Faster retinal ganglion cell thinning associated with higher risk for perimetric glaucoma
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Key takeaways:
- Faster rates of GCIPL and cpRNFL thinning were associated with increased risk for developing perimetric glaucoma.
- Evaluation via macular OCT may help monitor progression in eyes with suspected glaucoma.
Monitoring rates of ganglion cell/inner plexiform layer and circumpapillary retinal nerve fiber layer thinning may help determine glaucoma progression in eyes with suspected glaucoma, according to data published in JAMA Ophthalmology.
“Evaluation of [circumpapillary retinal nerve fiber layer] and specifically macular OCT should be considered in clinical practice for monitoring the course of eyes with suspected glaucoma,” Vahid Mohammadzadeh, MD, from the Shiley Eye Institute at the University of California, San Diego, and colleagues wrote.
In an observational cohort study of 658 eyes from 462 participants (mean age, 63.3 years; 60% women) with suspected glaucoma, researchers examined rates of ganglion cell/inner plexiform layer (GCIPL) and circumpapillary retinal nerve fiber layer (cpRNFL) thinning over a mean follow-up of 3.2 years. They compared eyes with suspected glaucoma that did and did not develop perimetric glaucoma.
According to results, 23% of eyes developed perimetric glaucoma. The mean global GCIPL thickness for eyes with suspected glaucoma that did vs. did not develop perimetric glaucoma was 72.1 µm and 76.4 µm, respectively (P < .001), while the mean minimum GCIPL thickness was 67.9 µm vs. 73.5 µm, respectively (P < .001).
In addition, mean rates of GCIPL thinning were faster in eyes that developed perimetric glaucoma, with researchers reporting that for every 1-µm per year faster rate of minimum GCIPL thinning there was a 2.4-times higher risk for development of perimetric glaucoma (P < .001).
Further, researchers reported that for every 1-µm per year faster rate of global cpRNFL thinning there was a 1.9 higher risk for developing perimetric glaucoma (P < .001).
Predictive factors that increased the risk for developing perimetric glaucoma included African American race, male sex and higher IOP during follow-up, all of which were significant.
“A faster rate of GCIPL and cpRNFL thinning was associated with a significantly higher risk of developing perimetric glaucoma,” Mohammadzadeh and colleagues wrote. “In addition, the rate of minimum GCIPL thinning was two times faster in eyes with suspected glaucoma that developed perimetric glaucoma compared with those that did not develop perimetric glaucoma.”
Perspective
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Clinically, it is challenging to interpret the relevance of minute declines with sequential global and regional OCT measurements. The authors of this study demonstrated the significance of small rates of change (1 micron or less) in pre-perimetric glaucoma by evaluating rate as a predictive value for conversion to perimetric glaucoma. Shifts as small as 1 micron per year in both cpRNFL and retinal ganglion cell complex (RGCc) were shown to have a twofold increase in risk for conversion to perimetric glaucoma.
Variability is a concern when relying on rate of change as a predictive value. Shifts of one micron or more are not unusual with sequential readings in the clinical setting where measurements can be influenced by number of factors including signal strength, erroneous segmentation and the presence of comorbidities. The authors used a mean number of 5.5 scans over 3.2 years with a scan quality minimum of 6 and expert evaluation regarding segmentation and removal of artifacts. These parameters may be more ideal than those encountered in a clinical setting, and their interpretations should be applied with caution. To mitigate effects of variance, one potential approach might include frequent measurements of the cpRNFL and RGCc in pre-perimetric glaucoma with an emphasis on ideal scans.
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