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

Association of choroidal thickness and blood flow features with asymmetric axial lengths in children with unilateral myopic anisometropia

BACKGROUND

Considering that changes in the choroidal thickness are closely related to ocular growth, we studied the choroidal thickness (CT) and the blood flow features in children with unilateral myopic anisometropia (UMA) as well as investigating the relationship between choroidal changes and myopia.

METHODS

Subjective refractive, axial length (AL), and biometric parameters were measured in 98 UMA children (age: 8-15 years). CT and choroidal blood-flow features, including the choroidal vessel volume (CVV), choroidal vascularity index (CVI), and choriocapillaris perfusion area (CCPA), were measured through swept-source optical coherence tomography angiography. The macular region was categorized into four concentric circles of diameters 0-1 mm (central fovea), 1-3 mm (parafovea), 3-6 mm (perifovea), and 6-9 mm (extended), and further categorized into superior (S), inferior (I), temporal (T), and nasal (N) quadrants.

RESULTS

The aforementioned four regions of myopic eyes displayed significantly lower CT, CVV, and CVI than those of non-myopic eyes. CCPA changes differed across different regions of both the eyes (parts of N and T quadrants). There was an inverse association between CT and the interocular AL difference (central and other regions S, T quadrant). No correlation was noted between CVV and CVI with interocular AL difference. CT and CVV were positively correlated in the 0-6-mm macular region of myopic eyes (Spearman correlation coefficient = 0.763, P < 0.001).

CONCLUSIONS

In UMA children, CCT and blood flow may be related to myopia progression. A robust correlation between CT and CVV in the 0-6-mm macular region and reduced CT and diminished blood flow indicated an association with myopia.

Use of a dexamethasone implant to treat macular edema following pars plana vitrectomy and removal of the primary epiretinal membrane

PURPOSE

The purpose of this study was to evaluate the effectiveness and safety of an intravitreal dexamethasone (DEX) implant for the treatment of macular edema (ME) following pars plana vitrectomy (PPV) and removal of the primary epiretinal membrane (ERM) and to assess the impact of the integrity of the ellipsoid zone (EZ) and disorganization of the retinal inner layer (DRIL) grade on visual and anatomical outcomes.

METHODS

Forty-two pseudophakic patients who developed ME following PPV and removal of the primary stage 2-3 ERM were included. Patients were divided into two groups when ME was diagnosed via spectral domain optic coherence tomography (SD-OCT). In the DEX group (n = 22), DEX was implanted for the treatment of ME. In the control group (n = 20), only observation was conducted, without any treatment. The best-corrected visual acuity (BCVA) and macular thickness (MT) of the two groups were compared at baseline and 1, 6, and 12 months after DEX implantation. The effects of OCT parameters such as EZ integrity and DRIL grade were also evaluated in terms of decreases in MT and increases in VA in the treatment of ME with DEX implantation. Intraocular pressure (IOP), number of DEX implantations and adverse effects were also recorded.

RESULTS

While a statistically significant increase in the mean BCVA was observed in the DEX group (p < 0.001 at months 1, 6, and 12, respectively), no such increase was detected in the control group (p = 0.169, p = 0.065, and p = 0.058 at months 1, 6 and 12, respectively) compared with the baseline. A statistically significant decrease in the mean MT was observed in the DEX group (p  < 0.001 at months 1, 6, and 12); however, no significant difference was observed in the control group (p  = 0.081, p  = 0.065, and p  = 0.054 at months 1, 6 and 12, respectively) compared with the baseline. Significant differences were found between the two groups in terms of the increase in BCVA (p  < 0.01) and decrease in MT (p  < 0.01) at all visits, with the outcomes being more favorable in the DEX group. A statistically significant relationship was found between the increase in VA and EZ integrity and DRIL grade in both groups. Ten patients (45.4%) received two injections of DEX during the follow-up. An increase in IOP was observed in five patients (22.7%) who were treated with topical antiglaucomatous drops. No significant side effects were observed.

CONCLUSION

DEX implantation was found to be effective and safe for the treatment of ME following PPV and primary ERM removal, although some eyes may require repeated injections to achieve visual and anatomical success. Additionally, a relationship was found between EZ integrity, DRIL grade and visual-anatomical outcomes.

3D nanoprinted catadioptric fiber sensor for dual-axis distance measurement during vitrectomy

Retinal damage is a common intraoperative complication during vitrectomy, caused by a complex interplay between the suction of the vitrectome, the cut- and aspiration rate, and the distance of the instrument to the retina. To control this last factor, we developed two miniaturized fiber-optic distance sensors based on low-coherence interferometry for direct integration into the vitrectome. Both sensors have a diameter of 250 µm, which makes them compatible with a 25G vitrectome. The first sensor measures distance in the lateral direction. The second sensor is capable of simultaneously measuring distance in both the lateral and the axial direction. Axial and lateral directions correspond to the direction of the cutter port of the vitrectome and the direction along the vitrectome's shaft, respectively. In both sensors, a free-form mirror deflects and focuses the beam in the lateral direction. In the dual-axis distance sensor, an additional lens is integrated into the free-form mirror for distance measurement in the axial direction. The beam-shaping micro-optics at the tip of the sensor fibers were fabricated through two-photon polymerization and are selectively gold coated for increased reflectivity of the mirror. Distance measurements were successfully demonstrated in artificial samples and in ex vivo pig eyes with a back-end that uses a current-tuned VCSEL as a swept-source. We experimentally demonstrate that the complete sensor system can attain a S N R max of up to 80 dB. The small dimensions of the developed sensors make them a potential solution for various other medical applications.

