Visualization of the posterior vitreous with dynamic focusing and windowed averaging swept source optical coherence tomography

Imaging the Vitreous with a Novel Boosted Optical Coherence Tomography Technique: Vitreous Degeneration and Cisterns

PURPOSE

To evaluate the degenerative findings including cistern formation in the premacular vitreous using optical coherence tomography (OCT).

METHODS

A novel enhanced vitreous imaging method by which 4 A-scans at each position were averaged prior to the Fourier transform increased the image quality per frame so that subsequent image registration for averaging could occur. Analysis of B-scans and volume rendered images of eyes in subjects of various ages was performed.

RESULTS

There were 43 eyes of 23 subjects ranging in age from 23 - 68 years. The texture in the vitreous images suggests specific orientations of the vitreous fibers in the macular region; there were fibers circumferential to the retina immediately anterior to the premacular bursa. The pattern of the vitreous fibers seemed less well defined internal to the zone of circumferential fibers. In younger eyes, there were striations oriented in a roughly inferior to superior direction in this zone. In older eyes there were striations in the same orientation but actually were alternating zones of vitreous synchysis and syneresis. In these same eyes numerous cisterns appeared at various levels in the vitreous gel. With extensive vitreous condensation and synchysis, definition of the premacular bursa was lost.

CONCLUSIONS

With this novel method of enhanced vitreous imaging, the vitreous appeared to have stereotypic patterns of degeneration. The formation of vitreous syneresis and synchysis may be related to organization architecture of the vitreous, including the pattern of vitreous collagen deposition, and the effects of eye motion through decades of time.

B-SCAN ULTRASONOGRAPHY OF VITREOUS DYNAMICS DURING INTRAVITREAL ADMINISTRATION OF ANTIANGIOGENICS

PURPOSE

To study the distribution of angiogenesis inhibitors (anti-Vascular Endothelial Growth Factor) injected into the vitreous cavity by means of simultaneous ultrasonography.

METHODS

Three hundred and thirty-two B-scan ultrasound sequences of 121 eyes from 95 patients were recorded simultaneously to the intravitreal anti-Vascular Endothelial Growth Factor administration. The dynamics of the injected substance and the presence of reflux were studied, associating them with the presence/absence of total posterior vitreous detachment.

RESULTS

Three well-defined patterns were distinguished. Pattern A: the medication penetrates the vitreous in a linear manner until reaching the retina (3.6%, n = 12). Pattern B: the medication adopts a globular shape and then moves down reaching the retrohyaloid space (37%, n = 123). Pattern C: the medication remains in a globular form (54%, n = 180). The pattern was not identified in 17 (5.1%) injections. Pattern A was only observed in vitrectomized eyes. The reflux (7.8%) was exclusive in eyes showing a C pattern. A relationship (P < 0.001) was observed between the presence/absence of total posterior vitreous detachment, the patterns, and the presence of reflux.

CONCLUSION

This study document for the first time the behavior of antiangiogenic medication injected into the vitreous cavity and how its distribution and the presence of reflux is conditioned by the previous state of the vitreous body.

Evaluating posterior vitreous detachment by widefield 23-mm swept-source optical coherence tomography imaging in healthy subjects

Posterior vitreous detachment (PVD) is a separation between the posterior vitreous cortex and internal limiting membrane. Although PVD was historically considered an acute event, recent studies using spectral-domain optical coherence tomography (SD-OCT) revealed a gradual progression of PVD in healthy subjects. Although SD-OCT improved PVD studies, the narrow imaging angle and long examination time were problematic to allow wide angle capture. The Xephilio OCT-S1 (Canon), a swept-source OCT (SS-OCT) device, can obtain up to 23-mm of widefield B-scan images in a single acquisition. We used this widefield SS-OCT to quantitatively evaluate the PVD stage in 214 healthy subjects aged 4–89 years and determine whether PVD stages differ between the bilateral eyes of each patient. Age was significantly positively correlated with the overall PVD stage (ρ = 0.7520, P < 0.001). Interestingly, partial PVD occurred in children as young as 5 years, indicating that initial PVD onset may occur much earlier than previously reported. Furthermore, PVD stages of the bilateral eyes were highly consistent in 183 subjects (85.5%). Widefield 23-mm SS-OCT thus revealed that PVD started earlier than anticipated, and age was correlated with the symmetry of PVD stage. Widefield 23-mm SS-OCT may also be clinically useful for the evaluation of diseased eyes.

