Comprehensive Genotyping and Phenotyping Analysis of GUCY2D-Associated Rod- and Cone-Dominated Dystrophies.

PURPOSE: To describe the genetic and clinical spectrum of GUCY2D-associated retinopathies and to accurately establish their prevalence in a large cohort of patients. DESIGN: Retrospective case series. METHODS: Institutional study of 47 patients from 27 unrelated families with retinal dystrophies carrying disease-causing GUCY2D variants from the Fundación Jiménez Díaz hospital dataset of 8000 patients. Patients underwent ophthalmological examination and molecular testing by Sanger or exome sequencing approaches. Statistical and principal component analyses were performed to determine genotype-phenotype correlations. RESULTS: Four clinically different associated phenotypes were identified: 66.7% of families with cone/cone-rod dystrophy, 22.2% with Leber congenital amaurosis, 7.4% with early-onset retinitis pigmentosa, and 3.7% with congenital night blindness. Twenty-three disease-causing GUCY2D variants were identified, including 6 novel variants. Biallelic variants accounted for 28% of patients, whereas most carried dominant alleles associated with cone/cone-rod dystrophy. The disease onset had statistically significant differences according to the functional variant effect. Patients carrying GUCY2D variants were projected into 3 subgroups by allelic combination, disease onset, and presence of nystagmus or night blindness. In contrast to patients with the most severe phenotype of Leber congenital amaurosis, 7 patients with biallelic GUCY2D had a later and milder rod form with night blindness in infancy as the first symptom. CONCLUSIONS: This study represents the largest GUCY2D cohort in which 4 distinctly different phenotypes were identified, including rare intermediate presentations of rod-dominated retinopathies. We established that GUCY2D is linked to about 1% of approximately 3000 molecularly characterized families of our cohort. All of these findings are critical for defining cohorts for inclusion in future clinical trials.

Unilateral cataract and congenital stationary night blindness in a child with novel variants in TRPM1.

Unilateral cataract can cause pediatric vision impairment. Although the majority of unilateral cataracts are idiopathic in nature, genetic causes have been reported. We present the case of a 4-week-old child of nonconsanguineous parents who was affected with unilateral cataract. Whole-genome sequencing using DNA extracted from blood and the lens epithelial cells following cataract surgery revealed two presumed pathogenic variants in the TRPM1 gene, the founding member of the melanoma-related transient receptor potential (TRPM) subfamily. TRPM1 is responsible for regulating cation influx to hyperpolarized retinal ON bipolar cells, and mutations in this gene are a major cause of autosomal recessive congenital stationary night blindness (CSNB). Electroretinography revealed findings consistent with CSNB, a phenotype that was not initially suspected, and which would likely have been missed without genome sequencing. It remains unclear whether the TRPM1 variants are associated with the cataract phenotype.

Mutation analysis reveals novel and known mutations in SAG gene in first two Egyptian families with Oguchi disease.

BACKGROUND: Oguchi disease is a rare type of congenital stationary night blindness associated with an abnormal fundus appearance. It is inherited in an autosomal recessive manner where two types exist according to the gene affected; type 1 associated with S-antigen (SAG) gene mutations and type 2 associated with rhodopsin kinase (GRK1) gene mutations. PURPOSE: The aim of this work was to describe the clinical and genetic findings of the first two reported families of Oguchi disease in Egypt and African region. METHODS: Four members of two consanguineous Egyptian families with history of night blindness since childhood underwent complete ophthalmological examination, standard automated static perimetry, fundus color photography, fundus autofluorescence (FAF), fundus fluorescein angiography (FFA) in light-adapted state and spectral-domain optical coherence tomography (SD-OCT) of both the macula and the optic nerve head as well as central corneal thickness with repeated fundus photography following prolonged dark adaptation. Mutation screening of 7 coding exons of GRK1 gene and 15 coding exons of SAG gene as well as some flanking regions were performed using Sanger sequencing technique. The variants were tested for pathogenicity using different in silico functional analysis tools. RESULTS: The clinical examination and investigations confirmed Oguchi disease phenotype. One patient showed p.R193* (c.577C > T) which is a previously reported SAG gene mutation in a homozygous form. The other three patients from a different family showed (c.649-1 G > C), a novel canonical splice site SAG gene mutation in a homozygous form. CONCLUSION: The identification of the novel canonical splice site SAG gene variant in three members of the same family with clinically confirmed Oguchi disease reinforces its pathogenicity. A fourth patient from another family carried a previously reported mutation in the same gene. SAG gene variants may be the underlying genetic cause for Oguchi disease in Egypt. Our findings have expanded the spectrum of Oguchi disease-associated mutations in SAG gene and may serve as a basis for genetic diagnosis for Oguchi disease.