Advanced nanomaterials for imaging of eye diseases

Background and purpose

Vision impairment and blindness present significant global challenges, with common causes including age-related macular degeneration, diabetes, retinitis pigmentosa, and glaucoma. Advanced imaging tools, such as optical coherence tomography, fundus photography, photoacoustic microscopy, and fluorescence imaging, play a crucial role in improving therapeutic interventions and diagnostic methods. Contrast agents are often employed with these tools to enhance image clarity and signal detection. This review aims to explore the commonly used contrast agents in ocular disease imaging.

Experimental approach

The first section of the review delves into advanced ophthalmic imaging techniques, outlining their importance in addressing vision-related issues. The emphasis is on the efficacy of therapeutic interventions and diagnostic methods, establishing a foundation for the subsequent exploration of contrast agents.

Key results

This review focuses on the role of contrast agents, with a specific emphasis on gold nanoparticles, particularly gold nanorods. The discussion highlights how these contrast agents optimize imaging in ocular disease diagnosis and monitoring, emphasizing their unique properties that enhance signal detection and imaging precision.

Conclusion

The final section, we explores both organic and inorganic contrast agents and their applications in specific conditions such as choroidal neovascularization, retinal neovascularization, and stem cell tracking. The review concludes by addressing the limitations of current contrast agent usage and discussing potential future clinical applications. This comprehensive exploration contributes to advancing our understanding of contrast agents in ocular disease imaging and sets the stage for further research and development in the field.

Low rates of optical coherence tomography utilization in the diagnosis and management of retinovascular diseases in a lower middle-income economy

Background

Optical coherence tomography (OCT) is widely used as the standard of care in evaluating macular and retinovascular diseases. However, the degree of OCT utilization is yet to be researched in a resource-limited country where wide gaps exist in access to healthcare.

Aim

To determine the rate of utilization of the OCT in diagnosis, pre-treatment, and post-treatment evaluation of macular and retinovascular diseases treated with intravitreal anti-vascular endothelial growth factor injection (IVI).

Patients and Methods

Retrospective, consecutive, and non-comparative case series of eyes diagnosed and treated from Jan 2017 to Jan 2022 for seven macular and retinovascular diseases in five eye clinics in Nigeria. Data extracted include demographics, indication for IVI, eye treated, use or non-use of OCT at the diagnosis (pre-treatment) and after the last IVI (post-treatment), and central macular thickness (CMT) of pre-treatment OCT scans.

Results

Seven hundred and forty two eyes were diagnosed with retinovascular and macular diseases (389 right eyes and 353 left eyes).The male to female ratio was 430: 312 eyes. The mean age was, 63.89 years (SD 12.58). Four hundred and fifty two eyes (60.9%) had a pre-treatment OCT, 235 eyes (31.7%) had a post-treatment OCT, and 190 eyes (25.6%) had both pre- and post-treatment OCTs. The rate of pre-treatment OCT varied with the diagnosis (P = 0.000); DME had the highest rate, 74.4%, and HRVO had the lowest, 40%. Post-treatment OCT rate varied with the diagnosis (P = 0.009); non-AMD CNVM had the highest rate, 49.1%, and PCV had the lowest, 24.6%. Pre-treatment OCT rate was influenced by clinic location (P = 0.000); higher in clinics having an OCT. Post-treatment OCT was not influenced by clinic location (P = 0.37). A CRVO eye had the highest maximum CMT (1031 microns) of all the pre treatment eyes and the lowest minimum CMT of all the pre treatment eyes was in a BRVO eye (138 microns). Mean CMT was highest in HRVO (475.33 microns) and lowest in CNVM (307.62 microns).

Conclusion

Though OCT is the standard of care for managing retinovascular and macular diseases, this research quantifies the extent of its use in Nigeria and finds it to be low. A post-treatment OCT rate of 32% suggests that urgent steps are required to improve access to OCT for IVI patients.

OCT Angiography in Noninfectious Uveitis: A Description of Five Cases and Clinical Applications

BACKGROUND

Optical coherence tomography angiography (OCTA) is a noninvasive imaging modality used to analyze the retinochoroidal vasculature and detect vascular flow. The resulting images can be segmented to view each vascular plexus individually. While fluorescein angiography is still the gold standard for the diagnosis of posterior uveitis, it has limitations, and can be replaced by OCTA in some cases.

METHODS

This case series describes five patients with posterior noninfectious uveitis and their description by OCTA.

