medwireNews: The degree of nerve fibre layer (NFL)-focal loss volume (FLV) and the presence of disc haemorrhage may predict the rate of visual field (VF) loss in patients with open angle glaucoma, US researchers report.
These parameters, along with others such as ganglion cell complex (GCC)-FLV, pattern standard deviation, central corneal thickness (CCT) and VF index (VFI) “may be useful in the baseline evaluation of glaucoma and initial determination of treatment intensity (i.e., setting target [intraocular pressure]) and follow-up frequency”, David Huang (Oregon Health & Science University, Portland) and co-authors remark.
However, they caution that “the absolute predictive accuracies of these baseline parameters were not high, and there is room for further improvement in the development of novel predictive measurements.”
The study included 150 eyes from 103 patients with perimetric glaucoma who had completed at least nine visits during 4 years of follow-up.
Of these, 15.3% of eyes had confirmed rapid significant progression (CRSP), defined as a VFI slope below –1.0% per year or a mean deviation (MD) slope below –0.5 dB per year, confirmed at two consecutive visits, while 53.3% had slow progression, defined as a VFI slope at or above –0.5% per year or a MD slope at or above –0.25 dB/year.
The researchers found that the rate of VF progression, as measured by both VFI and MD, was highest in eyes with moderate, rather than mild or advanced, glaucoma.
“Thus there is evidence that glaucoma progression appears to decelerate in the advanced stages, at least as measured by the global VF parameters”, they say, adding that this “may be due to the greater intensity of treatment for advanced glaucoma patients.”
On univariate analysis, NFL-FLV was the strongest predictor of CRSP, with each standard deviation (SD) increase associated with a significant 2.3-fold increased likelihood of CRSP.
Increased GCC-FLV and pattern standard deviation also predicted an increased likelihood of CRSP, at odds ratios (ORs) of 2.0 and 1.6, respectively, per SD increase, whereas increased VFI and CCT were associated with a decreased likelihood, at ORs of 0.57 and 0.58 per SD increase, respectively.
The converse was true for predicting slow progression, with the likelihood increasing with increased VFI and CCT, and decreasing with higher NFL-FLV, GCC-FLV, and pattern standard deviation, but the associations were only significant for VFI and NFL-FLV.
Disc haemorrhage during follow-up was also significantly associated with progression rate, at odds ratios of 2.6 and 0.2 per occurrence for CRSP and slow progression, respectively.
On multivariate analysis, NFL-FLV and disc haemorrhage during follow-up remained significant predictors of both CRSP and slow progression, while VFI was associated with slow progression only.
Huang and team conclude in the American Journal of Ophthalmology: “Several [optical coherence tomography] and VF parameters were predictive of the speed of VF progression.”
They add: “Because glaucoma is mostly a chronic disease spanning many years, patient risk factors can change over time, and the risk assessment is likely to require continual updates and follow-on longitudinal analysis.”
By Laura Cowen
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