Association of Aberrant Posterior Vitreous Detachment and Pathologic Tractional Forces With Myopic Macular Degeneration

Purpose

The purpose of this study was to assess whether the tractional elements of pathologic myopia (PM; e.g. myopic traction maculopathy [MTM], posterior staphyloma [PS], and aberrant posterior vitreous detachment [PVD]) are associated with myopic macular degeneration (MMD) independent of age and axial length, among highly myopic (HM) eyes.

Methods

One hundred twenty-nine individuals with 239 HM eyes from the Myopic and Pathologic Eyes in Singapore (MyoPES) cohort underwent ocular biometry, fundus photography, swept-source optical coherence tomography, and ocular B-scan ultrasound. Images were analyzed for PVD grade, and presence of MTM, PS, and MMD. The χ² test was done to determine the difference in prevalence of MMD between eyes with and without PVD, PS, and MTM. Multivariate probit regression analyses were performed to ascertain the relationship between the potential predictors (PVD, PS, and MTM) and outcome variable (MMD), after accounting for possible confounders (e.g. age and axial length). Marginal effects were reported.

Results

Controlling for potential confounders, eyes with MTM have a 29.92 percentage point higher likelihood of having MMD (P = 0.003), and eyes with PS have a 25.72 percentage point higher likelihood of having MMD (P = 0.002). The likelihood of MMD increases by 10.61 percentage points per 1 mm increase in axial length (P < 0.001). Subanalysis revealed that eyes with incomplete PVD have a 22.54 percentage point higher likelihood of having MMD than eyes with early PVD (P = 0.04).

Conclusions

Our study demonstrated an association between tractional (MTM, PS, and persistently incomplete PVD) and degenerative elements of PM independent of age and axial length. These data provide further insights into the pathogenesis of MMD.

Swept Source Optical Coherence Tomography Compared to Ultrasound and Biomicroscopy for Diagnosis of Posterior Vitreous Detachment

Background

Biomicroscopy, B-scan ultrasound imaging, and SD-OCT are all modalities used to characterize a posterior vitreous detachment (PVD). Our objective is to assess the precision of the diagnosis of PVD by SS-OCT.

Methods

This prospective observational study examines ninety-five eyes of forty-nine patients with biomicroscopy, B-scan ultrasound, and SS-OCT for the presence or absence of a complete PVD. All SS-OCT images were reviewed by two retina specialists (RWSC, ZM). All three diagnostic methods were evaluated for agreement by Cohen’s kappa statistic.

Results

The inter-rater reliability between retina specialists reading the SS-OCT images was 97.9% (κ = 0.957). Agreement on PVD status between SS-OCT and biomicroscopy was 85.3% (κ = 0.711). Agreement between SS-OCT and B-scan ultrasound was 83.2% (κ = 0.667). Agreement between B-scan ultrasound and biomicroscopy was 87.4% (κ = 0.743).

Conclusion

For the diagnosis of complete PVD, SS-OCT allows for high accuracy and agreement between graders.

Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA)

The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.

Swept Source Optical Coherence Tomography Assessment of Bursa Premacularis in Healthy Eyes

Purpose

To describe the reliability and the limits of bursa premacularis (BPM) evaluation using a swept source optical coherence tomography (SS-OCT) device with enface and 16 mm-high definition (HD) longitudinal scans.

Methods

60 eyes of 60 subjects were enrolled and imaged with SS-OCT system (PLEX Elite 9000, Carl Zeiss Meditec Inc., Dublin, CA, USA). BPM area was measured using enface scans imported to ImageJ. HD horizontal and vertical longitudinal scans centered at the fovea were used to detect width (W) and central thickness (CT) of BPM at baseline (T₀) and after 30 minutes (T₃₀) performed by two different observers. An enhanced vitreous visualization software provided by the manufacturer of the device was used to highlight vitreous structures.

