Achromatopsia (ACHM) is an autosomal-recessive retinal dystrophy characterized by color blindness, photophobia, nystagmus, and severely reduced visual acuity. Its prevalence has been estimated to ...about 1 in 30,000 individuals. Four genes, GNAT2, PDE6C, CNGA3, and CNGB3, have been implicated in ACHM, and all encode functional components of the phototransduction cascade in cone photoreceptors. Applying a functional-candidate-gene approach that focused on screening additional genes involved in this process in a cohort of 611 index cases with ACHM or other cone photoreceptor disorders, we detected a homozygous single base change (c.35C>G) resulting in a nonsense mutation (p.Ser12∗) in PDE6H, encoding the inhibitory γ subunit of the cone photoreceptor cyclic guanosine monophosphate phosphodiesterase. The c.35C>G mutation was present in three individuals from two independent families with a clinical diagnosis of incomplete ACHM and preserved short-wavelength-sensitive cone function. Moreover, we show through immunohistochemical colocalization studies in mouse retina that Pde6h is evenly present in all retinal cone photoreceptors, a fact that had been under debate in the past. These findings add PDE6H to the set of genes involved in autosomal-recessive cone disorders and demonstrate the importance of the inhibitory γ subunit in cone phototransduction.
To describe the natural course, phenotype, and genotype of patients with X-linked retinoschisis (XLRS).
Retrospective cohort study.
Three hundred forty patients with XLRS from 178 presumably ...unrelated families.
This multicenter, retrospective cohort study reviewed medical records of patients with XLRS for medical history, symptoms, visual acuity (VA), ophthalmoscopy, full-field electroretinography, and retinal imaging (fundus photography, spectral-domain SD OCT, fundus autofluorescence).
Age at onset, age at diagnosis, severity of visual impairment, annual visual decline, and electroretinography and imaging findings.
Three hundred forty patients were included with a mean follow-up time of 13.2 years (range, 0.1-50.1 years). The median ages to reach mild visual impairment and low vision were 12 and 25 years, respectively. Severe visual impairment and blindness were observed predominantly in patients older than 40 years, with a predicted prevalence of 35% and 25%, respectively, at 60 years of age. The VA increased slightly during the first 2 decades of life and subsequently transitioned into an average annual decline of 0.44% (P < 0.001). No significant difference was found in decline of VA between variants that were predicted to be severe and mild (P = 0.239). The integrity of the ellipsoid zone (EZ) as well as the photoreceptor outer segment (PROS) length in the fovea on SD OCT correlated significantly with VA (Spearman's ρ = -0.759 P < 0.001 and -0.592 P = 0.012, respectively). Fifty-three different RS1 variants were found. The most common variants were the founder variant c.214G→A (p.(Glu72Lys)) (101 patients 38.7%) and a deletion of exon 3 (38 patients 14.6%).
Large variabilities in phenotype and natural course of XLRS were seen in this study. In most patients, XLRS showed a slow deterioration starting in the second decade of life, suggesting an optimal window of opportunity for treatment within the first 3 decades of life. The integrity of EZ as well as the PROS length on SD OCT may be important in choosing optimal candidates for treatment and as potential structural end points in future therapeutic studies. No clear genotype-phenotype correlation was found.
Purpose
A major point of concern in uveitis is the development of irreversible retinal changes after inflammation. In this study, we assess how nonanterior childhood uveitis affects retinal function ...using full‐field electroretinography (ERG).
Methods
Cross‐sectional study. ERGs of 63 uveitis eyes (33 children) were measured according to extended International Society for Clinical Electrophysiology of Vision (ISCEV) protocols. ERG abnormalities were investigated in relation to the following clinical parameters: demographics, uveitis characteristics, including severity of inflammation, treatment, best corrected visual acuity (BCVA), cystoid macular oedema (CME) on optical coherence tomography and fluorescein angiography score.
Results
The ERG showed abnormalities in 34 eyes (54%). The most frequent ERG abnormalities were prolonged implicit times of the cone b‐wave (37%; n = 23/63) and an abnormal 30‐Hz flicker response (implicit time and/or amplitude) (33%; n = 21/63). Factors associated with these ERG abnormalities were CME (p = 0.021) and 3+ vitreous cells (p = 0.021). BCVA in eyes with and without these ERG abnormalities did not statistically differ and was relatively good (median: 0.05 LogMAR, IQR: 0.00–0.15 LogMAR).