RESULTS

Cases included lupus retinopathy (n = 1) for which OCTA showed ischemic maculopathy as areas of flow deficit at the superficial and deep capillary plexus; choroidal granulomas (n = 1) with a non-detectable flow signal in the choroid; active punctate inner choroiditis and multifocal choroiditis (n = 1) with OCTA that showed active inflammatory chorioretinal lesions as non-detectable flow signals in choriocapillaris and choroid; dense type 2 inflammatory secondary neovascularization (n = 1) associated with active choroiditis; and acute posterior multifocal placoid pigment epitheliopathy (APMPPE) (n = 1) without flow abnormalities at the superficial and deep retinal plexuses but non-detectable flow at the levels of the choriocapillaris and choroid.

CONCLUSIONS

Ophthalmologists can use OCTA to identify inflammatory changes in retinal and choroidal vasculature, aiding in the diagnosis, management, and monitoring of posterior uveitis.

Characteristics of the Optic Nerve Head in Myopic Eyes Using Swept-Source Optical Coherence Tomography

Purpose

To investigate the characteristics of the optic nerve head (ONH) in myopia using swept-source optical coherence tomography (SS-OCT).

Methods

Participants were divided into three groups according to the axial length (AL). The optic disc morphology, retinal nerve fiber layer (RNFL) thickness, and radial peripapillary capillary (RPC) vessel density (VD), optic disc tilt, rotation, Bruch's membrane opening distance (BMOD), border length (BL), border tissue angle, focal lamina cribrosa (LC) defects, β- and γ-zone peripapillary atrophy (PPA), microvasculature dropout (MvD), choroidal thickness (CT), and the choroidal vascularity index (CVI) were compared. Linear regression analysis evaluated relationships between spherical equivalent, AL, and ONH parameters.

Results

One hundred five, 98, and 118 eyes were included in groups 1, 2, and 3, respectively. With AL increasing, the mean, superior and temporal CT, central mean and temporal, pericentral mean, inferior and nasal RPC VD, and temporal CVI decreased, whereas the mean and temporal RNFL thickness, optic disc, RIM and β-PPA area, presence and area of γ-PPA, BMOD and BL increased. Compared to other groups, group 3 depicted a larger cup area, more focal LC defect and total and juxtapapillary MvD; a lower central superior, inferior and nasal, pericentral superior, and temporal RPC VD. Group 1 demonstrated more tilted disc, larger inferior and nasal CT, mean, superior, inferior, and nasal CVI.

Conclusions

Myopia eyes have larger ONH changes, PPAs, regional RNFL, and MvD, but smaller regional CTs, RPC VD, and CVIs. SS-OCT may be useful in detecting ONH variations during myopia.

Small dome-shaped pigment epithelium detachment in polypoidal choroidal vasculopathy: an under-recognized sign of polypoidal lesions on optical coherence tomography?

PURPOSE

To evaluate the diagnostic accuracy of spectral-domain optical coherence tomography (SD-OCT) and swept-source optical coherence tomographic angiography (SS-OCTA) to identify polypoidal lesions in serous or serosanguinous maculopathy.

MATERIALS AND METHODS

A retrospective review of patients presenting pigment epithelial detachments (PEDs) with the diagnosis of polypoidal choroidal vasculopathy (PCV), neovascular age-related macular degeneration (nAMD), and central serous chorioretinopathy (CSC), all of which underwent SD-OCT, SS-OCTA, and indocyanine green angiography (ICGA). Typical features of polypoidal lesions on SD-OCT included sharply peaked PED, notched PED, and hyperreflective ring underneath PED. SS-OCTA feature was vascularized PEDs on cross-sectional images corresponding to cluster-like structures on en face images. The parameters of PEDs were measured for analysis.

RESULTS

Of 72 eyes, 30 had PCV, 22 had nAMD, and 20 had CSC. A total of 128 localized PEDs were detected on SD-OCT. Typical features on SD-OCT had a high specificity (94.0%) but a limited sensitivity (73.8%). SS-OCTA features provided a higher sensitivity (96.7%). PEDs of the polypoidal lesions unrecognized by SD-OCT were dome-shaped, with smaller ratio of height to base diameter and less area, and almost had heterogeneous internal reflectivity and a connected double-layer sign. Some lesions misidentified by SS-OCTA developed into ICGA-proven polypoidal lesions at follow-up visits.

CONCLUSION

A small dome-shaped PED with heterogeneous internal reflectivity and a connected double-layer sign on SD-OCT may suggest a polypoidal lesion of PCV. SS-OCTA may be a helpful tool to investigate preclinical PCV and observe the formation of polypoidal lesions.

Masking of macular neovascular membranes by subretinal hyperreflective material on optical coherence tomography angiography

PURPOSE

The purpose of this study was to determine whether subretinal hyperreflective material (SHRM) may mask the detection of macular neovascular membranes (MNV) on optical coherence tomography angiography (OCTA).