Results

BPM was identifiable in 100% of eyes using both horizontal and vertical longitudinal scans. On horizontal scan, BPM was not entirely measurable in 21.7% and in 18.3% of cases at T₀ and T₃₀, respectively. On vertical scan, BPM was not entirely measurable in 75.0% and in 81.7% at T₀ and T₃₀, respectively. No statistically significant differences were found between the two different time measurements with an intraclass correlation coefficient above 70%. Median BPM area was 26.9 (Q₁-Q₃: 19.5-40.5) mm². In en face imaging, the most frequent BPM shape was the boat one.

Conclusion

SS-OCT is a reliable tool for a detailed quantification and mapping of BPM, and it is able to add useful details about the morphological BPM features in youth population. However, the enhanced visualization of the vitreous structures is still a challenge, also with the most forefront devices.

Imaging the Choroid: From Indocyanine Green Angiography to Optical Coherence Tomography Angiography

The choroid is the vascular structure nourishing the retinal pigment epithelium and the outer retina and it plays a key role in the homeostasis of the eye both under physiological and pathological conditions. In the last 20 years we have moved from "guessing" what was happening beyond the retinal pigment epithelium to actually visualize structural and functional changes of the choroid in vivo noninvasively. In this review we describe the state of the art of choroidal imaging, focusing on the multiple techniques available in the clinical and research setting including indocyanine green angiography, labeled-cells angiographies, optical coherence tomography (OCT), enhanced depth imaging, swept source OCT, and OCT angiography. In the first section of the article, we describe their main applications and the basic principles to interpret the imaging results. Increasing evidence suggests that the choroid is much more involved than we used to think in many pathological conditions from uveitis to intraocular tumors, from vascular diseases to age-related macular degeneration. All clinicians should hence know which is the most appropriate imaging investigation to explore the choroid in the disease they are dealing with and how to interpret the results. For this reason the second section of this review summarizes the best imaging approach and the most common findings visible on choroidal imaging in different diseases of the eye.

Accuracy of Spectral-Domain OCT of the Macula for Detection of Complete Posterior Vitreous Detachment

PURPOSE

To assess the accuracy of macular spectral-domain OCT in detecting complete posterior vitreous detachment (PVD).

DESIGN

Evaluation of diagnostic test or technology using a retrospective comparative study.

PARTICIPANTS

One hundred seventy-five eyes in 175 patients (111 women and 64 men; mean age, 65 years) with preoperative OCT within 90 days of vitrectomy.

METHODS

Posterior vitreous detachment status on preoperative macular OCT was compared with PVD determination during vitrectomy. Attached vitreous was identified on OCT by visualizing the posterior vitreous cortex or premacular bursa. Complete PVD was identified by the absence of these findings and considered a positive outcome for the purpose of analysis.

MAIN OUTCOME MEASURES

Sensitivity, specificity, positive predictive value, and negative predictive value of macular OCT for detection of complete PVD compared with findings at surgery.

RESULTS

Of the 38 eyes graded as showing complete PVD on OCT, 20 eyes were found to have pre-existing PVD at the time of surgery (true-positive results), and 18 eyes were found to have attached vitreous at the time of surgery (false-positive results). Of the 137 eyes graded as showing attached vitreous on OCT, 129 eyes had attached vitreous at the time of surgery (true-negative results), and 8 eyes had pre-existing PVD at the time of surgery (false-negative results). The sensitivity of OCT for detecting complete PVD was 71% and the specificity was 88%. In the study population, the positive predictive value of an OCT scan showing complete PVD was 53%, whereas the negative predictive value of an OCT scan showing attached vitreous was 94%.

CONCLUSIONS

If the premacular bursa or posterior vitreous cortex are visualized on macular OCT, an accurate determination of attached vitreous can be made. The diagnosis of complete PVD by macular OCT is less accurate and requires ultrasound.

Ultra-Widefield Optical Coherence Tomographic Imaging of Posterior Vitreous in Eyes With High Myopia

PURPOSE

To investigate the morphological changes of posterior vitreous in highly myopic (HM) eyes of patients 50 years of age and older.

DESIGN

Retrospective, observational case series.

METHODS

Ultra-widefield swept-source OCT (UWF-OCT) examinations were performed on 768 eyes of 448 HM patients (50-89 years of age) and 54 eyes of 52 non-HM subjects with scan widths of 23 mm and depths of 5 mm. HM was defined as an axial length longer than 26.5 mm. The area and morphology of the posterior vitreous detachments (PVDs) and adhesions onto retinal vessels were examined for in 167 HM eyes and in 11 non-HM eyes in which the vitreal images were clear.

