The Role of the Endothelin System in the Vascular Dysregulation Involved in Retinitis Pigmentosa

In depth understanding of retinitis pigmentosa pathogenesis through optical coherence tomography angiography analysis: a narrative review

Retinitis pigmentosa (RP) is the most recognized inherited retinal disorder involving progressive photoreceptors degeneration which eventually causes blindness. However, the pathogenesis of RP is still unclear, making it difficult to establish satisfying treatments. Evidence have been found to support the theory that vascular dysfunction is associated with the progression of RP. Optical coherence tomography angiography (OCTA) is a newly developed technology that enables visualization as well as quantitative assessment of retinal and choroidal vasculature non-invasively. Advances in OCTA have opened a window for in-depth understanding of RP pathogenesis. Here, we propose a hypothesis of RP pathogenesis based on the current OCTA findings in RP, which includes four stages and two important key factors, vascular dysfunction and microglia activation. Further, we discuss the future animal experiments needed and how advanced OCTA technology can help to further verity the hypothesis. The final goal is to explore potential treatment options with enhanced understanding of RP pathogenesis.

Choroidal Thickness in Different Types of Inherited Retinal Dystrophies

Purpose

To compare the choroidal thickness among eyes with retinitis pigmentosa (RP), Stargardt disease, Usher syndrome, cone-rod dystrophy, and healthy eyes of sex- and age-matched individuals.

Methods

In this comparative study, 503 eyes with RP (n = 264), cone-rod dystrophy (n = 109), Stargardt disease (n = 76), and Usher syndrome (n = 54) were included. To validate the data, 109 healthy eyes of 56 sex- and age-matched individuals were studied as controls. Choroidal imaging was performed using enhanced depth imaging-optical coherence tomography. Choroidal thickness was measured manually using MATLAB software at 13 points in nasal and temporal directions from the foveal center with the interval of 500 µm and the choroidal area encompassing the measured points was calculated automatically.

Results

The mean age was 36.33 ± 13.07 years (range, 5 to 72 years). The mean choroidal thickness at 13 points of the control eyes was statistically significantly higher than that in eyes with RP (P < 0.001) and Usher syndrome (P< 0.05), but not significantly different from that in eyes with Stargardt disease and cone-rod dystrophy. Among different inherited retinal dystrophies (IRDs), the choroidal thickness was the lowest in eyes with RP (P < 0.001). Choroidal thickness in the subfoveal area correlated negatively with best-corrected visual acuity (r = -0.264, P < 0.001) and the duration of ocular symptoms (r = -0.341, P < 0.001) in all studied IRDs. No significant correlation was observed between the subfoveal choroidal thickness and central macular thickness (r = -0.24, P = 0.576).

Conclusion

Choroidal thinning in four different types of IRDs does not follow a similar pattern and depends on the type of IRD and the duration of ocular symptoms. A larger cohort is required to verify these findings

Multimodal Imaging in Retinitis Pigmentosa: Correlations among Microvascular Changes, Macular Function and Retinal Structure

Purpose:

To analyze microvascular changes in patients with retinitis pigmentosa (RP) with relatively preserved visual acuity (VA), using swept source optical coherence tomography (SS-OCT) angiography to correlate results to macular function and structure.

Methods:

This was a case–control study conducted over 70 eyes of 35 RP patients with relatively preserved VA. All patients underwent a complete ophthalmic examination, including SS-OCT, OCT angiography (OCT-A), fundus autofluorescence (FAF), and multifocal electroretinogram (mfERG). Thirty-four eyes of 34 healthy controls of age-, sex-, and axial length-matched (control group), were also analyzed. The main outcome measures were foveal and parafoveal vascular densities (FVDs and PFVDs) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP), foveal avascular zone (FAZ) and its enlargement coefficient and their correlation with macular function (by means of VA and mfERG), and structure (by means of FAF and SS-OCT).

Results:

In the RP group, PFVD was 25.99 ± 5.2% in the SCP and 34.47 ± 2.37% in the DCP and were significantly lower as compared to control group (P < 0.0001; P = 0.0026, respectively). Enlargement coefficient of FAZ was 1.78 ± 0.79. We found a statistically significant correlation between VA and PFVD in the DCP (P < 0.0001), FAZ disruption in the SCP (P = 0.006) and enlargement coefficient of FAZ (P = 0.01). The parafoveal DCP density was significantly correlated with P1 amplitude (P = 0.005) in rings 2, 3, 4, and 5 of the mfERG. We found a statistically significant correlation between parafoveal density in the DCP, thickness of ganglion cell complex (GCC) (P = 0.001), and the width of ellipsoid band (P = 0.041). Parafoveal SCP density was also correlated to GCC (P = 0.033).