METHODS

In this observational study, eyes with active neovascular age-related macular degeneration (nAMD), co-existing SHRM & intraretinal or subretinal fluid or hemorrhage on structural OCT, underwent OCTA & fundus fluorescein angiography (FFA) imaging. 6 × 6 mm choriocapillaris and outer retinal slabs on OCTA were examined to determine the presence of MNV underneath the SHRM. The corresponding area on FFA was used as a reference arm to confirm activity.

RESULTS

Thirty eyes of thirty patients with SHRM and active nAMD were recruited. All eyes failed to show a MNV in the choriocapillaris & avascular slabs of the OCTA underneath the SHRM, but showed active hyperfluorescent MNVs that increased in size and intensity in the late stages of FFA. In one eye, parts of a MNV under the SHRM were undetectable due to signal attenuation, while parts extending beyond the SHRM were detected on the choriocapillaris en face slab with flow on the B scan.

CONCLUSIONS

SHRM may act as a reflecting surface that limits the passage of light waves in OCTA, creating areas of signal attenuation and diminishing its ability to detect underlying MNVs.

External Limiting Membrane, Photoreceptor Ellipsoid Zone Disruption, and Retinal Pigment Epithelium Alterations in Diabetic Retinopathy

Objective Diabetic retinopathy (DR), a microvascular complication of diabetes, is a leading cause of preventable blindness. Spectral domain optical coherence tomography (SD-OCT) provides cross-sectional and topographical imaging of the retina. SD-OCT resolves outer retinal layers into three hyperreflective bands—external limiting membrane (ELM), ellipsoid zone (EZ), and retinal pigment epithelium (RPE). In this article, we have studied the role of these outer retinal layers in structural and molecular changes taking place in DR.

Materials and Methods Articles with clinical features, pathogenesis, diagnosis, and treatment of DR were thoroughly studied. Articles were searched on PubMed, MEDLINE, and Cochrane Library from 2000 to 2020. Studies focusing on the role of ELM, EZ, and RPE in pathogenesis of DR based on SD-OCT were included.

Results The long-standing hyperglycemia leads to protein glycosylation resulting in formation of advanced glycation end products (AGEs). AGEs have an impact through their effect on retinal microvasculature, vascular endothelial growth factor (VEGF), intercellular adhesion molecule-1, nitrosative and oxidative stress, and vitamin D and calcium metabolism. All these factors have been linked with disruption of outer retinal layers. AGEs lead to vascular endothelial dysfunction and release of proangiogenic factors by increasing the expression of VEGF in retinal pericytes and RPE cells. This leads to leakage and fluid accumulation resulting in diabetic macular edema (DME). In DME, there is sequential disruption of ELM and EZ and decrease in visual acuity (VA). The RPE alterations have been reported to be associated with the severity of DR and decrease in VA. Anti-VEGF therapy, most common treatment of DME, leads to restoration of barrier effect of ELM, it was found to be restored first followed by EZ restoration. Newer anti-AGEs agents and their receptor blockers are being developed which have a positive effect on maintaining the health of RPE.

Conclusion A complex molecular association exists between the structural changes in ELM, EZ, and RPE in DR. SD-OCT is an indispensable tool to study these changes as integrity of these outer layers of retina is essential for maintaining visual function of retina in DR.

CHOROIDAL IMAGING BIOMARKERS TO PREDICT HIGHLY RESPONSIVE AND RESISTANT CASES TREATED WITH STANDARDIZED ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR REGIMEN IN NEOVASCULAR AGE-RELATED MACULAR DEGENERATION

PURPOSE

To determine structural predictors of treatment response in neovascular age-related macular degeneration analyzing optical coherence tomography (OCT)-related biomarkers.

METHODS

A retrospective review of patients undergoing treatment for neovascular age-related macular degeneration at a tertiary institute was performed at presentation. High-intensity regimen included eyes on long-term anti-vascular endothelial growth factor treatment with the inability to extend beyond a month without a relapse and needed double the dose of medication (n = 25). Low-intensity regimen had eyes that went into long-term remission after at least three injections and remained dry for more than a year until the last visit (n = 20). Multimodal imaging including fluorescein angiogram, OCT, and comprehensive ocular evaluation were done. Choroidal vascularity index, total choroidal area, luminal area, subfoveal choroidal thickness, choriocapillaris thickness and Haller and Sattler layer thickness were analyzed for statistical significance.

RESULTS

The groups had no significant difference at baseline in age, gender, incidence of reticular pseudodrusen, polypoidal choroidal vasculopathy feature on OCT, type of choroidal neovascular membrane, and geographic atrophy. Multinomial logistic regression revealed that thicker subfoveal choroidal thickness and larger total choroidal area were the significant predictors of poor response to anti-vascular endothelial growth factor treatment (E = 0.02; P = 0.02; E = 1.82; P = 0.0075).

CONCLUSION

Thicker subfoveal choroidal thickness and higher total choroidal area are useful variables to predict a poor treatment response.

