Simultaneous confocal scanning laser ophthalmoscopy combined with high-resolution spectral-domain optical coherence tomography: a review

Associations of retinal neurovascular dysfunction with inner retinal layer thickness in non-proliferative diabetic retinopathy

PURPOSE

Neurovascular coupling impairment and inner retinal layer thinning are early detectable retinal changes in diabetes, and both worsen during progression of diabetic retinopathy (DR). However, direct interactions between these features have not been investigated so far. Therefore, we aimed to analyze associations between the retinal functional hyperemic response to light stimulation and the thickness of individual neuroretinal layers in eyes with early non-proliferative DR.

METHODS

Thirty patients with type 1 diabetes featuring mild (n = 15) or moderate (n = 15) non-proliferative DR and 14 healthy subjects were included in this cross-sectional study. Retinal vessel diameters were measured before and during illumination with flickering light using a dynamic vessel analyzer. Individual layer thickness in the macula was analyzed from spectral domain optical coherence tomography.

RESULTS

Flicker light-induced vessel dilation was significantly reduced in patients compared to healthy controls (veins: 3.0% vs. 6.1%, p < 0.001; arteries: 1.3% vs. 5.1%, p = 0.005). Univariately, the response in retinal veins of diabetes patients correlated significantly with ganglion cell layer (GCL) thickness (r = 0.46, p = 0.010), and negatively with hemoglobin A1c (HbA1c) levels (r=-0.41, p = 0.023) and age (r=-0.38, p = 0.037), but not with baseline diameters, glucose levels, or diabetes duration. In a multiple regression model only GCL thickness (p = 0.017, β = 0.42) and HbA1c (p = 0.045, β=-0.35) remained significantly associated with the vascular flicker light response.

CONCLUSION

The results indicate that thinner GCL and worse glycemic control both contribute to reduced retinal neurovascular coupling in patients with clinical signs of DR. Progression of neurovascular dysfunction in DR might be related to structural degeneration of the neurovascular complex in the inner retina.

Fast and Automated Hyperreflective Foci Segmentation Based on Image Enhancement and Improved 3D U-Net in SD-OCT Volumes with Diabetic Retinopathy

Purpose

To design a robust and automated hyperreflective foci (HRF) segmentation framework for spectral-domain optical coherence tomography (SD-OCT) volumes, especially volumes with low HRF-background contrast.

Methods

HRF in retinal SD-OCT volumes appear with low-contrast characteristics that results in the difficulty of HRF segmentation. Therefore to effectively segment the HRF we proposed a fully automated method for HRF segmentation in SD-OCT volumes with diabetic retinopathy (DR). First, we generated the enhanced SD-OCT images from the denoised SD-OCT images with an enhancement method. Then the enhanced images were cascaded with the denoised images as the two-channel input to the network against the low-contrast HRF. Finally, we replaced the standard convolution with slice-wise dilated convolution in the last layer of the encoder path of 3D U-Net to obtain long-range information.

Results

We evaluated our method using two-fold cross-validation on 33 SD-OCT volumes from 27 patients. The average dice similarity coefficient was 70.73%, which was higher than that of the existing methods with significant difference (P < 0.01).

Conclusions

Experimental results demonstrated that the proposed method is faster and achieves more reliable segmentation results than the current HRF segmentation algorithms. We expect that this method will contribute to clinical diagnosis and disease surveillance.

Translational Relevance

Our framework for the automated HRF segmentation of SD-OCT volumes may improve the clinical diagnosis of DR.

Correlation of retinal neurodegeneration with measures of peripheral autonomic neuropathy in type 1 diabetes

Purpose

To evaluate the relationship of neuroretinal layer thickness with sensitive measures of cardiovascular autonomic neuropathy in diabetic patients with non‐proliferative diabetic retinopathy (NPDR).

Methods

Twenty‐seven eyes of 27 patients with type 1 diabetes presenting with mild‐to‐moderate NPDR were compared to 27 healthy control (HC) eyes matched for age and gender. The total macular volume (TMV) and the volumes of individual neurosensory layers in the macula were analysed from spectral domain optical coherence tomography using automated layer segmentation. Cardiovascular autonomic regulation was assessed by short‐term power spectrum analysis of heart rate variability (HRV) before, during and after an orthostatic challenge.

Results

The patients had an age of 46 ± 12 years and diabetes since 28 ± 9 years. Diastolic and mean arterial pressure was lower in the patients compared to HCs. TMV (r = 0.58, p = 0.002), inner plexiform layer volume (IPLV; r = 0.39, p = 0.047) and inner nuclear layer volume (INLV; r = 0.60, p = 0.001) were associated with reduced recovery of low‐frequency (LF) spectral power of HRV after orthostatic load in diabetic patients but not in HCs. The response of LF spectral power during the orthostatic manoeuvre was blunted in patients compared to HCs (p = 0.02). Diabetes duration was negatively associated with TMV and INLV, whereas IPLV was significantly reduced in eyes with moderate NPDR compared to HCs.