RESULTS

Paramacular PVD, perifoveal PVD, peripapillary PVD, and complete PVD were found in 9%, 47%, 41%, and 3% of the 167 HM eyes, respectively, and in 37%, 45%, 18%, and 0% of the 11 non-HM eyes, respectively. In eyes with vitreofoveal adhesions, the PVDs were more commonly asymmetrical relative to the fovea in the HM eyes than in the non-HM eyes (94% vs. 44%, respectively; P < .001). The area of the PVD corresponded with the area where the sclera protruded posteriorly. A thickened vitreous was observed to adhere to the retinal vessels at multiple points and was accompanied by paravascular abnormalities including lamellar holes in HM eyes. A total of 54 of the 167 HM eyes had macular retinoschisis, and the eyes commonly had vitreal traction on retinal vessels compared to HM eyes without macular retinoschisis (P = .031).

CONCLUSIONS

PVD progressed asymmetrically and were associated with scleral curvature in HM eyes. Vitreous traction spanning a wide distance may lead to myopic traction maculopathy.

Impact of Binarization Thresholding and Brightness/Contrast Adjustment Methodology on Optical Coherence Tomography Angiography Image Quantification

PURPOSE

Binarization is a critical technique in optical coherence tomography angiography (OCTA) image analysis, but there is no consistency in the method used in published OCTA studies. This study assessed whether differences in OCTA binarization and brightness and contrast adjustments affect quantification measurements.

DESIGN

Prospective cross-sectional validity study.

METHODS

This was a single-center study examining 21 eyes of 11 healthy individuals. All eyes were imaged using a swept-source OCTA (Zeiss), and quantitative measurements resulting from five binarization thresholding and five brightness/contrast adjustment methods were compared. All measurements were calculated for the superficial plexus and choriocapillaris (CC), as well as unaveraged and averaged en face OCTA images.

RESULTS

There were statistically significant differences between measurements from different binarization thresholding methods (P < 0.0001), as well as measurements from different histogram adjustments (P < 0.0001). The binarization thresholds yielded different measurements when combined with variable brightness/contrast adjustments. The method of analysis also affected the directionality of trends in imaging measurements between unaveraged and averaged CC images.

CONCLUSIONS

The method of OCTA image binarization thresholding and histogram adjustment significantly alters quantitative measurements and the directionality of trends. Results obtained from different OCTA binarization methods should be seen as valid only for that given method. This has significant consequences for clinical trials using OCTA measurements as outcome measurements. A consensus is needed across the research community for a consistent method for OCTA image quantification and greater attention paid to fully describing methods in published studies.

Does the Bursa Pre-Macularis protect the fovea from shear stress? A possible mechanical role

Purpose of present study is to evaluate whether the Pre-Macular Bursa (PMB) modifies Wall Shear Stress (WSS) at the retinal surface during saccadic movements. We created a mathematical model consisting of 25,000 grid cells and simulated a horizontal saccade spanning 50° in 0.17s, both in absence and in presence of the PMB. Wall Shear Stress SS was computed throughout the retinal surface and the posterior pole was divided into 3 Zones comprising 400 nodes each: Zone 1 (radius 3.5 mm; 0°-17°) corresponding to the PMB area; Zone 2 (concentric annular area 5 mm in radius; 22°) and Zone 3 (concentric annular area 5.5 mm; 28°). The PMB reduced WSS significantly at the macula and increased it in the immediate surroundings. Average WSS in Zone 1 was 1.53 ± 1.01 (max 4.23 Pa) with PMB Vs 6.94 ± 9.23 (max 35.83 Pa) without. Zone 2 WSS was 9.39 ± 10.33 (max 48.36 Pa) with PMB Vs 6.95 ± 9.40 (max 38.60 Pa) without Zone 3 WSS was 8.41 ± 10.03 (max 43.16 Pa) with PMB Vs 6.88 ± 9.42 (max 39.43 Pa) without (p < 0.001 in all cases). The PMB significantly reduces WSS over the retinal surface underlying the bursa region; conversely, WSS slightly increases it in the immediate neighboring areas.

