assessment of disease progression in patients with established or suspected glaucoma is an ongoing, multi-step, and essential process, according to Robert N. Weinreb, MD, speaking here at the 2008 World Ophthalmology Congress.
Dr. Weinreb pointed out the importance of assessing disease progression not only in cases of established disease, but also in patients in whom glaucoma is suspected.
Confirmation of loss of visual function also is critical, Dr. Weinreb said.
"If you have a functional test [result] that changes, it's not sufficient to accept that change without repeating the test to confirm that the visual function test has changed," he said.
Dr. Weinreb also reminded practitioners to be aware of the potential for variability in structural measurements.
"It has often been said that visual function testing has a disadvantage because it's subjective, and that structural testing is 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 testing method, Dr. Weinreb advised.
"Very often, this can be done by comparing change with change over time with a healthy group of individuals," he said.
Structural, functional together
Finally, use structural and functional testing together to detect the progression of glaucoma, he said.
"In the case of healthy eyes, we use structural and functional testing to detect any change that might indicate the presence of glaucoma," Dr. Weinreb said. "The combination of the two is also valuable to monitor progression."
Textbooks traditionally have characterized glaucoma as both a structural and a functional change that correspond to one other.
"We know from numerous studies that many of these technologies have results that don't necessarily correspond to each other," Dr. Weinreb said. "For glaucoma diagnosis, corresponding functional and structural loss can sometimes be identified. Glaucoma can also be diagnosed in individuals who have a confirmed change in visual function, even in the absence of detectable structural change."
Similarly, in patients who have a healthy structural appearance but in whom structural change-from healthy to unhealthy-can be confirmed, the diagnosis of glaucoma can be made even in the absence of a change in visual function or an abnormality in visual function, he said.
In diagnosed glaucoma
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 progression," he said. "So, in the case of a patient who has existing glaucoma in which we see a change in the visual function, we might say that this patient's disease condition has progressed even though the structure has remained stable.
"Conversely, if we can confirm a structural change in the optic disc or the retinal nerve fiber layer in a patient who has stable function, we can say, 'This patient has progressive change as well,' " Dr. Weinreb said.
He added that such structural changes can be confirmed using a hand-held lens, at the slit-lamp, with photographs using scanning laser polarimetry, or through optical coherence tomography.