Enhanced Depth Imaging Spectral Domain Optical Coherence Tomography Versus Ultrasonography B-Scan for Measuring Retinochoroidal Thickness in Normal Eyes

In Brief Purpose: To assess the accuracy of retinochoroidal thickness measurements obtained by ultrasonography (USG) B-Scan (over eyelids) and high-resolution immersion USG (with lids open) compared with enhanced depth imaging optical coherence tomography (EDI-OCT) in normal subjects. Methods: Retinochoroidal thickness measurements were performed in normal subjects using USG over eyelids and high-resolution immersion USG (with lids open) using the 20-MHz probe keeping EDI-OCT as the gold standard. Mean retinochoroidal thickness at the fovea, 1.5 mm nasally and temporally were analyzed for interobserver agreement using intraclass correlation coefficient test. Paired t-test was used to compare the values obtained by the three techniques. A 10% difference was defined as clinically significant in the measurements obtained using USG compared with EDI-OCT. Results: Thirty-two eyes of 18 healthy volunteers (15 men) with normal baseline ophthalmologic examination (spherical equivalent, −2 to +2 diopter) were enrolled. Retinochoroidal thickness measurements showed good interobserver agreement for EDI-OCT (intraclass correlation coefficient = 0.999), immersion USG (intraclass correlation coefficient = 0.983), and USG over eyelids (intraclass correlation coefficient = 0.97). Mean retinochoroidal thickness using the above 3 techniques measured 631.77 ± 98.48, 617.17 ± 95.22, and 953 ± 151.28 μm, respectively. Immersion USG measurements were not significantly different from the gold standard, that is, EDI-OCT. However, over eyelids USG provided significantly higher values (P < 0.001) when compared with EDI-OCT and immersion USG. Conclusion: Ultrasonography over eyelids overestimates the retinochoroidal thickness. Immersion USG provides values comparable with EDI-OCT and high-quality imaging where EDI-OCT cannot be performed. Enhanced depth imaging optical coherence tomography is considered the gold standard technique for retinochoroidal thickness assessment but it is not always available. Two different ultrasonography techniques (over lids and immersion) are proposed as an option for retinochoroidal thickness measurements, and results obtained with both of them are compared with those of enhanced depth imaging optical coherence tomography. Over the lids ultrasonography provides higher values, whereas it is possible to obtain accurate measurements with immersion technique compared with enhanced depth imaging optical coherence tomography.