Defective Choroidal Blood Flow Baroregulation and Retinal Dysfunction and Pathology Following Sympathetic Denervation of Choroid

Sympathetic nervous system activity is associated with choroidal thickness and axial length in school-aged children

BACKGROUND/AIMS

We aim to explore the effect of sympathetic nervous system (SNS) on choroid thickness (ChT) and axial length (AL).

METHODS

Students of grade 2 and 3 from a primary school were included and followed for 1 year. Visual acuity, refraction, AL and ChT were measured. Morning urine samples were collected for determining SNS activity by analysing concentrations of epinephrine, norepinephrine and dopamine using the liquid chromatography-tandem mass spectrometry. The most important factor (factor 1) was calculated using factor analysis to comprehensively indicate the SNS activity.

RESULTS

A total of 273 students were included, with an average age of 7.77±0.69 years, and 150 (54.95%) were boys. Every 1 µg/L increase in epinephrine is associated with 1.60 µm (95% CI 0.30 to 2.90, p=0.02) decrease in average ChT. Every 1 µg/L increase in norepinephrine is associated with 0.53 µm (95% CI 0.08 to 0.98, p=0.02) decrease in the ChT in inner-superior region. The factor 1 was negatively correlated with the ChT in the superior regions. Every 1 µg/L increase in norepinephrine was associated with 0.002 mm (95% CI 0.0004 to 0.004, p=0.016) quicker AL elongation. The factor 1 was positively correlated with AL elongation (coefficient=0.037, 95% CI 0.005 to 0.070, p=0.023).

CONCLUSIONS

We hypothesised that chronic stress characterised by elevated level of the SNS, was associated with significant increase in AL elongation, probably through thinning of the choroid.

Retinal microvascular changes in patients with coronary artery disease and apnea

BACKGROUND

Optical coherence tomography angiography (OCT-A) allowed visualization of capillary level of retina; however, the relationship between coronary vascular status and retinal microvascular changes in patients with apnea is not known well. Our aim was to assess the retinal OCT-A parameters in patients with ischemia and angiographically proven microvascular disease and compare them with obstructive coronary disease in patients with apnea.

METHODS

Our observational study included 185 eyes of 185 patients, 123 eyes of patients with apnea (72 eyes from mild OSAS, 51 eyes from moderate to severe OSAS) and 62 eyes from healthy controls. Radial scans of the macula and OCT-A scans of the central macula (superficial (SCP) and deep (DCP) capillary plexuses) were performed on all participants. All participants had documented sleep apnea disorder within 2 years prior to coronary angiography. Patients were grouped by severity of apnea and coronary atherosclerosis (50 % stenosis cut-off value for obstructive coronary artery disease). Patients presented with myocardial ischemia and without coronary artery occlusion (<50 % diameter reduction or FFR > 0.80) constitute the microvascular coronary artery (INOCA) group.

RESULTS

Compared to healthy controls, patients with apnea showed deterioration in vascular density in all regions of the retina, regardless of obstructive or microvascular coronary artery disease on the ischemia background. This study has provided important observations of a high prevalence of INOCA in patients with OSAS and the presence of OSAS was a significant independent predictor of functional coronary artery disease. The relative decreases in vascular densities were more pronounced in the DCP layer according to SCP layer of macula. Only FAZ area values were significantly different according to the severity of OSAS (0.27 (0.11-0.62) and 0.23 (0.07-0.50) (p = 0.012)).

CONCLUSIONS

In patients with apnea, OCT-A can be used as a noninvasive tool to define coronary artery involvement, with similar retinal microvascular changes both in obstructive and microvascular coronary artery group. In patients with OSAS, we observed a high prevalence of microvascular coronary disease, supporting pathophysiological role of OSAS in ischemia of this group of patients.

Optical coherence tomography enhanced depth imaging of chorioretinal folds in patients with orbital tumors

AIM

To characterize spectral-domain optical coherence tomography (SD-OCT) features of chorioretinal folds in orbital mass imaged using enhanced depth imaging (EDI).