Conclusion

The results indicate a correlation between inner retinal tissue loss and diminished autonomic regulation in type 1 diabetic patients with mild‐to‐moderate NPDR. The observed changes can be interpreted as congruent early signs of retinal and systemic neuropathy in diabetes.

Relationship Between Dry Retinal Volume and Visual Acuity in Diabetic Macular Edema

BACKGROUND AND OBJECTIVE

To evaluate the relationship between a novel spectral-domain optical coherence tomography (SD-OCT) parameter, predicted dry retinal volume (DRV), and visual acuity (VA) in subjects with diabetic macular edema.

PATIENTS AND METHODS

Twenty-eight eyes of 26 subjects with macular edema secondary to diabetic retinopathy (cases) and 10 healthy eyes of normal volunteers (controls) were included. Spectral-domain optical coherence tomography volume scans (512 × 128) were obtained before and 6 months to 12 months after anti-vascular endothelial growth factor therapy. The borders of the neurosensory retina, nerve fiber layer (NFL), and vitreous were manually defined using previously described grading software. NFL reflectivity was used to normalize the signal between eyes, allowing a normalized total retinal intensity to be computed for each eye by summing the brightness of every pixel in the retina on all B-scans. Using this normalized retinal intensity, a ratio of retinal intensity of cases over retinal intensity of normal was generated. The predicted DRV was computed by multiplying this calculated ratio with total retinal volume at baseline for each eye. Correlation analysis was performed between DRV at baseline and VA at baseline and final follow-up.

RESULTS

The mean ± standard deviation age of the cohort was 69 years ± 9.8 years, and 28% were female. Mean best-corrected VA (logMAR) improved from 0.56 ± 0.36 at baseline to 0.44 ± 0.32 at follow-up (P = .001). The uncorrected ("wet") total retinal volume of 13.25 mm³ ± 2.73 mm³ at baseline declined significantly to a posttreatment retinal volume of 10.92 mm³ ± 1.42 mm³. The predicted DRV (10.79 mm³ ± 1.42 mm³) was statistically similar to the post-treatment, actual retinal volume. No significant correlation was observed between DRV and post-treatment VA.

CONCLUSIONS

The predicted DRV at baseline showed good agreement with the actual observed posttreatment retinal volume. Thus, DRV may be a potentially useful parameter to estimate the extent of retinal tissue loss that may be obscured by the presence of concomitant edema. The lack of correlation between DRV and VA, however, suggests that other parameters, such as the integrity of the outer retinal bands, are likely important for visual outcome prediction. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:510-515.].

Macular Diagnostic Ability in OCT for Assessing Glaucoma in High Myopia

PURPOSE

To compare the diagnostic abilities of spectral-domain optical coherence tomography (SD-OCT; Spectralis OCT) and time-domain OCT (TD-OCT; Stratus OCT). Changes in macular parameters in highly myopic eyes of glaucoma patients and highly myopic eyes of glaucoma suspects were evaluated and compared.

METHODS

We collected data from 72 highly myopic eyes (spherical equivalent, ≤-6.0D). Forty-one eyes had perimetric glaucoma and 31 eyes were suspected to have glaucoma (control group). All eyes underwent SD-OCT and TD-OCT imaging. Area under the receiver operating characteristic (AUROC) curve and sensitivity were examined on macular volume and thickness parameters at a fixed specificity and compared between groups.

RESULTS

The highest TD-OCT AUROC curves were found using outer inferior sector macular thickness (AUROC curve, 0.911) and volume (AUROC curve, 0.909). The highest SD-OCT AUROC curves were found using outer inferior region thickness (AUROC curve, 0.836) and volume (AUROC curve, 0.834). The difference between the two imaging modalities was not statistically significant (thickness, p = 0.141; volume, p = 0.138). The sensitivity of TD-OCT macular outer inferior average thickness was highest and was 88.2%, with a specificity of 80.4%. The sensitivity of TD-OCT average volume measurements in this same region was 76.5%, with a specificity of 91.3%. The SD-OCT average thickness measurements also had the highest sensitivity in this region, which was 78.6%, with a specificity of 82.1%. The SD-OCT volume measurements had a sensitivity of 67.9%, with a specificity of 92.3%.

CONCLUSIONS

Both SD-OCT and TD-OCT measurements of outer inferior macular thickness and volume can differentiate between eyes of glaucoma patients and glaucoma suspects with high myopia. These independent predictors all had good sensitivity. Based on our results, SD-OCT and TD-OCT have similar diagnostic abilities. These parameters may provide useful additional data in highly myopic eyes to complement standard glaucoma diagnosis tools.

