Understanding the variability of handheld spectral-domain optical coherence tomography measurements in supine infants

Early Single-Examination Optical Coherence Tomography Biomarkers for Treatment-Requiring Retinopathy of Prematurity

Purpose

Optical coherence tomography (OCT) is an emerging adjunct imaging modality to evaluate retinopathy of prematurity (ROP). From an 11-year research database, we identify early OCT biomarkers that predict treatment-requiring ROP (TR-ROP).

Methods

For preterm infants with acceptable OCT images at 32 ± 1 weeks postmenstrual age (PMA), we extracted the following measures: total retina, inner retinal layer (IRL), and outer retinal layer (ORL) thicknesses at the fovea and the parafovea, inner nuclear layer (INL) and choroidal thickness, parafovea/fovea (P/F) ratio, and presence of macular edema. Using univariable and multivariable logistic regression models, we evaluated the association between retinal and choroidal OCT measurements at 32 ± 1 weeks PMA and development of TR-ROP.

Results

Of 277 eyes (145 infants) with usable OCT images, 67 eyes had TR-ROP. Lower P/F ratio (P < 0.0001), thicker foveal IRL (P = 0.0001), and thinner choroid (P = 0.03) were associated with TR-ROP in univariable analysis, but lost significance of association when adjusted for gestational age and race. Absence of macular edema was associated with TR-ROP when adjusted for gestational age and race (P = 0.01). In 185 eyes without macular edema, P/F ratio was associated with TR-ROP in both univariable analysis (P < 0.0001) and multivariable analysis (P = 0.02) with adjustment for gestational age and race.

Conclusions

Presence of macular edema at 32 ± 1 weeks PMA in infants with lower gestational age may be protective against TR-ROP. In infants without macular edema, P/F ratio may be an early OCT biomarker for development of TR-ROP. Incorporation of early OCT biomarkers may be useful in prediction of TR-ROP.

Measurement of Foveal Retinal Thickness in Myopic Patients Using Different Display Modes on Optical Coherence Tomography: A Retrospective, Cross-Sectional Study

INTRODUCTION

The aim of this work is to investigate the differences in the measurement of foveal retinal thickness in myopic patients between two display modes (1:1 pixel and 1:1 micron) on optical coherence tomography (OCT).

METHODS

Horizontal OCT line scan through the central fovea was used for manual measurement of foveal retinal thickness under the two display modes, and the values were compared using Wilcoxon signed-rank test. Correlations between the OCT image tilting angle (OCT ITA) and differences in OCT measurement were analyzed by Spearman's test.

RESULTS

127 participants with a median age of 28 years, a median spherical equivalent (SE) of - 8.5 D, and a median axial length (AL) of 27.04 mm. There were significant differences between the two display modes, with a median absolute difference (median relative difference) of 13.33 μm (2.75%) for the central foveal thickness (CFT), 5.33 μm (1.28%) for the Henle fiber and outer nuclear layer thickness (HFL + ONL), 3 μm (6.47%) for the external limiting membrane to ellipsoid zone distance (ELM-EZ), and 4 μm (8.77%) for the ellipsoid zone to retinal pigment epithelium distance (EZ-RPE) (all p < 0.05). The differences in foveal retinal thickness between the two display modes were significantly correlated with the OCT ITA (r = 0.732 for CFT, 0.561 for HFL + ONL, 0.642 for ELM-EZ, and 0.471 for EZ-RPE, all p < 0.05).

CONCLUSIONS

Disparities between the two display modes were found in the manual measurement of foveal retinal thickness and correlated to the OCT ITA.

Posterior Segment Optical Coherence Tomography in Uncooperative Paediatric Patients Using Exo-Illumination and Microscope-Integrated Optical Coherence Tomography

BACKGROUND AND OBJECTIVE

To describe a non-invasive technique for the acquisition of retinal optical coherence tomography (OCT) scans in paediatric patients undergoing examination under general anaesthesia (EUA) using microscope-integrated OCT (MIOCT).