METHODS

Prospective observational case-control study was conducted in 20 eyes of 20 patients, the uninvolved eye served as a control. All the patients underwent clinical fundus photography, computed tomography, EDI SD-OCT imaging before and after surgery. Two patients with cavernous hemangiomas underwent intratumoral injection of bleomycin A5; the remaining patients underwent tumor excision. Patients were followed 1 to 14mo following surgery (average follow up, 5.8mo).

RESULTS

Visual acuity prior to surgery ranged from 20/20 to 20/200. Following surgery, 5 patients' visual acuity remained unchanged while the remaining 15 patients had a mean letter improvement of 10 (range 4 to 26 letters). Photoreceptor inner/outer segment defects were found in 10 of 15 patients prior to surgery. Following surgical excision, photoreceptor inner/outer segment defects fully resolved in 8 of these 10 patients.

CONCLUSION

Persistence of photoreceptor inner/outer segment defects caused by compression of the globe by an orbital mass can be associated with reduced visual prognosis. Our findings suggest that photoreceptor inner/outer segment defects on EDI SD-OCT could be an indicator for immediate surgical excision of an orbital mass causing choroidal compression.

EFEMP1 is a potential biomarker of choroid thickness change in myopia

Purpose

To explore the possible molecular mechanism by which epidermal growth factor-containing fibulin-like extracellular matrix protein 1 (EFEMP1) regulates choroid thickness (CT) in the development of myopia.

Methods

In total, 131 subjects were divided into the emmetropia (EM) group, non-high myopia (non-HM) group and high myopia (HM) group. Their age, refraction, intraocular pressure, and other ocular biometric parameters were collected. A 6 × 6 mm area centered on the optic disc was scanned by coherent optical tomography angiography (OCTA) to measure CT, and the tear concentrations of EFEMP1 were quantified using enzyme-linked immunosorbent assay (ELISA) analysis. Twenty-two guinea pigs were divided into the control group and the form-deprivation myopia (FDM) group. The right eye of the guinea pig in the FDM group was covered for 4 weeks, and the diopter and axial length of the right eye of the guinea pig were measured before and after the treatment. After the measurement, the guinea pig was euthanized, and the eyeball was removed. Quantitative reverse transcription polymerase chain reaction, western blotting assays and immunohistochemistry were used to assess the expression of EFEMP1 in the choroid.

Results

There were significant differences in CT among the three groups (p < 0.001). CT was positively correlated with age in HM (r = -0.3613, p = 0.0021), but no significant correlation with SE (p > 0.05) was observed. Furthermore, there were increased levels of EFEMP1 in the tears of myopic patients. After 4 weeks of covering the right eye of the FDM guinea pigs, there was a significant increase in axial length and a decrease in diopter (p < 0.05). The mRNA and protein expression of EFEMP1 was significantly increased in the choroid.

Conclusion

Choroidal thickness was significantly thinner in myopic patients, and the expression level of EFEMP1 in the choroid increased during the development of FDM. Therefore, EFEMP1 may be involved in the regulation of choroidal thickness in myopia patients.

Corneal morphology correlates with choriocapillaris perfusion in myopic children

AIMS

The present study investigated the difference in choriocapillaris (CC) perfusion between different AL/K ratio groups with similar spherical equivalent refraction (SER) and analyzed factors affecting CC perfusion.

METHODS

This cross-sectional study included 129 children with low-to-moderate myopia. Axial length (AL), average K-reading (Ave-K), and SER were measured. Choroidal vascularity, including the total choroidal area (TA), choroidal luminal area (LA), stromal area (SA), choroidal vascularity index (CVI), CC flow voids (FVs), and FVs%, was obtained using optical coherence tomography angiography.

