[10 years of screening for retinopathy of prematurity (2009-2019) : Results analysis of two German level-1 neonatal intensive care units (NICUs) with university on-site screening and a telemedical approach in the non-university NICU]. / 10 Jahre Screening auf Frühgeborenenretinopathie (2009­2019) : Ergebnisanalyse zweier deutscher Level-1-Perinatalzentren mit universitärem Vor-Ort-Screening und telemedizinischem Ansatz in dem nicht universitären Zentrum.

BACKGROUND: Retinopathy of prematurity (ROP) is one of the most common causes of childhood blindness in Germany and worldwide and adequate screening is essential. The telemedical approach with objective documentation of retinal findings opens up the possibility of reliably diagnosing all ROP stages independent of the examiner, if a team of ophthalmologists specialized in ROP evaluates the images. OBJECTIVE: A 10-year comparison of ROP screening at two level­1 neonatal intensive care units (NICU): university and on-site vs. non-university and telemedical. MATERIAL AND METHODS: Retrospective analysis of screened premature infants by gestational age (GA), birth weight (BW), sex, multiple births, time of ROP occurrence, treatment needs and time as well as examination frequency. RESULTS: From 2009 to 2019, we screened 1191 infants of whom 29 had been screened before by an external clinic. The internal 1162 infants were screened on-site with 3713 retinal examinations. We diagnosed 34% with ROP and treated 5.4% (3.7% in Giessen, 7.2% in Siegen). Mean GA was 28.9 weeks (±â€¯2.5 weeks); mean BW 1155 g (±â€¯417.5 g). The number of ROP diagnoses increased by 227.3% in Giessen and by 111.1% in Siegen due to the increasing number of premature births in neonatal care. CONCLUSION: Comparative analysis confirmed nationally and internationally increasing ROP screening and children with acute ROP. Telemedical screening was equivalent to on-site screening and safe. Both screening methods identified infants requiring treatment on time. No child with GA > 29 weeks required treatment, analogous to Swedish ROP registry results; however, in the German ROP registry some premature babies with GA ≥ 30 weeks required treatment.

Real-World Clinical Experience With Idebenone in the Treatment of Leber Hereditary Optic Neuropathy.

BACKGROUND: Leber hereditary optic neuropathy (LHON) leads to bilateral central vision loss. In a clinical trial setting, idebenone has been shown to be safe and to provide a trend toward improved visual acuity, but long-term evidence of effectiveness in real-world clinical practice is sparse. METHODS: Open-label, multicenter, retrospective, noncontrolled analysis of long-term visual acuity and safety in 111 LHON patients treated with idebenone (900 mg/day) in an expanded access program. Eligible patients had a confirmed mitochondrial DNA mutation and had experienced the onset of symptoms (most recent eye) within 1 year before enrollment. Data on visual acuity and adverse events were collected as per normal clinical practice. Efficacy was assessed as the proportion of patients with either a clinically relevant recovery (CRR) or a clinically relevant stabilization (CRS) of visual acuity. In the case of CRR, time to and magnitude of recovery over the course of time were also assessed. RESULTS: At time of analysis, 87 patients had provided longitudinal efficacy data. Average treatment duration was 25.6 months. CRR was observed in 46.0% of patients. Analysis of treatment effect by duration showed that the proportion of patients with recovery and the magnitude of recovery increased with treatment duration. Average gain in best-corrected visual acuity for responders was 0.72 logarithm of the minimal angle of resolution (logMAR), equivalent to more than 7 lines on the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. Furthermore, 50% of patients who had a visual acuity below 1.0 logMAR in at least one eye at initiation of treatment successfully maintained their vision below this threshold by last observation. Idebenone was well tolerated, with most adverse events classified as minor. CONCLUSIONS: These data demonstrate the benefit of idebenone treatment in recovering lost vision and maintaining good residual vision in a real-world setting. Together, these findings indicate that idebenone treatment should be initiated early and be maintained more than 24 months to maximize efficacy. Safety results were consistent with the known safety profile of idebenone.

Biallelic mutation of human SLC6A6 encoding the taurine transporter TAUT is linked to early retinal degeneration.

