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ELECTRORETINOGRAM (ERG) Lafiona Grezelda (37540) Rani Mahita Aji (36519) Katarina Dara A (36417)

Electroretinogram (Erg)

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Page 1: Electroretinogram (Erg)

ELECTRORETINOGRAM (ERG)

Lafiona Grezelda (37540)Rani Mahita Aji (36519)Katarina Dara A (36417)

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ERG

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HISTORY The first human ERG recordings were obtained in

1877 by James Dewar, but recordings were not stable enough for quantitative measurements until the introduction of the contact lens electrode in 1941 by Lorrin Riggs.

In 1991, Erich Sutter developed a new method, combining the advantages of the focal and pattern stimulation into one procedure called multifocal ERG.

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WHAT IS ELECTRORETINOGRA

PHY ? Electroretinography (ERG) is an eye test used to

detect abnormal function of the retina (the light-detecting portion of the eye).

Specifically, in this test, the light-sensitive cells of the eye, the rods and cones, and their connecting ganglion cells in the retina are examined.

During the test, an electrode is placed on the cornea (at the front of the eye) to measure the electrical responses to light of the cells that sense light in the retina at the back of the eye. These cells are called the rods and cones.

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HUMAN EYE

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HOW EYE CAN DETECT COLOR ?

There are about 120 million rods and about 6 to 7 million cones, in the human eye.

Rods are more sensitive than the cones but they are not sensitive to colour, they perceive images as black, white and different shades of grey

Each cone contains one of three pigments sensitive to either RED GREEN or BLUE.

Each pigment absorbs a particular wavelength of colour. There are short wavelength cones that absorb blue light, middle wavelength cones that absorb green light, and long wavelength cones that absorb red light.

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HOW AN ERG DONE ?The ISCEV Standard specifies five responses: (1) Dark-adapted 0.01 ERG (rod response); (2) Dark-adapted 3.0 ERG (combined rod-cone

response); (3) Dark-adapted 3.0 oscillatory potentials; (4) Light-adapted 3.0 ERG (cone response); (5) Light-adapted 3.0 flicker (30 Hz flicker).

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HOW AN ERG DONE ?

Pre-adaptation of dark

Dark-adapted 0.01 ERG (rod response)

Dark-adapted 3.0 ERG (combined rod–cone

response)

Dark-adapted 3.0 oscillatory potentials

Pre-adaptation of light

Light-adapted 3.0 ERG (single-flash cone

response)

Light-adapted 3.0 flicker ERG (30 Hz flicker)

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DARK-ADAPTED 0.01 ERG (ROD RESPONSE)

Dark-adapt the patient for a minimum of 20 min before recording the dark-adapted ERG (and longer if the patient had been exposed to unusually bright light).

The Dark-adapted 0.01 ERG is normally the first signal measured after dark adaptation, because it is the most sensitive to light adaptation.

The stimulus is a dim white flash of 0.01 cd.s.m-2; with a minimum interval of 2 s between flashes.

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DARK-ADAPTED 3.0 ERG (COMBINED ROD–CONE

RESPONSE) This is produced by a white 3.0 cd.s.m-2 flash in the

dark-adapted eye. There should be an interval of at least 10 s between stimuli.

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DARK-ADAPTED 3.0 OSCILLATORY POTENTIALS

Dark-adapted oscillatory potentials should be obtained from the dark-adapted eye, using the 3.0 cd.s.m-2 flash stimulus.

The high-pass filter must be set at 75–100 Hz, and the low pass filter set at 300 Hz or above.

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LIGHT-ADAPTED 3.0 ERG (SINGLE-FLASH CONE RESPONSE)

Use a 3.0-cd.s.m-2 stimulus, with at least 0.5 s between flashes.

To achieve stable and reproducible cone ERGs, a minimum of 10 min light adaptation is required,

The background luminance should be 30 cd.m-2

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LIGHT-ADAPTED 3.0 FLICKER ERG (30 HZ FLICKER) Flicker ERGs also reflect activity of the cone

system, and should be obtained with 3.0-cdsm-2 stimuli,

Flashes should be presented at a rate of approximately 30 stimuli per second (30 Hz), and the rate that is chosen should be constant for the laboratory.

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HOW AN ERG DONE ? During the ERG test, you will wear eye patches and sit

in a dark room for 20 - 40 minutes. Then the researcher will tape electrodes to your

forehead (this is painless, as are all uses of electrodes in these tests) and remove the eye patches.

The surfaces of your eyes will be numbed with eye drops, and contact lenses will be placed on your eyes. You will look inside a hollow, dark globe and see a series of light flashes.

Then a light will be turned on inside the globe, and more flashes will appear. The contact lenses sense small electrical signals generated by the retina when the light flashes.

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WHAT DO THE ELECTRODES DO?

Function :The electrodes measure the electrical activity of the retina in response to light. The information that comes from each electrode is transmitted to a monitor where it is displayed as two types of waves, labeled the A waves and B waves.

