Purpose
To evaluate reliability and repeatability of computer-assisted measurements of cone photoreceptor metrics on Heidelberg Engineering Spectralis™ High Magnification Module (HMM™) Automatic ...Real-time Tracking (ART™) images.
Methods
We analyzed HMM™ images in three separate study arms. Computer-assisted cone identification software was validated using an open-access adaptive optics (AO) dataset. We compared results of the first arm to data from AO and histology. We evaluated intersession repeatability of our computer-assisted cone analysis in the second arm. We assessed the capability of HMM™ to visualize cones in the presence of pathology in the third arm.
Results
We included 10 healthy subjects in the first arm of our study, 5 additional healthy participants in the second arm and 5 patients in the third arm. In total, we analyzed 225 regions of interest on HMM™ images. We were able to automatically identify cone photoreceptors and assess corresponding metrics at all eccentricities between 2 and 9° from the fovea. Cone density significantly declined with increasing eccentricity (
p
= 4.890E-26, Friedman test). With increasing eccentricity, we found a significant increase in intercell distance (
p
= 2.196E-25, Friedman test) and nearest neighbor distance (
p
= 1.997E-25, Friedman test). Cone hexagonality ranged between 71 and 85%. We found excellent automated intersession repeatability of cone density counts and spacing measurements. In pathology, we were also able to repeatedly visualize photoreceptors.
Conclusion
Computer-assisted cone photoreceptor analysis on Spectralis™ HMM™ images is feasible, and most cone metrics show excellent repeatability. HMM™ imaging may be useful for photoreceptor analysis as progression marker in outer retinal disease.
Chronic central serous chorioretinopathy (cCSC) is characterized by fluid accumulation between photoreceptors and the retinal pigment epithelium of which the cause is unknown. Associations with ...steroid use, stress, pregnancy, and the male sex suggest a role for the steroid hormone system in the disease. Here, we performed a comprehensive analysis of the steroid hormone system in active cCSC.
Serum hormone levels of 17 steroid hormones were measured in 46 male Caucasian patients with active cCSC and 46 male Caucasian age-matched controls using the AbsoluteIDQ stero17 kit.
Elevated levels of androsterone, estrone, etiocholanolone, and androstenedione were observed in cCSC patients compared with controls. Median hormone levels in cCSC patients versus controls, respectively, were as follows: androsterone, 0.84 ng/mL (interquartile range IQR = 0.61-1.06) versus 0.69 ng/mL (IQR = 0.48-0.96, P = 0.031); estrone, 0.12 ng/mL (IQR = 0.10-0.15) versus 0.10 ng/mL (IQR = 0.08-0.11; P = 0.0048); etiocholanolone, 0.19 ng/mL (IQR = 0.15-0.29) versus 0.13 ng/mL (IQR = 0.099-0.20, P = 0.0061). Mean levels of androstenedione were 3.10 ng/ml (SD = 1.03) versus 2.55 ng/mL (SD = 0.95), in cCSC patients versus controls, respectively. Additionally, Spearman's correlations between aldosterone and 11-deoxycortisol, androsterone, DHEA, DHEAS, and E1 differed between cCSC patients and controls, as well as between andosterone and E1, and between DHT and 17OHP.
We present a comprehensive overview of the status of the steroid hormone system in active cCSC. Levels of four hormones were elevated in cCSC patients compared with controls, and the relationships between steroid hormones was altered, indicating that the balance in the steroid hormone system is altered in cCSC patients.
Recently introduced, the Heidelberg Engineering™ high magnification module enables in vivo visualization of cone photoreceptor cells. Currently, a reliable analysis of cone mosaic on high ...magnification module images is hindered by an unfavorable signal-to-noise ratio. In this paper, we describe how a novel high magnification module high-pass filter may enhance cone signals in healthy participants and patients. We compared the cone counts of our filter-based algorithm to the counts of two human graders. We found a good to excellent intragrader and intergrader correlation in both patients and healthy participants. We identified a good correlation between the average cone counts of both graders and high-pass filter cone counts in patients and healthy participants. We observed no significant difference between manual and filter-based counts via the Bland–Altman analysis. In conclusion, a quantitative cone analysis on high magnification module images is feasible manually by human graders and automatically by a filter-based algorithm. However, larger datasets are needed to improve repeatability and consistency by training human graders.
Purpose
High Magnification Module (HMM™, Heidelberg Engineering, Heidelberg, Germany) imaging is a novel technique, designed to visualize the retina at a cellular level. To assess the potential of ...HMM™‐based metrics as endpoints for future trials, we evaluated correlations between structural HMM™ cone metrics, spectral‐domain OCT (SD‐OCT, Heidelberg Engineering, Heidelberg, Germany) and retinal sensitivity on microperimetry (MP, MAIA, CenterVue, Padova, Italy) in healthy subjects and p.(Arg142Trp) PRPH2‐associated Central Areolar Choroidal Dystrophy (CACD) patients.