We previously reported that inactivation of the transmembrane taurine transporter (TauT or solute carrier 6a6) causes early retinal degeneration in mice. Compatible with taurine's indispensability for cell volume homeostasis, protein stabilization, cytoprotection, antioxidation, and immuno- and neuromodulation, mice develop multisystemic dysfunctions (hearing loss; liver fibrosis; and behavioral, heart, and skeletal muscle abnormalities) later on. Here, by genetic, cell biologic, in vivo1H-magnetic resonance spectroscopy and molecular dynamics simulation studies, we conducted in-depth characterization of a novel disorder: human TAUT deficiency. Loss of TAUT function due to a homozygous missense mutation caused panretinal degeneration in 2 brothers. TAUTp.A78E still localized in the plasma membrane but is predicted to impact structural stabilization. 3H-taurine uptake by peripheral blood mononuclear cells was reduced by 95%, and taurine levels were severely reduced in plasma, skeletal muscle, and brain. Extraocular dysfunctions were not yet detected, but significantly increased urinary excretion of 8-oxo-7,8-dihydroguanosine indicated generally enhanced (yet clinically unapparent) oxidative stress and RNA oxidation, warranting continuous broad surveillance.-Preising, M. N., Görg, B., Friedburg, C., Qvartskhava, N., Budde, B. S., Bonus, M., Toliat, M. R., Pfleger, C., Altmüller, J., Herebian, D., Beyer, M., Zöllner, H. J., Wittsack, H.-J., Schaper, J., Klee, D., Zechner, U., Nürnberg, P., Schipper, J., Schnitzler, A., Gohlke, H., Lorenz, B., Häussinger, D., Bolz, H. J. Biallelic mutation of human SLC6A6 encoding the taurine transporter TAUT is linked to early retinal degeneration.

[The Phenotypic Spectrum of Ophthalmic Changes in CEP290 Mutations]. / Das phänotypische Spektrum der Augenveränderungen bei CEP290-Sequenzvariationen.

PURPOSE: Inherited retinal diseases (IRDs) may be caused by variations in genes affecting the connecting cilium of photoreceptor cells and intraflagellar transport, manifested as ciliopathies. CEP290 is frequently mutated in non-syndromic, but also syndromic IRDs. In preparation for clinical treatment trials, detailed phenotypic work-up including longitudinal follow-up is mandatory. METHODS: We performed genotype-phenotype correlations in 30 patients with biallelic mutations in CEP290. The study was approved by the IRB of the medical faculty of the Justus-Liebig University Giessen. The patients received a comprehensive clinical examination, including spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence (FAF) recording, and electrophysiology whenever possible. RESULTS: Thirty patients aged 1 month to 84 years (median at first visit 0.6 y) were followed between 5 months and 25.7 years (median 4.8 y). Twenty-three of these patients carried the c.2991+1655A>G mutation (30/60 allele 2, 7 homozygous). The second most frequent mutation was p.K1575* (9/60 alleles). The full-field electroretinogram showed residual response in a few patients only. After progression, electrophysiological responses were below threshold in all patients. Severely reduced visual acuity persisted from birth. Eight patients had quantifiable best corrected visual acuity (BCVA, logMAR 2 - 0.3), in one case up to the age of 84 y. Absent fixation of targets was noted in 15 patients during the first months of life. Ten of these patients did not improve during follow-up past the second year of life. The other patients developed at least light perception (LP, n = 7) or hand movement (HM, n = 3). Better BCVA was not restricted to the c.2991+1655A>G mutation. Fundus photography documented degenerative changes throughout the retina with macular degeneration and circular increased fundus autofluorescence signals (9/30 patients) in the perimacular ring and in the rod ring, and spotty changes in the periphery. SD-OCT (6/30 patients) disclosed reduced photoreceptor layer (OPL to OS) thickness and preserved inner retinal thickness (RNFL to INL). Better BCVA did not correlate to genotype or central photoreceptor layer thickness. CONCLUSION: As reported earlier, CEP290 variations are one of the most frequent causes of IRDs with infancy onset. In our patient cohort of 30 patients, only 33% had no LP, 67% at least LP, and among these 26% logMAR 2 to 0.3. Together with preserved ganglion cell and nerve fibre cell layers, success with gene therapeutic approaches appears possible.

Where are the missing gene defects in inherited retinal disorders? Intronic and synonymous variants contribute at least to 4% of CACNA1F-mediated inherited retinal disorders.