Comparison of Macular Thickness Measurements Using Swept-Source and Spectral-Domain Optical Coherence Tomography in Healthy and Diabetic Subjects

Purpose: To establish normative data for macular thickness in Chinese aged 30 to 80 years using the swept-source optical coherence tomography (SS-OCT) device.Methods: The study included 290 normal eyes, 430 NDR eyes and 150 DR eyes of community residents aged 30 to 80 years in Guangzhou, China. Mean macular thicknesses in Early Treatment Diabetic Retinopathy Study (ETDRS) subfields, central point thicknesses (CPT), and macular volume was measured by SS-OCT (Triton DRI OCT, Topcon, Tokyo, Japan) and Spectral-Domain OCT (SD-OCT; Heidelberg Engineering, Heidelberg, Germany). We assessed agreement between SS-OCT and SD-OCT measurements by intraclass correlation coefficients (ICC) and Bland-Altman plots. We established a conversion equation relating central subfield (CSF), CPT and macular volume between the two OCT devices.Results: Macular thickness measurements in SS-OCT were significantly thinner than in SD-OCT. The mean CSF thickness in normal eyes measured by SS-OCT and SD-OCT were 227.8 ± 19.4 μm and 260.0 ± 19.7 μm (p < .0001). CSF thickness was a significantly difference between genders (SS-OCT: male 237.2 ± 18.8 μm vs female 222.0 ± 17.5 μm, p < .0001). In all three groups, the agreement between SS-OCT and SD-OCT was excellent (all ICC > 0.9). The conversion equations for CSF, CPT and macular volume from SS-OCT to SD-OCT were derived, with over 95% of the predicted values fell within 10% of the actual measurements in DR and NDR eyes.Conclusion: We propose SS-OCT CSF thicknesses of 275 μm for males and 260 μm for females as the minimum criteria for macular edema in Chinese aged 30 to 80 years based on 2 SDs above the mean CSF. SS-OCT measurements were significantly thinner than SD-OCT. We derived equations from converting SS-OCT measurements to SD-OCT equivalents.

Choroidal thickness in lamellar macular holes

PURPOSE

(1) To assess the thickness of the central choroid (BM-CSI) in swept-source optical coherence tomography (SS-OCT) examination of lamellar macular holes (LMHs). (2) To establish correlations between the thickness of the central choroid (BM-CSI) in the LHM and the parameters of best-corrected visual acuity and reading vision in patients with LMH.

METHODS

This prospective case-control study assessed a group of 30 patients (30 eyes) with LMHs and a control group of 45 patients (90 eyes). The thickness of the central choroid (BM-CSI) was measured with an SS-OCT device. The average choroidal thickness in the fovea was defined as average thickness in the central area of 1000 μm in diameter, according to the Early Treatment Diabetic Retinopathy Study (ETDRS). The results were correlated with best-corrected visual acuity (BCVA), and reading vision.

RESULTS

The average choroidal thickness in the study group (SG) with LMH was 160.34 μm (SD = 77.1), whereas in the control group (CG), it was 225.11 μm (SD = 93.8). The difference of 64.77 μm was statistically significant (p < 0.05). The BCVA was within the range between 0.7 (logMAR) and 0.1 (logMAR), with an average of 0.36 (logMAR) (SD = 0.23). Reading vision was within the range between - 0.2 (logMAR) and 0.3 (logMAR), with an average of 0.27 (logMAR) (SD = 0.12). A significant correlation between BCVA and the choroid (BM-CSI) was found. The correlation coefficient is average (r = 0.44) and positive. With better BCVA, a significantly thicker choroid (BM-CSI) can be observed. No significant correlation between BM-CSI and reading vision was found. The correlation coefficient value is minor (r = - 0.289), whereas lower values of BM-CSI can be observed with worse reading vision.

CONCLUSION

We suggest that the choroid may take part in the pathogenesis of LMH development. Its significant thinning may be responsible for the ischemic degenerative mechanism degenerating outer layers of retina, apart from tractional mechanism.

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.

Choroidal Differences between Spectral and Swept-source Domain Technologies

PURPOSE OF THE STUDY

To assess differences in healthy eyes in volume (CV) and choroidal thicknesses (CT) across all macular Early Treatment Diabetic Retinopathy Study (ETDRS) areas measured by swept source (SS)-OCT and spectral domain (SD)-OCT with enhanced depth imaging (EDI).

MATERIALS AND METHODS

One hundred and fifty healthy eyes were studied in patients aged between 21-68 years. All of these patients underwent an ophthalmic examination that included axial length (AL), a fast macula protocol with EDI by Spectralis SD-OCT, and a 3D macular cube by DRI-Triton SS-OCT. CT and CV values were measured after a manual segmentation with SD-OCT and automatically with SS-OCT.

RESULTS

The values obtained by SD-OCT were statistically higher than the values obtained by SS-OCT in all ETDRS areas. To determine the differences that were related to total CV or AL, the eyes were divided depending on their total CV and AL values into two groups. There were persistent differences between the two devices that were not related to the total CV. In subjects with a higher AL, these differences were not present in either the total CV or the subfoveal CT. In longer eyes, the differences diminished, and there were no statistical differences between the devices in the subfoveal area, temporal quadrants, inferior inner ring, or CV.

