**Abstract**  
  
 **VEP/VER** \- The visual evoked response (VER) and visual evoked potential
(VEP) evaluate the visual nervous system pathways from the eyes to the
occipital cortex of the brain. By measuring the function of the entire visual
pathway, it helps to separate eye disease from central nervous system defects.
VER/VEP involves stimulation of the retina and optic nerve with a shifting
checkerboard pattern or flash method. This external visual stimulus causes
measurable electrical activity in neurons within the visual pathways. The VER
is recorded by electroencephalography electrodes located over the occiput
producing a characteristic waveform. Abnormalities may be seen in a variety of
pathologic processes involving the optic nerve and its radiations. Pattern-
shift VER is a highly sensitive means of documenting lesions in the visual
system.  
  
**ERG** \- The full field electroretinogram (ERG) is used to detect loss of
retinal function or distinguish between retinal and optic nerve lesions. ERG
measures the electrical activity generated by neural and non-neuronal cells in
the retina in response to a light stimulus. ERGs are usually obtained using
electrodes embedded in a corneal contact lens, or a thin wire inside the lower
eyelid, which measure a summation of retinal electrical activity at the
corneal surface. The International Society for Clinical Electrophysiology of
Vision (ISCEV) introduced minimum standards for the ERG in 1989. The ERG helps
to distinguish retinal degeneration and dystrophies. Multi-focal
electroretinography (mfERG) is a higher resolution form of ERG, enabling
assessment of ERG activity in small areas of the retina. Pattern ERG (PERG) to
assess retinal ganglion cell (RGC) function in glaucoma is being investigated.  
  
**Indications of Coverage**  
  
 **Visual Evoked Potentials or Responses (VEPs/VERs)**

  1. Confirm diagnosis of multiple sclerosis when clinical criteria are inconclusive
  2. Evaluate diseases of the optic nerve, such as: 
    1. Optic neuritis
    2. Ischemic optic neuropathy
    3. Toxic amblyopias
    4. Nutritional amblyopias
    5. Neoplasms compressing the anterior visual pathways
    6. Optic nerve injury or atrophy
    7. Malingering/functional vision loss (to rule out)
  3. Monitor the visual system during optic nerve (or related) surgery (monitoring of short-latency evoked potential studies).

**Electroretinography (ERG)**

  1. To diagnose loss of retinal function or distinguish between retinal lesions and optic nerve lesions: 
    1. Toxic retinopathies, including those caused by intraocular metallic foreign bodies and Vigabatrin
    2. Diabetic retinopathy
    3. Ischemic retinopathies including central retinal vein occlusion (CRVO), branch vein occlusion (BVO), and sickle cell retinopathy
    4. Autoimmune retinopathies such as Cancer Associated Retinopathy (CAR), Melanoma Associated Retinopathy (MAR), and Acute Zonal Occult Outer Retinopathy (AZOOR)
    5. Retinal detachment
    6. Assessment of retinal function after trauma, especially in vitreous hemorrhage, dense cataracts, and other conditions where the fundus cannot be visualized photoreceptors; absent b-wave indicates abnormality in the bipolar cell region.
    7. Retinitis pigmentosa and related hereditary degenerations
    8. Retinitis punctata albescens
    9. Leber's congenital amaurosis
    10. Choroideremia
    11. Gyrate atrophy of the retina and choroid
    12. Goldman-Favre syndrome
    13. Congenital stationary night blindness
    14. X-linked juvenile retinoschisis
    15. Achromatopsia
    16. Cone dystrophy
    17. Disorders mimicking retinitis pigmentosa
    18. Usher Syndrome
  2. To detect chloroquine (Aralen) and hydroxychloroquine (Plaquenil) toxicity (mfERG) per AAO guidelines (10).

**VEP/ERG in Glaucoma**

A 2011 report by the AAO on "Assessment of Visual Function in Glaucoma" noted
that while VEP and ERG, as objective measures of visual function, provided
testing free of patient input, issues prevent their adoption for glaucoma
management (1). It concluded that advances in technology have yet to produce
definitive guidance on the diagnosis of glaucoma or its progression over time
and that further research on an objective measure of visual function is
needed.  
  
Since then several studies (2-5) have investigated the use of VEP and ERG
technology to differentiate between normal healthy eyes and eyes with early to
advanced visual field loss resulting from glaucoma. The authors indicated that
VEP and ERG may allow earlier diagnosis of glaucoma. However, NGS has
determined that without larger studies, AAO's 2011 conclusion, that these
technologies have yet to produce definitive guidance on the diagnosis of
glaucoma or its progression over time, remains. This was also the conclusion
of a 2013 study which prospectively monitored progressive changes of RGC
function in early glaucoma using PERG (6). The authors concluded that further
follow-up is required to determine whether PERG losses are predictors of
future visual field loss.

Neither of the 2015 AAO Preferred Practice Guidelines, "Primary Open-Angle
Glaucoma Suspect" or "Primary Open-Angle Glaucoma," mention VEP or ERG as
diagnostic tools (7,8). Also, the UpToDate review on "Open-angle glaucoma:
Epidemiology, clinical presentation, and diagnosis," likewise omits reference
to either test (9).

There remain no verified guidelines for normal vs abnormal that would be
easily applicable to an individual patient. NGS, therefore, considers the use
of VEP or ERG for either glaucoma diagnosis or management investigational.

**Limitations**

Testing shall be performed by physicians who have evidence of knowledge,
training, and expertise to perform and interpret these tests. This training
and expertise must have been acquired within the framework of an accredited
school, residency or fellowship program.