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

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.

Five degrees-of-freedom mechanical arm with remote center of motion (RCM) device for volumetric optical coherence tomography (OCT) retinal imaging

Handheld optical coherence tomography (HH-OCT) is gaining popularity for diagnosing retinal diseases in neonates (e.g. retinopathy of prematurity). Diagnosis accuracy is degraded by hand tremor and patient motion when using commercially available handheld retinal OCT probes. This work presents a low-cost arm designed to address ergonomic challenges of holding a commercial OCT probe and alleviating hand tremor. Experiments with a phantom eye show enhanced geometric uniformity and volumetric accuracy when obtaining OCT scans with our device compared to handheld imaging approaches. An in-vivo porcine volumetric image was also obtained with the mechanical arm demonstrating clinical deployability.

Preterm infant retinal OCT markers of perinatal health and retinopathy of prematurity

The increasing survival of preterm infants has led to the importance of improving long-term outcomes associated with preterm birth. Antenatal and perinatal insults not only impact mortality, but also long-term disability. While in the intensive care nursery, preterm infants are also exposed to various stressors that lead to long-term cognitive deficits. It is therefore critical to identify early, low-stress, non-invasive biomarkers for preterm infant health. Optical coherence tomography (OCT) is a powerful imaging modality that has recently been adapted to the infant population and provides noninvasive, high-resolution, cross-sectional imaging of the infant eye at the bedside with low stress relative to conventional examination. In this review we delve into discussing the associations between preterm systemic health factors and OCT-based retinal findings and their potential contribution to the development of non-invasive biomarkers for infant health and for retinopathy of prematurity (ROP).

Association of Optical Coherence Tomography-Measured Fibrovascular Ridge Thickness and Clinical Disease Stage in Retinopathy of Prematurity

Importance

Accurate diagnosis of retinopathy of prematurity (ROP) is essential to provide timely treatment and reduce the risk of blindness. However, the components of an ROP examination are subjective and qualitative.

Objective

To evaluate whether optical coherence tomography (OCT)-derived retinal thickness measurements at the vascular-avascular junction are associated with clinical diagnosis of ROP stage.

Design, Setting, and Participants

This cross-sectional longitudinal study compared OCT-based ridge thickness calculated from OCT B-scans by a masked examiner to the clinical diagnosis of 2 masked examiners using both traditional stage classifications and a more granular continuous scale at the neonatal intensive care unit (NICU) of Oregon Health & Science University (OHSU) Hospital. Infants who met ROP screening criteria in the OHSU NICU between June 2021 and April 2022 and had guardian consent were included. One OCT volume and en face image per patient per eye showing at least 1 to 2 clock hours of ridge were included in the final analysis.

Main Outcomes and Measures

Comparison of OCT-derived ridge thickness to the clinical diagnosis of ROP stage using an ordinal and continuous scale. Repeatability was assessed using 20 repeated examinations from the same visit and compared using intraclass correlation coefficient (ICC) and coefficient of variation (CV). Comparison of ridge thickness with ordinal categories was performed using generalized estimating equations and with continuous stage using Spearman correlation.

Results

A total of 128 separate OCT eye examinations from 50 eyes of 25 patients were analyzed. The ICC was 0.87 with a CV of 7.0%. Higher ordinal disease classification was associated with higher axial ridge thickness on OCT, with mean (SD) thickness measurements of 264.2 (11.2) μm (P < .001), 334.2 (11.4) μm (P < .001), and 495.0 (32.2) μm (P < .001) for stages 1, 2, and 3, respectively and with continuous stage labels (ρ = 0.739, P < .001).

Conclusions and Relevance

These results suggest that OCT-based quantification of peripheral stage in ROP may be an objective and quantitative biomarker that may be useful for clinical diagnosis and longitudinal monitoring and may have implications for disease classification in the future.

The Development and Clinical Application of Innovative Optical Ophthalmic Imaging Techniques

The field of ophthalmic imaging has grown substantially over the last years. Massive improvements in image processing and computer hardware have allowed the emergence of multiple imaging techniques of the eye that can transform patient care. The purpose of this review is to describe the most recent advances in eye imaging and explain how new technologies and imaging methods can be utilized in a clinical setting. The introduction of optical coherence tomography (OCT) was a revolution in eye imaging and has since become the standard of care for a plethora of conditions. Its most recent iterations, OCT angiography, and visible light OCT, as well as imaging modalities, such as fluorescent lifetime imaging ophthalmoscopy, would allow a more thorough evaluation of patients and provide additional information on disease processes. Toward that goal, the application of adaptive optics (AO) and full-field scanning to a variety of eye imaging techniques has further allowed the histologic study of single cells in the retina and anterior segment. Toward the goal of remote eye care and more accessible eye imaging, methods such as handheld OCT devices and imaging through smartphones, have emerged. Finally, incorporating artificial intelligence (AI) in eye images has the potential to become a new milestone for eye imaging while also contributing in social aspects of eye care.