Inherited retinal disorders (IRD) represent clinically and genetically heterogeneous diseases. To date, pathogenic variants have been identified in ~260 genes. Albeit that many genes are implicated in IRD, for 30-50% of the cases, the gene defect is unknown. These cases may be explained by novel gene defects, by overlooked structural variants, by variants in intronic, promoter or more distant regulatory regions, and represent synonymous variants of known genes contributing to the dysfunction of the respective proteins. Patients with one subgroup of IRD, namely incomplete congenital stationary night blindness (icCSNB), show a very specific phenotype. The major cause of this condition is the presence of a hemizygous pathogenic variant in CACNA1F. A comprehensive study applying direct Sanger sequencing of the gene-coding regions, exome and genome sequencing applied to a large cohort of patients with a clinical diagnosis of icCSNB revealed indeed that seven of the 189 CACNA1F-related cases have intronic and synonymous disease-causing variants leading to missplicing as validated by minigene approaches. These findings highlight that gene-locus sequencing may be a very efficient method in detecting disease-causing variants in clinically well-characterized patients with a diagnosis of IRD, like icCSNB.

[Overview of Congenital Stationary Night Blindness with Predominantly Normal Fundus Appearance]. / Überblick über die kongenitale stationäre Nachtblindheit mit überwiegend normalem Fundus.

Congenital stationary night blindness (CSNB) is a clinically and genetically heterogeneous group of non-progressive retinal disorder with largely normal fundus appearance. The mode of inheritance can be autosomal dominant (adCSNB), autosomal recessive (arCSNB) or X-chromosomal (XLCSNB). Additional ocular signs can be myopia, hyperopia, strabismus, nystagmus and reduced visual acuity. The Riggs and Schubert-Bornschein form of CSNB can be discriminated by electroretinography. While the Riggs form represents a dysfunction of the rods, a signal transmission defect from photoreceptors to bipolar cell is described in patients with the more frequently occurring Schubert-Bornschein form. The Schubert-Bornschein form can be further divided into incomplete (icCSNB) and complete (cCSNB) showing different electroretinograms (ERGs). While patients with cCSNB show a dysfunction of the ON-signaling pathway, patients with icCSNB show a dysfunction of the ON- and OFF-signaling pathways, affecting visual acuity as well. Using classical linkage, candidate gene analyses and more recent next-generation sequencing approaches, to date, mutations in 13 different genes have been associated with this disease. In vitro and in vivo models showed a correlation of the phenotype of patients with the expression, protein localization and function of the respective molecules: genes, mutated in patients with the Riggs form of CSNB have an important role in the rod phototransduction cascade. Genes mutated in patients with icCSNB, code for proteins important for glutamate neurotransmitter release at the synaptic cleft of the photoreceptors. Genes mutated in patients with cCSNB, code for proteins important for glutamate uptake and further signal transmission to the ON-bipolar cells. Preliminary in vivo studies showed that CSNB may be cured by gene therapy. These studies concerning CSNB are important for the precise diagnosis of patients with this disease, but are also helpful in deciphering key molecules essential for signal transmission from photoreceptors to bipolar cells. So far, it is a poorly understood field.

Two patients with the heterozygous R189H mutation in ACTA2 and Complex congenital heart defects expands the cardiac phenotype of multisystemic smooth muscle dysfunction syndrome.

De novo heterozygous mutations changing R179 to histidine, leucine, or cysteine in the ACTA2 gene are associated with Multisystemic Smooth Muscle Dysfunction Syndrome (MSMDS). Characteristic hallmarks of this condition, caused only by these specific ACTA2 mutations, are congenital mydriasis (mid-dilated, non-reactive pupils), a large persistent ductus arteriosus (PDA), aortic aneurysms evolving during childhood, and cerebrovascular anomalies. We describe two patients, a 3-day-old newborn and a 26-year-old woman, with this unique mutation in association with a huge PDA and an aorto-pulmonary window. In addition, one showed a coarctation of the aortic arch and the other a complete interruption of the aortic arch type A; thereby expanding the spectrum of cardiac congenital heart defect of this syndrome. Each patient displayed a huge PDA and an extra-cardiovascular phenotype consistent with MSMDS. These observations exemplify that a functional alpha 2 smooth muscle actin is necessary for proper cardiovascular organ development, and demonstrate that a very exceptional congenital heart defect (aortopulmonary window) can be caused by a mutation in a gene encoding a contractile protein of vascular smooth muscle cells. © 2017 Wiley Periodicals, Inc.

Optical Coherence Tomography (OCT) Device Independent Intraretinal Layer Segmentation.