RESULTS

Participants with similar SER were divided into two groups (high AL/K ratio, n = 57; low AL/K ratio, n = 72). The high AL/K group had lower LA, TA, and CVI (P < 0.01) and lower FVs (inner ring and fovea, P < 0.05) and FVs% (outer ring, inner ring, and fovea, P < 0.05). The AL/K ratio and FVs% were negatively correlated in the outer ring (r =  - 0.174, P < 0.05) and inner ring (r =  - 0.174, P < 0.05). The Ave-K and inner FVs (r = 0.178, P < 0.05), outer FVs% (r = 0.175, P < 0.05), and inner FVs% (r = 0.196, P < 0.05) were positively correlated. In stepwise multiple regression for the outer ring, the horizontal CVI was related to FVs (β = 0.175, P < 0.05), and the vertical CVI was related to FVs% (β = 0.232, P < 0.01). Independent risk factors associated with inner FVs area were vertical CVI (β = 0.329; P < 0.001) and SER (β =  - 0.196, P < 0.05); FVs% was also associated with vertical CVI (β = 0.360, P < 0.01) and SER (β =  - 0.196, P < 0.05).

CONCLUSION

With a similar SER, myopic eyes with a higher AL/K ratio maintained more CC perfusion and lower CVI, which may indicate rapid myopic progression. Low K-reading eyes had more CC perfusion and less CVI, which may explain the relatively poor myopia control efficacy in the clinic.

EVALUATİON OF THE EFFECT OF OBSTRUCTİVE SLEEP APNEA SYNDROME ON RETİNAL MİCROVASCULARİTY BY OPTİCAL COHERENCE TOMOGRAPHY ANGİOGRAPHY

PURPOSE

Using optical coherence tomography angiography (OCTA), we sought to determine whether there are retinal microvascular changes in patients with obstructive sleep apnea syndrome (OSAS).

METHOD

The study included 56 patients diagnosed with OSAS by polysomnography [21 patients with mild OSAS (group 1), 14 with moderate OSAS (group 2) and 21 with severe OSAS (group 3)], and 26 healthy individuals as a control group (group 4). The vascular densities of the superficial capillary plexus and deep capillary plexus of the retinal segmentations, together with the foveal avascular zone (FAZ) width, were measured for all participants, using OCTA.

RESULT

Compared with the control group, vascular densitiy in whole image of superficial capillary plexus were found to be significantly lower in group 2. In addition, vascular densitiy in fovea region of superficial capillary plexus was significantly lower in group 1 than the control group. In deep capillary plexus, vascular densitiy of whole image, superior hemi and nasal regions were found to be significantly lower in group 2 and group 3 compared with the control group. Parafoveal region in group 3 had significantly lower vascular densities than the controls. A significantly larger FAZ was also found in group 1 and group 3 in the deep capillary plexus, compared with the controls.

CONCLUSION

We detected smaller vascular densities in both the superficial capillary plexus and deep capillary plexus and a larger deep capillary plexus FAZ in OSAS patients. Therefore, OCTA may be useful as a non-invasive method to understand the systemic effects of OSAS.

Ocular Autonomic Nervous System: An Update from Anatomy to Physiological Functions

The autonomic nervous system (ANS) confers neural control of the entire body, mainly through the sympathetic and parasympathetic nerves. Several studies have observed that the physiological functions of the eye (pupil size, lens accommodation, ocular circulation, and intraocular pressure regulation) are precisely regulated by the ANS. Almost all parts of the eye have autonomic innervation for the regulation of local homeostasis through synergy and antagonism. With the advent of new research methods, novel anatomical characteristics and numerous physiological processes have been elucidated. Herein, we summarize the anatomical and physiological functions of the ANS in the eye within the context of its intrinsic connections. This review provides novel insights into ocular studies.

Markers of the sympathetic, parasympathetic and sensory nervous system are altered in the human diabetic choroid

BACKGROUND

We sought to evaluate alterations in markers of the autonomic nervous system in human diabetic choroid.

