The document provides information on electroretinography (ERG) and electrooculography (EOG). It discusses the history and basic components of the ERG waveform. It describes how ERGs can be used to evaluate different retinal conditions like retinitis pigmentosa and macular degeneration by isolating rod and cone responses. It also outlines the International Society for Clinical Electrophysiology of Vision standardized ERG protocol. The document concludes by explaining how EOG works by measuring the electrical potential between the cornea and fundus under dark and light adapted conditions.
Electrooculography is a technique for measuring the corneo-retinal standing potential that exists between the front and the back of the human eye. The resulting signal is called the electrooculogram. Primary applications are in the ophthalmological diagnosis and in recording eye movements
Electrooculography is a technique for measuring the corneo-retinal standing potential that exists between the front and the back of the human eye. The resulting signal is called the electrooculogram. Primary applications are in the ophthalmological diagnosis and in recording eye movements
DIRECT DOWNLOAD LINK ❤❤https://healthkura.com/ocular-ultrasound/❤❤
Dear viewers Check Out my other piece of works at___ https://healthkura.com
Ocular Ultrasonography (Ocular USG/ Ophthalmic USG), ophthalmic ultrasound/ ophthalmic ultrasonography/ ocular ultrasound/ Ultrasound of eye and orbit
PRESENTATION LAYOUT
Introduction
History
Physics
Principles & instrumentation
Terminologies
Indications & contraindications
Methods - A-Scan - B-Scan
Interpretation
Definition
Ultrasound Waves are acoustic waves that have frequencies greater than 20 KHz
The human ear can respond to an audible frequency range, roughly 20 Hz - 20 kHz
......................
For Further Reading
Clinical Procedures in Optometry by J. D. Barlett, J. B. Eskridge & J. F. Amos
Ophthalmic Ultrasound: A Diagnostic Atlas by C. W. DiBernardo & E. F. Greenberg Internet
DIRECT DOWNLOAD LINK ❤❤https://healthkura.com/ocular-ultrasound/❤❤
Dear viewers Check Out my other piece of works at___ https://healthkura.com
Ocular Ultrasonography (Ocular USG/ Ophthalmic USG), ophthalmic ultrasound/ ophthalmic ultrasonography/ ocular ultrasound/ Ultrasound of eye and orbit
PRESENTATION LAYOUT
Introduction
History
Physics
Principles & instrumentation
Terminologies
Indications & contraindications
Methods - A-Scan - B-Scan
Interpretation
Definition
Ultrasound Waves are acoustic waves that have frequencies greater than 20 KHz
The human ear can respond to an audible frequency range, roughly 20 Hz - 20 kHz
......................
For Further Reading
Clinical Procedures in Optometry by J. D. Barlett, J. B. Eskridge & J. F. Amos
Ophthalmic Ultrasound: A Diagnostic Atlas by C. W. DiBernardo & E. F. Greenberg Internet
Electroretinography measures the electrical responses of various cell types in the retina, including the photoreceptors, inner retinal cells, and the ganglion cells. Electrodes are placed on the surface of the cornea or on the skin beneath the eye to measure retinal responses.
Electrophysiological techniques allow clinical investigations to include a ‘dissection’ of the visual system. Using suitable electrophysiological techniques, the ‘dissection’ allows function to be ascribed to the different photoreceptors (rod and cone photoreceptors), retinal layers, retinal location or the visual pathway up to the visual cortex. Combined with advances in genetics, retinal biochemistry, visual fields and ocular imaging, it is now possible to obtain a better understanding of diseases affecting the retina and visual pathways.
The clinical electro-oculogram is an electrophysiological test of function of the outer retina and retinal pigment epithelium in which the change in the electrical potential between the cornea and the fundus is recorded during successive periods of dark and light adaptation.
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdfJim Jacob Roy
Cardiac conduction defects can occur due to various causes.
Atrioventricular conduction blocks ( AV blocks ) are classified into 3 types.
This document describes the acute management of AV block.
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...VarunMahajani
Disruption of blood supply to lung alveoli due to blockage of one or more pulmonary blood vessels is called as Pulmonary thromboembolism. In this presentation we will discuss its causes, types and its management in depth.
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
2. ERG
History
Holmgren in 1865 first demonstrated that
an alteration in electrical potential
occurred when light fell on retina.
In1877. Dewar recorded light evoked
electrical response, ERG, from humans
for the first time.
In1941, Riggs introduced the contact lens
electrode in humans
3. ERG
Full-field Electroretinogram (ERG) is a
mass electrical response of the retina to
photic stimulation.