Conclusions:

We showed that vascular alteration in RP begins at the level of the DCP, which affects the outer retina and leads to a narrowing of the ellipsoid. The alteration of the SCP would occur later in the evolution of the disease. Vascular changes occur early during RP and were highly correlated to retinal function and structure. OCT-A seems to be a good tool to quantify vascular network loss and could play a central role in staging, prognosis, and monitoring disease progression.

EDI-OCT evaluation of choroidal thickness in retinitis pigmentosa

PURPOSE

To evaluate choroidal thickness (CT) in retinitis pigmentosa (RP) using enhanced depth imaging (EDI) optical coherence tomography (OCT).

METHODS

A retrospective analysis of a group of patients with RP who underwent EDI-OCT was performed. Choroidal thickness measurements were compared with those of age- and sex-matched healthy subjects. In the RP group, the possible association between subfoveal CT and some clinical parameters (visual acuity, age, age at disease onset, duration of the disease, macular thickness, visual field loss, electroretinography [ERG]) was evaluated.

RESULTS

The study recruited 39 patients with RP with an average age of 43.3 ± 11.3 years while the control group consisted of 73 healthy subjects with an average age of 42.9 ± 12.10 years. On average, CT was significantly thinner in the RP group compared to the controls (p<0.0001). In the RP group, we could not find any significant association between CT and the considered clinical parameters even if there was a trend for decreasing CT with increasing age (r = -0.23, p = 0.096). In the control group, subfoveal CT showed a slightly significant correlation with age (r = -0.21, p = 0.04) but not with macular thickness and visual acuity.

CONCLUSIONS

In our series, CT was significantly lower in the RP group in comparison with the controls, as measured by EDI-OCT, but did not correlate with age, age at onset, duration of the disease, macular thickness, visual acuity, visual field loss, or ERG responses. Although the clinical implications of choroidal changes in RP have not yet been clearly determined, the evaluation of choroidal features may provide information that could be useful to clarify the pathophysiology of the disease.

Findings of Optical Coherence Tomography Angiography in Best Vitelliform Macular Dystrophy

PURPOSE

To evaluate the vascular anatomy of eyes with Best vitelliform macular dystrophy (BVMD) using optical coherence tomography angiography (OCTA).

METHODS

This retrospective case-control study enrolled 11 consecutive BVMD patients and 13 age-matched healthy participants. Both eyes of each participant were imaged using a macular OCTA scan (3 × 3 mm) by 70-kHz 840-nm spectral-domain OCT. The flow signal was calculated using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm.

RESULTS

Qualitative analysis showed uneven hypo- and hyperintense signal changes at the choriocapillary level in OCTA images of BVMD patients. Quantitative analysis showed significant reductions in the flow density of the superficial vascular layer (whole: 49.2% vs. 53.9%, p < 0.001) and the choriocapillary flow area (5.1 vs. 5.5 mm2, p = 0.02) in BVMD patients compared to controls. The choriocapillary flow area in the postvitelliform group was reduced compared to that of the vitelliform group. There was a statistically significant association between choriocapillary flow area and superficial vascular flow density (p = 0.045), choriocapillary flow area and foveal avascular zone area (p = 0.03).

CONCLUSIONS

Vascular changes in BVMD were apparent in the choriocapillary layer. The changes became more striking in late stages of the disease. OCTA provides useful quantitative measurements for staging and monitoring the progression of BVMD.

