A-scan Rate Research Articles

Quantification of capillary blood flow speeds in diabetic retinopathy using variable interscan time analysis (VISTA) OCTA.

To investigate retinal capillary plexus capillary flow speed and vessel density in diabetic retinopathy (DR) and normal subjects using variable interscan time analysis (VISTA) optical coherence tomography angiography (OCTA). High speed swept source OCTA imaging using multiple interscan times was performed over a 5 mm x 5 mm field-of-view with 600 kHz A-scan rate. Second-generation VISTA OCTA was used to measure a surrogate marker for capillary blood flow speed, VISTA flow speed (VFS), in the superficial and intermediate capillary plexuses, (SCP + ICP)VFS, and deep capillary plexus, DCPVFS. Vessel density was measured using OCTA. Fifty-seven eyes with different DR severity and 37 normal eyes were analyzed. VISTA OCTA provided diverse blood flow speed information, including pseudo-color OCTA and mean flow speed in different regions. Both DCPVFS and DCPVFS/(SCP + ICP)VFS were higher in DR compared to normal eyes. Elevated DCPVFS correlated with decreased DCP vessel density in non-proliferative DR. VISTA OCTA can measure a quantitative biomarker for blood flow speed alterations in DR and normal eyes as well as the association with vessel density in different capillary plexuses. VISTA OCTA is promising for studies of pathogenesis and early flow alterations which may precede non-perfusion.

Applying optical coherence tomography to inline quality monitoring of unidirectional glass-fiber-reinforced thermoplastic tapes

Originally developed for biomedical applications and diagnosis, optical coherence tomography (OCT) has recently been demonstrated to be a powerful non-destructive and non-invasive measurement method for detecting defects in glass-fiber reinforced polymer composites. While previous studies have focused mainly on the use of OCT in the analysis of thermoset composites, we were able to show in offline experiments that OCT can be used to quickly detect typical defects (e.g., dry fiber regions, gaps and fiber breakage) in thermoplastic unidirectional (UD) tapes at high resolution. To investigate the applicability of OCT to inline monitoring, we advanced our previously published approach in two major steps: First, we incorporated the OCT system into an industrial-scale UD-tape production line, and derived optimal settings for inline detection of dry region defects from a comprehensive design of experiments (DoE) to find an optimal balance between accuracy and data size for a stationary tape sample by varying A-scan sampling rate, A-scan averaging and OCT transverse travel velocity. Second, using these optimal settings, we went on to investigate moving tapes over a range of industrially relevant take-off speeds. Microscopy was used for validation in both cases. We developed a fast and robust statistical analysis of B-scans that visualizes the quality of full cross-sections in an interpretable manner for potential use in a real-time setting. Within an industrially relevant production speed range of up to 15 m/min, we are thus now able to investigate 120 mm wide (and potentially wider) UD tapes inline at a transverse resolution of 22 µm, producing only 21 MB of data per measurement.

Wide Dynamic Range Digital Aberration Measurement and Fast Anterior-Segment OCT Imaging †.

Ocular aberrometry with a wide dynamic range for assessing vision performance and anterior segment imaging that provides anatomical details of the eye are both essential for vision research and clinical applications. Defocus error is a major limitation of digital wavefront aberrometry (DWA), as the blurring of the detected point spread function (PSF) significantly reduces the signal-to-noise ratio (SNR) beyond the ±3 D range. With the aid of Badal-like precompensation of defocus, the dynamic defocus range of the captured aberrated PSFs can be effectively extended. We demonstrate a dual-modality MHz VCSEL-based swept-source OCT (SS-OCT) system with easy switching between DWA and OCT imaging modes. The system is capable of measuring aberrations with defocus dynamic range of 20 D as well as providing fast anatomical imaging of the anterior segment at an A-scan rate of 1.6 MHz.

Optical Assessment of Photoreceptor Function Over the Macula.