CONCLUSIONS

The choroidal values obtained with the SD-OCT are statistically higher than those measured by SS-OCT. Both techniques are able to clearly visualize the choroidoscleral interface and provide different values that are highly correlated. These differences are smaller in eyes with a longer AL and are not related to the total CV.

Morphological characteristics of ocular toxoplasmosis and its regression pattern on swept-source optical coherence tomography angiography: a case report

Background

To report the successful treatment of ocular toxoplasmosis and present the use of multimodal imaging to describe the changes in ocular toxoplasmic lesions subsequent to treatment.

Case presentation

A 73-year-old female visited the clinic with decreased visual acuity in the left eye. Fundus examination showed severe vitreous haze with yellow-white infiltrates near the foveal center. Spectral-domain optical coherence tomography (SD-OCT) revealed disorganization of the retinal structure with markedly thickened choroid beneath the active lesion. Highly elevated serum titers of IgG antibodies against Toxoplasma gondii were observed. Topical and systemic steroids with oral Bactrim were administered after a diagnosis of ocular toxoplasmosis was made. After improvement in the severity of vitritis, structural en face swept-source optical coherence tomography (SS-OCT) imaging demonstrated diffuse choroidal dilation with many collateral vascular branches surrounding the active lesion. Eight intravitreal injections of clindamycin (1 mg/0.1 ml) were administered at 1- to 2-week intervals along with systemic antibiotics and steroids. After the treatment, the toxoplasmic lesion resolved to an atrophic chorioretinal scar. Dilated choroidal vessel size was normalized and collateral vascular branches were markedly constricted on structural en face SS-OCT images.

Conclusions

This is the first detailed report on the morphological changes in the choroidal vasculature surrounding ocular toxoplasmic lesions that were characterized using SS-OCT-A imaging. Multimodal imaging with SS-OCT-A can be valuable in clinical diagnosis as well as in clarifying the mechanism of choroidal structural changes in ocular toxoplasmosis.

Systematic ultrastructural comparison of swept-source and full-depth spectral domain optical coherence tomography imaging of diabetic macular oedema

BACKGROUND/AIMS

Optical coherence tomography (OCT) is commonly used to diagnose and assess diabetic macular oedema (DME). Swept-source OCT (SS-OCT) promises improved imaging depth and more independence from media opacities. Heidelberg Spectralis full-depth imaging (FDI) combines details at different depths to one representation. The aim of this study was to determine the comparability of the imaging methods concerning DME ultrastructure.

METHODS

Two graders assessed the presence of typical DME phenomena in eyes with centre-involving DME on Topcon Atlantis SS-OCT and Heidelberg Spectralis FDI spectral-domain OCT (SD-OCT) B-scans. Retinal layer segmentation was corrected and choroidal layers were manually segmented. Graders measured cyst and subretinal fluid (SRF) diameters and counted hyper-reflective foci (HRF). Findings were recorded and statistically analysed.

RESULTS

Statistically significant systematic biases (Spectralis-Atlantis) were found for the HRF count (outside the central mm, -6.39, p=0.0338), chorioretinal thickness (central mm: -35.45 µm, p=0.00034), choroidal thickness (central mm: -60.97 µm, p=0.00004) and Sattler's layer thickness (-42.69 µm, p=0.0001). Intergrader agreement was excellent or very good for posterior vitreous detachment, vitreomacular attachment (central mm) and SRF presence in both devices. Manually delineated Sattler's layer thickness showed an intraclass correlation of 0.85 with FDI SD-OCT but 0.26 with SS-OCT (p=0.003).

CONCLUSION

Prominent aspects such as cysts in the outer nuclear layer and SRF can be identified with comparable confidence, while a significant systematic bias underlies chorioretinal, choroidal and Sattler's layer thickness and HRF count. Specialists should use the same device at every examination during longitudinal clinical consideration or cross-sectional evaluation of these ultrastructural biomarkers.

A quantitative comparison of five optical coherence tomography angiography systems in clinical performance

AIM

To compare the clinical performance of 4 spectral-domain (SD) optical coherence tomography angiography (OCTA) systems: AngioVue™, AngioPlex™, Spectralis^® OCTA, AngioScan, and 1 swept-source (SS) OCTA SS OCT Angio™.

METHODS

Twenty-seven undilated right eyes of 27 participants underwent OCTA examination using five different systems respectively for both 3×3 and 6×6 mm² scan pattern (Spectralis OCTA for 3×3 mm² scan only). Image quality, including vessel valid visibility and the number of motion artifacts, and acquisition time were evaluated. Repeated measures analysis of variance (ANOVA) with Bonferroni's post-test and Friedman test with Dunn's post-test were used to compare measurements.

RESULTS

The age of the subjects was 28.19±5.55y (range, 23-49y). The spherical equivalent refraction was -2.55±1.84 D (range, 0.00 to -5.25 D). Significant difference was observed in the evaluation of vessel valid visibility (AngioVue the highest: 0.111±0.031 for 3×3 mm² scan and 0.128±0.020 for 6×6 mm² scan), number of motion artifacts (AngioVue the fewest: 0.778±1.086 for 3×3 mm² scan and 0.333±0.620 for 6×6 mm² scan) and acquisition time (AngioPlex the shortest: 8.537±1.921s for 3×3 mm² scan and 8.298±1.741s for 6×6 mm² scan; all P<0.001).

