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.
Full-field electroretinogram is an important objective retinal function test. Our method optimizes retinal dark adaptation to acquire valid and reliable full-field ERG responses in infants and young children under anesthesia. Performing full-field ERG in young children under general anesthesia in the operating room improves patient safety and facilitates the performance of the job they noticed testing.
Full-filled ERG is important for detecting retinal dysfunction, including early onset inherited retinal diseases, such as Leber congenital amaurosis in settings, in which approved gene therapy and clinical trials are available. After selecting an appropriate operating room, install black washable opaque non-reflective stain and bacterial resistant curtains onto tracks to fully cover the operating room door and window openings without light leakage. Place translucent red filter films over monitors.
And opaque black tape over LEDs and other light sources and check for unblocked light sources. set up a portable dark room that is easy to install and store and large enough to enclose the patient's head, ERG examiner and full-field ERG stimulus. The backside of the portable dark room should be modified with a small opening with flaps to allow the routing of connections and cables without light leak.
After obtaining informed consent, administer ocular anesthetic to each eye, followed by the delivery of pupillary dilation combo drops. To patch the eyes for retinal dark adaptation with the eyelids gently and completely closed, place one regular sized self-adhesive eye occlusion patch in a conventional horizontal orientation over each eye with the wider end of the patch, temporarily oriented. Place a second patch over the first patch and adjust the position with a tilt to prevent nasal light leak.
After both patches have been placed, cover eyes with opaque black tape, with a small vertical cut at the inferior edge over the bridge of the nose without applying significant pressure to the eyes. Then place a black opaque, relaxation sleeping mask with a headband over the patched eyes for at least 30 minutes of retinal dark adaptation. For dark adapted scotopic ERG recording transfer the patch patient to the operating room And administer general anesthesia.
According to standard hospital protocols. Before starting the dark adapted the ERG recording, put on a very dim red light mounted on a forehead band and place a ground ERG electrode coated with conductive jelly on one ear lobe. Insert the ground ERG electrode connection and full field ERG light stimulus cable through the modified flat opening of the portable dark room.
And have the ERG technician connect the cables to the ERG system outside of the dark room. Then turn off the room lights and cover any remaining uncovered light sources with black tape. Using the minimum amount of dim red light, remove the black mask covering both eyes and remove the black tape and patches from the right eye.
Place the corneal ERG recording electrode on the right eye and use a handheld full-field light stimulus in accordance to ISCEV standards to record this scotopic full-field ERG responses. After checking for ERG electrode impedance and electrical baseline stability, record the dark adapted rod responses the combined rod cone responses and the dark adapted flash Oscillatory Potential responses. Then remove the black tape and patches from the left eye.
And repeat this scotopic full-field ERG recording for the left eye as just demonstrated. When all of the scotopic full-field ERG readings have been recorded, turn on all of the overhead room lights and disconnect the ERG electrode connections and full-field ERG light stimulus cable from the ERG recording system. Remove the portable dark room and light adapt to both eyes for 10 minutes with the overhead lights in accordance with the ISCEV standards.
During the light adaptation, keep the bipolar Burian-Allen electrode ERG electrodes in place for both eyes, then connect the ERG electrode connections and full field ERG light stimulus cable to the ERG system. At the end of the light adaptation period, record the cone flash and Cone flicker Responses in accordance with ISCEV standards. Using the method as demonstrated, valid, reliable, interpretable, normal and abnormal full field ERG responses are feasibly obtained in the operating room for infants and young children under sedation or general anesthesia.
For example, the preservation of scotopic full-field ERG responses is important for differentiating Leber congenital amaurosis from achromatopsia as the cone full-field ERG responses are diminished in both conditions but the scotopic full-field ERG responses are preserved in achromatopsia only. The presence of a negative b-wave in a scotopic combined rod cone full-field ERG response is a key feature of congenital stationary night blindness. The method can also be used to reliably determine disease progression over time.
For example, this systemic features of Alstrom syndrome are subtle in very young patients and the initial full-field ERG responses may be similar to achromatopsia with a relative preservation of scotopic full field ERG responses and diminished cone responses. Over time, the scotopic full-field ERG responses worsen as in this case of Alstrom syndrome demonstrating a cornea dysfunction pattern that is also seen in conditions such as cone-rod dystrophy and other secondary syndromic cone-rod degenerations. Important parts of our procedure is to dilate the pupils fully, to place the multi-layer eye patches and mask well, and to use the least amount of dim in light during the dark adapted ERG recording.
After the procedure, a filmic examination, retinal imaging including OCT and fundus photos and a blood draw for genetic testing can also be performed for patient diagnosis and management.