Methods
We projected a default 10° MP grid on composite HMM™ images and performed automated cone density (CD), intercell distance (ICD) and nearest neighbour distance (NND) analysis at stimuli located at 3° and 5° retinal eccentricity. We manually measured intrasubject outer retinal thickness on SD‐OCT in absolute and relative scotomas, located outside of focal atrophy.
Results
We included 15 CACD patients and five healthy subjects. We found moderate‐to‐strong correlations of HMM™ metrics and MP sensitivity at 3° eccentricity from the fovea. We found the outer retina at the locations of absolute scotomas to be statistically significant thinner (p = 0.000003, one‐sample t‐test), as the outer retinal thickness at locations of relative scotomas. Interestingly, HMM™ metrics of these areas did not differ significantly.
Conclusions
We found significant correlations between structural photoreceptors metrics on HMM™ imaging and retinal sensitivity on MP in healthy subjects and CACD patients. A multimodal approach, combining SD‐OCT, MP and HMM™ imaging, allows for detailed mapping of retinal photoreceptor integrity and restitution potential, important data that could serve as biomarkers in future clinical trials.
The cause of autosomal-dominant retinitis pigmentosa (adRP), which leads to loss of vision and blindness, was investigated in families lacking a molecular diagnosis. A refined locus for adRP on ...Chr17q22 (RP17) was delineated through genotyping and genome sequencing, leading to the identification of structural variants (SVs) that segregate with disease. Eight different complex SVs were characterized in 22 adRP-affected families with >300 affected individuals. All RP17 SVs had breakpoints within a genomic region spanning YPEL2 to LINC01476. To investigate the mechanism of disease, we reprogrammed fibroblasts from affected individuals and controls into induced pluripotent stem cells (iPSCs) and differentiated them into photoreceptor precursor cells (PPCs) or retinal organoids (ROs). Hi-C was performed on ROs, and differential expression of regional genes and a retinal enhancer RNA at this locus was assessed by qPCR. The epigenetic landscape of the region, and Hi-C RO data, showed that YPEL2 sits within its own topologically associating domain (TAD), rich in enhancers with binding sites for retinal transcription factors. The Hi-C map of RP17 ROs revealed creation of a neo-TAD with ectopic contacts between GDPD1 and retinal enhancers, and modeling of all RP17 SVs was consistent with neo-TADs leading to ectopic retinal-specific enhancer-GDPD1 accessibility. qPCR confirmed increased expression of GDPD1 and increased expression of the retinal enhancer that enters the neo-TAD. Altered TAD structure resulting in increased retinal expression of GDPD1 is the likely convergent mechanism of disease, consistent with a dominant gain of function. Our study highlights the importance of SVs as a genomic mechanism in unsolved Mendelian diseases.
Mutations in PRPH2, encoding peripherin‐2, are associated with the development of a wide variety of inherited retinal diseases (IRDs). To determine the causality of the many PRPH2 variants that have ...been discovered over the last decades, we surveyed all published PRPH2 variants up to July 2020, describing 720 index patients that in total carried 245 unique variants. In addition, we identified seven novel PRPH2 variants in eight additional index patients. The pathogenicity of all variants was determined using the ACMG guidelines. With this, 107 variants were classified as pathogenic, 92 as likely pathogenic, one as benign, and two as likely benign. The remaining 50 variants were classified as variants of uncertain significance. Interestingly, of the total 252 PRPH2 variants, more than half (n = 137) were missense variants. All variants were uploaded into the Leiden Open source Variation and ClinVar databases. Our study underscores the need for experimental assays for variants of unknown significance to improve pathogenicity classification, which would allow us to better understand genotype‐phenotype correlations, and in the long‐term, hopefully also support the development of therapeutic strategies for patients with PRPH2‐associated IRD.
BACKGROUNDTwo of the most widely accepted approaches to map eloquent cortical areas preoperatively are positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). As yet, no ...study has compared these two modalities within the same frame of reference in tumour patients.
AIMWe employed O-H2O-PET and fMRI in patients undergoing presurgical evaluation and compared the results with those obtained by direct electrical cortical stimulation (DECS).
METHODSTwenty-five patients with tumours of different aetiology near the central region were investigated. fMRI and PET were processed using the same methods, i.e. statistical parametric mapping (SPM) without anatomical normalization, and transformed into the same frame of reference.
RESULTSfMRI activity was found in more cranial and lateral sections, i.e. closer to the brain surface, in comparison with PET, which demonstrated parenchymal activation. The mean localization difference between fMRI and PET was 8.1±4.6 mm (range, 2–18 mm). fMRI and O-H2O-PET could reliably identify the central sulcus, as demonstrated by DECS.
CONCLUSIONSfMRI and O-H2O-PET demonstrate comparable results and are sensitive and reliable tools to map the central region, especially in cases of infiltrating brain tumours. However, fMRI is more prone to artefacts, such as the visualization of draining veins, which may explain the more cranial and lateral activation visualized by fMRI, whereas PET depicts capillary perfusion changes and therefore shows activation closer to the parenchyma.
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