CONCLUSION

There is poor agreement of measurements among systems. AngioVue provides images with the highest vessel valid visibility and the fewest motion artifacts. AngioPlex achieves the shortest acquisition.

Swept-source OCT in patients with multiple evanescent white dot syndrome

Background

Swept-source optical coherence tomography (SS-OCT) has a higher scanning rate and longer wavelength in comparison with spectral-domain OCT (SD-OCT), allowing an improved imaging of retinal vascular plexuses and choriocapillaris. The present two patients diagnosed with multiple evanescent white dot syndrome (MEWDS) underwent fundus autofluorescence (FAF), en-face SS-OCT, and SS-OCT angiography (OCTA) imaging, and its features were described and correlated.

Results

The clinical and imaging findings of both cases were consistent with the diagnosis of MEWDS. Color fundus photograph revealed subtle deep retinal white spots in the posterior pole and around the optic disk. FAF showed several hyperautofluorescent lesions corresponding topographically to the subtle deep retinal white lesions observed on color fundus photographs. Cross-sectional SS-OCT showed disruption of the ellipsoid zone (EZ) within the macular area in all study patients. En-face SS-OCT at the level of the outer retina showed lower reflectivity correspondent to the diffuse attenuation due to the EZ disruption on cross-sectional OCT. SS-OCTA demonstrated flow preservation within the retinal vasculature and choriocapillaris.

Conclusions

SS-OCT imaging allows a better visualization of the choriocapillaris, and its normal appearance in MEWDS may suggest that the outer retina and photoreceptors represent the primary site of inflammation.

QUANTITATIVE ANALYSIS OF THE INNER RETINAL LAYER THICKNESSES IN AGE-RELATED MACULAR DEGENERATION USING CORRECTED OPTICAL COHERENCE TOMOGRAPHY SEGMENTATION

PURPOSE

To characterize inner retinal damage in patients with dry age-related macular degeneration (AMD) using high-resolution spectral domain optical coherence tomography images.

METHODS

Sixty eyes of 60 patients with AMD were categorized using the Age-Related Eye Disease Study (AREDS) severity scale. Spectral domain optical coherence tomography images of these patients were quantified by manually correcting the segmentation of each retinal layer, including the retinal nerve fiber layer, ganglion cell layer, and inner plexiform layer to ensure accurate delineation of layers. The mean ganglion cell complex thickness values (ganglion cell layer + inner plexiform layer + retinal nerve fiber layer) were compared with 30 eyes of 30 healthy subjects.

RESULTS

Ninety percent of eyes (81 eyes) required manual correction of segmentation. Compared with healthy subjects, mean ganglion cell complex thicknesses significantly decreased in more advanced dry AMD eyes, and this decrease was predominantly related to a change in inner plexiform layer thickness. There was no significant difference in thickness-related measurements between milder dry AMD (AREDS-2) eyes and healthy eyes (P > 0.05).

CONCLUSION

In patients with dry AMD, automatic optical coherence tomography segmentation algorithms may be erroneous. As the severity of dry AMD increases, the inner plexiform layer layer becomes thinned, suggesting that transsynaptic degeneration may be occurring, as the photoreceptor layer is affected by AMD.

High-Performance Virtual Reality Volume Rendering of Original Optical Coherence Tomography Point-Cloud Data Enhanced With Real-Time Ray Casting

Purpose

Feasibility testing of a novel volume renders technology to display optical coherence tomography data (OCT) in a virtual reality (VR) environment.

Methods

A VR program was written in C++/OpenGL to import and display volumetric OCT data in real time with 180 frames per second using a high-end computer and a tethered head-mounted display. Following exposure, participants completed a Simulator Sickness Questionnaire (SSQ) to assess for nausea, disorientation, and oculomotor disturbances. A user evaluation study of this software was conducted to explore the potential utility of this application.

Results

Fifty-seven subjects completed the user testing (34 males and 23 females). Mean age was 48.5 years (range, 21–77 years). Mean acquired work experience of the 35 ophthalmologists (61.40%) included in the group was 15.46 years (range, 1–37 years). Twenty-nine participants were VR-naïve. The SSQ showed a mean total score of 5.8 (SD = 9.44) indicating that the system was well tolerated and produced minimal side effects. No difference was reported between VR-naïve participants and experienced users. Overall, immersed subjects reported an enjoyable VR-OCT presence effect.

Conclusions

A usable and satisfying VR imaging technique was developed to display and interact with original OCT data.

Translational Relevance

An advanced high-end VR image display method was successfully developed to provide new views and interactions in an ultra high-speed projected digital scenery using point-cloud OCT data. This represents the next generation of OCT image display technology and a new tool for patient engagement, medical education, professional training, and telecommunications.