Conclusion
The ERG is frequently affected in childhood uveitis indicating a global retinal dysfunction. ERG abnormalities seem to be associated with a more severe posterior segment inflammation and a younger age. If an association between ERG abnormalities and long‐term visual outcome can be made in the future, these early ERG findings during the course of childhood uveitis have significance for treatment strategies.
Retinitis pigmentosa (RP) comprises a group of inherited retinal dystrophies characterized by the degeneration of rod photoreceptors, followed by the degeneration of cone photoreceptors. As a result ...of photoreceptor degeneration, affected individuals experience gradual loss of visual function, with primary symptoms of progressive nyctalopia, constricted visual fields and, ultimately, central vision loss. The onset, severity and clinical course of RP shows great variability and unpredictability, with most patients already experiencing some degree of visual disability in childhood. While RP is currently untreatable for the majority of patients, significant efforts have been made in the development of genetic therapies, which offer new hope for treatment for patients affected by inherited retinal dystrophies. In this exciting era of emerging gene therapies, it remains imperative to continue supporting patients with RP using all available options to manage their condition. Patients with RP experience a wide variety of physical, mental and social-emotional difficulties during their lifetime, of which some require timely intervention. This review aims to familiarize readers with clinical management options that are currently available for patients with RP.
Purpose
To investigate the retinal structure and function in patients with CRB1‐associated retinal dystrophies (RD) and to explore potential clinical endpoints.
Methods
In this prospective ...cross‐sectional study, 22 patients with genetically confirmed CRB1‐RD (aged 6–74 years), and who had a decimal best‐corrected visual acuity (BCVA) ≥ 0.05 at the last visit, were studied clinically with ETDRS BCVA, corneal topography, spectral‐domain optical coherence tomography (SD‐OCT), fundus autofluorescence, Goldmann visual field (VF), microperimetry, full‐field electroretinography (ERG) and full‐field stimulus testing (FST). Ten patients were from a genetic isolate (GI).
Results
Patients had retinitis pigmentosa (n = 19; GI and non‐GI), cone‐rod dystrophy (n = 2; GI) or macular dystrophy (n = 1; non‐GI). Median age at first symptom onset was 3 years (range 0.8–49). Median decimal BCVA in the better and worse‐seeing eye was 0.18 (range 0.05–0.83) and 0.08 (range light perception‐0.72), respectively. Spectral‐domain optical coherence tomography (SD‐OCT) showed cystoid maculopathy in 8 subjects; inner retinal thickening (n = 20), a well‐preserved (para)foveal outer retina (n = 7) or severe (para)foveal outer retinal atrophy (n = 14). All retinal layers were discernible in 13/21 patients (62%), with mild to moderate laminar disorganization in the others. Nanophthalmos was observed in 8 patients (36%). Full‐field stimulus testing (FST) provided a subjective outcome measure for retinal sensitivity in eyes with (nearly) extinguished ERG amplitudes.
Conclusions
Despite the generally severe course of CRB1‐RDs, symptom onset and central visual function are variable, even at advanced ages. Phenotypes may vary within the same family. Imaging and functional studies in a prospective longitudinal setting should clarify which endpoints may be most appropriate in a clinical trial.
To investigate the relative frequency of the genetic causes of the Schubert-Bornschein type of congenital stationary night blindness (CSNB) and to determine the genotype-phenotype correlations in ...CSNB1 and CSNB2.
Clinic-based, longitudinal, multicenter study.
A total of 39 patients with CSNB1 from 29 families and 62 patients with CSNB2 from 43 families.
Patients underwent full ophthalmologic and electrophysiologic examinations. On the basis of standard electroretinograms (ERGs), patients were diagnosed with CSNB1 or CSNB2. Molecular analysis was performed by direct Sanger sequencing of the entire coding regions in NYX, TRPM1, GRM6, and GPR179 in patients with CSNB1 and CACNA1F and CABP4 in patients with CSNB2.
Data included genetic cause of CSNB, refractive error, visual acuity, nystagmus, strabismus, night blindness, photophobia, color vision, dark adaptation (DA) curve, and standard ERGs.