The purpose of this study was to develop next-generation functional photoreceptor imaging using ultrahigh-speed swept-source optical coherence tomography (UHS-SS-OCT) and split-spectrum amplitude-decorrelation optoretinography (SSADOR) algorithm. The advancement enables rapid surveying of large retinal areas, promising non-contact, objective, and quantifiable measurements of macular visual function. We designed and built a UHS-SS-OCT prototype instrument using a wavelength tunable laser with 1 MHz A-scan rate. The functional scanning protocol records 5 repeated volumes in 3 seconds. A flash pattern selectively exposes the imaged retina area. SSADOR quantifies photoreceptor light response by extracting optical coherence tomography (OCT) signal changes within the photoreceptor outer segment before and after the flash. The study prospectively enrolled 16 eyes from 8 subjects, demonstrating the ability to measure photoreceptor light response over a record field of view (3 × 3mm2) with high topographical resolution (approximately 100 µm). The measured SSADOR signal corresponds to the flashed pattern, whose amplitude also correlates with flash strength, showing consistency and reproducibility across subjects. The integration of high-performance UHS-SS-OCT and SSADOR enables characterizing photoreceptor function over a clinically meaningful field of view, while maintaining a workflow that can be integrated into routine clinical tests and trials. The new approach allows detecting changes in photoreceptor light response with high sensitivity and can detect small focal impairments. This innovative advance can enable us to detect early photoreceptor abnormalities, as well as help to stage and monitor degenerative retinal diseases, potentially providing a surrogate visual function marker for retinal diseases and accelerating therapeutic development through a safe and efficient outcome endpoint.

Exploring single-mode VCSEL wavelength tuning for low-cost 3D optical coherence tomography and OCT angiography.

Low-cost optical coherence tomography has recently emerged as a growing field due to the increased need for general availability of OCT devices outside of the clinics. One of the main obstacles in creating low-cost SS-OCT systems is the price of the laser. In this work, we study the influence of different tuning parameters (e.g., frequency, duty cycle, modulation curve, temperature) on the resulting bandwidth of the previously proposed low-cost single-mode thermally-tunable vertical-cavity surface-emitting laser (VCSEL) source at 850 nm. With optimal parameters, the laser achieves a tuning bandwidth of 10.2 nm at a 50 kHz A-scan rate. In addition, we show the first 3D rendered volume scans of both anterior and posterior segment using a custom VCSEL-based low-cost OCT setup. With the help of deep-learning-based denoising, it was possible to critically reduce the noise in single scans. Moreover, by investigating the phase stability, it became apparent that phase stability between sweeps increases with rising modulation frequencies, making the auxiliary interferometer obsolete. Thus, the system's 50 kHz tuning regimen is also suitable for functional extensions such as OCT angiography.

Time-Resolved Dynamic Optical Coherence Tomography for Retinal Blood Flow Analysis.

Optical coherence tomography (OCT) representations in clinical practice are static and do not allow for a dynamic visualization and quantification of blood flow. This study aims to present a method to analyze retinal blood flow dynamics using time-resolved structural OCT. We developed novel imaging protocols to acquire video-rate time-resolved OCT B-scans (1024 × 496 pixels, 10 degrees field of view) at four different sensor integration times (integration time of 44.8 µs at a nominal A-scan rate of 20 kHz, 22.4 µs at 40 kHz, 11.2 µs at 85 kHz, and 7.24 µs at 125 kHz). The vessel centers were manually annotated for each B-scan and surrounding subvolumes were extracted. We used a velocity model based on signal-to-noise ratio (SNR) drops due to fringe washout to calculate blood flow velocity profiles in vessels within five optic disc diameters of the optic disc rim. Time-resolved dynamic structural OCT revealed pulsatile SNR changes in the analyzed vessels and allowed the calculation of potential blood flow velocities at all integration times. Fringe washout was stronger in acquisitions with longer integration times; however, the ratio of the average SNR to the peak SNR inside the vessel was similar across all integration times. We demonstrated the feasibility of estimating blood flow profiles based on fringe washout analysis, showing pulsatile dynamics in vessels close to the optic nerve head using structural OCT. Time-resolved dynamic OCT has the potential to uncover valuable blood flow information in clinical settings.

Mid-infrared optical coherence tomography with a stabilized OP-GaP optical parametric oscillator.

We demonstrate mid-infrared time-domain optical coherence tomography (OCT) with an orientation-patterned GaP optical parametric oscillator. Instantaneous broadband mid-infrared spectra provide reduced scattering for OCT applications including cultural heritage, quality assurance, and security. B-scan calibrations performed across the wavelength tuning range show depth resolutions of 67 µm at 5.1 µm and 88 µm at 10.5 µm. Volumetric imaging inside a plastic bank card is demonstrated at 5.1 µm, with a 1 Hz A-scan rate that indicates the potential of stable broadband OPO sources to contribute to mid-infrared OCT.

