Novel TTLL5 Variants Associated with Cone-Rod Dystrophy and Early-Onset Severe Retinal Dystrophy.

Variants of the TTLL5 gene, which encodes tubulin tyrosine ligase-like family member five, are a rare cause of cone dystrophy (COD) or cone-rod dystrophy (CORD). To date, only a few TTLL5 patients have been clinically and genetically described. In this study, we report five patients harbouring biallelic variants of TTLL5. Four adult patients presented either COD or CORD with onset in the late teenage years. The youngest patient had a phenotype of early onset severe retinal dystrophy (EOSRD). Genetic analysis was performed by targeted next generation sequencing of gene panels and assessment of copy number variants (CNV). We identified eight variants, of which six were novel, including two large multiexon deletions in patients with COD or CORD, while the EOSRD patient harboured the novel homozygous p.(Trp640*) variant and three distinct USH2A variants, which might explain the observed rod involvement. Our study highlights the role of TTLL5 in COD/CORD and the importance of large deletions. These findings suggest that COD or CORD patients lacking variants in known genes may harbour CNVs to be discovered in TTLL5, previously undetected by classical sequencing methods. In addition, variable phenotypes in TTLL5-associated patients might be due to the presence of additional gene defects.

AUTOSOMAL DOMINANT VITREORETINOCHOROIDOPATHY: When Molecular Genetic Testing Helps Clinical Diagnosis.

PURPOSE: Autosomal dominant vitreoretinochoroidopathy is an extremely rare disease, which belongs to the BEST1-related disease spectrum. METHODS: Report of five patients with an initial diagnosis of atypical rod-cone dystrophy, for whom autosomal dominant vitreoretinochoroidopathy was retrospectively diagnosed on genetic results using targeted next-generation sequencing. Each patient had a comprehensive ophthalmic examination including multimodal retinal imaging and functional evaluation. RESULTS: Visual acuity ranged from <20/800 to 20/25. Two patients had narrowed angle with history of acute angle-closure glaucoma for one patient. Full-field electroretinogram showed severe reduction of both scotopic and photopic responses for 3/5 patients. Electrooculogram could be performed for one of the two patients with moderate alterations of full-field electroretinogram. It revealed severe light rise abnormalities with decreased Arden ratio (125% right eye, 145% left eye) in keeping with generalized severe dysfunction of the retinal pigment epithelium. On fundoscopy, the pathognomonic circumferential hyperpigmented band of the peripheral retina was totally absent in two patients. CONCLUSION: This report highlights the high phenotypic variability of autosomal dominant vitreoretinochoroidopathy, which may be misdiagnosed, especially in advanced forms with severe generalized photoreceptor dysfunction mimicking retinitis pigmentosa. Targeted next-generation sequencing can contribute to the proper clinical diagnosis, especially in case of atypical phenotypic features of autosomal dominant vitreoretinochoroidopathy.

Phenotype Analysis of Retinal Dystrophies in Light of the Underlying Genetic Defects: Application to Cone and Cone-Rod Dystrophies.

Phenotypes observed in a large cohort of patients with cone and cone-rod dystrophies (COD/CORDs) are described based on multimodal retinal imaging features in order to help in analyzing massive next-generation sequencing data. Structural abnormalities of 58 subjects with molecular diagnosis of COD/CORDs were analyzed through specific retinal imaging including spectral-domain optical coherence tomography (SD-OCT) and fundus autofluorescence (BAF/IRAF). Findings were analyzed with the underlying genetic defects. A ring of increased autofluorescence was mainly observed in patients with CRX and GUCY2D mutations (33% and 22% of cases respectively). "Speckled" autofluorescence was observed with mutations in three different genes (ABCA4 64%; C2Orf71 and PRPH2, 18% each). Peripapillary sparing was only found in association with mutations in ABCA4, although only present in 40% of such genotypes. Regarding SD-OCT, specific outer retinal abnormalities were more commonly observed in particular genotypes: focal retrofoveal interruption and GUCY2D mutations (50%), foveal sparing and CRX mutations (50%), and outer retinal atrophy associated with hyperreflective dots and ABCA4 mutations (69%). This study outlines the phenotypic heterogeneity of COD/CORDs hampering statistical correlations. A larger study correlating retinal imaging with genetic results is necessary to identify specific clinical features that may help in selecting pathogenic variants generated by high-throughput sequencing.

