Visual Electrophysiology

Details

Title

Visual Electrophysiology

Type

Stage Two

Module code

HPS258

Requirement

Optional

Module objective

By the end of this module the Clinical Scientist in HSST, in respect to visual electrophysiology, will be able to analyse, interpret and provide comprehensive clinical supervised reports on electrophysiological recordings. They will be able to use electroretinography (ERG), pattern electroretinography (PERG) and multifocal electroretinography (mfERG) to: (i) assess the function of different retinal cell types and layers to distinguish between generalised retinal dysfunction and localised macular dysfunction; (ii) separate the function of the retinal rod system and the cone system; and (iii) distinguish between disease affecting the photoreceptor layer and inner retinal disease. They will be able to use the electro-oculograms (EOGs) to assess the generalised function of the retinal pigment epithelium. They will be able to interpret visual evoked potentials (VEPs) and be aware of the need to take confounding factors, such as nystagmus, media opacity, etc., into account. They will be able, using PERG and/or mfERG in conjunction with the VEP, to distinguish between post-retinal dysfunction and more anterior disturbances of vision. They will be able to form differential diagnoses, taking into account clinical factors such as the history, inheritance patterns, relevant imaging features, etc. They will be aware of the need to recommend prompt medical intervention or further investigation by other healthcare practitioners in patients with possible intracranial lesions, which may result in irreversible visual loss unless rapidly diagnosed and treated, and treatable retinal disorders, such as vitamin A deficiency. The Clinical Scientist in HSST will also be able to formulate an appropriate plan for investigation and management, in conjunction with medical colleagues, being aware of the need to expedite investigation in suspected serious disease.

Stage 2 HSST education and training is designed to ensure the Clinical Scientist in HSST is learning and working at the cutting edge of science. Where necessary, given the speed at which science and technology develops, those delivering training and the Clinical Scientist in HSST together are expected to identify emerging developments that may be outside those specifically detailed in the Stage 2 modules and gain the knowledge and skills to take them forwards.

Knowledge and understanding

By the end of this module the Clinical Scientist in HSST will analyse, synthesise, critically evaluate and apply their expert knowledge with respect to the design and application of appropriate electrophysiological measurements in OVS discipline and clinical assessment. This will include expert understanding of:

• the importance of performing all electrophysiological tests in consideration of and to incorporate existing International Standard and Guidelines documents;
• electro-oculography and the assessment of the function of the retinal pigment epithelium (RPE), and the interaction between the RPE and the (rod) photoreceptors;
• the mechanism of the EOG light rise and the role of bestrophin;
• the effects of photoreceptor disease on the EOG;
• the recognition of primary RPE dysfunction where there is a discrepancy between the severity of rod ERG abnormality and the degree of EOG light rise reduction;
• application of the EOG to diagnosis in primary genetically determined disorders of RPE function such as Best vitelliform macular dystrophy, autosomal dominant vitreoretinochoroidopathy (ADVIRC) and autosomal recessive bestrophinopathy (ARB);
• application of the EOG to diagnosis of acquired disorders involving RPE function, such as acute zonal occult outer retinopathy (AZOOR);
• ERG and its application in the diagnosis of disorders of retinal function;
• the ERG localisation of disease to outer or inner retinal structures;
• the relevance and application of extended protocols such as photopic On- and Off-response recording, S-cone ERGs and the photopic negative response (PhNR);
• the role of ERG in the diagnosis and assessment of inherited photoreceptor dystrophies such as rod-cone dystrophy, cone-rod dystrophy and cone dystrophy;
• the role of the ERG in the diagnosis of congenital disorders such as Leber congenital amaurosis, and rod and s-cone monochromacy;
• the ERG distinction between generalised retinal dysfunction and localised or restricted loss of function;
• the role of the ERG in detecting more generalised disease in patients with clinical evidence of macular dysfunction;
• the role of the ERG in acquired disorders of photoreceptor dysfunction such as retinal toxicity, nutritional disorders, inflammatory retinal disease, disturbance of ophthalmic artery function, parasitic disease, autoimmune retinopathy and paraneoplastic photoreceptor dysfunction;
• the significance of the ‘negative’ ERG in the identification of disease affecting post-phototransduction retinal function;
• the role of the ERG in the diagnosis of genetically determined causes of a ‘negative’ ERG such as congenital stationary night blindness (CSNB), X-linked retinoschisis, Batten disease and Duchenne muscular dystrophy;
• the ERG distinction between the ‘complete’ and ‘incomplete’ forms of CSNB;
• the role of the ERG in the diagnosis and management of acquired causes of a ‘negative’ ERG such as retinal vascular disease, inner retinal toxicity (e.g. quinine, vigabatrin, methanol, siderosis), inflammatory disease, paraneoplastic disease (usually melanoma-associated retinopathy, occasionally carcinoma- associated retinopathy) and parasitic disease;
• the use of PERG in the assessment of the function of the macula and of the retinal ganglion cells;
• the role of the P50 component of the PERG in the assessment of macular function;
• the need to combine PERG and full-field ERG data in inherited disorders of macular function in which there may be generalised retinal dysfunction (e.g. disease related to mutation in ABCA4 or PRPH2);
• the effects of optical factors on the P50 component of the PERG;the effects of primary ganglion cell dysfunction, such as Leber hereditary optic neuropathy or dominantly inherited optic atrophy, on the N95 component of the
• the effects of primary ganglion cell dysfunction, such as Leber hereditary optic neuropathy or dominantly inherited optic atrophy, on the N95 component of the PERG;
• the effects of retrograde degeneration of the retinal ganglion cells from optic nerve disease on the PERG;
• the role of the multifocal ERG in the assessment of central retinal cone function;
• the role of the VEP in the diagnosis of intracranial visual pathway dysfunction using pattern reversal (PR), pattern appearance (Pa) and diffuse flash stimulation (F);
• the significance of the delayed pattern reversal VEP (PRVEP) in demyelinating, inflammatory, toxic, nutritional, compressive and infiltrative optic neuropathy;
• the significance of the delayed PRVEP in amblyopia (commonly strabismic amblyopia);
• the significance of a reduced amplitude normal peak-time PRVEP in non- arteritic anterior ischaemic optic neuropathy;
• the significance of a reduced amplitude normal peak-time PRVEP in amblyopia (commonly anisometropic amblyopia);
• the role of multichannel PRVEPs in the diagnosis of chiasmal and retrochiasmal disease, including an awareness of the complexities of ‘paradoxical lateralisation’;
• the importance of excluding macular dysfunction as a cause of PRVEP delay, even if the macula has normal appearance/structure;
• the role of the VEP in the assessment and diagnosis of non-organic visual loss;
• the use of VEPs in the objective assessment of visual system resolution, a surrogate for visual acuity;
• the role of PaVEPs and FVEPs in the assessment of albinism misrouting;
• the role of PaVEPs and FVEPs in the diagnosis of achiasmia;
• the role of PaVEPs and FVEPs in the identification of chiasmal dysfunction due to hydrocephalus, chiasmal glioma, or tumour;the role of the multifocal ERG in the assessment of central retinal cone function;
• the role of the FVEP as a complement to PRVEP and in patients unable or unwilling to comply with the demands of PRVEP (including babies and infants);
• specialised VEPs, such as those to colour or motion stimuli;
• the role of electrophysiological biomarkers of treatment efficacy;
• the role of analysis statistics and mathematical modelling of waveforms to optimise data interpretation, e.g. Laplacian VEP averaging and source derivation, modelling Plll, correlation coefficients of lateral VEP channel activity;
• the importance of technical considerations such as:
  • filter settings and amplifier characteristics
  • the principles of computerised signal averaging and artefact rejection
  • recognition and correction of common artefacts during recording
  • the importance of regular stimulus calibration
  • the effects of pupillary diameter
  • the effects of media opacitiesthe role of the FVEP as a complement to PRVEP and in patients unable or unwilling to comply with the demands of PRVEP (including babies and infants);
  • electrode characteristics:
• formulating a plan for investigation and management, in collaboration with medical colleagues.

Technical and clinical skills

By the end of this module the Clinical Scientist in HSST, with respect to ophthalmic and visual pathway disorders, will be able to demonstrate a critical understanding of current knowledge and research and its application to the performance and mastery of the following technical skills:

• performance of all electrophysiological investigations;
• design and development of new tests according to need and clinical condition.