Mid-infrared optical coherence tomography with MHz axial line rate for real-time non-destructive testing

Non-destructive testing (NDT) is crucial for ensuring product quality and safety across various industries. Conventional methods, such as ultrasonic, terahertz, and x-ray imaging, have limitations in terms of probe-contact requirement, depth resolution, or radiation risks. Optical coherence tomography (OCT) is a promising alternative to solve these limitations, but it suffers from strong scattering, limiting its penetration depth. Recently, OCT in the mid-infrared (MIR) spectral region has attracted attention with a significantly lower scattering rate than in the near-infrared region. However, the highest reported A-scan rate of MIR-OCT has been 3 kHz, which requires long data acquisition time to take an image, unsatisfying industrial demands for real-time diagnosis. Here, we present a high-speed MIR-OCT system operating in the 3–4 µm region that employs the frequency-swept spectrum detection in OCT technique based on time-stretch infrared spectroscopy. By integrating a broadband femtosecond MIR pulsed laser operating at a repetition rate of 50 MHz, we achieved an A-scan rate of 1 MHz with an axial resolution of 11.6 µm, a 10 dB roll-off depth of about 700 µm, and a sensitivity of 55 dB. As a proof-of-concept demonstration, we imaged the surface of substrates covered by highly scattering paint coatings. The demonstrated A-scan rate surpasses previous state of the art by more than two orders of magnitude, paving the way for real-time NDT of industrial products, cultural assets, and structures.

Imaging of human corneoscleral junction (Limbus) vasculature with 100 KHz A-scan rate swept-source optical coherence tomography/angiography (OCT/A) system

The study demonstrates in-vivo three-dimensional depth-resolved Optical Coherence Tomography Angiography (OCTA) and Doppler OCT imaging performed on the anterior segment of the human eye. A high-speed swept-source OCT system was developed utilizing a swept-source laser having a 100 kHz A-scan sweep rate and centre wavelength at 1060 nm. The proposed system has an axial resolution of 4.5 µm and a transverse imaging resolution of 14 µm. The Doppler OCT provides information regarding the direction of blood flow in corneoscleral junction vessels, which employs the Joint Spectral and Time domain OCT (STdOCT) method. Parameters influencing the imaging of various vessels, like scanning density, A-scan rate, B-scan averaging, and number of BM scanning repeats, were also studied. Slit lamp images and OCT angiography en-face projections produced from PVOCTA (Phase-variance OCTA) and STdOCTA from the same regular patients were compared in order to demonstrate the additional potential of the system. The vascular systems at the Limbus consisting of circulatory, lymphatic, and aqueous outflow systems were imaged and presented. The output clinical parameters of the system will contribute to understanding the blood circulation with directionality at the limbus location, which can be further utilized to identify glaucoma. In the author's opinion, this article represents the first attempt to provide Doppler OCTA data for the anterior chamber of the human eye.

Microaneurysm detection using high-speed megahertz optical coherence tomography angiography in advanced diabetic retinopathy.

To compare detection rates of microaneurysms (MAs) on high-speed megahertz optical coherence tomography angiography (MHz-OCTA), fluorescein angiography (FA) and colour fundus photography (CF) in patients with diabetic retinopathy (DR). For this exploratory cross-sectional study, MHz-OCTA data were acquired with a swept-source OCT prototype (A-scan rate: 1.7 MHz), and FA and CF imaging was performed using Optos® California. MA count was manually evaluated on en face MHz-OCTA/FA/CF images within an extended ETDRS grid. Detectability of MAs visible on FA images was evaluated on corresponding MHz-OCTA and CF images. MA distribution and leakage were correlated with detectability on OCTA and CF imaging. 47 eyes with severe DR (n = 12) and proliferative DR (n = 35) were included. MHz-OCTA and CF imaging detected on average 56% and 36% of MAs, respectively. MHz-OCTA detection rate was significantly higher than CF (p < 0.01). The combination of MHz-OCTA and CF leads to an increased detection rate of 70%. There was no statistically significant association between leakage and MA detectability on OCTA (p = 0.13). For CF, the odds of detecting leaking MAs were significantly lower than non-leaking MAs (p = 0.012). Using MHz-OCTA, detection of MAs outside the ETDRS grid was less likely than MAs located within the ETDRS grid (outer ring, p < 0.01; inner ring, p = 0.028). No statistically significant difference between rings was observed for CF measurements. More MAs were detected on MHz-OCTA than on CF imaging. Detection rate was lower for MAs located outside the macular region with MHz-OCTA and for leaking MAs with CF imaging. Combining both non-invasive modalities can improve MA detection.