MERTK mutation update in inherited retinal diseases.

MER tyrosine kinase (MERTK) encodes a surface receptor localized at the apical membrane of the retinal pigment epithelium. It plays a critical role in photoreceptor outer segment internalization prior to phagocytosis. Mutations in MERTK have been associated with severe autosomal recessive retinal dystrophies in the RCS rat and in humans. We present here a comprehensive review of all reported MERTK disease causing variants with the associated phenotype. In addition, we provide further data and insights of a large cohort of 1,195 inherited retinal dystrophies (IRD) index cases applying state-of-the-art genotyping techniques and summarize current knowledge. A total of 79 variants have now been identified underlying rod-cone dystrophy and cone-rod dystrophy including 11 novel variants reported here. The mutation spectrum in MERTK includes 33 missense, 12 nonsense, 12 splice defects, 12 small deletions, two small insertion-deletions, three small duplications, and two exonic and three gross deletions. Altogether, mutations in MERTK account for ∼2% of IRD cases with a severe retinal phenotype. These data are important for current and future therapeutic trials including gene replacement therapy or cell-based therapy.

Intravitreal dexamethasone implant (Ozurdex) for macular edema secondary to retinitis pigmentosa.

BACKGROUND: To evaluate the anatomical and functional outcomes of intravitreal dexamethasone implant in patients with macular edema (ME) secondary to retinitis pigmentosa (RP). METHODS: Three patients (four eyes), aged 24 to 46 years, presented with refractory ME secondary to RP. Intravitreal dexamethasone implant (Ozurdex) was administered to treat ME. The anatomical (central macular thickness [CMT]) and functional (best-corrected visual acuity [BCVA]) outcomes as well as adverse events were recorded. RESULTS: All patients completed 6 months follow-up. After intravitreal Ozurdex all patients showed regression of ME. At baseline, mean CMT was 443 ± 185 µm (range 213-619 µm); ME improved to 234 ± 68 µm (range 142-307 µm) at 1 month, to 332 ± 177 µm (range 139-513 µm) at 3 months, and to 305 ± 124 µm (range 144-447 µm) at 6 months. Recurrent ME was recorded in 2 patients (both patients at 3 months from intravitreal dexamethasone implant). Retreatment with intravitreal Ozurdex was performed in two patients. Mean BCVA improved form 20/160 (range 20/50-20/200) (baseline) to 20/100 (range 20/40-20/125) at 1 month, to ∼20/125 (range 20/100-20/200) at 3 months, and to ∼ 20/125 (range 20/100-20/160) at 6 months. No serious ocular and systemic adverse events were observed during the study period. CONCLUSIONS: Intravitreal dexamethasone implant provides anatomic and functional improvements and may represent a valuable treatment option for patients with ME secondary to RP.

Non-vasogenic cystoid maculopathies.

Besides cystoid macular edema due to a blood-retinal barrier breakdown, another type of macular cystoid spaces referred to as non-vasogenic cystoid maculopathies (NVCM) may be detected on optical coherence tomography but not on fluorescein angiography. Various causes may disrupt retinal cell cohesion or impair retinal pigment epithelium (RPE) and Müller cell functions in the maintenance of retinal dehydration, resulting in cystoid spaces formation. Tractional causes include vitreomacular traction, epiretinal membranes and myopic foveoschisis. Surgical treatment does not always allow cystoid space resorption. In inherited retinal dystrophies, cystoid spaces may be part of the disease as in X-linked retinoschisis or enhanced S-cone syndrome, or occur occasionally as in bestrophinopathies, retinitis pigmentosa and allied diseases, congenital microphthalmia, choroideremia, gyrate atrophy and Bietti crystalline dystrophy. In macular telangiectasia type 2, cystoid spaces and cavitations do not depend on the fluid leakage from telangiectasia. Various causes affecting RPE function may result in NVCM such as chronic central serous chorioretinopathy and paraneoplastic syndromes. Non-exudative age macular degeneration may also be complicated by intraretinal cystoid spaces in the absence of fluorescein leakage. In these diseases, cystoid spaces occur in a context of retinal cell loss. Various causes of optic atrophy, including open-angle glaucoma, result in microcystoid spaces in the inner nuclear layer due to a retrograde transsynaptic degeneration. Lastly, drug toxicity may also induce cystoid maculopathy. Identifying NVCM on multimodal imaging, including fluorescein angiography if needed, allows guiding the diagnosis of the causative disease and choosing adequate treatment when available.