A diagnosis of CSNB1 or CSNB2 was based on standard ERGs. The photopic ERG was the most specific criterion to distinguish between CSNB1 and CSNB2 because it showed a "square-wave" appearance in CSNB1 and a decreased b-wave in CSNB2. Mutations causing CSNB1 were found in NYX (20 patients, 13 families), TRPM1 (10 patients, 9 families), GRM6 (4 patients, 3 families), and GPR179 (2 patients, 1 family). Congenital stationary night blindness 2 was primarily caused by mutations in CACNA1F (55 patients, 37 families). Only 3 patients had causative mutations in CABP4 (2 families). Patients with CSNB1 mainly had rod-related problems, and patients with CSNB2 had rod- and cone-related problems. The visual acuity on average was better in CSNB1 (0.30 logarithm of the minimum angle of resolution logMAR) than in CSNB2 (0.52 logMAR). All patients with CSNB1 and only 54% of the patients with CSNB2 reported night blindness. The dark-adapted threshold was on average more elevated in CSNB1 (3.0 log) than in CSNB2 (1.8 log). The 3 patients with CABP4 had a relative low visual acuity, were hyperopic, had severe nonspecific color vision defects, and had only 1.0 log elevated DA threshold.
Congenital stationary night blindness 1, despite different causative mutations, shows 1 unique CSNB1 phenotype. Congenital stationary night blindness 2 caused by mutations in CABP4 merely shows cone-related problems and therefore appears to be distinct from CSNB2 caused by mutations in CACNA1F.
The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Foveal hypoplasia and optic nerve misrouting are developmental defects of the visual pathway and only co-occur in connection with albinism; to date, they have only been associated with defects in the ...melanin-biosynthesis pathway. Here, we report that these defects can occur independently of albinism in people with recessive mutations in the putative glutamine transporter gene SLC38A8. Nine different mutations were identified in seven Asian and European families. Using morpholino-mediated ablation of Slc38a8 in medaka fish, we confirmed that pigmentation is unaffected by loss of SLC38A8. Furthermore, by undertaking an association study with SNPs at the SLC38A8 locus, we showed that common variants within this gene modestly affect foveal thickness in the general population. This study reveals a melanin-independent component underpinning the development of the visual pathway that requires a functional role for SLC38A8.
Purpose
To assess the longitudinal vision‐related quality of life among patients with CRB1‐associated inherited retinal dystrophies.
Methods
In this longitudinal questionnaire study, the National Eye ...Institute Visual Function Questionnaire (39 items, NEI VFQ‐39) was applied at baseline, two‐year follow‐up, and 4‐year follow‐up in patients with pathogenic CRB1 variants. Correction added on 20 November 2023, after first online publication: The preceding sentence has been updated in this version. Classical test theory was performed to obtain subdomain scores and in particular ‘near activities’ and ‘total composite’ scores. The Rasch analysis based on previous calibrations of the NEI VFQ‐25 was applied to create visual functioning and socio‐emotional subscales.
Results
In total, 22 patients with a CRB1‐associated retinal dystrophy were included, … with a median age of 25.0 years (interquartile range: 13–31 years) at baseline and mean follow‐up of 4.0 ± 0.3 years. Correction added on 20 November 2023, after first online publication: The preceding sentence has been updated in this version. A significant decline at 4 years was observed for ‘near activities’ (51.0 ± 23.8 vs 35.4 ± 14.7, p = 0.004) and ‘total composite’ (63.0 ± 13.1 vs 52.0 ± 12.1, p = 0.001) subdomain scores. For the Rasch‐scaled scores, the ‘visual functioning’ scale significantly decreased after 2 years (−0.89 logits; p = 0.012), but not at 4‐year follow‐up (+0.01 logits; p = 0.975). Correction added on 20 November 2023, after first online publication: In the preceding sentence, “…after 4 years…” has been corrected to “…after 2 years…” in this version. The ‘socio‐emotional’ scale also showed a significant decline after 2 years (−0.78 logits, p = 0.033) and 4 years (−0.83 logits, p = 0.021).
Conclusion
In the absence of an intervention, a decline in vision‐related quality of life is present in patients with pathogenic CRB1 variants at 4‐year follow‐up. Patient‐reported outcome measures should be included in future clinical trials, as they can be a potential indicator of disease progression and treatment efficacy.
