Electroretinogram Recording for Infants and Children under Anesthesia to Achieve Optimal Dark Adaptation and International Standards

Summary

Adhering to international standards and maintaining retinal dark adaptation are critical to acquire valid full-field electroretinogram responses in the diagnosis and management of inherited retinal diseases. A practical protocol using a portable darkroom is provided to obtain full-field electroretinogram for infants and children under sedation or general anesthesia in the operating room setting.

Abstract

Electroretinogram (ERG) is the only clinical objective test available to assess retinal function. Full-field ERG (ffERG) measures the panretinal rod and cone photoreceptor function as well as inner retinal function and is an important measure in the diagnosis and management of inherited retinal diseases as well as inflammatory, toxic, and nutritional retinopathies. Adhering to international standards and maintaining retinal dark adaptation are critical to acquire valid and reliable dark-adapted (scotopic) and light-adapted (photopic) ffERG responses. Performing ffERG in infants and children is challenging and often requires general anesthesia in the operating room. However, maintaining retinal dark adaptation in the operating room is becoming increasingly difficult given the numerous light sources from anesthesiology monitoring systems and other equipment. A practical and widely applicable method for ffERG testing is described in the operating room that optimizes retinal dark adaptation. The method reduces operating room time by dark-adapting the patient before general anesthesiology is instituted. The operating room is modified for dark adaptation and any remaining light source in the darkened operating room is minimized with the use of a modified portable foldable darkroom that encloses the patient’s head and the ERG examiner during ffERG scotopic recordings. The simple method adheres to ffERG international standards and provides valid reliable scotopic and photopic ffERG recordings that are critical to assess objective retinal function in this young age group where subjective assessment of visual function such as visual acuity and visual fields are not possible. Furthermore, the ffERG is the gold standard clinical test in detecting early onset inherited retinal diseases including Leber congenital amaurosis where approved gene therapy has become available. In sedated conditions, very low amplitude ffERG signals can be detected due to minimal orbicularis muscle activity interference, which is particularly relevant in patients after gene therapy to detect improved amplitude responses.

Introduction

The electroretinogram (ERG) is the only clinical objective test available to assess retinal function and the full-field ERG (ffERG) is the only objective test to assess rod-photoreceptor generated activities^1,2. The ffERG measures the electrical responses from the entire retina elicited by a full-field flash stimulus and is a gold standard test in the diagnosis and management of inherited retinal diseases^2,3. Thus, the ffERG is an important test in infants and young children to detect early onset inherited retinal diseases such as Leber congenital amau....

Protocol

The protocol follows the operating room guidelines of the Bascom Palmer Eye Institute, University of Miami and is applicable to infants, young children, and uncooperative adults. Patients who cannot have general anesthesia due to safety issues should not have the procedure.

1. Operating room selection and modification

1. Select an operating room with low 60 Hz background electric current noise and proper electrical grounding, to avoid ERG recording interference. Use a room with an isolated electrical circuit without connection to or is near heavy appliances (e.g., refrigerator).
   1. Perform trial ERG recordings in the opera....

Results

Using the method described, valid, reliable, interpretable normal and abnormal ffERG responses are feasibly obtained in the operating room for infants and young children under sedation or general anesthesia. In particular, falsely low scotopic ffERG responses are avoided, and common retinal causes of decreased vision and nystagmus in this age group are readily identified. For instance, the preservation of scotopic ffERG responses is important to differentiate Leber congenital amaurosis from achromatopsia where the cone f.......

Discussion

The methodology and protocol describe how to effectively perform valid and reliable ffERG in infants and children under sedation or general anesthesia in the operating room. The major concept and aim of the technique are to provide and maintain optimal retinal dark adaptation during scotopic ffERG recordings. This is essential to provide accurate objective assessment of rod photoreceptor function given retinal dark adaptation is rapidly diminished by exposure even to dim light leading to erroneous recorded responses. The.......

Materials

Name	Company	Catalog Number	Comments
Black tape	3M Industrial Adhesives and Tapes Division, St Paul, MN 55144-1000 USA	3M ID 70016070396
Conduction and abrasive paste	Redux Paste (Electrolyte Paste) Hewlett Packard company, USA. Nuprep (Sking Prep Gel) and Ten20 (Conductive Neurodiagnostic Electrode Paste) Weaver and Company, CO, USA	67-05
Darkroom - Portable foldable	Scientex	B-LP1/B-LP1-X	Available in different sizes
Dark adaptation mask (relaxation sleeping mask)	Mindfold Inc, Durango, CO, USA	6576493	Flexible black plastic face plate backed with a high-density soft foam padding that allows total darkness.
Ear clips for electric grounding	Grass	F-E34DG-72	Grass 10mm Gold Cup EEG Ear Clip with touchproof connector 72" wire - Set of 2
Electrodes ERG recording (Burian-Allen, DTL)	Burian-Allen, Hansen Ophthalmic Develoment Lab, Iowa, USA; DTL, Diagnosys, Lowell, MA 01854, USA.	303-20LA, 303-20A, 303-20P, 303-20I, 303-20SI	Available in different sizes, requires modification as described in Protocol.
ERG systems including handheld full-field stimulus	Any system meeting the standards established by the International Society for Clinical Electrophysiology of Vision (ISCEV).		Authors use Diagnosys and Roland systems; other ISCEV standard systems available.
Eye drops, propracaine, metilcellulose, phenilephrine, ciclopentolate,	Tropicamide 1% Phenylephrine 2.5% Cyclopentolate 1% Proparacaine 0.5% Akorn, Inc. Forest, IL 60045 GONIOTAIRE (Hypromellose 2.5%) Altaire Pharmaceuticals, Inc. NY, NY, USA 11931
Eye Patch	BSN Medical Inc, Rutherford College, NC	46430-00	Coverlet eye occlusor for treatment of lazy eye
Head band with light	REMIX PRO. Princeton Tec, Trenton, NJ 08650	RMX300PRO-RD-BK	Requires placing layers of red filters over LED as described in protocol