METHODS

Eighteen eyeballs from subjects with diabetes and 22 eyeballs from subjects without diabetes were evaluated in this study. Synaptophysin, tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DβH), neuronal nitric oxide synthase (nNOS), choline acetyltransferase (ChAT), vesicular monoamine transporter II (VMAT-2), vesicular acetylcholine transporter (VAChT), vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) levels were detected by western blot analysis and immunofluorescence was performed in some cases. Furthermore, differences in adrenergic (α1- and β2-subtypes) and cholinergic (M1 and M3) receptor levels between diabetic subjects and controls were noted.

RESULTS

Decreased synaptophysin levels were found in diabetic choroids by western blot analysis and a reduction of synaptophysin-immunoreactive nerves was also found by immunofluorescence. Furthermore, a decrease of the levels of the key enzyme (TH) and transporter (VMAT2) of norepinephrine was evident both by western blot analysis and immunofluorescence. Additionally, increased NPY, VAChT, nNOS, and CGRP levels were observed in diabetic choroids. The levels of adrenergic (β2 subtype) and acetylcholine (M1 subtype) receptors decreased in diabetic choroids, as shown by western blotting and although the differences in α1 and M3 were not significant, there was a downward trend.

CONCLUSIONS

In the diabetic choroid, the levels of neurotransmitters, enzymes, and receptors associated with choroidal blood flow regulation are altered. These changes may affect the regulation of choroidal blood flow and may be associated with impaired retinal function and retinal pathology.

Pulsatile Filling of Dilated Choroidal Vessels in Macular Watershed Zones

PURPOSE

To describe pulsatile filling of dilated choroidal veins in the watershed zones and propose an alteration in choroidal perfusion pressure.

METHODS

Retrospective review of original and digital subtraction indocyanine green angiography (ICGA).

RESULTS

We observed pulsating blood flow within choroidal vein segments in the posterior pole in 14 eyes (diagnosis of polypoidal choroidal vasculopathy, central serous chorioretinopathy, or neovascular age-related macular degeneration). Pulsating dye front was observed in single or multiple large choroidal vein(s) in a location that is ordinarily a watershed zone between the segmental areas of venous drainage and vessels proximal and distal were often dilated. The pulsatile venous segments filled more slowly that the neighboring veins. In digital subtraction ICGA, the dye front advanced in an incremental fashion or oscillated in a back-and forth manner during several cardiac cycles during the filling of these larger choroidal veins. With ICGA, we observed dilated choroidal veins which violated the macula watershed zone, localized bulbous dilations, and arteriole-over-vein crossings with apparent compression.

CONCLUSIONS

These novel observations suggest the pressure gradient for flow in the affected veins varied, from low gradients when the filling was slow to higher gradients when the filling was faster. The vessels violated the physiological watershed zone and seem to function as anastomoses between the ordinarily segmented venous drainage of the choroid. The dilated segments may result in pooling of venous blood as part of venous outflow abnormalities that may be operative in these diseases.

Role of the superior salivatory nucleus in parasympathetic control of choroidal blood flow and in maintenance of retinal health

The vasodilatory pterygopalatine ganglion (PPG) innervation of the choroid is under the control of preganglionic input from the superior salivatory nucleus (SSN), the parasympathetic portion of the facial motor nucleus. We sought to confirm that choroidal SSN drives a choroid-wide vasodilation and determine if such control is important for retinal health. To the former end, we found, using transscleral laser Doppler flowmetry, that electrical activation of choroidal SSN significantly increased choroidal blood flow (ChBF), at a variety of choroidal sites that included more posterior as well as more anterior ones. We further found that the increases in ChBF were significantly reduced by inhibition of neuronal nitric oxide synthase (nNOS), thus implicating nitrergic PPG terminals in the SSN-elicited ChBF increases. To evaluate the role of parasympathetic control of ChBF in maintaining retinal health, some rats received unilateral lesions of SSN, and were evaluated functionally and histologically. In eyes ipsilateral to choroidal SSN destruction, we found that the flash-evoked scotopic electroretinogram a-wave and b-wave peak amplitudes were both significantly reduced by 10 weeks post lesion. Choroidal baroregulation was evaluated in some of these rats, and found to be impaired in the low systemic arterial blood pressure (ABP) range where vasodilation normally serves to maintain stable ChBF. In retina ipsilateral to SSN destruction, the abundance of Müller cell processes immunolabeled for glial fibrillary acidic protein (GFAP) and GFAP message were significantly upregulated. Our studies indicate that the SSN-PPG circuit mediates parasympathetic vasodilation of choroid, which appears to contribute to ChBF baroregulation during low ABP. Our results further indicate that impairment in this adaptive mechanism results in retinal dysfunction and pathology within months of the ChBF disturbance, indicating its importance for retinal health.