By the end of this module the Clinical Scientist in HSST will be expected to critically reflect and apply in practice a range of clinical and communication skills to advise and communicate effectively with patients, relevant clinicians and the public, and other healthcare professionals and will:

• take a comprehensive history, understanding the nature of the visual complaint, and select the electrophysiological investigations according to signs, symptoms, medical and family history;
• analyse all electrophysiological data;
• provide a clinical interpretation of the electrophysiological data, placing the results in the context of history, clinical examination and, if a genetically determined disorder, inheritance pattern;
• produce a clear and informative clinical report with recommendations for further diagnostics and/or treatments;
• advise clinicians on the efficacy of treatment intervention in appropriate disorders and, if appropriate, advise on potential changes in therapeutic strategy;
• communicate, where appropriate, the implications of the findings to patients and families;
• reflect on the challenges of applying research to practice in relation to these areas of practice and suggest improvements, building on a critique of available evidence;
• make a holistic approach to diagnosis and take electrophysiological recordings that provide an accurate and comprehensive assessment of the patient’s clinical problem;critically assess and evaluate personal and team-related performance in the context of evidence-based patient care, identify areas of good practice and
• strive to adapt current tests and develop novel investigations better to facilitate diagnosis and management;
• reflect on the impact these disorders have on everyday quality of life and, in inherited disease, on the family.

Professional practice:

• adapt current tests, develop, validate and implement novel investigations to better to facilitate diagnosis and management within current ethical and governance frameworks;
• consistently work to high standards of clinical practice applying knowledge and evidence, evidence-based decision making and evaluating the impact of those decisions;
• monitor, evaluate and maintain personal clinical practice standards and the standards of the service they lead;
• balance data confidentiality, security and protection, and the sharing of data with relevant stakeholders, including patients, to ensure high-quality patient- centred care;
• explain the principles and relevance of the novel procedures to patients at an appropriate level of complexity and involve patients in the development process appropriately;
• support conclusions draw from evidence with reasoned argument;
• appreciate the impact of new evidence on patients and carers;
• facilitate effective and empathic communication with respect to the evidence base underpinning vascular science;
• act in accordance with the principles and practice of patient-centred care, regularly reflecting on personal practice and revising judgements and changing behaviour in the light of new evidence;
• critically assess and evaluate personal and team-related performance in the context of evidence-based patient care, identify areas of good practice and make improvements where necessary;
• seek feedback from patients on their own and the team’s performance and adapt practice accordingly.

Advances in scientific and clinical practice:

• identify opportunities for innovative approaches to the development, delivery and evaluation of new clinical services;
• present these new developments in a concise and appropriate manner to the multidisciplinary team, including healthcare management, in order to influence and progress their implementation;
• keep up to date with scientific research in Neurophysiological Science;
• adopt a mindset that actively seeks creative solutions to problems through engagement with individual creativity, approaches and techniques;
• work with and encourage others to find creative solutions to problems through engagement with group creativity approaches and techniques;
• be positive and confident about developing ideas and putting them into action;
• actively seek out opportunities for collaborative discussions and research, being open to new developments, attending conferences and keeping up to date with the literature;
• adopt a forward-looking, progressive approach and be receptive to new ideas, looking out for emerging technologies;
• promote a sustainable, engrained culture of innovation in an individual, department and/or organisation;
• ensure clinical and scientist colleagues are kept up to date with novel techniques used within the service;
• ensure patients fully understand any procedure that is undertaken;
• continue to monitor any safety issues relating to a novel procedure introduced to the diagnostic or follow-up service.

Leading scientific services:

• critically review the literature and disseminate findings and scientific data and make recommendations for future activity;
• ensure clinical and scientist colleagues are kept up to date with new and novel techniques used within the service;
• work with patients and parents to develop and update patient information materials appropriate to service requirements;
• share data on clinical practice standards with service users and managers to encourage dialogue and debate;
• be committed to, support and lead continuous improvement of neurophysiological scientific services, with particular reference to auditing practice, evidence-based practice, innovation, and the introduction and use of new and improved technologies;
• reflect on the challenges of applying research to practice in relation to these areas of practice and suggest improvements, building on a critique of available evidence.