Neurological Conditions

Visual electrophysiology for neurological conditions 

Autism 

Autism, or Autism Spectrum Disorder (ASD), is a neurodevelopmental condition that affects how a person perceives and interacts with the world. It is characterized by challenges in social communication and interaction, as well as restricted, repetitive behaviors and interests. Exploration of full-field electroretinogram (ERG) presentations in patients with autism show reduced dark-adapted b-wave amplitudes along with a diminished cone-ON bipolar cell responses. 

Brain Tumors 

Screening for optic nerve gliomas (ONGs) in children with neurofibromatosis type 1 (NF1) presents challenges, as visual acuity (VA) assessments can be unreliable. Visual evoked potential (VEP) testing offers a sensitive and cost-effective method for detecting ONG in NF1 patients. VEP may facilitate earlier diagnosis, particularly in children with ambiguous or challenging ophthalmic examinations. Any compressions of the optic nerve can cause reductions in VEP amplitudes.  

Idiopathic Intracranial Hypertension 

Idiopathic intracranial hypertension (IIH) is characterized by elevated intracranial pressure (ICP) in the absence of detectable brain structural abnormalities or cerebrospinal fluid (CSF) issues. In patients with IIH, evaluating retinal ganglion cell (RGC) function through electrophysiological measures provides valuable insights into the disease’s impact on the visual system. 

Research indicates that two electrophysiological tests, the photopic negative response (PhNR) and pattern electroretinogram (pERG), offer complementary data on RGC dysfunction in IIH. The pERG is particularly effective in detecting macular RGC abnormalities, with response amplitudes correlating with both structural and functional impairments. While the correlation between the full-field PhNR (PhNR) and these measures is somewhat weaker, the PhNR is valuable in detecting RGC dysfunction that predominantly affects the peripheral retina. Together, these tests provide a more comprehensive assessment of RGC health in IIH patients. 

Non-Organic Vision Loss 

Non-organic vision loss, also known as functional vision loss or psychogenic vision loss, refers to a reduction or loss of visual function that cannot be explained by any detectable structural or organic abnormality in the eyes, visual pathways, or brain. This type of vision loss is often related to psychological or emotional factors, rather than physical damage or disease. ISCEV suggests that sweep visually evoked potentials (Sweep VEP) can be used to objectively assess visual acuity to confirm a patient’s visual potential. 

Optic Neuritis 

Optic neuritis describes any condition that causes the inflammation of the optic nerve; it may be associated with demyelinating diseases, infectious or inflammatory processes. These cases often present delays in visually evoked potentials (VEPs) due to the disruption of normal neural signal transmission.  

Schizophrenia and Bipolar Disorder 

Schizophrenia and bipolar disorder are psychiatric disorders which may reveal biomarkers through the retina. Electroretinogram (ERG) waveform parameters have shown potential to accurately distinguish between the two conditions, suggesting that ERG could serve as a valuable tool in aiding clinicians with the differential diagnosis of schizophrenia and bipolar disorder in stabilized, medicated patients. 

Traumatic Brain Injury 

Traumatic brain injury (TBI) usually results from a jarring blow or jolt to the head or body. An object that goes through brain tissue, such as a bullet or shattered piece of skull, also can cause traumatic brain injury. Traumatic brain injury can result in temporary or prolonged effects. Effects of TBI can be detected through the visual system. Visually evoked potentials (VEPs) may present with delayed P100 latencies. Photopic negative responses (PhNR) are also affected as a result of leaky calcium channels.  

Alzheimer’s 

Alzheimer’s Disease is a type of dementia that affects memory, thinking, and behavior. Patients with this neurodegenerative disease often complain of visual disturbances well in advance of the full disease onset. In fact, self-reported visual changes can occur as many as 10 years prior to onset of a disease’s symptoms and signs. This provides an opportunity for early intervention.  

Research shows that visual electrophysiology tests such as electroretinography (ERG) and visually evoked potentials (VEP) present consistent patterns of expression in the retina. Alzheimer’s disease tends to present a decreased latency of the second peak of the flash VEP. 

Multiple Sclerosis  

Multiple sclerosis (MS) is a disease where the body’s immune system impairs myelin, the protective sheath that covers nerve fibers running through the central nervous system. Damaged myelin affects communication between the brain and the rest of the body. As a result, MS can lead to irreversible disability, including difficulty walking. 

Demyelination can be detected using visually evoked potentials (VEPs), which show delayed responses as demyelination occurs. VEPs are also used to assess the effectiveness of drugs aimed at promoting remyelination.