POSTERIOR PRECORTICAL VITREOUS POCKETS IN HIGH MYOPIA OBSERVED BY ENHANCED VITREOUS IMAGING OF SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

To observe the vitreous in highly myopic eyes with posterior precortical vitreous pockets (PPVPs) using enhanced vitreous imaging of spectral domain optical coherence tomography.

METHODS

Fifty-two highly myopic eyes with PPVPs of 36 patients were included in this study. All subjects underwent enhanced vitreous imaging optical coherence tomography. The size of PPVPs was measured, and the frequency of imaging features was recorded.

RESULTS

Nine imaging features of the vitreous in highly myopic eyes with PPVPs were found. The average age of subjects was 38.1 ± 10.8 years. The mean height of PPVPs was 1,177 ± 704 μm, and the mean width was 7,440 ± 755 μm. Hyperreflective line and the interlayer were observed in 30 (57.7%) eyes. Hyperreflective dots were found in 37 (71.2%) eyes. More central vitreous space was more frequently detected in younger patients. Prevascular vitreous fissure was detected in 7 (13.5%) eyes. W-shaped cavity, identified as an empty space with a smooth W-shaped edge, was demonstrated to be the fusion of Cloquet's canal and the extension of PPVPs. Perpendicular hyperreflective parallel strands were detected in 3 (5.8%) eyes. Hyperreflective network was observed in 10 (19.2%) eyes. Hyperreflective parapapillary tubercle was found in 7 (13.5%) eyes.

CONCLUSION

Nine imaging features of the vitreous in highly myopic eyes with PPVPs were visualized by enhanced vitreous imaging optical coherence tomography.

Segmentation error in spectral domain optical coherence tomography measures of the retinal nerve fibre layer thickness in idiopathic intracranial hypertension

BACKGROUND

Optical Coherence Tomography (OCT) imaging is being increasingly used in clinical practice for the monitoring of papilloedema. The aim is to characterise the extent and location of the Retinal Nerve Fibre Layer (RNFL) Thickness automated segmentation error (SegE) by manual refinement, in a cohort of Idiopathic Intracranial Hypertension (IIH) patients with papilloedema and compare this to controls.

METHODS

Baseline Spectral Domain OCT (SDOCT) scans from patients with IIH, and controls with no retinal or optic nerve pathology, were examined. The internal limiting membrane and RNFL thickness of the most severely affected eye was examined for SegE and re-segmented. Using ImageJ, the total area of the RNFL thickness was calculated pre and post re-segmentation and the percentage change was determined. The distribution of RNFL thickness error was qualitatively assessed.

RESULTS

Significantly greater SegE (p = 0.009) was present in RNFL thickness total area, assessed using ImageJ, in IIH patients (n = 46, 5% ± 0-58%) compared to controls (n = 14, 1% ± 0-6%). This was particularly evident in moderate to severe optic disc swelling (n = 23, 10% ± 0-58%, p < 0.001). RNFL thickness was unable to be quantified using SDOCT in patients with severe papilloedema.

CONCLUSIONS

SegE remain a concern for clinicians using SDOCT to monitor papilloedema in IIH, particularly in the assessment of eyes with moderate to severe oedema. Systematic assessment and manual refinement of SegE is therefore important to ensure the accuracy in longitudinal monitoring of patients.

Choriocapillaris Imaging Using Multiple En Face Optical Coherence Tomography Angiography Image Averaging

Importance

Imaging of the choriocapillaris in vivo is challenging with existing technology. Optical coherence tomography angiography (OCTA), if optimized, could make the imaging less challenging.

Objective

To investigate multiple en face image averaging on OCTA images of the choriocapillaris.

Design, Setting, and Participants

Observational, cross-sectional case series at a referral institutional practice in Los Angeles, California. From the original cohort of 21 healthy individuals, 17 normal eyes of 17 participants were included in the study. The study dates were August to September 2016.

Exposures

All participants underwent OCTA imaging of the macula covering a 3 × 3-mm area using OCTA software (Cirrus 5000 with AngioPlex; Carl Zeiss Meditec). One eye per participant was repeatedly imaged to obtain 9 OCTA cube scan sets. Registration was first performed using superficial capillary plexus images, and this transformation was then applied to the choriocapillaris images. The 9 registered choriocapillaris images were then averaged. Quantitative parameters were measured on binarized OCTA images and compared with the unaveraged OCTA images.