Electronegative electroretinogram in the modern multimodal imaging era.

BACKGROUND: The electronegative electroretinogram (ERG) reflecting inner retinal dysfunction can assist as a diagnostic tool to determine the anatomical location in eye disease. The aim of this study is to determine the frequency and aetiology of electronegative ERG in a tertiary ophthalmology centre and to develop a clinical algorithm to assist patient management. METHODS: Retrospective review of ERGs performed at the Save Sight Institute from January 2011 to December 2020. ERGs were performed according to ISCEV standard. The b:a ratio was analysed in dark adapted (DA) 3.0 or 12.0 recordings. Patients with ratio of ≤1.0 were included. RESULTS: A total of 4421 patients had ERGs performed during study period, of which 139 patients (3.1%) had electronegative ERG. The electronegative ERG patients' median age at referral time was 37 (0.7-90.6) years. The causative aetiologies were photoreceptor dystrophy (48, 34.5%), Congenital Stationary Night Blindness (CSNB) (33, 23.7%), retinal ischemia (18, 12.9%), retinoschisis (15, 10.8%), paraneoplastic autoimmune retinopathy (PAIR) and nonPAIR (14, 10.1%), batten disease (4, 2.9%), and inflammatory retinopathy (4, 2.9%). There were three patients with an unclassified diagnosis. Thirty-two patients (23%) had good vision and a normal fundus appearance. Eleven patients (7.9%) had good vision and normal results in all multimodal imaging. CONCLUSIONS: The frequency of electronegative ERG in our referral centre was 3.1% with photoreceptor dystrophy as the main aetiology. A significant number of the cases had good vision with normal fundus or normal multimodal imaging. This further highlights the value of an ERG in this modern multimodal imaging era.

Negative electroretinograms: genetic and acquired causes, diagnostic approaches and physiological insights.

The dark-adapted human electroretinogram (ERG) response to a standard bright flash includes a negative-going a-wave followed by a positive-going b-wave that crosses the baseline. An electronegative waveform (or negative ERG) results when the b-wave is selectively reduced such that the ERG fails to cross the baseline following the a-wave. In the context of a normally sized a-wave, it indicates a site of retinal dysfunction occurring after phototransduction (commonly at the photoreceptor to bipolar cell synapse). This is an important finding. In genetic disease, the pattern of ERG abnormality can point to variants in a small group of genes (frequently those associated with congenital stationary night blindness and X-linked retinoschisis, but negative ERGs can also be seen in other conditions including syndromic disease). In acquired disease, there are numerous causes, but specific features may point to melanoma-associated retinopathy (MAR). In some cases, the visual symptoms precede the diagnosis of the melanoma and so the ERG findings can initiate investigations facilitating early detection and treatment. Negative ERGs can occur in other paraneoplastic conditions, and in a range of other diseases. This review will outline the physiological basis for the negative ERG, report prevalences in the literature from different cohorts, discuss the range of causes, displaying examples of a number of ERG phenotypes, highlight features of a clinical approach to patients, and briefly discuss further insights relating to current flows shaping the a-wave trough and from single-cell transcriptome analysis.

Serum concentration of vitamin A and its relationship with body adiposity, oxidative stress, and cardiovascular risk in women with recommended dietary intake of vitamin A.

