The electrophysiology equipment as all the eye care providers know can provide us with valuable information for the patients who have unexplained loss of vision. These tests complement, and supplement, other visual methods of assessment.

The machine RETI port is a state of art equipment and is the full system including the hand held ERG for pediatric patients, multifocal ERG, pattern ERG and pattern VEP. We believe that this would add to the diagnostic power of all the ophthalmologists in this part of the state and the patients will not have to rush to far flung places for these diagnostic tests. We welcome everyone's suggestions and promise to hold workshops for everyone to know and understand this machine better in future. Electrophysiology can contribute significantly in diagnostics of unexplained visual loss both in adults and in children. The tests are objective, safe, noninvasive, swift and easy to administer.

A complete eye examination - not only the usual reading of the chart-is mandatory, especially after the age of 40. Those at risk of developing glaucoma include

What does electrophysiology encompass?

The electroretinogram (ERG) indicates the massed retinal responses to the full field luminance stimulation, which reflects the function of the photoreceptors and the inner nuclear layers of the retina and the visual evoked potential (VEP) reflects optic pathway function beyond the eye to the visual cortex. Newer multifocal ERGs (mf ERG) are available which are more macular specific and give a pictorial representation of macular pathologies

Diagnostic applications: ERG

The flash ERG plays its most vital role in conditions where ophthalmoscopy shows a normal or questionably normal, fundus and optic disc appearance and yet poor vision.

• Both rods and cones are affected. In Leber's congential amaurosis, both rod and cone ERGs are most usually non-detectable.
• Predominantly rods are affected. Rod dysfunction can occur in isolation as in retinitis pigmentosa (RP) or conditions like vitamin A deficiency.
• Predominantly cones are affected. In children with rod monochromatism (achromatopsia), the scotopic ERG is usually normal but ERG elicited under photopic conditions and 30 Hz flicker response is not detectable.
• Inner retinal dysfunction. When the b wave amplitude is markedly attenuated or not detectable, the ERG has a larger than average a wave. This is associated with X linked congenital stationary night blindness, X linked retinoschisis, Bull's eye maculopathy, infantile and juvenile neuronal ceroid lipofuschinosis.

Diagnostic applications: VEP

ERG and VEPs recorded together can give valuable information in pediatric population regarding the macular and extramacular areas and the quality of macular pathway function.

• Ocular opacity. Bright flashes usually penetrate all but the densest ocular opacities, and flash VEPs and ERGs are particularly valuable when ocular opacities prevent adequate visualization of the perimacular fundus
• Optic nerve disorders. Monocular stimulation and transoccipital flash VEP recording will indicate whether a disease process is affecting the optic nerve, chiasm or pathway beyond the chiasm.
  • Optic Neuritis.
  • Optic nerve hypoplasia.
  • Optic nerve compression
  • Craniofacial dysostosis

INDICATIONS

• It is advantageous to use visual electro diagnostic tests in preliminary disease stages in young infants.
• It also helps in emotional acceptance and allows for easier implementation of educational programs.
• Unexplained visual loss.
• Traumatic visual loss with normal fundus.
• Patients on neurotoxic medications like Ethambutol etc.
• In sibling affected with the known retinal disorders.
• Pediatric Neurology problems, developmental delay children with normal fundus to estimate their visual potential.
• Multifocal ERG to find out the retinal function in macular disorders and to demarcate the areas of normal function.
• Pattern ERG and VEP to differentiate between the retinal and the optic nerve dysfunction.