Sickle Cell Maculopathy: Microstructural Analysis Using OCTA and Identification of Genetic, Systemic, and Biological Risk Factors.

PURPOSE: To identify genetic, systemic, and biological factors associated with the occurrence of sickle cell maculopathy (SCM). To evaluate microvascular macular alterations using optical coherence tomography angiography (OCTA) in sickle cell disease (SCD). DESIGN: Cross-sectional study. METHODS: One hundred fifty-one eyes of 78 adult SCD patients (43 HbSS, 30 HbSC, 4 S/ß+, and 1 HbS Lepore) and 40 eyes of 20 healthy controls underwent spectral-domain optical coherence tomography (SDOCT) and OCTA using Spectralis HRA+OCT (Heidelberg Engineering, Heidelberg, Germany). We analyzed the occurrence of SCM, the foveal avascular zone (FAZ) area, and the severity of macular ischemia and studied their relationships with genetic, systemic, and biological parameters using multivariate logistic regression analysis. RESULTS: Maculopathy occurred in 66 eyes (44%), and more frequently in HbSS patients (71%, P = .004). Multivariate analysis identified HbSS genotype and lower prothrombin ratio (PR) as independently associated with SCM (P = .01). Proliferative sickle cell retinopathy was also associated with SCM (P = .02). FAZ enlargement was associated with higher lactate dehydrogenase level (P = .02). Macular ischemia was more severe in patients with lower hemoglobin level (P = .004) and lower PR (P = .01). No flow areas were identified with OCTA even in eyes with no macular thinning (36 eyes, 42%) and appeared more frequently in the temporal superior subfield (36%). CONCLUSIONS: HbSS genotype, abnormal coagulation and hemolysis increase the risk of SCM. OCTA provides valuable criteria to identify potential risk factors of SCM. OCTA also improves detection of early microvascular changes before the onset of macular thinning.

Partial recovery of visual function in a blind patient after optogenetic therapy.

Optogenetics may enable mutation-independent, circuit-specific restoration of neuronal function in neurological diseases. Retinitis pigmentosa is a neurodegenerative eye disease where loss of photoreceptors can lead to complete blindness. In a blind patient, we combined intraocular injection of an adeno-associated viral vector encoding ChrimsonR with light stimulation via engineered goggles. The goggles detect local changes in light intensity and project corresponding light pulses onto the retina in real time to activate optogenetically transduced retinal ganglion cells. The patient perceived, located, counted and touched different objects using the vector-treated eye alone while wearing the goggles. During visual perception, multichannel electroencephalographic recordings revealed object-related activity above the visual cortex. The patient could not visually detect any objects before injection with or without the goggles or after injection without the goggles. This is the first reported case of partial functional recovery in a neurodegenerative disease after optogenetic therapy.

Size and vitreomacular attachment of primary full-thickness macular holes.

PURPOSE: To study the relationship between the size of primary full-thickness macular hole (MH) and the vitreomacular attachment status. DESIGN: Single-centre retrospective observational case series. METHODS: The records of 100 consecutive eyes operated for primary full-thickness MH were retrospectively reviewed. The vitreous status and MH diameter were assessed on the preoperative optical coherence tomography scans. MH were classified depending on the presence or absence of vitreomacular traction (VMT) and their size as small (<250 µm), medium (250-400 µm) and large (>400 µm), as suggested in the International VMT Study Group Classification. RESULTS: 22% of MH had VMT and 13% had both VMT and a diameter <400 µm. The MH diameter was not significantly different depending on the presence or absence of VMT (respectively, 339±134 and 423±191 µm (p=0.094)), with large overlap between groups. Small, medium and large MH were similarly distributed regardless of the presence or absence of VMT (p=0.69). CONCLUSIONS: Our series of 100 MH did not reveal any significant relationship between the MH size and the presence or absence of VMT. Only 13% of MH had VMT and a diameter <400 mm, then were eligible for intravitreal ocriplasmin as a possible treatment.

Next-generation sequencing applied to a large French cone and cone-rod dystrophy cohort: mutation spectrum and new genotype-phenotype correlation.

