Abstract
Purpose:
Different SD-OCT systems yield different results in measuring retinal nerve fiber layer thickness. We tested the influence of macular edema on the difference in retinal thickness using two different SD-OCT (RTVue Optovue 6.2 and Spectralis Heidelberg 5.7.5) and assessed their reliability.
Methods:
96 scans from 54 participants were included in this observational clinical study with a breakdown of 34 normal eyes, 35 diabetic eyes with diabetic macular/retinal changes (DME, PDR, and BDR), 20 eyes with dry/wet AMD, and 7 eyes with macular edema not related to diabetes. 30 were females (56%) and 24 were males (44%) aged 59 +/-21 years old. Scans were excluded if a major artifact was present or if the scan or ETDRS measurement scale was not centered on the fovea and if high myopia was present (D≥-10.00) as the retinal nerve fiber layer is significantly thinner in severe myopia.<br /> Patients were imaged with both SD-OCT on the same clinic visit by the same operator and readings were displayed using the ETDRS scale. Patients were categorized into two group according to the cutoff value of macular edema using Heidelberg 318um .15 scans were above the cutoff. In 41 out of 54 participants, both eyes were scanned to test for intra-reliability in both SD-OCT using the Intra-class coefficient (ICC)
Results:
Using the RTVue ICC values were 0.97 and 0.82 for healthy and pathological eyes, respectively. With Spectralis the values were 0.98, and 0.87. A single factor ANOVA revealed a statistically significant influence on the mean difference (MD) using the two SD-OCT when Significant Macular Edema was present. R squared revealed a 16% interaction level between macular edema and mean difference.
Conclusions:
Reliability of both SD-OCTsystems was influenced by the presence of anatomical disruption in the retina. Significant macular edema should be taken into special consideration when applying an equation to use the two devices interchangeably.