INTRODUCTION: Background: evidence indicates a role of vitamin A in the regulation of fat mass influencing obesity and cardiovascular diseases. Material and methods: a cross-sectional study in 200 women, paired by age and by the recommended dietary intake of vitamin A. Subjects were divided into four groups according to body mass index (BMI): 80 eutrophic (E), 40 overweight (OW), 40 class I obesity (OI) and 40 class II obesity (OII). Lipid and glycemic profiles were measured and oxidative stress was evaluated through serum concentrations of uric acid, glutathione peroxidase (GSH-Px), and thiobarbituric acid reactive substances (TBARS). Results: the cutoff points for deficiency of serum retinol and ß-carotene levels were < 1.05 µmol/L and 40 µg/dL, respectively. For the recommended dietary intake of vitamin A it was 700 µg/day. Retinol and ß-carotene deficiency was found in the E group at 5 % and 15 %, respectively, reaching 77.5 % and 82.5 % in the OII group. Conclusions: a correlation was observed between serum concentrations of retinol and ß-carotene and glycemic, lipid, and markers of oxidative stress profiles in the groups studied. It was observed that OI and OII subjects who had retinol and ß-carotene deficiency presented a risk that was 16 and 20.7 times greater, respectively, of having a diagnosis with DM2 as compared to E subjects with adequate concentrations of vitamin A. Increased demand of vitamin A may be related to increased BMI, body adiposity, and oxidative stress even when a recommended intake of vitamin A is reached.

INTRODUCCIÓN: Introducción: la evidencia indica un papel de la vitamina A en la regulación de la masa grasa que influye en la obesidad y las enfermedades cardiovasculares. Material y métodos: estudio transversal con 200 mujeres emparejadas por edad y por la ingesta dietética de vitamina A recomendada. Se dividieron en cuatro grupos según el índice de masa corporal (IMC): 80 eutróficas (E), 40 con sobrepeso (OW), 40 con obesidad de clase I (OI) y 40 con obesidad de clase II (OII). Se midieron los perfiles lipídicos y glucémicos y se evaluó el estrés oxidativo a través de las concentraciones séricas de ácido úrico, glutatión-peroxidasa (GSH-Px) y sustancias reactivas del ácido tiobarbitúrico (TBARS). Resultados: los puntos de corte para la deficiencia de las concentraciones séricas de retinol y caroteno fueron de 1,05 µmol/L y 40 g/dL, respectivamente. Para la ingesta dietética recomendada de vitamina A fue de 700 g/día. Se encontró deficiencia de retinol y caroteno en el grupo E, del 5 % y 15 %, respectivamente, alcanzando un 77,5 % y 82,5 % en el grupo OII. Conclusiones: se observó correlación entre las concentraciones séricas de retinol y caroteno y los perfiles glucémico, lipídico y de marcadores de perfiles de estrés oxidativo en los grupos estudiados. Se observó que los sujetos con OI y OII que tenían deficiencia de retinol y caroteno presentaban un riesgo 16 y 20,7 veces mayor, respectivamente, de ser diagnosticados de DM2 en comparación con los E con concentraciones adecuadas de vitamina A. El aumento de la demanda de vitamina A puede estar relacionado con el aumento del IMC, la adiposidad corporal y el estrés oxidativo, incluso cuando se alcanza la ingesta recomendada de vitamina A.

Night Blindness in a Healthy Middle-Class Child.

How do you clinically approach a night-blind child in a vegetarian family, with no obvious dystrophy and no obvious malnutrition? This case reviews some of the issues, and it reminds us of some of the cautions. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:286-288.].

Night Blindness in Cystic Fibrosis: The Key Role of Vitamin A in the Digestive System.

Vitamin A is a fundamental micronutrient that regulates various cellular patterns. Vitamin A deficiency (VAT) is a worldwide problem and the primary cause of nocturnal blindness especially in low income countries. Cystic fibrosis (CF) is a known risk factor of VAD because of liposoluble vitamin malabsorption due to pancreatic insufficiency. We describe a case of a 9-year-old girl who experienced recurrent episodes of nocturnal blindness due to profound VAD. This little girl is paradigmatic for the explanation of the key role of the gut-liver axis in vitamin A metabolism. She presents with meconium ileus at birth, requiring intestinal resection that led to a transient intestinal failure with parenteral nutrition need. In addition, she suffered from cholestatic liver disease due to CF and intestinal failure-associated liver disease. The interaction of pancreatic function, intestinal absorption and liver storage is fundamental for the correct metabolism of vitamin A.

