ELECTRORETINOGRAM IN RECENT OPTOMETRY.pptx

ELECTRORETINOGRAM IN RECENT OPTOMETRY

1. SEMINAR PRESENTED ON ELECTRORETINOGRAM PRESENTED BY: UFOMBA IHEANYI 13/91516 MBUKO CHINURU 13/91523 DEPARTMENT OF OPTOMETRY LECTURER: DR. ANDREW OMAKA 16 TH DEC. 2021

2. ELECTRORETINOGRAM * Introduction *History *The need for an electroretinogram *Test procedures of an electroretinogram *Types of electroretinogram measurement *Types of electroretinogram recording *Limitations of electroretinogram test *Risk factors associated with electroretinogram test. *Conclusion *References.

3. INTRODUCTION Electroretinogram (ERG) is a test that measures the electrical response of the light sensitive cells in the eyes. These cells are known as the rods and cones. The rods are located in the peripheral part of the retina while the cones are more concentrated in the fovea centralis . The cones are responsible for the eyes color sensitivity while the rods are sensitive to light than the cone. ERG is indicated for pre-operative examination of cataract and early diagnosis of inherited disease. It is used worldwide to assess the status of the retina in eye disease in human patient and in laboratory animals used as model of retina diseases

4. HISTORY 1865 holmgren , James Dewar of scotland (humans ) 1903 GOTCH was the first to report that the eyes to light flash consisted of two waves 1908 Einthoven and Jolly separated ERG response into three components. 1941 Lorin Riggs introduce a contact lens electro for ERG recording. 1967 Grant’s studies were primary conducted on dark-adapted rod-dominated cat retina 1989 ISCEV standards (international society for clinical electropysiology of vision). 1992 Enrich Sutter mfERG (multifocal electroretinogram )

5. THE NEED FOR AN ELECTRORETINOGRAM An eye doctor may perform an ERG to determine if a patient has an inherited or acquired disorder of the retina, such as: 1. Retinitis pigmentosa , which is a genetic disease causing loss of peripheral and night vision. 2. Macular degeneration, which is a loss of vision due to the death of cells in the macula. 3. Retinoblastoma, which is a cancer of the retina. 4. Retinal separation, which is a detachment of the retina from the back of the eyeball.

6. TEST PROCEDURES OF AN ELECTRORETINOGRAM The following occurs during an ERG: 1. Your doctor will ask you to lie down or sit in a comfortable position. 2. The eye is usually dialated with mydricyl eye drops, to enable better accessment of the fundus . 3 . If your doctor is placing an electrode directly on the eye, they will place anesthetic drops in your eyes, which will make them numb. 4. A device known as a retractor is used to hold open the eyelids . This will enable them to carefully place a small electrode on each eye. One type of electrode is about the size of a contact lens. Another type is a fine thread placed on the cornea. 5. Your doctor will attach another electrode to your skin so that it functions as a ground for the faint electrical signals made by the retina. Depending on what your doctor is looking for, they may only place electrodes on the skin around the eye instead of in the eye. 6. You’ll then watch a flashing light. Your doctor will conduct the test in normal light and in a darkened room. The electrode enables the doctor to measure your retina’s electrical response to light. The responses recorded in a light room will mainly be from your retina’s cones. The responses recorded in a darkened room will mainly be from your retina’s rods. 7. The information from the electrodes transfers to a monitor. The monitor displays and records the information. It appears as a-waves and b-waves. The a-wave is a positive wave that originates mainly from your eye’s cornea. It represents the initial negative deflection of a flash of light measuring rods and cones. The b-wave, or positive deflection, follows. The plot of the b-wave’s amplitude reveals how well your eye reacts to light.  

7. TYPES OF ELECTRORETINOGRAM MEASUREMENT Full-field Electroretinogram ( ffERG ): ffERG is useful in diseases that have Wide spread of retina dysfunction. The focal ERG (FERG) is used primarily to measure the functional integrity of central macular and is therefore useful in providing information in diseases limited to the macular. Multi-focal ERG ( mfERG ) this provides important information that is lacking in the ffERG allowing dysfunction within macular that might missed by the ffERG . The Pattern ERG pERG uses contrast reversing pattern stimuli to access macular retina ganglion cells (RGC) activity.

8. TYPES OF ELECTRORETINOGRAM RECORDING Burian -Allen (BA) Dawson-Trick- Litzkow (DTL) Jet: disposable plastic lens with a gold-plated peripheral circumference. Skin Electrode Mylar Electrode Cootton -wick. Hawlina-Konec Electrode.

9. LIMITATIONS OF ELECTRORETINOGRAM TEST ERG can not detect amplitude change in isolated lesions, like hole hemorrhage, a small patch of chlorioretinistis or localized area of retinal detachment. Disorder involving ganglion cells ( e.g tay sachs ’’ disease), optic nerve or striate cortex do not produce any ERG abnormality.

10. RISK FACTORS ASSOCIATED WITH ELECTRORETINOGRAM TEST. Duration of stimulus Size of retinal area illuminated Interval between stimuli Size of pupil Systemic circulation and drugs Development of retina Clarity of ocular media Age ERG amplitude can be reduced in high myopia Anesthesia

11. CONCLUSION Electrophysiological recording is a valuable asset for the clinician Electroretinogram test measure the function of different cell types and layers. ERG aid the clinicians to distinquish symptomatically similar diseases. It is essential that all electroretinogram tests are performed according to the standard established by ISCEV.

12. REFERENCES McCulloch DL, Marmor MF, Brigell MG, Hamilton R, Holder GE, Tzekov R, Bach M (2015). ISCEV Standard for full-field clinical electroretinography (2015 update). Doc Ophthalmol 130:1–12 Hood DC, Bach M, Brigell M, Keating D, Kondo M, Lyons JS, Marmor MF, McCulloch DL, Palmowski -Wolfe AM (2012). ISCEV Standard for clinical multifocal electroretinography (2011 edition). Doc Ophthalmol 124:1–13 Bach M, Brigell MG, Hawlina M, Holder GE, Johnson MA, McCulloch DL, Meigen T, Viswanathan S (2013). ISCEV standard for clinical pattern electroretinography (PERG) – 2012 update. Doc Ophthalmol 126:1–7 Frishman L, Sustar M, Kremers J, McAnany JJ, Sarossy M, Tzekov R, Viswanathan S. (2018). Protocol for the photopic negative response ( PhNR ) of the full-field electroretinogram . Doc Oph . 136:207-211. Brigell M, Bach M, Barber C, Moskowitz A, Robson J (2003). Guidelines for calibration of stimulus and recording parameters used in clinical electrophysiology of vision. Doc Ophthalmol 107:185–193.

13. THANK YOU