PURPOSE: To develop and test an algorithm to segment intraretinal layers irrespectively of the actual Optical Coherence Tomography (OCT) device used. METHODS: The developed algorithm is based on the graph theory optimization. The algorithm's performance was evaluated against that of three expert graders for unsigned boundary position difference and thickness measurement of a retinal layer group in 50 and 41 B-scans, respectively. Reproducibility of the algorithm was tested in 30 C-scans of 10 healthy subjects each with the Spectralis and the Stratus OCT. Comparability between different devices was evaluated in 84 C-scans (volume or radial scans) obtained from 21 healthy subjects, two scans per subject with the Spectralis OCT, and one scan per subject each with the Stratus OCT and the RTVue-100 OCT. Each C-scan was segmented and the mean thickness for each retinal layer in sections of the early treatment of diabetic retinopathy study (ETDRS) grid was measured. RESULTS: The algorithm was able to segment up to 11 intraretinal layers. Measurements with the algorithm were within the 95% confidence interval of a single grader and the difference was smaller than the interindividual difference between the expert graders themselves. The cross-device examination of ETDRS-grid related layer thicknesses highly agreed between the three OCT devices. The algorithm correctly segmented a C-scan of a patient with X-linked retinitis pigmentosa. CONCLUSIONS: The segmentation software provides device-independent, reliable, and reproducible analysis of intraretinal layers, similar to what is obtained from expert graders. TRANSLATIONAL RELEVANCE: Potential application of the software includes routine clinical practice and multicenter clinical trials.

Mosaic synaptopathy and functional defects in Cav1.4 heterozygous mice and human carriers of CSNB2.

Mutations in CACNA1F encoding the α1-subunit of the retinal Cav1.4 L-type calcium channel have been linked to Cav1.4 channelopathies including incomplete congenital stationary night blindness type 2A (CSNB2), Åland Island eye disease (AIED) and cone-rod dystrophy type 3 (CORDX3). Since CACNA1F is located on the X chromosome, Cav1.4 channelopathies are typically affecting male patients via X-chromosomal recessive inheritance. Occasionally, clinical symptoms have been observed in female carriers, too. It is currently unknown how these mutations lead to symptoms in carriers and how the retinal network in these females is affected. To investigate these clinically important issues, we compared retinal phenotypes in Cav1.4-deficient and Cav1.4 heterozygous mice and in human female carrier patients. Heterozygous Cacna1f carrier mice have a retinal mosaic consistent with differential X-chromosomal inactivation, characterized by adjacent vertical columns of affected and non-affected wild-type-like retinal network. Vertical columns in heterozygous mice are well comparable to either the wild-type retinal network of normal mice or to the retina of homozygous mice. Affected retinal columns display pronounced rod and cone photoreceptor synaptopathy and cone degeneration. These changes lead to vastly impaired vision-guided navigation under dark and normal light conditions and reduced retinal electroretinography (ERG) responses in Cacna1f carrier mice. Similar abnormal ERG responses were found in five human CACNA1F carriers, four of which had novel mutations. In conclusion, our data on Cav1.4 deficient mice and human female carriers of mutations in CACNA1F are consistent with a phenotype of mosaic CSNB2.

Increasing the yield in targeted next-generation sequencing by implicating CNV analysis, non-coding exons and the overall variant load: the example of retinal dystrophies.

Retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA) are major causes of blindness. They result from mutations in many genes which has long hampered comprehensive genetic analysis. Recently, targeted next-generation sequencing (NGS) has proven useful to overcome this limitation. To uncover "hidden mutations" such as copy number variations (CNVs) and mutations in non-coding regions, we extended the use of NGS data by quantitative readout for the exons of 55 RP and LCA genes in 126 patients, and by including non-coding 5' exons. We detected several causative CNVs which were key to the diagnosis in hitherto unsolved constellations, e.g. hemizygous point mutations in consanguineous families, and CNVs complemented apparently monoallelic recessive alleles. Mutations of non-coding exon 1 of EYS revealed its contribution to disease. In view of the high carrier frequency for retinal disease gene mutations in the general population, we considered the overall variant load in each patient to assess if a mutation was causative or reflected accidental carriership in patients with mutations in several genes or with single recessive alleles. For example, truncating mutations in RP1, a gene implicated in both recessive and dominant RP, were causative in biallelic constellations, unrelated to disease when heterozygous on a biallelic mutation background of another gene, or even non-pathogenic if close to the C-terminus. Patients with mutations in several loci were common, but without evidence for di- or oligogenic inheritance. Although the number of targeted genes was low compared to previous studies, the mutation detection rate was highest (70%) which likely results from completeness and depth of coverage, and quantitative data analysis. CNV analysis should routinely be applied in targeted NGS, and mutations in non-coding exons give reason to systematically include 5'-UTRs in disease gene or exome panels. Consideration of all variants is indispensable because even truncating mutations may be misleading.

