Cortical and Macular Visual Electrophysiology

Details

Title

Cortical and Macular Visual Electrophysiology

Type

Stage Two

Module code

HPS254

Requirement

Compulsory

Module objective

By the end of this module the Clinical Scientist in HSST, in respect to cortical and macular visual electrophysiology, will be able to analyse, interpret and provide a supervised clinical report on pattern electroretinography (PERG) and visual evoked potentials (VEPs). They will be able to use PERG to show macular function. They will be able to interpret 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 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. 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.

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 visual electrophysiological measurements in the Neurophysiology discipline and clinical assessment. This will include expert understanding of:

• the importance of performing all related electrophysiological tests in consideration of and to incorporate existing International Standard and Guidelines documents;
• the role of the P50 component of the PERG in the assessment of macular function;
• the effects of optical factors on the P50 component of the PERG;
• 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 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 identification of chiasmal dysfunction due to hydrocephalus, chiasmal glioma, or tumour;
• 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);
• an awareness of specialised VEPs, such as those to colour or motion stimuli;
• the importance of technical considerations such as:
  • • electrode characteristics:
      • filter settings and amplifier characteristics
      • the principles of computerised signal averaging and artefact rejection
      • recognition and correction of common artefacts during recordingthe effects of retrograde degeneration of the retinal ganglion cells from optic nerve disease on the PERG;
      • the importance of regular stimulus calibration.

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 a pattern and flash visual evoked potential (PaVEP + FVEP);
• performance of multichannel PaVEPs;
• performance of PERG.

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 appropriate electrophysiological investigations according to signs, symptoms, medical and family history;
• analyse all recorded electrophysiological data;
• provide a provisional clinical interpretation of the electrophysiological data, placing the results in the context of history and clinical examination, and produce a clear and informative clinical report;
• 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;
• strive to adapt current tests and develop novel investigations better to facilitate diagnosis and management;communicate, where appropriate, the implications of the findings to patients and families;
• reflect on the impact these disorders have on everyday quality of life and, in inherited disease, on the family.