Novel findings in enhanced S-cone syndrome: a case with macular retinal neovascularization and severe retinal vasculitis.

PURPOSE: To describe a novel association of enhanced S-cone syndrome (ESCS) with macular retinal neovascularization and severe retinal vasculitis. METHODS: Clinical examination, spectral domain optical coherence tomography, fluorescein angiography, fundus autofluorescence, infrared reflectance and electroretinography were used to study a 25-year-old male with a history of night blindness from early childhood and recent accelerated visual loss in right eye. RESULTS: Pigmented lesions were observed along the arcades without peripheral retinal involvement. Intraretinal cystoid spaces, retinal neovascularization of posterior pole and severe peripheral and posterior retinal vasculitis were found on clinical examination and multimodal imaging. Based on characteristic clinical and electroretinographic findings, a diagnosis of ESCS was made. CONCLUSION: This case highlights novel associations of retinal neovascularization and vasculitis with ESCS.

Case Report: Vitamin A Deficiency and Nyctalopia in a Patient with Chronic Pancreatitis.

SIGNIFICANCE: Vitamin A deficiency is a known concern in developing countries, but it is often overlooked in developed regions. A history of conditions causing alimentary malabsorption should be considered when patients present with complaints of nyctalopia. PURPOSE: A case of vitamin A deficiency with nyctalopia in a patient with chronic pancreatitis including pertinent diagnostic testing, treatment, and management is presented. The intent is to draw attention to the condition as a differential diagnosis for nyctalopia due to increased prevalence of conditions causing malabsorption. CASE REPORT: A patient with a history of chronic pancreatitis and pancreatic tumor presented with symptoms of nyctalopia and xerophthalmia. Given his systemic history, testing was ordered to determine serum vitamin A levels and retinal function. After results had confirmed depleted vitamin A levels and diminished retinal function, treatment with both oral and intramuscular vitamin A supplementation was initiated to normalize vitamin A levels and improve retinal photoreceptor function. Subjective improvement in symptoms was reported shortly after beginning supplementation, and ultimately, vitamin A levels and retinal function showed improvement after intramuscular treatment. CONCLUSIONS: Detailed case history and a careful review of systems along with serum vitamin A testing and, if available, electroretinography to assess retinal function can help to make a definitive diagnosis. With appropriate comanagement with the patient's primary care physician, it is possible for those with nyctalopia to begin vitamin A supplementation and regain retinal function.

Case Report: Delayed Vitamin A Retinopathy Secondary to Bariatric Surgery.

SIGNIFICANCE: Although rare, vitamin A retinopathy should be considered by the clinicians in their differentials for conditions that can lead to nyctalopia, especially in those patients who have undergone bariatric surgery. Patients must be educated on this potential delayed adverse effect of the surgery and possible lifelong vitamin A supplementation. PURPOSE: The purpose of this study was to report a rare case of delayed vitamin A retinopathy that occurred because of vitamin A malabsorption secondary to bariatric surgery. CASE REPORT: A 55-year-old woman presented with nyctalopia and dark adaptation problems. The patient had a history of gastric bypass surgery 22 years earlier. Fundus examination revealed a large number of small white dots in the midperiphery of both eyes. Electrophysiology testing revealed flat-lined scotopic responses. Vitamin A levels were found to be severely reduced. Subsequent vitamin A supplementation resulted in the reversal of all signs and symptoms. CONCLUSIONS: This case report demonstrates the importance of considering vitamin A deficiency in patients who present with symptoms of nyctalopia with a history of bariatric surgery. Clinicians should be aware of a possible delayed onset and refer for appropriate testing and treatment, as vitamin A retinopathy has been shown to be reversible. Because other conditions can present with nyctalopia and retinal white spots, clinicians also need to consider the appropriate differential diagnoses. Lifelong monitoring is indicated because reoccurrences have been reported.

Novel truncating mutation in CACNA1F in a young male patient diagnosed with optic atrophy.

