Significant structural relationships found between macular thickness and visual field defects

A macular OCT scan may complement other diagnostic modalities to help diagnose and manage glaucoma.

Issue: January 25, 2013

A retrospective study of glaucoma patients who underwent macular optical coherence tomography scans and automated visual field exams found predictable and significant relationships between macular thickness parameters and anatomically related visual field defects.

“I believe macular scanning using optical coherence tomography has the potential to be very useful in a clinical setting,” Louis B. Cantor, MD, an OSN Glaucoma Board Member and study coauthor, said. “We traditionally focus on various types of nerve fiber bundle defects, describing glaucoma vision loss as starting off in the periphery and the side vision, and then working itself in. But in reality, what we have also known for some time is that glaucoma patients subjectively notice a lot of other problems with their vision, such as color and contrast, which are macular functions.”

Although researchers have demonstrated a global vision loss with glaucoma, they have not concentrated much on the central aspects of vision, he said.

The study was published in Journal of Glaucoma.

Louis B. Cantor

Study methods

The same equipment was used on 127 eyes of 127 glaucoma patients: a Stratus OCT, software version 4.0.1, and a Humphrey Visual Field Analyzer (both Carl Zeiss Meditec).

The macular scans recorded the superior and inferior inner and outer sectors, whereas the visual fields recorded the threshold sensitivities of the 16 points within the central visual field in an effort to establish a correlation with the macular scans.

“We expected some correlation but were surprised by how robust these correlations actually were,” Cantor told Ocular Surgery News. “However, there was not any particular area of the macula that truly stood out more than any other, which I think is probably consistent with what we would have thought: that all areas of the macula are important. Of all the macular areas that we looked at, roughly 80% to 90% of them had P values of .001. This is a highly statistically significant correlation.”

For instance, the superior inner macula showed a positive correlation with the inferior inner visual field line, and the superior outer macula strongly corresponded to the inferior outer visual field line.

Combining data

Cantor said that clinicians need to take a closer look at macular data when diagnosing and managing glaucoma patients and to listen closely to what patients say about macular function. In glaucoma diagnosis and follow-up, there is generally no one parameter that is followed.

“It is the correlation between multiple data sets that allows us to make the best decisions. So knowing what the pressure is, seeing what the visual field looks like, noticing what the retinal nerve fiber looks like on scan, and putting that all together helps us make the best decision,” Cantor said

Adding macular thickness measuring to the equation may improve outcomes in a patient who, for example, has changes in macular thickness that correlate with visual field defects, along with borderline IOP and a retinal nerve fiber layer that appears slightly thinner in some areas. Using all of this information may tip treatment decisions one way or another, Cantor said.

“Adding one more parameter to the mix may improve the sensitivity and specificity of our testing,” he said.

While the study demonstrates a decisive correlation between macular thickness and glaucomatous visual fields, “I don’t think we know yet exactly how to apply these data for decision-making,” Cantor said. “Meanwhile, I would encourage my colleagues to begin assessing macular thickness to see if it looks low or abnormal in a given patient or if it has changed in a patient over time.”

Cantor and colleagues continue to collect data on additional macular OCT scans, hoping to double the number of eyes under study. – by Bob Kronemyer

Reference:

Boling W, et al. J Glaucoma. 2012;doi:10.1097/IJG.0b013e318239c32b.

For more information:

Louis B. Cantor, MD, can be reached at Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, 1160 W. Michigan St., Indianapolis, IN 46202; 317-278-2651; email: lcantor@iupui.edu.
Disclosure: Cantor has no relevant financial disclosures.