STUDY DESIGN

Prospective observational study Methods and Material: The study included 10 paediatric patients undergoing EUA for posterior segment pathology. These patients underwent OCT using MIOCT. No sclerotomy was made during imaging. The fundus was externally illuminated with a 25 gauge endoilluminator probe placed at the limbus and directed towards the posterior pole to aid in image acquisition by MIOCT (exo-illumination). Imaging for all patients was done by two trained vitreoretinal surgeons independently. Acquisition time was recorded for each surgeon. Interobserver variability in acquisition time and image quality was assessed to estimate the reliability of the novel imaging technique.

RESULTS

In nine cases (90%), MIOCT successfully imaged the posterior segment pathology while in one case (10%) of X-linked retinoschisis, it failed to detect an inner retinal break located anteriorly at the equator. The mean acquisition time for surgeons one and two was 211.75 ± 26.00 and 212.58 ± 23.47 seconds, respectively. There was no significant difference in total image acquisition time between the two surgeons (P = 1.0) and the findings of both surgeons were comparable for structural morphology. 4x4 mm-sized scans provided the best delineation in macular pathology, while a 16x16 mm scan size was best suited for localising the area of interest and post-equatorial pathology.

CONCLUSION

Using this technique acquisition of posterior segment OCT scans can be achieved non-invasively, using exo-illumination and MIOCT in paediatric patients undergoing EUA.

Advances in Optical Coherence Tomography Imaging Technology and Techniques for Choroidal and Retinal Disorders

Optical coherence tomography (OCT) imaging has played a pivotal role in the field of retina. This light-based, non-invasive imaging modality provides high-quality, cross-sectional analysis of the retina and has revolutionized the diagnosis and management of retinal and choroidal diseases. Since its introduction in the early 1990s, OCT technology has continued to advance to provide quicker acquisition times and higher resolution. In this manuscript, we discuss some of the most recent advances in OCT technology and techniques for choroidal and retinal diseases. The emerging innovations discussed include wide-field OCT, adaptive optics OCT, polarization sensitive OCT, full-field OCT, hand-held OCT, intraoperative OCT, at-home OCT, and more. The applications of these rising OCT systems and techniques will allow for a closer monitoring of chorioretinal diseases and treatment response, more robust analysis in basic science research, and further insights into surgical management. In addition, these innovations to optimize visualization of the choroid and retina offer a promising future for advancing our understanding of the pathophysiology of chorioretinal diseases.

Insights into the developing fovea revealed by imaging

Early development of the fovea has been documented by histological studies over the past few decades. However, structural distortion due to sample processing and the paucity of high-quality post-mortem tissue has limited the effectiveness of this approach. With the continuous progress in high-resolution non-invasive imaging technology, most notably optical coherence tomography (OCT) and OCT angiography (OCT-A), in vivo visualization of the developing retina has become possible. Combining the information from histologic studies with this novel imaging information has provided a more complete and accurate picture of retinal development, and in particular the developing fovea. Advances in neonatal care have increased the survival rate of extremely premature infants. However, with enhanced survival there has been an attendant increase in retinal developmental complications. Several key abnormalities, including a thickening of the inner retina at the foveal center, a shallower foveal pit, a smaller foveal avascular zone, and delayed development of the photoreceptors have been described in preterm infants when compared to full-term infants. Notably these abnormalities, which are consistent with a partial arrest of foveal development, appear to persist into later childhood and adulthood in these eyes of individuals born prematurely. Understanding normal foveal development is vital to interpreting these pathologic findings associated with prematurity. In this review, we first discuss the various advanced imaging technologies that have been adapted for imaging the infant eye. We then review the key events and steps in the development of the normal structure of the fovea and contrast structural features in normal and preterm retina from infancy to childhood. Finally, we discuss the development of the perifoveal retinal microvasculature and highlight future opportunities to expand our understanding of the developing fovea.