Evaluation of retinal vessel density and foveal avascular zone measurements in patients with obstructive sleep apnea syndrome

PURPOSE

To compare retinal capillary plexus vessel densities, choroidal thickness, optic disc vessel densities and foveal avascular zone measurements between normal subjects and subjects with obstructive sleep apnea syndrome (OSAS) using spectral-domain OCT angiography (OCTA).

METHODS

Forty eyes of patients with overall OSAS, 20 eyes of patients with mild-moderate OSAS, 20 eyes of patients with severe OSAS on polysomnography and 21 controls were evaluated with the RTVue-XR Avanti OCTA (Optovue, Inc., Fremont, CA). Superficial and deep retinal capillary plexus vessel densities, choroidal thickness and foveal avascular zone (FAZ) parameters (area, diameter, acircularity index of the FAZ, foveal density-300) were measured for all subjects.

RESULTS

Superficial capillary plexus vessel densities of the groups were similar. Deep capillary plexus (DCP) vessel densities of all three OSAS groups decreased in the parafoveal region (< 0.001). In the perifoveal region, DCP vessel densities were decreased in the Overall OSAS group (p = 0.023) and in the Severe OSAS group (p = 0.021), whereas it was similar in the Mild-moderate OSAS group. Choroidal thickness decreased in all three OSAS groups (p < 0.001). All FAZ measurements and foveal density-300 measurements were similar compared to the control group.

CONCLUSION

Our findings indicate that in severe OSAS patients, deep parafoveal, perifoveal vascular densities decrease and the choroid layer becomes thinner. When evaluating a patient with OSAS, it should be kept in mind that there may be eye involvement due to the disease.

Quantitative evaluation of retinal and choroidal changes in Fabry disease using optical coherence tomography angiography

To examine the retinal and choroidal changes in patients with Fabry disease (FD) using optical coherence tomography angiography (OCTA). FD patients and age- and sex-matched healthy subjects were enrolled. A detailed ophthalmological examination was performed for all participants. The retinal thickness, ganglion cell layer with inner plexiform layer (GCIPL) thickness, choroidal thickness (CT), vessel length density (VLD), vessel perfusion density (VPD), and foveal avascular zone (FAZ) were analyzed in a detailed way with OCTA. Moreover, all FD patients underwent several laboratory tests to evaluate systemic conditions. A total of 54 subjects comprising 26 FD patients and 28 normal controls were enrolled. The retinal thickness, GCIPL thickness, and FAZ area showed no significant differences between the two groups (all P > 0.05). Only the superior CT in FD patients was significantly thinner than that in the normal subjects (P = 0.040). The macular VLD and VPD in the FD group were significantly reduced compared with the healthy controls (P = 0.026, P = 0.008). The macular VLD in FD patients had no significant correlations with different laboratory results (all P > 0.05), while the macular VPD were negatively correlated with creatinine (r = - 0.432, P = 0.028) and cystatin C (r = - 0.422, P = 0.032). FD patients may have retinal vascular dropout and choroidal vascular alterations. Analysis of vessel density using OCTA might be useful in the clinical assessment in FD patients.