Main Outcome and Measure

Vessel caliber measurement.

Results

Seventeen eyes of 17 participants (mean [SD] age, 35.1 [6.0] years; 9 [53%] female; and 9 [53%] of white race/ethnicity) with sufficient image quality were included in this analysis. The single unaveraged images demonstrated a granular appearance, and the vascular pattern was difficult to discern. After averaging, en face choriocapillaris images showed a meshwork appearance. The mean (SD) diameter of the vessels was 22.8 (5.8) µm (range, 9.6-40.2 µm). Compared with the single unaveraged images, the averaged images showed more flow voids (1423 flow voids [95% CI, 967-1909] vs 1254 flow voids [95% CI, 825-1683], P < .001), smaller average size of the flow voids (911 [95% CI, 301-1521] µm2 vs 1364 [95% CI, 645-2083] µm2, P < .001), and greater vessel density (70.7% [95% CI, 61.9%-79.5%] vs 61.9% [95% CI, 56.0%-67.8%], P < .001). The distribution of the number vs sizes of the flow voids was skewed in both unaveraged and averaged images. A linear log-log plot of the distribution showed a more homogeneous distribution in the averaged images compared with the unaveraged images.

Conclusions and Relevance

Multiple en face averaging can improve visualization of the choriocapillaris on OCTA images, transforming the images from a granular appearance to a level where the intervascular spaces can be resolved in healthy volunteers.

CHANGES IN THE POSTERIOR VITREOUS AFTER CATARACT SURGERY ASSESSED BY SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

To assess changes in the posterior vitreous caused directly by phacoemulsification with implantation of an intraocular lens, using the enhanced vitreous swept-source optical coherence tomography system (Topcon, Tokyo, Japan).

METHODS

Consecutive patients with cataract without posterior vitreous detachment were enrolled. Swept-source optical coherence tomography examinations were performed 1 day before and several days after surgery, using enhanced vitreous visualization. We compared preoperative and postoperative posterior vitreous status and measured the distance between the internal limiting membrane and the posterior vitreous membrane at 26 locations at the posterior pole.

RESULTS

Images of 33 eyes (21 patients) could be analyzed. The perifoveal posterior vitreous detachment was not extended in any eyes, and the internal limiting membrane to posterior vitreous membrane distance before and after surgery did not differ at any location measured (P = 0.071-1.000). The posterior precortical vitreous pocket was dilated in three eyes. Age, gender, axial length, preoperative visual activity, nuclear sclerosis, duration of surgery, and duration between surgery and swept-source optical coherence tomography did not differ between the dilated vitreous pocket group (n = 3) and the unchanged group (n = 30).

CONCLUSION

The height of the posterior vitreous membrane remained unchanged after surgery, although the posterior precortical vitreous pocket was dilated in three patients. Cataract surgery procedures seem to have little influence on the posterior vitreous membrane.

An Assessment of Vitreous Degeneration in Eyes with Vitreomacular Traction and Macular Holes

Purpose. To compare the stages of vitreous degeneration in patients with vitreomacular traction (VMT) and macular holes (MH). Methods. A retrospective study was performed analyzing stages of vitreous degeneration of eyes with VMT or MH using swept-source optical coherence tomography (SS-OCT) and spectral-domain optical coherence tomography (SD-OCT). An analogous review was performed on a control group of eyes with contralateral posterior vitreous detachments. Thirty-four eyes with VMT/MH and 39 control eyes were reviewed. Results. Twenty-seven VMT/MH eyes and 31 control eyes were included. Eyes with VMT/MH demonstrated significantly earlier stages of vitreous degeneration when compared to the control group (p = 0.048) despite significantly greater age (p = 0.032). Conclusions. Vitreoretinal interface disease is more often associated with a formed vitreous and an intact premacular bursa. This is contrary to previous assumptions implicating degeneration of vitreous as a precipitating factor of interface disease when in conjunction with abnormal vitreomacular separation.

REAL-TIME FULL-DEPTH VISUALIZATION OF POSTERIOR OCULAR STRUCTURES: Comparison Between Full-Depth Imaging Spectral Domain Optical Coherence Tomography and Swept-Source Optical Coherence Tomography

PURPOSE

To compare the real-time visualization of vitreoretino-choroidal structures using full-depth imaging (FDI) spectral domain optical coherence tomography (SD-OCT) and swept-source (SS)-OCT.