Long-range frequency-domain optical delay line based on a spinning tilted mirror for low-cost ocular biometry.

Optical biometers are routinely used to measure intraocular distances in ophthalmic applications such as cataract surgery planning or myopia monitoring. However, due to their high cost and reduced transportability, access to them for screening and surgical planning is still limited in low-resource and remote settings. To increase patients' access to optical biometry we propose a novel low-cost frequency-domain optical delay line (FD-ODL) based on an inexpensive stepper motor spinning a tilted mirror, for integration into a time-domain (TD)-biometer, amenable to a compact footprint. In the proposed FD-ODL, the axial scan range and the A-scan rate are decoupled from one another, as the former only depends on the spinning mirror tilt angle, while the A-scan rate only depends on the motor shaft rotational speed. We characterized the scanning performance and specifications for two spinning mirror tilt angles, and compared them to those of the standard, more expensive FD-ODL implementation, employing a galvanometric scanner for group delay generation. A prototype of the low-cost FD-ODL with a 1.5 deg tilt angle, resulting in an axial scan range of 6.61 mm and an A-scan rate of 10 Hz was experimentally implemented and integrated in a dual sample beam optical low-coherence reflectometry (OLCR) setup with a detour unit to replicate the measurement window around the anterior segment and the retina. The intraocular distances of a model eye were measured with the proposed low-cost biometer and found to be in good agreement with those acquired by a custom swept-source optical coherence tomography (SS-OCT) system and two commercial biometers, validating our novel design.

Multimodal feedback systems for smart laser osteotomy: Depth control and tissue differentiation.

The study aimed to improve the safety and accuracy of laser osteotomy (bone surgery) by integrating optical feedback systems with an Er:YAG laser. Optical feedback consists of a real-time visual feedback system that monitors and controls the depth of laser-induced cuts and a tissue sensor differentiating tissue types based on their chemical composition. The developed multimodal feedback systems demonstrated the potential to enhance the safety and accuracy of laser surgery. The proposed method utilizes a laser-induced breakdown spectroscopy (LIBS) system and long-range Bessel-like beam optical coherence tomography (OCT) for tissue-specific laser surgery. The LIBS system detects tissue types by analyzing the plasma generated on the tissue by a nanosecond Nd:YAG laser, while OCT provides real-time monitoring and control of the laser-induced cut depth. The OCT system operates at a wavelength of 1288 ± 30 nm and has an A-scan rate of 104.17 kHz, enabling accurate depth control. Optical shutters are used to facilitate the integration of these multimodal feedback systems. The proposed system was tested on five specimens of pig femur bone to evaluate its functionality. Tissue differentiation and visual depth feedback were used to achieve high precision both on the surface and in-depth. The results showed successful real-time tissue differentiation and visualization without any visible thermal damage or carbonization. The accuracy of the tissue differentiation was evaluated, with a mean absolute error of 330.4 μm and a standard deviation of ±248.9 μm, indicating that bone ablation was typically stopped before reaching the bone marrow. The depth control of the laser cut had a mean accuracy of 65.9 μm with a standard deviation of ±45 μm, demonstrating the system's ability to achieve the pre-planned cutting depth. The integrated approach of combining an ablative laser, visual feedback (OCT), and tissue sensor (LIBS) has significant potential for enhancing minimally invasive surgery and warrants further investigation and development.

THE EFFECT OF INCREASING ACQUISITION SPEED ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IMAGES: A Qualitative and Quantitative Analysis.