Portable boom-type ultrahigh-resolution OCT with an integrated imaging probe for supine position retinal imaging

To expand the clinical applications and improve the ease of use of ultrahigh-resolution optical coherence tomography (UHR-OCT), we developed a portable boom-type ophthalmic UHR-OCT operating in supine position that can be used for pediatric subjects, bedridden patients and perioperative conditions. By integrating the OCT sample arm probe with real-time iris display and automatic focusing electric lens for easy alignment, coupling the probe on a self-locking multi-directional manipulator to reduce motion artifacts and operator fatigue, and installing the OCT module on a moveable cart for system mobility, our customized portable boom-type UHR-OCT enables non-contact, high-resolution and high-stability retinal examinations to be performed on subjects in supine position. The spectral-domain UHR-OCT operates at a wavelength of 845 nm with 130 nm FWHM (full width at half maximum) bandwidth, achieving an axial resolution of ≈2.3µm in tissue with an A-line acquisition rate up to 128 kHz. A high-definition two-dimensional (2D) raster protocol was used for high-quality cross-sectional imaging while a cube volume three-dimensional (3D) scan was used for three-dimensional imaging and en-face reconstruction, resolving major layer structures of the retina. The feasibility of the system was demonstrated by performing supine position 2D/3D retinal imaging on healthy human subjects, sedated infants, and non-sedated awake neonates.

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.

Advantages of Widefield Optical Coherence Tomography in the Diagnosis of Retinopathy of Prematurity

Recent advances in portable optical coherence tomography (OCT) and OCT angiography (OCTA) have resulted in wider fields of view (FOV) and shorter capture times, further expanding the potential clinical role of OCT technology in the diagnosis and management of retinopathy of prematurity (ROP). Using a prototype, handheld OCT device, retinal imaging was obtained in non-sedated infants in the neonatal intensive care unit (NICU) as well as sedated infants in the operating room of Oregon Health & Science University (OHSU) Hospital. In this observational study, we provide an overview of potential advantages of OCT-based disease assessment in ROP. We observed that next-generation OCT imaging (a) may be sufficient for objective diagnosis and zone/stage/plus disease categorization, (b) allows for minimally-invasive longitudinal monitoring of disease progression and post-treatment course, (c) provides three-dimensional mapping of the vitreoretinal interface, and (d) with OCTA, enables dye-free visualization of normal and pathologic vascular development.

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.

Birth Weight Is a Significant Predictor of Retinal Nerve Fiber Layer Thickness at 36 Weeks Postmenstrual Age in Preterm Infants

PURPOSE

To assess retinal nerve fiber layer (RNFL) thickness in preterm infants.

DESIGN

Prospective observational study.

METHODS

We imaged 83 awake infants (159 eyes) at 36 ± 1 weeks postmenstrual age (defined as the time elapsed between the first day of the last maternal menstrual period and the time at imaging) using a handheld optical coherence tomography (OCT) system at the bedside. Blinded graders semi-automatically segmented RNFL in the papillomacular bundle (-15 to +15° relative to the fovea-optic nerve axis). We correlated RNFL thickness and 7 characteristics of interest (sex, race, ethnicity, gestational age, birth weight, stage of retinopathy at prematurity, and presence of pre-plus or plus disease) via univariable and multivariable regressions.

RESULTS

RNFL was 3.4 μm thicker in the right eyes than in the left eyes (P < .001). Among 7 characteristics, birth weight was the only independent predictor of RNFL thickness (P < .001). A 250-g increase in birth weight was associated with 5.2 μm (95% confidence interval: 3.3-7.0) increase in RNFL thickness. Compared with very preterm infants, extremely preterm infants had thinner RNFL (58.0 ± 10.7 μm vs 63.4 ± 10.7 μm, P = .03), but the statistical significance disappeared after adjustment for birth weight (P = .25). RNFL thickness was 11.2 μm thinner in extremely low birth weight infants than in very low birth weight infants (55.5 ± 8.3 μm vs. 66.7 ± 10.2 μm; P < .001). The difference remained statistically significant after adjustment for gestational age.

CONCLUSION

Birth weight is a significant independent predictor of RNFL thickness near birth, implying that the retinal ganglion cells reserve is affected by intrauterine processes that affect birth weight.