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158 results on '"Parry, Neil R. A."'

2. Clinical and genetic variability in children with partial albinism

Author

Campbell, Patrick, Ellingford, Jamie M., Parry, Neil R. A., Fletcher, Tracy, Ramsden, Simon C., Gale, Theodora, Hall, Georgina, Smith, Katherine, Kasperaviciute, Dalia, Thomas, Ellen, Lloyd, I. Chris, Douzgou, Sofia, Clayton-Smith, Jill, Biswas, Susmito, Ashworth, Jane L., Black, Graeme C. M., and Sergouniotis, Panagiotis I.

Published
2019
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6. Electroretinographic responses to luminance and cone-isolating white noise stimuli in macaques

Author

Kremers, Jan, Aher, Avinash J., Parry, Neil R. A., Patel, Nimesh B., and Frishman, Laura J.

Subjects
General Neuroscience, ddc:610
Abstract

Electroretinograms (ERGs) are mass potentials with a retinal origin that can be measured non-invasively. They can provide information about the physiology of the retina. Often, ERGs are measured to flashes that are highly unnatural stimuli. To obtain more information about the physiology of the retina, we measured ERGs with temporal white noise (TWN) stimuli that are more natural and keep the retina in a normal range of operation. The stimuli can be combined with the silent substitution stimulation technique with which the responses of single photoreceptor types can be isolated. We characterized electroretinogram (ERG) responses driven by luminance activity or by the L- or the M-cones. The ERGs were measured from five anesthetized macaques (two females) to luminance, to L-cone isolating and to M-cone isolating stimuli in which luminance or cone excitation were modulated with a TWN profile. The responses from different recordings were correlated with each other to study reproducibility and inter-individual variability. Impulse response functions (IRFs) were derived by cross-correlating the response with the stimulus. Modulation transfer functions (MTFs) were the IRFs in the frequency domain. The responses to luminance and L-cone isolating stimuli showed the largest reproducibility. The M-cone driven responses showed the smallest inter-individual variability. The IRFs and MTFs showed early (high frequency) components that were dominated by L-cone driven signals. A late component was equally driven by L- and M-cone activity. The IRFs showed characteristic similarities and differences relative to flash ERGs. The responses to TWN stimuli can be used to characterize the involvement of retinal cells and pathways to the ERG response. It can also be used to identify linear and non-linear processes.

Published
2022

7. Retinal gene therapy in RPE-65 gene mediated inherited retinal dystrophy

Author

Jalil, Assad, Ivanova, Tsveta, Moussa, George, Parry, Neil R. A., and Black, Graeme C. M.

Abstract

Background: Voretigene neparvovec (VN) is a gene therapeutic agent for treatment of retinal dystrophies caused by bi-allelic RPE65mutations. We illustrate, both the benefits and pitfalls associated with ocular gene therapy in the same patient. Methods: Two eyes of one patient with bi-allelic RPE65mutations have been treated with VN. The clinical examinations included visual acuity (VA, in normal and low luminance), colour vision, contrast sensitivity, International Society for Clinical Electrophysiology of Vision (ISCEV) standard retinal electrophysiology and dark-adapted full-field stimulus threshold (FST), Goldmann VF analysis and imaging studies, including optical coherence tomography (OCT) and autofluorescence. These were performed at baseline, 2-weeks, 3 and 6-months, 1 and 2-years follow-up. Results: The first eye showed improvement in rod photoreceptor function with increased peripheral and low luminance vision (baseline VA: 0.9 logMAR and 2-years post-operative VA: 0.7 logMAR). The second eye, whilst showing increased light sensitivity, suffered a drop in central vision (at 2-weeks) with loss of foveal photoreceptors as shown by the loss of ellipsoid zone on OCT scan (baseline VA: 0.6, 2-year post-operative VA: 1.2). FST improvements were maintained in both eyes indicating a sustained efficacy of VN with little waning of its effect. Conclusions: We present a previously unreported adverse complication of subretinal VN therapy in bi-allelic RPE65, indicating a probable immune response in treatment of the second eye, resulting in loss of foveal photoreceptors. This case-series highlights the potential and pitfalls of retinal gene therapy in the same patient. The immune responses of the body to a ‘foreign vector’, remains a challenge.

Published
2023
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36. Visual Electrodiagnosis in Glaucoma Screening

Author

Tsaousis, Konstantinos T., primary, Plainis, Sotiris, additional, Parry, Neil R. A., additional, Pallikaris, Ioannis G., additional, Tsilimbaris, Miltiadis K., additional, and Detorakis, Efstathios T., additional

Published
2013
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38. Optic neuropathy in methylmalonic acidemia and propionic acidemia.

Author

Alvarez, Lidia Martinez, Jameson, Elisabeth, Parry, Neil R. A., Lloyd, Chris, and Ashworth, Jane L.