Automated segmentation of pathological cavities in optical coherence tomography scans.

PURPOSE: To develop and evaluate a method for automated segmentation and quantitative analysis of pathological cavities in the retina visualized by spectral-domain optical coherence tomography (SD-OCT) scans. METHODS: The algorithm is based on the segmentation of the gray-level intensities within a B-scan by a k-means cluster analysis and subsequent classification by a k-nearest neighbor algorithm. Accuracy was evaluated against three clinical experts using 130 bullous cavities identified on eight SD-OCT B-scans of three patients with wet age-related macular degeneration (AMD) and five patients with X-linked retinoschisis, as well as on one volume scan of a patient with X-linked retinoschisis. The algorithm calculated the surface area of the cavities for the B-scans and the volume of all cavities for the volume scan. In order to validate the applicability of the algorithm in clinical use, we analyzed 31 volume scans taken over the course of 4 years for one AMD patient with a serous retinal detachment. RESULTS: Discrepancies in area measurements between the segmentation results of the algorithm and the experts were within the range of the area deviations among the experts. Volumes interpolated from the B-scan series of the volume scan were comparable among experts and algorithm (0.249 mm³ for the algorithm, 0.271 mm³ for expert 1, 0.239 mm³ for expert 2, and 0.262 mm³ for expert 3). Volume changes of the serous retinal detachment were quantifiable. CONCLUSIONS: The segmentation algorithm represents a method for the automated analysis of large numbers of volume scans during routine diagnostics and in clinical trials.

Improving detection of mild loss of retinal light increment sensitivity at the posterior pole with the microperimeter MP1.

PURPOSE: With "standard" stimuli (white, Goldmann size III, 200 ms), the Nidek Microperimeter MP1 underestimates retinal light increment sensitivity (LIS). We thoroughly analyze this problem, suggest alternative settings to improve sensitivity to detect dysfunction, and provide true normal values. METHODS: LIS was tested at 55 positions in the macular region using a 4-2-1 staircase strategy with 200 ms white or red stimuli on a 1.3 cd m⁻² background. Stimulus size was Goldmann III and I, and additionally II in the healthy subjects. All participants underwent a complete ophthalmologic examination, spectral domain optical coherence tomography (OCT), and fundus autofluorescence (FAF). RESULTS: In normals, distributions of LIS for white Goldmann sizes II and III within the central 6° to 10° were clipped off at 20 dB--the MP1 cannot attenuate them any further. When the stimulus size was reduced to Goldmann I or the color changed to red, median LIS in the fovea (∼15 dB) was approximately 5 dB higher than at 10° eccentricity. Estimated from these results, central LIS for white Goldmann sizes II and III stimuli were 21 and 27 dB, respectively. In four patients with either focal or diffuse macular pathology, as confirmed by funduscopy, OCT, or FAF, reduced LIS was detected clearly with Goldmann size I stimuli, but not III. CONCLUSIONS: In all subjects reported here, standard central LIS was above the technical limit of the MP1. To measure true thresholds in healthy subjects, either smaller (Goldmann size I) or dimmer stimuli (red) must be used.

Automated segmentation of retinal blood vessels in spectral domain optical coherence tomography scans.