BACKGROUND: Cone and cone-rod dystrophies are clinically and genetically heterogeneous inherited retinal disorders with predominant cone impairment. They should be distinguished from the more common group of rod-cone dystrophies (retinitis pigmentosa) due to their more severe visual prognosis with early central vision loss. The purpose of our study was to document mutation spectrum of a large French cohort of cone and cone-rod dystrophies. METHODS: We applied Next-Generation Sequencing targeting a panel of 123 genes implicated in retinal diseases to 96 patients. A systematic filtering approach was used to identify likely disease causing variants, subsequently confirmed by Sanger sequencing and co-segregation analysis when possible. RESULTS: Overall, the likely causative mutations were detected in 62.1 % of cases, revealing 33 known and 35 novel mutations. This rate was higher for autosomal dominant (100 %) than autosomal recessive cases (53.8 %). Mutations in ABCA4 and GUCY2D were responsible for 19.2 % and 29.4 % of resolved cases with recessive and dominant inheritance, respectively. Furthermore, unexpected genotype-phenotype correlations were identified, confirming the complexity of inherited retinal disorders with phenotypic overlap between cone-rod dystrophies and other retinal diseases. CONCLUSIONS: In summary, this time-efficient approach allowed mutation detection in the most important cohort of cone-rod dystrophies investigated so far covering the largest number of genes. Association of known gene defects with novel phenotypes and mode of inheritance were established.

Targeted next generation sequencing identifies novel mutations in RP1 as a relatively common cause of autosomal recessive rod-cone dystrophy.

We report ophthalmic and genetic findings in families with autosomal recessive rod-cone dystrophy (arRCD) and RP1 mutations. Detailed ophthalmic examination was performed in 242 sporadic and arRCD subjects. Genomic DNA was investigated using our customized next generation sequencing panel targeting up to 123 genes implicated in inherited retinal disorders. Stringent filtering coupled with Sanger sequencing and followed by cosegregation analysis was performed to confirm biallelism and the implication of the most likely disease causing variants. Sequencing identified 9 RP1 mutations in 7 index cases. Eight of the mutations were novel, and all cosegregated with severe arRCD phenotype, found associated with additional macular changes. Among the identified mutations, 4 belong to a region, previously associated with arRCD, and 5 others in a region previously associated with adRCD. Our prevalence studies showed that RP1 mutations account for up to 2.5% of arRCD. These results point out for the necessity of sequencing RP1 when genetically investigating sporadic and arRCD. It further highlights the interest of unbiased sequencing technique, which allows investigating the implication of the same gene in different modes of inheritance. Finally, it reports that different regions of RP1 can also lead to arRCD.

Ophthalmologic impairment during adulthood in central congenital hypoventilation syndrome: a longitudinal cohort analysis of nine patients.

BACKGROUND: Congenital central hypoventilation syndrome (CCHS) is a rare dysgenetic form of neurocristopathy associated with dysfunction of the autonomic nervous system. Ophthalmologic abnormalities are reported in CCHS children, and range from pupillary and iris abnormalities to ptosis, strabismus and convergence deficiency. Since earlier CCHS diagnosis and multidisciplinary management, combined with improved ventilatory support techniques, the lifespan of children with CCHS has been considerably lengthened. The oldest of them have now reached adult age and we report in this study the results of their ophthalmologic examination. MATERIALS AND METHODS: Nine CCHS adult patients were prospectively included during a 14-month period. Each patient underwent complete ophthalmologic examination, static pupillometry with scotopic and photopic pupillary diameter (PD) measures, Humphrey 24-2 visual field analysis, macular OCT and complete orthoptic assessment including a Hess-Lancaster test. RESULTS: Ophthalmologic abnormalities were found in six of the nine patients (66%). The main features were strabismus in six patients (66%). Four patients (44%) displayed abnormal pupillary function, with a decrease in average scotopic PD (3.8 ± 1.4 mm), average photopic PD (3.5 ± 1.2 mm), and average percentage of pupillary constriction (7.6 ± 8.5%). Three patients (33%) exhibited iris abnormalities such as iris atrophy, smooth iris surface and atrophic sphincter. CONCLUSION: This study allowed the description of ophthalmologic abnormalities occurring in CCHS in a series of adult patients, thus improving current knowledge of the disease. The prevalence of pupillary and iris lesions were lower than those observed in a series of children, suggesting that they could be considered as systemic disease severity markers.