Subjects
GENETIC disorders, FAMILIAL diseases, EYE diseases, METHYLMALONIC acid, PROPIONIC acid
Abstract

Background Methylmalonic acidemia (MMA) and propionic acidemia (PA) are rare hereditary disorders of protein metabolism, manifesting early in life with ketoacidosis and encephalopathy and often resulting in chronic complications. Optic neuropathy (ON) has been increasingly recognised in both conditions, mostly through isolated case reports or small cases series. We here report the clinical features and visual outcomes of a case series of paediatric patients with a diagnosis of MMA or PA. Methods Retrospective observational case series. A database of patients attending the Willink Biochemical Genetics unit in Manchester was interrogated. Fifty-three patients had a diagnosis of either isolated MMA or PA, of which 12 had been referred for ophthalmic review. Results Seven patients had clinical findings compatible with ON. Visual outcomes in these patients were poor, with slow clinical progression or stability over time in five cases with follow-up. Presentation was acute in a context of metabolic crisis in two of the cases. Four patients with ON had electrodiagnostics showing absent pattern evoked potentials, with one showing a preserved flash response. All four showed marked attenuation of the dark-adapted electroretinogram with better preservation of the light-adapted response. Conclusions Our study suggests that ON is under-reported in patients with MMA and PA. Clinical presentation can be acute or insidious, and episodes of acute metabolic decompensation appear to trigger visual loss. Photoreceptor involvement may coexist. Active clinical surveillance of affected patients is important as comorbidities and cognitive impairment may delay diagnosis. [ABSTRACT FROM AUTHOR]

Published
2016
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47. X-Iinked retinoschisis: an update.

Author

Sikkink, Stephen K., Biswas, Susmito, Parry, Neil R. A., Stanga, Paulo E., and Trump, Dorothy

Subjects
RETINAL degeneration, CELL adhesion, AMINO acids, CELL communication, PROTEINS
Abstract

X-linked retinoschisis is the leading cause of macular degeneration in males and leads to splitting within the inner retinal layers leading to visual deterioration. Many missense and protein truncating mutations have now been identified in the causative retinoschisis gene (RS1) which encodes a 224 amino acid secreting retinal protein, retinoschisin. Retinoschisin octamerises is implicated in cell-cell interactions and cell adhesion perhaps by interacting with β2 laminin. Mutations cause loss of retinoschisin function by one of the three mechanisms: by interfering with protein secretion, by preventing its octamerisation or by reducing function in the secreted octamerised protein. The development of retinoschisis mouse models have provided a model system that closely resembles the human disease. Recent reports of RS1 gene transfer to these models and the sustained restoration of some retinal function and morphology suggest gene replacement may be a possible future therapy for patients. [ABSTRACT FROM AUTHOR]

Published
2007
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49. Abrogation of HMX1 Function Causes Rare Oculoauricular Syndrome Associated With Congenital Cataract, Anterior Segment Dysgenesis, and Retinal Dystrophy

Author

Gillespie, Rachel L., Urquhart, Jill, Lovell, Simon C., Biswas, Susmito, Parry, Neil R. A., Schorderet, Daniel F., Lloyd, I. Chris, Clayton-Smith, Jill, and Black, Graeme C.

Subjects
congenital cataract, coloboma, anterior segment dysgenesis, early-onset retinal dystrophy, oculoauricular syndrome
Abstract

PURPOSE. To define the phenotypic manifestation, confirm the genetic basis, and delineate the pathogenic mechanisms underlying an oculoauricular syndrome (OAS). METHODS. Two individuals from a consanguineous family underwent comprehensive clinical phenotyping and electrodiagnostic testing (EDT). Genome-wide microarray analysis and Sanger sequencing of the candidate gene were used to identify the likely causal variant. Protein modelling, Western blotting, and dual luciferase assays were used to assess the pathogenic effect of the variant in vitro. RESULTS. Complex developmental ocular abnormalities of congenital cataract, anterior segment dysgenesis, iris coloboma, early-onset retinal dystrophy, and abnormal external ear cartilage presented in the affected family members. Genetic analyses identified a homozygous c.650A> C; p.(Gln217Pro) missense mutation within the highly conserved homeodomain of the H6 family homeobox 1 (HMX1) gene. Protein modelling predicts that the variant may have a detrimental effect on protein folding and/or stability. In vitro analyses were able to demonstrate that the mutation has no effect on protein expression but adversely alters function. CONCLUSIONS. Oculoauricular syndrome is an autosomal recessive condition that has a profound effect on the development of the external ear, anterior segment, and retina, leading to significant visual loss at an early age. This study has delineated the phenotype and confirmed HMX1 as the gene causative of OAS, enabling the description of only the second family with the condition. HMX1 is a key player in ocular development, possibly in both the pathway responsible for lens and retina development, and via the gene network integral to optic fissure closure.

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