Non-syndromic retinitis pigmentosa

Retinitis pigmentosa (RP) encompasses a group of inherited retinal dystrophies characterized by the primary degeneration of rod and cone photoreceptors. RP is a leading cause of visual disability, with a worldwide prevalence of 1:4000. Although the majority of RP cases are non-syndromic, 20-30% of patients with RP also have an associated non-ocular condition. RP typically manifests with night blindness in adolescence, followed by concentric visual field loss, reflecting the principal dysfunction of rod photoreceptors; central vision loss occurs later in life due to cone dysfunction. Photoreceptor function measured with an electroretinogram is markedly reduced or even absent. Optical coherence tomography (OCT) and fundus autofluorescence (FAF) imaging show a progressive loss of outer retinal layers and altered lipofuscin distribution in a characteristic pattern. Over the past three decades, a vast number of disease-causing variants in more than 80 genes have been associated with non-syndromic RP. The wide heterogeneity of RP makes it challenging to describe the clinical findings and pathogenesis. In this review, we provide a comprehensive overview of the clinical characteristics of RP specific to genetically defined patient subsets. We supply a unique atlas with color fundus photographs of most RP subtypes, and we discuss the relevant considerations with respect to differential diagnoses. In addition, we discuss the genes involved in the pathogenesis of RP, as well as the retinal processes that are affected by pathogenic mutations in these genes. Finally, we review management strategies for patients with RP, including counseling, visual rehabilitation, and current and emerging therapeutic options.

The potential relationship between Flammer and Sjögren syndromes: the chime of dysfunction

Flammer syndrome (FS) is a term to blanket a cluster of vascular and nonvascular signs and symptoms linked to primary vascular dysregulation (PVD), increased sensitivity to various stimuli (stress, drugs, etc.) and altered sense regulation such as pain, smell and thirst perception. On one hand, disruption of blood barrier and homeostasis of the body are the main targets of vascular irregularity. Inflammation and immune disorders including autoimmunity are considered as a consequence of the abnormal vascular regulation processes. On the other hand, decreased thirst feeling typical for FS-affected individuals may lead to extensive body dehydration resulting in dry eye appearance and breast cancer (BC) risk, amongst others. To this end, recent research demonstrated FS as linked to BC development and progression into the metastatic disease. On the other side, Sjögren syndrome (SS) is an autoimmune disease characterised by a progressive sicca syndrome associated with the dry eye symptoms, specific immunologic complex and/or significant infiltrate at minor salivary gland biopsy. SS is relatively frequent, with a clinical diagnosis predominantly amongst women. Its physiopathology is a complex battery of both environmental and genetic factors. If left untreated, SS may be associated with and/or resulted in severe arthritis and the development of B cell lymphoma. In this mini-review, we summarise the facts and hypotheses connecting FS and SS symptoms together and mechanisms potentially overlapping in both syndromes. Unraveling the common denominators between these two syndromes not only providing more evidence for interaction between altered sense regulation, vascular dysregulation, immune system dysfunction but also focusing on the individual outcomes in terms of severity grade and potential complications exploring novel diagnostic, prognostic and treatment modalities. Multi-professional considerations presented here are an example how to effectively enter the new era of preventive, predictive and personalised medicine benefiting the patients and healthcare system as the whole.

Acupuncture benefits for Flammer syndrome in individuals with inherited diseases of the retina

BACKGROUND

Patients with inherited diseases of the retina (IRD) often exhibit signs and symptoms of Flammer syndrome (FS). Acupuncture treatment has shown its positive effect on visual function in patients with IRD. The aim of the present study is to examine the effect of acupuncture on signs and symptoms of FS in a cohort of patients suffering simultaneously FS and IRD.

PATIENTS AND METHODS

A prospective pilot study was performed on 17 patients with FS and IRD: rod-cone dystrophy, Nr: 12 (RCD); cone-rod dystrophy, Nr: 3 (CRD) and inherited macular dystrophy, Nr: 2 (IMD; 12♀, 5♂; mean age: 44.19 y; SD ±17.09 y). Acupuncture treatment was done applying needle acupuncture of the body and the ears. The treatment was scheduled at 10 half-hour sessions over 5 weeks. Primary outcome was evaluation of the post-acupuncture effect on the signs and symptoms of FS in IRD patients using multiple-choice questionnaires.

RESULTS

Following acupuncture, we found improvement in signs and symptoms of FS in patients suffering simultaneously IRD, as for instance (Nr. patients: improvement/suffering/total): a reduced tiredness (10/11/17), shorter sleep onset time (10/11/17), warmer feet and hands (10/10/17) and reduced frequency of headache attacks (9/11/17). Surprisingly, in four RCD patients and in one IMD patient, a reduction of macular edema was documented.

CONCLUSIONS

The applied acupuncture protocol for FS in IRD patients showed improvement in FS signs and symptoms and was tolerated well. Nevertheless, the objective evaluation of this complementary therapy on FS in IRD patients remains to be elucidated.