The correct segmentation of blood vessels in optical coherence tomography (OCT) images may be an important requirement for the analysis of intra-retinal layer thickness in human retinal diseases. We developed a shape model based procedure for the automatic segmentation of retinal blood vessels in spectral domain (SD)-OCT scans acquired with the Spectralis OCT system. The segmentation procedure is based on a statistical shape model that has been created through manual segmentation of vessels in a training phase. The actual segmentation procedure is performed after the approximate vessel position has been defined by a shadowgraph that assigns the lateral vessel positions. The active shape model method is subsequently used to segment blood vessel contours in axial direction. The automated segmentation results were validated against the manual segmentation of the same vessels by three expert readers. Manual and automated segmentations of 168 blood vessels from 34 B-scans were analyzed with respect to the deviations in the mean Euclidean distance and surface area. The mean Euclidean distance between the automatically and manually segmented contours (on average 4.0 pixels respectively 20 µm against all three experts) was within the range of the manually marked contours among the three readers (approximately 3.8 pixels respectively 18 µm for all experts). The area deviations between the automated and manual segmentation also lie within the range of the area deviations among the 3 clinical experts. Intra reader variability for the experts was between 0.9 and 0.94. We conclude that the automated segmentation approach is able to segment blood vessels with comparable accuracy as expert readers and will provide a useful tool in vessel analysis of whole C-scans, and in particular in multicenter trials.

Chromatic pupillometry dissects function of the three different light-sensitive retinal cell populations in RPE65 deficiency.

PURPOSE: The aim of the study was to objectively characterize the function of rods, cones, and intrinsic photosensitive retinal ganglion cells (ipRGCs) in patients with RPE65 mutations by using two published protocols for chromatic pupillometry, and to correlate the data with the clinical phenotype. METHODS: The study group comprised 11 patients with RPE65 mutations, and for control purposes, 32 healthy probands and 2 achromats. A custom-made binocular chromatic pupillometer (Bino I) connected to a ColorDome Ganzfeld stimulator was used to assess changes in pupil diameter in response to red (640 nm) and blue (462 nm) light stimuli. Light intensities, stimulus duration, and background varied depending on the protocol used. Results were compared to the clinical phenotype, that is, visual field (Goldmann perimetry), best corrected visual acuity, and full-field stimulus testing (FST). RESULTS: No significant differences in any of the pupil response parameters were observed in intraday or intervisit variability tests. Pupil responses to rod-weighted stimulation were significantly diminished in all RPE65 patients. Pupil responses to cone-weighted stimuli differed among RPE65 patients and did not always correlate with residual visual field and cone sensitivity loss in FST. Pupil responses to ipRGC-weighted answers were slightly but significantly diminished, and the postillumination pupil response was significantly increased. CONCLUSIONS: Chromatic pupillometry represents a highly sensitive and objective test to quantify the function of rods, cones, and ipRGCs in patients with RPE65 mutations.

Mutations in RD3 are associated with an extremely rare and severe form of early onset retinal dystrophy.

PURPOSE: To identify the underlying mutation and describe the phenotype in a consanguineous Kurdish family with Leber's congenital amaurosis (LCA)/early onset severe retinal dystrophy (EOSRD). METHODS: Members of the index family were followed up to 22 years by ophthalmological examinations, including best corrected visual acuity (BCVA), Goldmann visual field (GVF), two-color-threshold perimetry (2CTP) and Ganzfeld electroretinogram (ERG), fundus photographs, fundus autofluorescence (FAF), and optical coherence tomography (OCT). After excluding seven of nine known LCA/EOSRD genes in the index patient, linkage analysis was performed in the family using a microarray followed by microsatellite fine mapping and direct sequencing of candidate genes. RD3 was screened by direct sequencing of 85 independent patients with LCA/EOSRD presenting with a BCVA ≥ 1.0 LogMAR before the age of 2 years to assess the prevalence of RD3 mutations in LCA/EOSRD. Since RD3 and RetGC1 have a functional relation, study authors screened for a modifying effect of RD3 mutations in 17 independent patients with mutations in GUCY2D. RESULTS: BCVA was severely reduced from the earliest examinations (as early as 3 months), never exceeding 1.3 LogMAR. The disease presented as cone-rod dystrophy with dystrophic changes in the macula and bone spicules in the periphery on progression. Linkage analysis narrowed the region of interest towards the LCA12 locus. Direct sequencing of RD3 revealed a homozygous nonsense mutation (c.180C > A) in all affected members tested. Screening of additional unrelated LCA/EOSRD patients revealed only polymorphisms in RD3. CONCLUSIONS: This is the second family reported so far with mutations in RD3. Mutations in RD3 are a very rare cause of LCA associated with an extremely severe form of retinal dystrophy.

Whole-exome sequencing identifies mutations in GPR179 leading to autosomal-recessive complete congenital stationary night blindness.