To evaluate the effect of two different A-scan rates on qualitative and quantitative parameters on optical coherence tomography angiography images in a clinical setting. Subjects undergoing a comprehensive ophthalmic examination were scheduled for optical coherence tomography angiography imaging using a new SPECTRALIS device allowing for 85 and 125 kHz scan rate. Consecutive registered 20° × 20° optical coherence tomography angiography images using both speeds were acquired using the follow-up tool. The acquisition time and the quality values of each scan were extracted and analyzed. The image quality was also graded in pairs by two independent graders. Two-hundred and one eyes of 128 consecutive patients (67 males, 52.3%) were included. Mean acquisition time significantly decreased from 56.92 ± 24.6 seconds on the 85 kHz images to 39.39 ± 15.5 seconds on the 125 kHz images (P < 0.001). The percentage change in acquisition time showed a mean decrease of 28.47%. Mean Q value significantly decreased from 32.97 ± 2.8 dB on the 85 kHz images to 31.43 ± 2.6 dB on the 125 kHz images (P < 0.001). Overall, 92.5% of images were graded as equal or better at 125 kHz A-scan rate. The use of optical coherence tomography angiography in daily clinical practice may require higher A-scan rates for an optimal workflow. Increased speed may also reduce image sensitivity and thus image quality could be compromised. In this study, 125 kHz scan rate using SPECTRALIS showed significant benefit with reduction on the acquisition time and no clinically significant differences on image quality analysis. Further studies evaluating qualitative and quantitative data in specific retinal conditions and using other devices are required to confirm these results.

An innovative multi-modal retinal imaging system for in vivo retinal detection in small animals.

This paper presents an innovative retinal imaging system tailored for in vivo fundus detection in small animals. This system integrates Scanning Laser Ophthalmoscopy (SLO) and optical Coherence Tomography (OCT) techniques, enabling the simultaneous generation of images from various modalities, including SLO reflectance, SLO fluorescein angiogram, OCT, and OCT angiogram. The existing multi-modal retinal imaging systems generally encounter limitations such as the inability to detect peripheral lesion areas attributed to small Field of View (FOV) design and susceptibility to sample motion due to slow data acquisition speed. To address these challenges, it's essential to underscore that this proposed system offers a range of notable advantages, including its compact design, the capacity for widefield imaging with a FOV of up to 100°, and a rapid OCT A-scan rate of 250 kHz, notably exceeding the capabilities of pre-existing multi-modal retinal imaging systems. Validation of the system involved imaging the eyes of normal wild-type mice and diseased mice afflicted with retinal detachment and choroidal neovascularization (CNV). The favorable imaging results demonstrate the system's reliability in identifying retinal lesions in small animals.

Visible wavelength time-stretch optical coherence tomography.

Visible light optical coherence tomography (OCT) is an emerging non-invasive imaging modality that offers new opportunities for anatomical and functional imaging of biological tissues. Time-stretch dispersive Fourier transform, also known as photonic time-stretch, is an all-optical processing method that enables real-time Fourier transformation of ultrafast optical signals and allows for OCT at high A-scan rates. In this work, a working prototype of a photonic time-stretch OCT (TS-OCT) method in the visible wavelength region is proposed and experimentally demonstrated. The proposed visible-light TS-OCT system achieves unprecedented throughput of 100 giga voxels/second and OCT volume rate of 4,000 volumes/second and can be used to expand the range of applications of TS-OCT systems.

Impact of A-Scan Rate on Image Quality and Acquisition Time in OCT

Purpose This study aims to examine the impact of the A-scan rate in optical coherence tomography (OCT) on scan quality and acquisition time. Methods Two horizontal OCT scans per scan rate (20, 85, 125 kHz) of the right eye were captured with the same OCT device (Spectralis SHIFT, HRA + OCT, Heidelberg Engineering GmbH, Heidelberg, Germany) of patients who presented to the inherited retinal dystrophies consultation, thus predominantly challenging patients due to reduced fixation ability. Scan quality was measured by the Q score, a signal-to-noise-ratio (SNR). Acquisition time was measured in seconds. Results Fifty-one patients were included in the study. The highest quality was seen for an A-scan rate of 20 kHz (44.49 dB), succeeded by scans of an A-Scan rate of 85 kHz (38.53 dB) and of 125 kHz (36.65 dB). Differences in scan quality between the various A-scan rates were statistically significant. The acquisition time seen for an A-scan rate of 20 kHz (6.45 s) was significantly longer than those seen for an A-Scan rate of 85 kHz (1.51 s) and of 125 kHz (1.69 s). Conclusion An A-scan rate of 20 kHz resulted in a significantly higher scan quality but also a significantly longer acquisition time compared to scan rates of 85 kHz and 125 kHz. Differences between an A-scan rate of 85 kHz and 125 kHz were marginal.