Choroidal thickness measured using swept-source optical coherence tomography is reduced in patients with type 2 diabetes

OBJECTIVE

To compare choroidal thickness between patients with type 2 diabetes (T2D) and healthy controls measured using swept-source optical coherence tomography (SS-OCT).

METHODS

The sample comprised 157 eyes of 94 T2D patients, 48 eyes of which had diabetic macular edema (DME), and 71 normal eyes of 38 healthy patients. Subfoveal (SF) choroidal thickness, and choroidal thickness at 500-μm intervals up to 2500 μm nasal and temporal from the fovea were measured using the SS-OCT. Choroidal thicknesses were compared between groups using Student's t-test. Additionally, Pearson correlations were calculated between diabetes duration, glycosylated hemoglobin (HbA1c) levels, and choroidal thickness.

RESULTS

Mean diabetes duration was 16.6±9.5 years, while mean glycosylated hemoglobin was 7.7±1.3%. Overall, the choroid was significantly thinner in T2D patients. Individuals with DME had reduced choroidal thickness in all measurements, except at 2000 and 2500-μm nasal positions, compared to healthy controls. There was a moderate correlation between choroidal thickness and HbA1c levels in DME patients (SF: r = 0.342; p = 0.017). Diabetes duration did not correlate significantly with choroidal thickness.

CONCLUSION

SS-OCT measurements revealed that the choroid was significantly thinner in T2D patients, moderate non-proliferative diabetic retinopathy patients, and DME patients than in healthy individuals. Further studies are needed to clarify the effect of diabetes on this layer and the relationship between choroidal thickness and DME.

Automated Quantitation of Choroidal Neovascularization: A Comparison Study Between Spectral-Domain and Swept-Source OCT Angiograms

Purpose

To compare the lesion sizes of choroidal neovascularization (CNV) imaged with spectral-domain (SD) and swept-source (SS) optical coherence tomography angiography (OCTA) and measured using an automated detection algorithm.

Methods

Patients diagnosed with CNV were imaged by SD-OCTA and SS-OCTA systems using 3 × 3-mm and 6 × 6-mm scans. The complex optical microangiography (OMAG^C) algorithm was used to generate the OCTA images. Optical coherence tomography A datasets for imaging CNV were derived by segmenting from the outer retina to 8 μm below Bruch's membrane. An artifact removal algorithm was used to generate angiograms free of retinal vessel projection artifacts. An automated detection algorithm was developed to quantify the size of the CNV. Automated measurements were compared with manual measurements. Measurements from SD-OCTA and SS-OCTA instruments were compared as well.

Results

Twenty-seven eyes from 23 subjects diagnosed with CNV were analyzed. No significant differences were detected between manual and automatic measurements: SD-OCTA 3 × 3-mm (P = 0.61, paired t-test) and 6 × 6-mm (P = 0.09, paired t-test) scans and the SS-OCTA 3 × 3-mm (P = 0.41, paired t-test) and 6 × 6-mm (P = 0.16, paired t-test) scans. Bland-Altman analyses were performed to confirm the agreement between automatic and manual measurements. Mean lesion sizes were significantly larger for the SS-OCTA images compared with the SD-OCTA images: 3 × 3-mm scans (P = 0.011, paired sample t-test) and the 6 × 6-mm scans (P = 0.021, paired t-test).

Conclusions

The automated algorithm measurements of CNV were in agreement with the hand-drawn measurements. On average, automated SS-OCTA measurements were larger than SD-OCTA measurements and consistent with the results from using hand-drawn measurements.

Evaluation of Anterior Chamber Volume in Cataract Patients with Swept-Source Optical Coherence Tomography

Purpose. To evaluate the anterior chamber volume in cataract patients with Swept-Source Optical Coherence Tomography (SS-OCT) and its influencing factors. Methods. Anterior chamber volume of 92 cataract patients was evaluated with SS-OCT in this cross-sectional study. Univariate analyses and multiple linear regression were used to investigate gender, age, operated eye, posterior vitreous detachment, lens opacity grading, and axial length (AXL) related variables capable of influencing the ACV. Results. The average ACV was 139.80 ± 38.21 mm³ (range 59.41 to 254.09 mm³). The average ACV was significantly larger in male patients than in female patients (P = 0.001). ACV was negatively correlated with age and LOCS III cortical (C) grading of the lens (Pearson's correlation analysis, r = −0.443, P < 0.001, and Spearman's correlation analysis, ρ = −0.450, P < 0.001). ACV was also increased with AXL (Pearson's correlation analysis, r = 0.552, P < 0.001). Multiple linear regression showed that, with all of the covariates entered into the model, gender (P = 0.002), age (P = 0.015), LOCS III C grade (P = 0.043), and AXL (P = 0.001) were still associated with ACV (F = 10.252  P < 0.001  R² = 0.498). Conclusion. With SS-OCT, we found that, in healthy cataract patients, ACV varied significantly among different subjects. Influencing factors that contribute to reduced ACV were female gender, increased age, LOCS III C grade, and shorter AXL.

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.