Basic method of recording is by
stimulating the eye with a bright light
source such as a flash produced by LEDs
or a strobe lamp.
The flash of light elicits a biphasic
waveform recordable at the cornea.
4. Basic wave forms
The two components that are most often
measured are the a- and b-waves.
a-wave is the first large negative
component, followed by the b-wave which
is corneal positive and usually larger in
amplitude
5. Physiology of ERG
“a” wave aka late receptor potential
When light falls on photo receptors
Hyperpolarisation
Outer portion of photoreceptor becomes
positive
Inner part becomes negative
A wave shows downward deflection
Reflects the potential of photoreceptors in outer
6. b wave
b wave - Reflects the function of the inner
layers of the retina, including the ON
bipolar cells and the Muller cells.
Muller cell is a glial cell ( has no synaptic
connection )
It respond to potassium concentration in
extracellular space
7. Light strikes a photoreceptor
Potassium released from photorecptors
( amount dependent on Light Intensity )
Muller cell respond by changing its
membrane potential
b wave is dependent on the electrical
activity within photoreceptors
Muller cells can provide a b wave from
eithyer cone or rod receptors
8. c Wave
Positive wave
Reflects function of pigment epithelium in
response to rod signals only
d wave
Reflects Off bipolar cells
9.
10. Ops - some wavelets that occur on the rising
phase of the b-wave known as oscillitatory
potentials (OPs).
OPs are thought to reflect activity in amacrine
cells
11. Two principal measures of the ERG
waveform are taken:
1) The amplitude
2) The time
Amplitude:-
a wave- from the baseline to the negative
trough of the a-wave
b-wave measured from the trough of the a-
wave to the following peak of the b-wave
Time:-
(t)a from flash onset to the trough of the a-
wave (t)b from flash onset to the peak of the
b-wave
These times, reflecting peak latency, are
12.
13. ERG recording electrodes
Pupils are dilated
Different types of electrodes used
Burian Speculum that hold the eye open
and have a contact lens with a wire ring
that “floats” on the cornea supported by a
small spring.
Cotton wick electrodes
Gold Mylar tape that can be inserted
between the lower lid and sclera/cornea.
14.
15.
16.
17. Light stimulation for ERGs.
Strobe lamp and LEDs - mobile and can be
easily placed in front of a person whether sitting
or reclining.
Mobility of a strobe lamp or an array of LEDs is
a necessity in some situations such as at the
hospital bedside or in the operating room
18. Ganzfeld stimulation globe
The Ganzfeld allows the best control of
background illumination and stimulus
flash intensity.
19. Rod and cones erg
Implicit times and amplitudes vary
depending upon whether the eye is dark
adapted or not, and brightness and color
of the light stimulus.
These parameters allow separation of rod
and cone activity in retina.
Normally there are120 million rods in each
retina and about 6-7 million cones.
The ERG following a white flash is
dominated by the mass response of the
rods( due to large number )
20. Rod and cone activity can be isolated
Adaptation level
Background illumination
Rate of stimulation
Color of the flash
Flash intensity
21. Color stimulus
Peak wavelength sensitivity for rods is around
510 nm and the peak sensitivity of cones as a
group is about 560 nm
By using color filters such as the Kodak Blue
and Red Wratten series rods and cones can be
differentiated
22. Rod and cone ERGs can also be isolated using
dim flash stimuli into photopic (cone)and
scotopic (rod) signals
Dim red flashes stimulate both rod and cone
function producing a small photopic component
bx and larger rod b-wave.
Rods are about three log units more sensitive
than cones.
Cones recover faster than rods.
23.
24. Rate of stimulus
Rates (flicker) of stimulus presentation
also allows rod and cone contributions to
the ERG to be separated.
Even under ideal conditions rods cannot
follow a flickering light up to 20 per
second whereas cones can easily follow
a 30 Hz flicker.
This is the rate routinely used to test if a
retina has good cone physiology.
27. Standard Full Field ERG
ISCEV Standard ERG Protocol
In 1989, the International Society for
Clinical Electrophysiology of Vision
(ISCEV) developed a protocol to
standardize ERG testing so test results
could be compared worldwide.
The protocol consists of five separate
tests, each designed to evaluate different
areas or functions of the eye.
28. Dim Scotopic Flash ERG
This is the first step in the International
Society for Clinical Electrophysiology of
Vision (ISCEV) standard ERG protocol.