Recording Electrodes Reference Electrodes Ground Electrodes Skin Reference Electrodes Characteristic Electrode Stability Electrode Cleaning

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STIMULATION Light Diffusion Full-Field ( Ganzfeld ) stimulation Duration stimuli should consist of flashes having a

maximum duration of 5ms. Stimulus Wavelength Flash stimuli should have a

color temperature near 7,000 K Stimulus Strength:

(1) For rod stimulation: 0.01 cd.s.m-2

(2) For all other standard responses: 3.0 cd.s.m-2

(this flash was formerly designated as the “ Standard Flash” )(3) Light adaptation and background luminance: 30 cd.m-2

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LIGHT SOURCE Xenon flash tube. LED

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HOW ARE ELETRORETINOGRAPHY

READINGS MADE?

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WHAT DOES AN ABNORMAL ERG MEAN?

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WHAT DOES AN ABNORMAL ERG MEAN?

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WHAT DISEASES IS MY DOCTOR LOOKING FOR WITH AN ERG?

Retinitis pigmentosa choroideremia, gyrate atrophy of the retina, Goldman-Favre syndrome, congenital stationary night blindness X-linked juvenile retinoschisis Achromatopsia cone dystrophies Usher syndrome

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WHAT ARE THE RISKS OF AN ERG?

There are no risks specifically associated with an ERG. Some patients experience mild ocular discomfort during or after the procedure. Rarely, a corneal abrasion may occur, which is readily treated with early detection. If you believe you have irritation or a corneal abrasion following an ERG, you should call your eye doctor or the doctor who ordered your ERG

The test is painless. However, the electrode that rests on the eye may feel a little like an eyelash has lodged in the eye. This sensation may persist up to several hours following completion of the ERG.

But, one should not rub the eyes for an hour after an ERG (or any test in which the cornea has been anesthetized), lest one injure the cornea.

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QUESTIONS PLEASE..

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PERTANYAAN DAN JAWABAN Panjang gelombang dapat di representasikan

dalam satuan kelvin.Wien’s displacement Law

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achromatopsia itu apakah sama dengan buta warna?

Ya, achromatopsia merupakan buta warna penuh. Pada kelainan ini, hanya rod saja yang bekerja, sedangkan cone nya tidak. Jadi bagi penderita kelainan ini, dunia hanyalah hitam, putih dan abu abu

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Tes achromatopsia bisa dilakukan dengan menggunakan tulisan berwarna seperti yang biasa dilakukan di dokter biasa, mengapa pelu menggunakan ERG?

Tes buta warna memang dapat dilakukan dengan cara itu, namun hanya bisa dilakukan untuk orang dewasa. Untuk anak-anak yang belum bisa membaca, perlu dilakukan tes ERG untuk mendeteksi kelainan tersebut.

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Dimanakan letak cone dan rods?

Cone dan rods merupakan syaraf, dan berada di bagian belakang retina

Gambar

Lala ahlinya....

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Respon terhadap cahaya apakah hanya dilihat dari bentuk gelombang yang dihasilkan?

Tidak, selain dari bentuk gelombangnya, pembacaan bisa dilihat dari delay dan amplitude sinyal output ERG,

Terdapat data delay dan amplitude standar yang dimiliki mata normal

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Apakah beda prosedur dark adapted 3.0 ERG dan dan dark adapted 3.0 oscillatory potentials?

Keduanya memang menggunakan intensitas stimulus yang sama, 3.0 cd.s.m-2 . Bedanya ada pada delay antar stimulus.

Pada dark adapted 3.0 ERG jarak antar stimulusnya sebesar 10s sedangkan pada tes dark adapted 3.0 oscillator potential, jarak stimulus nya 15 s

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Pada hasil tes ERG penderita penyakit XL juvenille retinoschisis, left-right nya beda, mengapa? Apakah tiap tes juga diperiksa kanan dan kiri?

XL juvenille retinoschisis merupakan penyakit penurunan ketajaman penglihatan. Hasil mata kanan dan kiri bisa berbeda bentuk gelombangnya karena penurunan ketajaman penglihatannya pun juga berbeda.

Pada tiap tes mata kanan dan kiri di tes semua, namun pada mata normal harusnya respon mata dan kiri sama.

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Oscillatory potential fungsinya apa?

Oscillatory potential perlu di uji pada tes ERG karena oscillatory potential merupakan penggambaran dari respon antar saraf di retina. Penting bagi kita untuk tahu apakah keadaan antar saraf bekerja dengan normal atau tidak.

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Apakah kerja dokter dalam diagnosis hasil pembacaan erg bisa diganti mesin?

Bisa, hasil pembacaan ERG bisa dikuantisasi (diukur ukuran gelombang dengan pasti),

Dengan adanya database gelombang mata normal dan mata yang memiliki kelainan maka data tersebut dapat dikomparasi secara otomatis oleh software untuk selanjutnya didiagnosa. Jadi tidak harus dokter yg mendiagnosa

Namun, selama ini hasil tes ERG masih didiagnosa oleh dokter.

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Apa efek pengucekan setelah melakukan tes ERG?

Dara ahlinya....