BACKGROUND: Low vision in children can be accompanied by pallor of the optic disc with little or no characteristic morphologic changes of the retina. A variety of diseases can be the underlying cause, including hereditary optic atrophy, Leber's congenital amaurosis (LCA), achromatopsia, and calcium channel, voltage-dependent, L-type, alpha-1F subunit gene (CACNA1F)-associated retinopathy (most widely known as incomplete congenital stationary night blindness: iCSNB). Differentiation at early age is desirable due to large differences in prognosis, but may be difficult because phenotypes overlap and electrophysiological testing is challenging in young patients. We present the case of a 6-year-old boy with unexplained low vision and pallor of the optic disc who originally had been diagnosed with hereditary optic atrophy in the absence of recordable full-field electroretinography (ERG) due to poor patient cooperation. MATERIALS AND METHODS: Standard Sanger sequencing excluded mutations in the OPA1 gene (autosomal-dominant optic atrophy). To identify the underlying genetic cause, whole-exome sequencing was performed on patient's DNA. Recording of the full-field ERG was successfully performed 6 months later. RESULTS: We identified a novel truncating mutation in CACNA1F gene (NM_001256789: c.3895C > T in exon 33) which led to the correct diagnosis of CACNA1F-associated retinopathy in the young boy. ERG recordings showed a negative scotopic mixed response with preserved oscillatory potentials and a flicker ERG with reduced amplitude and biphasic waveform, compatible with a CACNA1F-asssociated phenotype. CONCLUSIONS: We show that genetic testing may help to differentiate between optic atrophy, LCA, and CACNA1F-associated retinopathy at a much earlier age, in absence of electrophysiological examination and by widely overlapping phenotypes.

Maternal uniparental isodisomy of chromosome 6 unmasks a novel variant in TULP1 in a patient with early onset retinal dystrophy.

Purpose: Inherited retinal dystrophies are a clinically and genetically heterogeneous group of disorders. Molecular diagnosis has proven utility for affected individuals. In this study, we report an individual enrolled in the Australian Inherited Retinal Disease Registry and DNA Bank diagnosed with clinical features overlapping between Leber congenital amaurosis and retinitis pigmentosa. Methods: DNA from the proband was sequenced using a gene panel for inherited retinal disorders, and a single nucleotide polymorphism (SNP) array was conducted to detect the presence of deletions and uniparental disomy. Results: We identified a novel homozygous variant (c.524dupC, p.(Pro176ThrfsTer7)) in TULP1 resulting from maternal uniparental isodisomy of chromosome 6. The patient had clinical features consistent with biallelic pathogenic variants in TULP1, including congenital nystagmus, night blindness, non-recordable electroretinogram, mild myopia, and mild peripheral pigmentary changes in the fundus. Conclusions: This is the first report of uniparental disomy 6 and a homozygous variant in TULP1 associated with a rod-cone dystrophy. Molecular diagnosis of inherited retinal dystrophies is essential to inform the mode of transmission and clinical management, and to identify potential candidates for future gene-specific therapies.

The importance of genetic testing as demonstrated by two cases of CACNA1F-associated retinal generation misdiagnosed as LCA.

PURPOSE: To describe in detail cases with an initial diagnosis of Leber congenital amaurosis that were later found to have a hemizygous mutation in the CACNA1F gene. METHODS: The patients underwent a detailed ophthalmological evaluation and full-field electroretinography (ERG). Selective targeted capture and whole-exome next-generation sequencing (NGS) were used to find the disease-causing mutations. RESULTS: Patient 1 presented at age 3 months with nystagmus, normal visual attention, and a normal fundus exam. ERG responses were severely decreased. Patient 2 presented with nystagmus, severe hyperopia, esotropia, and visual acuity of 20/360 oculus dexter (OD) and 20/270 oculus sinister (OS) at age 5 months. His fundus exam showed slightly increased pigmentation around the foveae. The scotopic ERG responses were severely decreased and photopic responses mildly decreased. Based on the initial presentation, both patients received the clinical diagnosis of Leber congenital amaurosis (LCA). However, genetic testing showed no mutations in known LCA genes. Instead, broader genetic testing using NGS showed point mutations in the CACNA1F gene, which is reported to be associated with type 2 congenital stationary night blindness (CSNB2). CONCLUSIONS: These two cases demonstrate the clinical overlap between LCA and CSNB in infants and young children. Genetic testing is an essential tool in these cases and provides a more accurate diagnosis and prognosis for patients with inherited retinal degenerative disorders.