Reproducibility of Retinal Nerve Fiber Layer and Macular Thickness Measurements Using Spectral Domain Optical Coherence Tomography

The objective of the research was to assess the reproducibility of retinal nerve fiber layer (RNFL) and macular thickness using spectral domain optical coherence tomography and to establish whether the same investigator can get the same or similar results when performing the scan thrice in an hour, without reference to the previous scan and the repeat function. Materials and Methods. In this prospective observational study, 200 subjects who fulfilled the inclusion and exclusion criteria were scanned 3 times according to predefined guidelines at 0, 30 and 60 minutes on the same day, by the same investigator, using spectral domain optical coherence tomography for measurements of RNFL and macular thickness; observations were statistically analyzed and correlated. Results. In RNFL thickness, the temporal sector showed the worst reproducibility as compared to other sectors. RNFL was the greatest in the superior quadrant and the thinnest in the temporal quadrant. For macular thickness, the temporal sector (mid zone) showed the worst reproducibility, while in the outer zone, the inferior sector showed the worst reproducibility; macular thickness was the thinnest at the central zone (innermost 1-mm ring), the thickest within the inner 3-mm ring and diminished peripherally. Conclusions. RNFL and macular thickness measurements using spectral domain optical coherence tomography by the same observer at 0, 30 and 60 minutes were very reproducible, except for the sectors specifically mentioned. The greater the thickness of the RNFL in any sector the better was the reproducibility in that sector. For macular thickness, the temporal sector (mid zone) showed the worst reproducibility.

Repeatability and Reproducibility of Axial and Lateral Measurements on Handheld Optical Coherence Tomography Systems Compared with Tabletop System

Purpose

To compare the repeatability and reproducibility of axial and lateral retinal measurements using handheld optical coherence tomography (OCT) systems and a tabletop OCT system.

Methods

Graders measured central foveal thickness (CFT), optic nerve-to-fovea distance (OFD), and retinal nerve fiber layer (RNFL) thickness on OCT scans of the right eye of 10 healthy adults. Three OCT systems were used: handheld Leica Envisu, investigational handheld swept-source OCT (UC3), and Heidelberg Spectralis tabletop system. All eyes were imaged five times with each OCT system by each of two imagers. A components of variance analysis provided estimates of repeatability (variation due to random error) and reproducibility (variation due to imager, grader, and random error) expressed as standard deviation and (coefficient of variation %).

Results

Repeatability of CFT (µm) for Envisu, UC3, and Spectralis was 5.9 (2.6%), 6.9 (2.9%), and 4.7 (2.1%), and the reproducibility was 6.1 (2.7%), 7.3 (3.1%), and 4.7 (2.1%), respectively. The repeatability of OFD (mm) was 0.13 (2.9%), 0.10 (2.3%), and 0.07 (1.6%), and the reproducibility was 0.13 (3.0%), 0.10 (2.3%), and 0.07 (1.6%,) respectively. The repeatability for RNFL thickness (µm) for Envisu, UC3, and Spectralis was 4.3 (7.8%), 2.7 (5.4%), and 2.9 (4.9%), and the reproducibility was 4.5 (8.3%), 2.9 (5.8%), and 2.9 (4.9%), respectively.

Conclusions

All three OCT systems had good repeatability and reproducibility with coefficients of variation of less than 3.5% for CFT and OFD measurements, and less than 8.5% for RNFL thickness.

Translational Relevance

Our findings inform the repeatability and reproducibility of retinal axial and lateral measurements on handheld OCT and are useful for both clinical research and patient care.

The future of retinal imaging

PURPOSE OF REVIEW

This article reviews emerging technologies in retinal imaging, including their scientific background, clinical implications and future directions.

RECENT FINDINGS

Fluorescence lifetime imaging ophthalmoscopy is a technology that will reveal biochemical and metabolic changes of the retina at the cellular level. Optical coherence tomography is evolving exponentially toward higher resolution, faster speed, increased portability and more cost effective. Adaptive optics scanning laser ophthalmoscopy fluorescein angiography will provide unprecedented detail of the retinal vasculature down to the level of capillaries, enabling earlier and more sensitive detection of retinal vascular diseases.

SUMMARY

Continued developments in retinal imaging focus on improved resolution, faster speed and noninvasiveness, while providing new information on the structure-function relationship of the retina inclusive of metabolic activity at the cellular level.