OCT Vital Tool In Identifying Glaucoma Progression

Synopsis
Structural evaluation with OCT as well as practical screening with visual fields must be used throughout the glaucoma condition continuum to detect progression.
Glaucoma worsens slowly in the majority of patients who are affected with the illness, but a significant number of patients with glaucoma show a minimum of progression  with time based upon monitoring with optical coherence tomography (OCT) and also visual fields.
Although OCT can detect progression in patients across all phases of illness, the findings from OCT as well as standard automated perimetry (SAP) regularly disagree, so do we have to look at both results or can we just rely on one.
As a result, it is essential that patients who have been diagnosed with glaucoma be followed for progression using both methods, according to an ophthalmologist for the best and most accurate results.
The above details and also referrals made by the doctor are based upon findings from evaluations of data gathered in the Duke Glaucoma Registry Research Study from over 27,000 eyes of over 14,000 patients with glaucoma or that were glaucoma suspects.
Throughout follow-up that ranged to almost 9 years, this large patient group had actually gone through more than 100,000 tests with spectral-domain (SD) OCT.
“We believe our undertaking is probably the biggest and largest analysis of longitudinal SD OCT and SAP results to date, the large sample size thus solidifying the authenticity of our subsequent outcomes” the doctor stated. “Visual field testing remains the key method of examining glaucomatous progression and may continue to remain so, however the findings of our research are practical for understanding where OCT works and may also be utilized.”
In examining the information, eyes were categorized as having slow, modest, fast, or catastrophic change over time based upon typical yearly change in SAP or typical retinal nerve fiber layer (RNFL) thickness change standards. As an example, eyes with <0.5 dB/year change in SAP or <1 μm/year loss of average RNFL were identified as experiencing slow modification, which could then be attributed to aging related factors.
The doctor explained that the cut-off of <1 μm/year was chosen to define slow change based on findings of a study that looked at the impact of normal aging on change in RNFL thickness.
Data from healthy subjects showed that the 95% confidence interval for age-related loss was up to 1 μm/year, which shows that the data is accurate to a very high degree.
“Therefore, a slope of RNFL thickness change that is <1 μm/year was selected to define slow change based upon findings of a study that considered the influence of normal aging on change in RNFL density. Data from healthy subjects revealed that the 95% confidence interval for age-related loss was up to 1 μm/ year.” Consequently, an incline of RNFL density adjustment that is > 1 μm/ year is most likely glaucoma progression, given other factors are constant and no other causation is affecting the results” he claimed. The results from assessing the information in the Duke Glaucoma registry revealed that roughly 30% of eyes experienced moderate or faster glaucomatous progression in time, which data can therefore be sufficiently relied on. When the subjects were grouped according to glaucoma severity, it was found that in the group with very early glaucoma at baseline, SD OCT found many more eyes that were advancing quickly than did visual fields, which may make us believe that both tests need to be necessarily looked at.
Amongst subjects who had severe glaucoma at baseline, the percentage recognized as having fast or catastrophic development was around the exact same using SD OCT as well as visual fields. The eyes determined by the 2 tests, however, were not the same.
“We found that many eyes determined as having fast or catastrophic progression by OCT would have been categorized as showing slow-moving or modest progression by their visual fields and also vice versa,” the doctor claimed. “This result drives our conclusion that both structural and also functional examinations ought to be utilized throughout the condition continuum to monitor for progression in patients with glaucoma.”


Clinical correlation
Although changes noted on serial OCT scans might suggest disease progression, medical professionals need to consider whether the modification is the outcome of worsening glaucoma or has some other cause.
An instance of a patient with vitreous traction shows this point. The OCT imaging in this patient showed a decline in RNFL thickness superiorly with time, however it was attributable to a region of vitreous traction that was pulling on the RNFL, as well as the change vanished after the traction was released, so the results were due to an altogether different factor.
The doctor likewise noted that different OCT instruments evaluate progression in a different way, yet it is constantly necessary to think about whether change is glaucoma-related.


Final thought
“The Guided Progression Analysis software application for an OCT system reports the analytical importance of an event evaluation gradually, but that attribute does not lower the significance of considering the scans over time as well as ensuring the quality is adequate,” he ended.
Nevertheless, the software users will certainly have to do some work to determine some final data.

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