Mizuo-Nakamura Phenomena.

A 21-year-old male presented with a chief complaint of night blindness since early childhood. The patient had no history of hemeralopia or photophobia, and no family history of such illness or use of glasses. On examination, his visual acuity was 6/6 in both eyes. Pupils were reacting normally. Dilated fundus examination revealed diffuse golden-yellow sheen throughout the fundus with prominent retinal vasculature, but arteries and veins were less distinguishable. Choroidal vessels were not visible. The patient was then patched and dark adapted for 6 hours. The dark-adapted fundus showed the disappearance of the golden sheen with normal visible choroidal and retinal vasculature. This characteristic phenomenon observed on fundus examination from dark-adapted state to light adaptation is known as Mizuo-Nakamura phenomenon. Although this phenomenon is classical of Oguchi disease, it is also seen in X-linked cone dystrophy and X-linked retinoschisis. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:1068.].

Paraneoplastic retinopathy associated with systemic follicular cell lymphoma.

The authors describe two rare cases of autoimmune retinopathy associated with follicular cell lymphoma, including a 54-year-old man who experienced nyctalopia for 1 year (patient 1) and a 59-year-old man who had bilateral loss of central vision for 6 months (patient 2). Visual field testing of patient 1 revealed nonspecific defects, and multifocal electroretinogram (ERG) testing showed mildly subnormal amplitudes more pronounced in the left than the right eye. Serologic testing detected antibodies against a 47-kD protein, presumed to be alpha-enolase. Goldmann perimetry of patient 2 showed dense central scotomas, and a full-field ERG revealed reduced amplitudes of bright scotopic responses. Serological testing yielded anti-bipolar cell antibodies. A variable presentation of autoimmune retinopathy can occur in the setting of follicular cell lymphoma. Disparate serum autoantibodies may have mediated the pathogenesis of retinal degeneration in these two patients and could explain the difference in course and severity of retinopathy.

Risk factors associated with night vision disturbances after phakic intraocular lens implantation.

PURPOSE: To investigate the incidence and severity of night vision disturbances after implantable collamer lens surgery and to analyze the risk factors. DESIGN: Retrospective, noncomparative study. METHODS: Medical charts from 50 eyes of 25 patients who underwent implantable collamer lens implantation were retrospectively reviewed. The incidence and severity of night vision disturbances were evaluated using questionnaires administered 6 months after surgery. Univariate simple and multiple logistic regression analyses were used to detect risk factors associated with postoperative night vision disturbances. Potential risk factors included in the analysis were keratometric value, anterior chamber depth, postoperative residual refractive error, higher-order aberrations, preoperative and postoperative mesopic pupil size, the difference between preoperative and postoperative mesopic pupil size, the difference between mesopic pupil size and implantable collamer lens optic zone diameter, white-to-white diameter, sulcus-to-sulcus diameter, and postoperative implantable collamer lens vaulting. The power, size, optic zone diameter, and toricity of the implantable collamer lens were also included as variables. RESULTS: The incidence of night vision disturbances was 34.0% for halos and 26.0% for glare. Halos were found to be significantly related to the difference between mesopic pupil size and implantable collamer lens optic zone diameter (P = .013), white-to-white diameter of the cornea (P = .028), and implantable collamer lens optic zone diameter (P = .030). For glare, toricity of the implantable collamer lens was revealed as a significant risk factor (P = .047). CONCLUSIONS: Although not severe, the incidence of night vision disturbances after implantable collamer lens implantation was not negligible. Possible risk factors for night vision disturbances include implantable collamer lens optic zone diameter, the difference between mesopic pupil size and implantable collamer lens optic zone diameter, and white-to-white diameter of the cornea for causing halos, and the toricity of the implantable collamer lens for causing glare.