METHODS

Foveal scans using both FDI SD-OCT (Heidelberg Spectralis) and SS-OCT (Topcon Deep Range Imaging-OCT-1) were obtained in 40 normal eyes, 40 eyes with macular pathologies, and 40 eyes with glaucoma. Full-depth imaging SD-OCT images were obtained by manually enhancing the vitreoretinal interface first and then the choroid while averaging each OCT B-scan 100 times. Swept-source-OCT images were obtained by averaging each B-scan 96 times. After masking and randomly mixing the original OCT images, two independent physicians graded visualization of the premacular bursa, interdigitation zone line, and chorioscleral boundary, and also sharpness of choroidal structures.

RESULTS

A real-time full-depth image of vitreoretino-choroidal structures was successfully achieved with FDI SD-OCT in 118 cases (98.3%) and with SS-OCT in 45 cases (37.5%, P < 0.001). Full-depth imaging SD-OCT imaging was superior to SS-OCT imaging in visualizing the anterior border of the premacular bursa in 109 eyes (90.8%), with average grading of 1.63 ± 0.53 for the FDI SD-OCT and 0.39 ± 0.52 for the SS-OCT (P < 0.001). Swept-source-OCT was similar to FDI SD-OCT in visualizing the chorioscleral boundary in 108 eyes (90.0%), with average grading of 1.81 ± 0.39 for the SS-OCT and 1.78 ± 0.38 for the FDI-OCT (P = 0.566). The visualization of the interdigitation zone line was identical in the 2 imaging instruments (P = 1.000). The sharpness of the choroidal structures was greater with SS-OCT than with FDI-OCT (P < 0.001).

CONCLUSION

Manual double-enhancing FDI technique using SD-OCT provided a good compromise between vitreous and retinochoroidal structures visualization in real time during scanning procedure. In contrast, SS-OCT imaged well details of choroidal sublayers. Appropriate OCT technology and software should be selected according to its application in clinical settings.

Microarchitecture of the Vitreous Body: A High-Resolution Optical Coherence Tomography Study

PURPOSE

To report novel vitreous body microarchitecture findings using high-resolution spectral-domain optical coherence tomography (HR-SD-OCT).

DESIGN

Prospective, cross-sectional study.

METHODS

Horizontal and vertical retinal cross-sectional images that were 10 mm long were acquired from 17 eyes of 17 young healthy volunteers using HR-SD-OCT with enhanced vitreous imaging (EVI). Images were acquired through the fovea, upper vessel arcade, and lower vessel arcade.

RESULTS

Three new findings on vitreous body microarchitecture were found. First, material located between the retina and posterior vitreous cortex was easily detected in 90% of upper and lower vessel arcade scans. Most scans contained hyperreflective dots and multilayered hyperreflective lines around the detached vitreous cortex. Second, a lamellar structure was observed in the vitreous body in 70%-80% of all scans, excluding vertical scans of the upper arcade vessel area. Third, tubular zones of hypodensity were detected in >80% of scans, excluding horizontal scans of the macula. Interestingly, the location of tubular zones of hypodensity seemed to correspond with the location of retinal vessels. Subject age, refractive error, and axial length were not significantly different in scans with and without material between the retina and vitreous, lamellar structures, and tubular zones of hypodensity.

CONCLUSIONS

The microarchitecture of the vitreous body can be visualized using HR-SD-OCT and EVI.

