Purpose: To compare optical coherence tomography (OCT) angiographic parameters in retina and choriocapillaris between control subjects and diabetic patients without diabetic retinopathy (NDR). Correlations were studied between OCT angiography parameters, retinal structure parameters, and systemic characteristics in all subjects. Methods: Sixty-two patients were included in the study: control subjects (n = 33) and patients with NDR (n = 29). Optical coherence topography angiographic parameters were as follows: vessel density (%) (in superficial, deep retinal vessel plexus and in choriocapillary layer) and foveal avascular zone (FAZ) area (mm²) in superficial and deep retinal vessel plexus of parafovea. Split-spectrum amplitude decorrelation angiography (SSADA) software algorithm was used for evaluation of vessel density and FAZ area (nonflow area tool). Spectral-domain OCT was used to assess full, inner, and outer retinal thickness and volume in parafovea. Results: In superficial and deep retina, vessel densities in NDR (44.35% ± 13.31% and 31.03% ± 16.33%) were decreased as compared to control subjects (51.39% ± 13.05%, P = 0.04; and 41.53% ± 14.08%, P < 0.01). Foveal avascular zone in superficial retina of NDR patients (0.37 ± 0.11 mm²) was greater than in controls (0.31 ± 0.10 mm², P = 0.02). Superficial vessel density significantly correlated with full retinal thickness and volume in parafovea (r = 0.43, P = 0.01; r = 0.43, P = 0.01) and with outer retinal volume in parafovea (r = 0.35, P < 0.05) of healthy subjects. Systolic blood pressure and ocular perfusion pressure significantly correlated with deep vessel density in NDR (r = −0.45, P = 0.02; r = −0.46, P = 0.01), but not in controls. Conclusions: Superficial and deep retinal vessel density in parafovea of diabetic patients without diabetic retinopathy are both decreased compared to healthy subjects. The associations between vessel density with retinal tissue thickness and with subject's clinical characteristics differ between healthy subjects and patients with NDR.

The aim of this narrative mini review is to analyze optical coherence tomography angiography (OCTA) parameters from reports that involved both superficial and deep vascular layers in patients with diabetes and to assess their relevance for the pathogenesis of diabetic retinopathy (DR). Papers published from January 2015 to August 2018 describing the use of OCTA in diabetes were identified and reviewed through a Medline/PubMed search. OCTA studies suggest that parameters are altered in patients with diabetes in all retinal vascular layers. From all included studies that evaluated both the superficial and the deep vascular layer, a number of studies suggested that the deep vascular layer was affected at an earlier stage of DR. OCTA parameter alterations were more prominent in the deep vascular layer than in the superficial vascular layer in patients with DR, and deep-vascular-layer alterations were most evident in patients with diabetic macular edema. Regarding that retinal venules originate from the deep vascular layer of the retina, alteration of OCTA parameters at the deep vascular layer in diabetic patients may imply a predominant affection of the venous side of the retinal vascular system in the pathogenesis of DR.

Background: Yoga exercises for eyes have been advocated as beneficial to eye health. In a previous study, we evaluated the effect of yoga exercises for eyes on the intraocular pressure (IOP). The other aspects of the effects of yoga exercises for eyes to ocular structure have not been investigated yet. Aim: The aim of this study is to evaluate the effect of yoga exercises for eyes on the macular structure using the optical coherence tomography (OCT) and OCT angiography (OCTA) parameters. Methods: Twenty-nine participants were included in this masked within participant comparison of healthy controls. Basic ophthalmic examination was performed, after which patients were evaluated for IOP, OCT, and OCTA before and after yoga exercises for eyes. OCT/A parameters that were evaluated were: average macular thickness (AMT) (μm), central macular thickness (μm), central choroidal thickness (μm) vessel density (%) in the superficial, deep vascular layers, and in the choriocapillaris. Results: IOP was significantly reduced (postexercise IOP = 13.02 mmHg ± 2.82 mmHg) from the initial value (preexercise IOP = 13.86 mmHg ± 2.85 mmHg, P = 0.02). AMT significantly increased (postexercise AMT = 275.40 μm ± 10.85 μm) from the preexercise measurement (preexercise AMT = 274.41 μm ± 10.89 μm; P = 0.02). Conclusion: After yoga ocular exercises, IOP significantly decreased and AMT significantly increased in healthy controls, suggesting an effect of these exercises on the macular thickness.

We thank Tang and Cheung 1 for their interest in our published article. 2 Tang and Cheung 1 suggest implementing projectionresolved (PR) algorithms to obtain accurate optical coherence tomography angiography (OCTA) images from the deeper retinal layers. Using a PR algorithm for OCTA image analysis allows for reduction of the flow-projection artifact. 3 The flowprojection artifact is intensity dependent. Low projection values are located on the layers with low OCT intensity signals, such as inner nuclear layer and outer nuclear layer, and high projection values are located on the layers with high-intensity signals, such as inner segment/outer segment junction and RPE. This means that the PR algorithm is particularly effective in reducing the projection artifacts from the outer retinal layer, which was not the subject of study in our article. However, by reducing the shadowing effect of the superficial blood vessels, the PR algorithm allowed for the distinction of three separate retinal capillary networks: superficial, intermediate, and deep. 3 Using the automatic slab segmentation software and slabsubtraction (SS) algorithm for projection artifact removal, two retinal capillary networks are presented: superficial and deep. 4 The vascular pattern similarity study showed that both the SS and the PR algorithm have a similar negative correlation (Pearson's correlation coefficient of-0.2 for PR algorithm and-0.2 to-0.3 for the SS algorithm) in the deep capillary plexus compared with the superficial and intermediate capillary plexus. 3 Therefore, we believe that implementing the PR algorithm would not alter our results concerning the deep capillary plexus significantly. However, we appreciate the continuous effort for increasing data quality and we are looking forward to further studies on the effect of diabetes on all three capillary layers in the retina.

Background and Objective: This study aims to investigate the prevalence of systemic and ophthalmic manifestations in different refractive groups in children and young adults with Down syndrome (DS). Materials and Methods: The study was a population-based, cross-sectional study that included 141 Caucasian children and young adults with DS. They were classified into the following three groups: myopia DS group (37 subjects, mean age 15.8 years), emmetropia DS group (41 subjects, mean age 11.7 years) and hyperopia DS group (63 subjects, mean age 10.9 years). The participants underwent inspection, slit-lamp examination, cycloplegic refraction, ocular alignment and ocular motility examination. Ten systemic manifestations were analyzed. Results: There was no difference in the prevalence of any systemic manifestations between the groups. Considering the ophthalmic manifestations, there was statistical difference in the distribution of proportions among the three groups for nystagmus (p = 0.011), iris-stromal atrophy (p = 0.048) and strabismus (p = 0.031). The prevalence of strabismus in our DS myopia group was 35.1%, and in DS hyperopia group 38.1%. Conclusions: The results of our study suggest that DS children and young adults with any refractive error do not have a higher chance of additional systemic manifestations. Myopia in DS was associated with a higher prevalence of nystagmus and iris stromal atrophy, whereas astigmatism was found to be more frequent in hyperopia.