Systems pharmacology identifies drug targets for Stargardt disease-associated retinal degeneration

A systems pharmacological approach that capitalizes on the characterization of intracellular signaling networks can transform our understanding of human diseases and lead to therapy development. Here, we applied this strategy to identify pharmacological targets for the treatment of Stargardt disease, a severe juvenile form of macular degeneration. Diverse GPCRs have previously been implicated in neuronal cell survival, and crosstalk between GPCR signaling pathways represents an unexplored avenue for pharmacological intervention. We focused on this receptor family for potential therapeutic interventions in macular disease. Complete transcriptomes of mouse and human samples were analyzed to assess the expression of GPCRs in the retina. Focusing on adrenergic (AR) and serotonin (5-HT) receptors, we found that adrenoceptor α 2C (Adra2c) and serotonin receptor 2a (Htr2a) were the most highly expressed. Using a mouse model of Stargardt disease, we found that pharmacological interventions that targeted both GPCR signaling pathways and adenylate cyclases (ACs) improved photoreceptor cell survival, preserved photoreceptor function, and attenuated the accumulation of pathological fluorescent deposits in the retina. These findings demonstrate a strategy for the identification of new drug candidates and FDA-approved drugs for the treatment of monogenic and complex diseases.

Effectiveness of averaging strategies to reduce variance in retinal nerve fibre layer thickness measurements using spectral-domain optical coherence tomography

BACKGROUND

Automated detection of subtle changes in peripapillary retinal nerve fibre layer thickness (RNFLT) over time using optical coherence tomography (OCT) is limited by inherent image quality before layer segmentation, stabilization of the scan on the peripapillary retina and its precise placement on repeated scans. The present study evaluates image quality and reproducibility of spectral domain (SD)-OCT comparing different rates of automatic real-time tracking (ART).

METHODS

Peripapillary RNFLT was measured in 40 healthy eyes on six different days using SD-OCT with an eye-tracking system. Image brightness of OCT with unaveraged single frame B-scans was compared to images using ART of 16 B-scans and 100 averaged frames. Short-term and day-to-day reproducibility was evaluated by calculation of intraindividual coefficients of variation (CV) and intraclass correlation coefficients (ICC) for single measurements as well as for seven repeated measurements per study day.

RESULTS

Image brightness, short-term reproducibility, and day-to-day reproducibility were significantly improved using ART of 100 frames compared to one and 16 frames. Short-term CV was reduced from 0.94 ± 0.31 % and 0.91 ± 0.54 % in scans of one and 16 frames to 0.56 ± 0.42 % in scans of 100 averaged frames (P ≤ 0.003 each). Day-to-day CV was reduced from 0.98 ± 0.86 % and 0.78 ± 0.56 % to 0.53 ± 0.43 % (P ≤ 0.022 each). The range of ICC was 0.94 to 0.99. Sample size calculations for detecting changes of RNFLT over time in the range of 2 to 5 μm were performed based on intraindividual variability.

CONCLUSION

Image quality and reproducibility of mean peripapillary RNFLT measurements using SD-OCT is improved by averaging OCT images with eye-tracking compared to unaveraged single frame images. Further improvement is achieved by increasing the amount of frames per measurement, and by averaging values of repeated measurements per session. These strategies may allow a more accurate evaluation of RNFLT reduction in clinical trials observing optic nerve degeneration.

Sensitivity of fluorescein angiography alone or with SD-OCT for the diagnosis of myopic choroidal neovascularization

BACKGROUND

Myopic choroidal neovascularization (mCNV) has certain characteristics and features that distinguish it from choroidal neovascularization secondary to age-related macular degeneration. There may be angiographic diagnostic difficulties even when using the scanning laser ophthalmoscope, which gives more contrast and better definition than traditional angiography. The aim of the study is to compare the sensitivity of fluorescein angiography (FA) alone or combined with Spectral Domain Optical Coherence Tomography (SD-OCT) for assessing the incidence of mCNV.

METHODS

In this retrospective study, two authors reviewed the charts and images of patients with recent (<30 days) vision deterioration, pathologic myopia, axial length >26 mm, documentation or suspicion of mCNV or macular exudative pathologies at FA and OCT. They only examined the images at first presentation obtained by the multi-modal imaging system that combines Infrared reflectance, FA, and SD-OCT, (Spectralis, Heidelberg Engineering, Germany). The images selected were then evaluated by three other investigators in blinded, independent conditions, in order to make their diagnosis, which was noted or rated as doubtful if it could not be decided on the basis of FA alone. SD-OCT images were then shown and compared to IR and FA by each of the three investigators individually to formulate a conclusive diagnosis.

RESULTS

A total of 71 eyes of 69 patients were suitable for the study, mean age 65.97±14.57 years, spherical equivalent refraction -8.82 ± 2.51 diopters. Concordance between the three examiners' interpretations of FA features and FA-guided SD-OCT was 50/71 (70.4 %) and 67/71 (94 %) respectively. Total agreement on diagnosis between the three examiners was achieved in 55 % of cases for FA (κ = 0.53, p < 0.001), and 94 % for FA-guided SD-OCT (k = -0.01, p = 0.5). The final diagnosis with FA and FA-guided SD-OCT differed in 29 cases (40 %; 95 % C.I. 29-42 %), whereas 12 (17 %) mCNV were overlooked at FA, and in 11 (15 %) cases none of the examiners reached a diagnosis based on FA alone.

CONCLUSIONS

On the basis of FA alone, active mCNV can be misdiagnosed. The use of SD-OCT combined with FA should therefore be strongly considered.