Advances of optical coherence tomography in myopia and pathologic myopia

The natural course of high-axial myopia is variable and the development of pathologic myopia is not fully understood. Advancements in optical coherence tomography (OCT) technology have revealed peculiar intraocular structures in highly myopic eyes and unprecedented pathologies that cause visual impairment. New OCT findings include posterior precortical vitreous pocket and precursor stages of posterior vitreous detachment; peripapillary intrachoroidal cavitation; morphological patterns of scleral inner curvature and dome-shaped macula. Swept source OCT is capable of imaging deeper layers in the posterior pole for investigation of optic nerve pits, stretched and thinned lamina cribrosa, elongated dural attachment at posterior scleral canal, and enlargement of retrobulbar subarachnoid spaces. This has therefore enabled further evaluation of various visual field defects in high myopia and the pathogenesis of glaucomatous optic neuropathy. OCT has many potential clinical uses in managing visual impairing conditions in pathologic myopia. Understanding how retinal nerve fibers are redistributed in axial elongation will allow the development of auto-segmentation software for diagnosis and monitoring progression of glaucoma. OCT is indispensable in the diagnosis of various conditions associated with myopic traction maculopathy and monitoring of post-surgical outcomes. In addition, OCT is commonly used in the multimodal imaging assessment of myopic choroidal neovascularization. Biometry and topography of the retinal layers and choroid will soon be validated for the classification of myopic maculopathy for utilization in epidemiological studies as well as clinical trials.

Is Optical Coherence Tomography a Useful Tool to Objectively Detect Actual Posterior Vitreous Adhesion Status?

Purpose. To objectively detect true posterior vitreous cortex (PVC) adhesion status using a commercially available swept-source OCT device (DRI OCT-1, Atlantis(©)). Material and Methods. Case report, review of the literature, and methodical discussion of concepts to improve OCT-guided PVC imaging. Results. Standard OCT imaging misdiagnosed PVC adhesion status as totally detached in this case report when using a horizontal 6 mm scan only. Contrariwise imaging the same eye with a 12 mm horizontal scan, partial posterior vitreous detachment (PVD) and the presence of a bursa premacularis were clearly discernible. Besides a broader scan, specific scan patterns, highest resolution, and contrast sensitivity, an anterior-to-posterior adjusted scan through the entire vitreous as well as the detection of characteristic undulating aftermovements might enhance the capability of OCT imaging to detect true PVC adhesion status. Conclusions. Further developments are needed to address these issues and to establish OCT recordings as the standard and objective method of choice in PVC adhesion status imaging.

Imaging Suprachoroidal Layer in Exudative Age-Related Macular Degeneration

PURPOSE

To evaluate the prevalence of a visible suprachoroidal layer (SCL) on optical coherence tomography (OCT) in exudative age-related macular degeneration (AMD).

MATERIALS AND METHODS

This retrospective study included 252 eyes of 252 patients with treatment-naive typical exudative AMD (n = 80), polypoidal choroidal vasculopathy (PCV) (n = 138) and retinal angiomatous proliferation (RAP) (n = 34). The presence of SCL was identified based on enhanced-depth imaging OCT images, and the prevalence was compared among the three disease groups. In addition, subfoveal choroidal thickness was compared between patients with and without SCL.

RESULTS

The SCL was noted in 56 eyes (22.2%). The prevalence was 22.5% in typical exudative AMD (18 of 80 eyes), 18.8% in PCV (26 of 138 eyes) and 35.3% in RAP (12 of 34 eyes) (p = 0.118). Patients with SCL showed significantly thinner choroid (207.5 ± 83.9 µm versus 279.7 ± 116.5 µm, p < 0.001) and were relatively older (72.1 ± 8.1 versus 70.1 ± 8.7 years, p = 0.124) than those without SCL.

CONCLUSION

The prevalence of visible SCL was 22.2% in patients with exudative AMD. Age-related changes, including choroidal thinning, may contribute to the development of a visible SCL.

Whole vitreous humor dissection for vitreodynamic analysis

The authors propose an effective technique to isolate whole, intact vitreous core and cortex from post mortem enucleated porcine eyes. While previous studies have shown the results of such dissections, the detailed steps have not been described, precluding researchers outside the field from replicating their methods. Other studies harvest vitreous either through aspiration, which does not maintain the vitreous structure anatomy, or through partial dissection, which only isolates the vitreous core. The proposed method isolates the whole vitreous body, with the vitreous core and cortex intact, while maintaining vitreous anatomy and structural integrity. In this method, a full thickness scleral flap in an enucleated porcine eye is first created and through this, the choroid tissue can be separated from the sclera. The scleral flap is then expanded and the choroid is completely separated from the sclera. Finally the choroid-retina tissue is peeled off the vitreous to leave an isolated intact vitreous body. The proposed vitreous dissection technique can be used to study physical properties of the vitreous humor. In particular, this method has significance for experimental studies involving drug delivery, vitreo-retinal oxygen transport, and intraocular convection.