To evaluate the clinical course, genetic etiology, and visual prognosis in patients with cone dystrophy (CD) and cone-rod dystrophy (CRD).
Clinic-based, longitudinal, multicenter study.
Consecutive ...probands with CD (N = 98), CRD (N = 83), and affected relatives (N = 41 and N = 17, respectively) from various ophthalmogenetic clinics in The Netherlands, Belgium, and the United Kingdom.
Data on best-corrected Snellen visual acuity, color vision, ophthalmoscopy, fundus photography, Goldmann perimetry, and full-field standard electroretinogram (ERG) from all patients were registered from medical charts over a mean follow-up of 19 years. The ABCA4, CNGB3, KCNV2, PDE6C, and RPGR genes were analyzed by direct sequencing in autosomal recessive (AR) and X-linked (XL), respectively. Genotyping was not undertaken for autosomal-dominant cases.
The 10-year progression of all clinical parameters and cumulative lifetime risk of low vision and legal blindness were assessed.
The mean age onset for CD was 16 years (standard deviation, 11), and of CRD 12 years (standard deviation, 11; P = 0.02). The pattern of inheritance was AR in 92% of CD and 90% of CRD. Ten years after diagnosis, 35% of CD and 51% of CRD had a bull's eye maculopathy; 70% of CRD showed absolute peripheral visual field defects and 37% of CD developed rod involvement on ERG. The mean age of legal blindness was 48 (standard error SE, 3.1) years in CD, and 35 (SE, 1.1; P<0.001) years in CRD. ABCA4 mutations were found in 8 of 90 (9%) of AR-CD, and in 17 of 65 (26%) of AR-CRD. Other mutations were detected in CNGB3 (3/90; 3%), KCNV2 (4/90; 4%), and in PDE6C (1/90; 1%). The RPGR gene was mutated in the 2 XL-CD and in 4 of 5 (80%) of XL-CRD. ABCA4 mutations as well as age of onset <20 years were significantly associated with a faster progression to legal blindness (P<0.001).
Although CD had a slightly more favorable clinical course than CRD, both disorders progressed to legal blindness in the majority of patients. Mutations in the ABCA4 gene and early onset of disease were independent prognostic parameters for visual loss. Our data may serve as an aid in counseling patients with progressive cone disorders.
Albinism is a pigment disorder affecting eye, skin and/or hair. Patients usually have decreased melanin in affected tissues and suffer from severe visual abnormalities, including foveal hypoplasia ...and chiasmal misrouting. Combining our data with those of the literature, we propose a single functional genetic retinal signalling pathway that includes all 22 currently known human albinism disease genes. We hypothesise that defects affecting the genesis or function of different intra-cellular organelles, including melanosomes, cause syndromic forms of albinism (Hermansky-Pudlak (HPS) and Chediak-Higashi syndrome (CHS)). We put forward that specific melanosome impairments cause different forms of oculocutaneous albinism (OCA1-8). Further, we incorporate GPR143 that has been implicated in ocular albinism (OA1), characterised by a phenotype limited to the eye. Finally, we include the SLC38A8-associated disorder FHONDA that causes an even more restricted “albinism-related” ocular phenotype with foveal hypoplasia and chiasmal misrouting but without pigmentation defects. We propose the following retinal pigmentation pathway, with increasingly specific genetic and cellular defects causing an increasingly specific ocular phenotype: (HPS1-11/CHS: syndromic forms of albinism)-(OCA1-8: OCA)-(GPR143: OA1)-(SLC38A8: FHONDA). Beyond disease genes involvement, we also evaluate a range of (candidate) regulatory and signalling mechanisms affecting the activity of the pathway in retinal development, retinal pigmentation and albinism. We further suggest that the proposed pigmentation pathway is also involved in other retinal disorders, such as age-related macular degeneration. The hypotheses put forward in this report provide a framework for further systematic studies in albinism and melanin pigmentation disorders.
•We propose a novel retinal pigmentation pathway including all albinism subtypes.•The GPR143 receptor plays central signalling role in ocular albinism.•SLC38A8 causing FHONDA acts downstream in the pathway in the neural retina.•L-DOPA, GPM6A, PEDF, VEGF, exosome release may be signalling events involved.•The pigmentation pathway may be involved in multiple (retinal) disorders.
PDF