Congenital stationary night blindness (CSNB) is a heterogeneous retinal disorder characterized by visual impairment under low light conditions. This disorder is due to a signal transmission defect from rod photoreceptors to adjacent bipolar cells in the retina. Two forms can be distinguished clinically, complete CSNB (cCSNB) or incomplete CSNB; the two forms are distinguished on the basis of the affected signaling pathway. Mutations in NYX, GRM6, and TRPM1, expressed in the outer plexiform layer (OPL) lead to disruption of the ON-bipolar cell response and have been seen in patients with cCSNB. Whole-exome sequencing in cCSNB patients lacking mutations in the known genes led to the identification of a homozygous missense mutation (c.1807C>T [p.His603Tyr]) in one consanguineous autosomal-recessive cCSNB family and a homozygous frameshift mutation in GPR179 (c.278delC [p.Pro93Glnfs(∗)57]) in a simplex male cCSNB patient. Additional screening with Sanger sequencing of 40 patients identified three other cCSNB patients harboring additional allelic mutations in GPR179. Although, immunhistological studies revealed Gpr179 in the OPL in wild-type mouse retina, Gpr179 did not colocalize with specific ON-bipolar markers. Interestingly, Gpr179 was highly concentrated in horizontal cells and Müller cell endfeet. The involvement of these cells in cCSNB and the specific function of GPR179 remain to be elucidated.

Long-term follow-up of the human phenotype in three siblings with cone dystrophy associated with a homozygous p.G461R mutation of KCNV2.

PURPOSE: To provide an up to 14-year overview of the early ocular phenotype in siblings with a homozygous p.G461R mutation in the KCNV2 gene. METHODS: Two brothers and their sister were followed-up clinically from ages 5 years, 4 years, and 2 months, respectively, including complete ophthalmological examinations. Goldmann visual fields, two-color-threshold (2CT) perimetry, color vision testing, optical coherence tomography (OCT), fundus autofluorescence (FAF), and Ganzfeld electroretinograms (ERGs) were performed according to age-related capabilities. Genetic analyses included whole genome linkage analysis, homozygosity mapping, and candidate gene sequencing. RESULTS: All three siblings were homozygous for the p.G461R mutation. At 5 months, the younger brother had no nystagmus and Teller-acuity of 3.2 cyc/deg. At older age, all three presented nystagmus, increased light sensitivity, reduced color discrimination, and relative central scotomas. Visual acuities ranged from 20/200 to 20/70. The macula developed minor irregularities of the RPE, thinning in optical coherence tomography, and a ring of increased FAF. Scotopic (rod) sensitivity was reduced by 2 log and photopic sensitivity by 1 log in two-color-threshold perimetry. ERG responses were markedly delayed. Photopic amplitudes were severely reduced. Scotopic b-waves rose steeply with flash intensity, but for the standard flash supernormal amplitudes were only reached in the girl. CONCLUSIONS: FAF was similar to that in cone-rod dystrophy. Although cone dysfunction was accompanied by rod dysfunction, and scotopic ERGs in patient 2 deteriorated, no patient demonstrated any unequivocal sign of rod degeneration. Grossly delayed b-waves with a steep response-versus-intensity relationship rather than supernormal amplitudes should remind clinicians of this specific condition.

Large deletions of the KCNV2 gene are common in patients with cone dystrophy with supernormal rod response.

Cone dystrophy with supernormal rod response (CDSRR) is considered to be a very rare autosomal recessive retinal disorder. CDSRR is associated with mutations in KCNV2, a gene that encodes a modulatory subunit (Kv8.2) of a voltage-gated potassium channel. In this study, we found that KCNV2 mutations are present in a substantial fraction (2.2-4.3%) of a sample of 367 independent patients with a variety of initial clinical diagnoses of cone malfunction, indicating that CDSRR is underdiagnosed and more common than previously thought. In total, we identified 20 different KCNV2 mutations; 15 of them are novel. A new finding of this study is the substantial proportion of large deletions at the KCNV2 locus that accounts for 15.5% of the mutant alleles in our sample. We determined the breakpoints and size of all five different deletions, which ranged between 10.9 and 236.8 kb. Two deletions encompass the entire KCNV2 gene and one also includes the adjacent VLDLR gene. Furthermore, we investigated N-terminal amino acid substitution mutations for its effect on interaction with Kv2.1 using yeast two-hybrid technology. We found that these mutations dramatically reduce or abolish this interaction suggesting a lack of assembly of heteromeric Kv channels as one underlying pathomechanism of CDSRR.