Multiple scan averaging to yield accurate quantitative analysis of optical coherence tomography angiograms

Hafi M Khan,Chi-Ho To,Andrew K C Lam,Alex Gentle,James A Armitage

doi:10.1038/s41598-020-62956-2

Hafi M Khan, Chi-Ho To + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-62956-2

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Abstract

Optical coherence tomography angiography (OCTA) is widely used in ophthalmic practice. Most OCTA studies based their findings on a single OCTA measurement. We conducted an observational study of 82 eyes from 82 healthy subjects to compare variations of OCTA parameters among five successive measurements. A 3 × 3 mm Early Treatment of Diabetic Retinopathy Study grid centred at fovea was used. An average from five successive OCTA measurements (both perfusion density and vessel density) was calculated to be used as the reference standard. There was no significant difference in perfusion and vessel densities among five successive OCTA measurements, and from different levels of averaging. Perfusion density was close to the reference standard when average from three measurements was used (discrepancy within 1.5%) as compared with using just one measurement (discrepancy from 3.2% to 4.5%). Vessel density was also close to reference standard when average from three measurements was used (within 0.8 mm−1) as compared with using just one measurement (2 mm−1). Software feature that allows OCTA devices to average quantitative parameters for analysis will be useful.

Highlights

Optical coherence tomography angiography (OCTA) is widely used in ophthalmic practice
In applanation tonometry, practitioners usually take two to three intraocular pressure (IOP) measurements to generate an average result to the IOP for a patient[4,5]; average results from three to five measurements are commonly required in clinical protocols for the use of ocular biometers[6]; three successive bidirectional applanation measurements are recommended in determining corneal hysteresis[7,8] and in pulsatile ocular blood flow assessment, an average of three successive measurements are necessary to detect a difference between normal subjects and glaucoma patients[9]
The five successive OCTA measurements were similar without any significant difference at the aggregated, para-foveal, and foveal regions (Table 1)

Summary

Introduction

Optical coherence tomography angiography (OCTA) is widely used in ophthalmic practice. An average from five successive OCTA measurements (both perfusion density and vessel density) was calculated to be used as the reference standard. There was no significant difference in perfusion and vessel densities among five successive OCTA measurements, and from different levels of averaging. Lei, et al.[10] found that vessel density was influenced by the signal strength of the image, there is currently no standard signal strength requirement across different OCTA devices. It is interesting that, unlike the other ophthalmic assessments described above, almost all OCTA studies based their findings on a single OCTA measurement[11,12,13], and it must be assumed that the collection of only one OCTA measurement remains the norm in clinical practice. The purpose of this study was to determine the minimum number of successful OCTA measurements necessary for acceptable accuracy during OCTA assessment

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