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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.
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.
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 activities1,2. 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 diseases2,3. Thus, the ffERG is an important test in infants and young children to detect early onset inherited retinal diseases such as Leber congenital amaurosis where approved gene therapy and clinical trials are available4,5.
Adherence to ffERG standards established by the International Society for Clinical Electrophysiology of Vision (ISCEV) are critical to acquire valid and reliable dark-adapted (scotopic) and light-adapted (photopic) ffERG responses1,3. Failure to properly maintain adequate retinal dark adaptation during scotopic ffERG recordings results in falsely-impaired recorded responses and patient mismanagement. Performing ffERG in infants and children is challenging given limited cooperation and often requires general anesthesia in the operating room6. A recent survey among ISCEV members showed 12-14% of ERG’s are performed under sedation or general anesthesia7. Maintaining retinal dark adaptation in the operating room is difficult given the numerous light sources from anesthesiology monitoring systems and other equipment. While anesthetic agents may have an effect in reducing ERG responses, ERG responses under sedation or general anesthesia are reliable in providing accurate diagnosis6,8,9.
A simple and widely applicable method is described for ffERG testing in the operating room that adheres to the international standards and optimizes retinal dark adaptation. The goal of this practical method is to provide valid reliable scotopic and photopic ffERG recordings to assess objective retinal function in infants and young children, which is particularly relevant in this young age group given subjective assessment of visual function such as visual acuity and visual fields are typically not possible. The operating room is modified to promote retinal dark adaptation, and the procedures reduce operating room time by dark-adapting the patient before sedation or general anesthesiology is instituted. A modified portable foldable darkroom encloses the patient’s head and the ERG examiner during ffERG scotopic recordings to minimize any remaining light source including light emission from the ERG system. The portable darkroom allows rapid access to the patient by the anesthesiologist when necessary. After the completion of ffERG, diagnostic retinal imaging including optical coherence tomography (OCT) and fundus imaging as well as venopuncture for genetic testing can easily be performed while the patient remains under anesthesia.
The method is suitable for practitioners and practices that manage pediatric patients with retinopathies. An average sized ocular operating room provides adequate space, and a room with low background electrical noise is desirable to allow quality ffERG recording. While the ERG examiner is inside the foldable darkroom during scotopic ffERG recording, a trained technician is needed to operate the ERG system outside of the foldable darkroom. Conferring with the anesthesiology team is essential in modifying the operating room and to promote the safety of the patient in a darkened environment.
The advantages of the method over alternative techniques include optimizing and maintaining retinal dark adaptation, promoting valid reliable ffERG recordings, improving patient safety, and facilitating additional diagnostic testing such as retinal imaging and venopuncture for genetic testing. Optimal dark adaptation is also critical given ffERG stimulators should be calibrated for complete darkness conditions as recommended by ISCEV10. Alternative methods include the use of oral agents such as chloral hydrate with variable sedative responses in infants and children, which affects the quality of ffERG recordings and causes difficulties in monitoring vital signs. While some children can cooperate with ffERG recording in the clinic, the testing session may be prolonged depending on cooperation, and the validity of ffERG recordings may be affected by eye movement and blink artifacts as well as difficulty in maintainng retinal dark adaptation4. The current method provides additional dark adaptation and safety measures compared to the previously described deep sedation ffERG method6.
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
2. Foldable portable darkroom selection and modification
3. Patient preparation and retinal dark adaption
4. Dark-Adapted full-field electroretinogram recording in the operating room
5. Light-Adapted full-field electroretinogram recording in the operating room
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...
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...
The authors have nothing to disclose.
This paper is supported in part by the James V. Bastek, M.D. Hereditary Retinal Disease Research Program, Bascom Palmer Eye Institute, University of Miami, FL, USA; NIH Center Core Grant P30EY014801; Research to Prevent Blindness Unrestricted Award and Career Development Awards; Florida Lions Eye Bank and the Beauty of Sight Foundation, Miami, FL, USA; and Henri and Flore Lesieur Foundation.
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 |
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