Multiple instance learning based classification of diabetic retinopathy in weakly-labeled widefield OCTA en face images

Diabetic retinopathy (DR), a pathologic change of the human retinal vasculature, is the leading cause of blindness in working-age adults with diabetes mellitus. Optical coherence tomography angiography (OCTA), a functional extension of optical coherence tomography, has shown potential as a tool for early diagnosis of DR through its ability to visualize the retinal vasculature in all spatial dimensions. Previously introduced deep learning-based classifiers were able to support the detection of DR in OCTA images, but require expert labeling at the pixel level, a labor-intensive and expensive process. We present a multiple instance learning-based network, MIL-ResNet,14 that is capable of detecting biomarkers in an OCTA dataset with high accuracy, without the need for annotations other than the information whether a scan is from a diabetic patient or not. The dataset we used for this study was acquired with a diagnostic ultra-widefield swept-source OCT device with a MHz A-scan rate. We were able to show that our proposed method outperforms previous state-of-the-art networks for this classification task, ResNet14 and VGG16. In addition, our network pays special attention to clinically relevant biomarkers and is robust against adversarial attacks. Therefore, we believe that it could serve as a powerful diagnostic decision support tool for clinical ophthalmic screening.

Retinal blood flow speed quantification at the capillary level using temporal autocorrelation fitting OCTA [Invited

Optical coherence tomography angiography (OCTA) can visualize vasculature structures, but provides limited information about blood flow speed. Here, we present a second generation variable interscan time analysis (VISTA) OCTA, which evaluates a quantitative surrogate marker for blood flow speed in vasculature. At the capillary level, spatially compiled OCTA and a simple temporal autocorrelation model, ρ(τ) = exp(-ατ), were used to evaluate a temporal autocorrelation decay constant, α, as the blood flow speed marker. A 600 kHz A-scan rate swept-source OCT prototype instrument provides short interscan time OCTA and fine A-scan spacing acquisition, while maintaining multi mm2 field of views for human retinal imaging. We demonstrate the cardiac pulsatility and assess repeatability of α measured with VISTA. We show different α for different retinal capillary plexuses in healthy eyes and present representative VISTA OCTA in eyes with diabetic retinopathy.

Live 4D-OCT denoising with self-supervised deep learning

By providing three-dimensional visualization of tissues and instruments at high resolution, live volumetric optical coherence tomography (4D-OCT) has the potential to revolutionize ophthalmic surgery. However, the necessary imaging speed is accompanied by increased noise levels. A high data rate and the requirement for minimal latency impose major limitations for real-time noise reduction. In this work, we propose a low complexity neural network for denoising, directly incorporated into the image reconstruction pipeline of a microscope-integrated 4D-OCT prototype with an A-scan rate of 1.2 MHz. For this purpose, we trained a blind-spot network on unpaired OCT images using a self-supervised learning approach. With an optimized U-Net, only a few milliseconds of additional latency were introduced. Simultaneously, these architectural adaptations improved the numerical denoising performance compared to the basic setup, outperforming non-local filtering algorithms. Layers and edges of anatomical structures in B-scans were better preserved than with Gaussian filtering despite comparable processing time. By comparing scenes with and without denoising employed, we show that neural networks can be used to improve visual appearance of volumetric renderings in real time. Enhancing the rendering quality is an important step for the clinical acceptance and translation of 4D-OCT as an intra-surgical guidance tool.

Quantitative and Qualitative Assessments of Retinal Structure with Variable A-Scan Rate Spectralis OCT: Insights into IPL Multilaminarity

The aim of this study was to evaluate the qualitative and quantitative differences between 20 and 85 kHz A-scan rate optical coherence tomography (OCT) images acquired by spectral domain OCT. The study included 60 healthy subjects analyzed with horizontal linear scans with a variable A-scan rate (SHIFT technology, Heidelberg Engineering, Heidelberg, Germany). The retinal thickness measurement of each retinal layer was performed in three different positions (subfoveal, nasal, and temporal). The qualitative assessment was performed by two independent observers who rated every image with a score ranging from 1 ("sufficient") to 3 ("excellent") on the basis of three parameters: visualization of the vitreo-retinal interface, characterization of the retinal layers, and visualization of the sclero-choroidal interface. No statistically significant differences in terms of retinal layer thickness between the two A-scan rate scans were observed (p > 0.05). The coefficient of variation of the retinal thickness values was lower in the 20 kHz group (25.8% versus 30.1% with the 85 kHz). The 20 kHz images showed a higher quality index for both observers. An inner plexiform layer (IPL) multilaminarity was detected in 78.3% of patients from the 20 kHz group and in 40% of patients from the 85 kHz group (p < 0.05).