It is conducted with a -25 dB flash.
In a dark-adapted eye, a dim flash tests
a response arising from the rods primarily
and associated glial cells.
29. Maximum Scotopic Flash
ERG This is the second step in the
International Society for Clinical
Electrophysiology of Vision (ISCEV)
standard ERG protocol.
It is conducted with a 0 dB flash.
In a dark-adapted eye, a moderate flash
tests a response from both the rods and
cones.
30. Oscillatory Potentials (OPs)
This is the third step
The oscillatory potentials are high-frequency
oscillations or wavelets seen on the leading-
edge of the b-wave.
The oscillatory potentials measure of function of
the amacrine cells and become abnormal early
in retinal ischemia.
31. Photopic Flash ERG / Single
Flash
Cone Response This is the fourth step
It is conducted with a 0 dB flash. In a
light-adapted eye, a moderate flash tests
a response arising from the cones
32. 30 Hz Flicker ERG
This is the fifth step
In a light-adapted eye, a flicker ERG tests
a response arising from the cones.
The flicker ERG has also been shown to
be useful in patients with diabetic
retinopathy.
34. The first two responses are scotopically matched
blue and red ERGs.
The blue flash was dim enough that no a-wave can
be discerned in a normal patient leaving only the rod-
dominated slower b-wave.
The red flash is bright enough that photopic
oscillations and bx component can be observed just
after the a-wave.
Bright white flash in the dark produces the largest
amplitude ERG.
The 30 Hz flicker illustrates the response of the
rapidly recovering cones.
Photopic response is representative of a normal
response with the more sensitive rods bleached by
background illumination.
Oscillatory potentials on the ascending b-wave are
seen in responses to moderate-high intensity white
flashes and in response to red, yellow, and green
35. Stationary rod dystrophies
Congenital stationary night blindness
(CSNB) is found in several forms.
Two types.
Type 1 have an abnormal dim scotopic
ERGs but the bright flash ERG maintains
oscillatory potentials on the ascending
limb of the b-wave.
Type 2 has a very abnormal dim scotopic
ERG and the bright flash scotopic ERG
has a large a-wave and no b-wave.
Oscillatory potentials are also missing
36.
37. The bright flash ERG b-wave is selectively attenuated
in:
Juvenile retinoschisis
Coat’s disease
Central retinal vein occlusion and central retinal artery
occlusion
Myotonic dystrophy
Congenital stationary night blindness Type 2
Oguchi’s disease
Lipopigment storage diseases (Batten’s disease)
Creutzfeldt-Jacob (CJD)
38. Disorders result in a completely extinguished
ERG
Leber’s congenital amaurosis
Severe retinitis pigmentosa
Retinal aplasia
Total detachment of retina
Ophthalmic artery occlusion
39. ERG in cone dystrophies
ERGs of a patient with a cone dystrophy
exhibit good rod b-waves that are just
slower.
The early “cone” portion (bx) of the
scotopic red flash ERG is missing.
The scotopic bright white ERG is fairly
normal in appearance but with slow
implicit times.
The 30 Hz flicker and photopic white
ERGs dependent upon cones are very
poor.
40.
41. ERGs in retinal vascular disease
Vascular occlusions –
avascular appearance to
select areas of the fundus
ERG with no b-wave
Ophthalmic artery
occlusions usually result
in unrecordable ERGs.
42. Foreign bodies and Trauma
A small piece of stainless steel or plastic
outside the macula may have a minor
affect on the retina.
A piece of copper or iron have deleterious
affects within a few weeks
In general if b-wave amplitudes are
reduced 50% or greater compared to the
fellow eye, it is unlikely that the retinal
physiology will recover unless the foreign
body is removed.
43.
44. Drug toxicities.
Several drugs taken in high doses or for
long periods of time can cause retinal
degeneration with pigmentary changes.
Thioridazine
Chlorpromazine
Vigabatrin
Chloroquine
Hydroxychloroquine
The effects of toxic medications can be
detected and quantified using ERGs.
45. The effects of toxic medications can be
detected and quantified using ERGs.
Chloroquine retinopathy appears as a
characteristic “bullseye” maculopathy
46. The better substitute for chloroquine,
Plaquenil, can also have macular effects
noticeable by multifocal
electroretinograms.
Hydroxychloroquine (Plaquenil) is usually
less disruptive to the retina than
chloroquine, but ERG changes can still
occur.
Vigabatrin, a pediatric seizure medication,
can be toxic to the retina.
Attenuation of full-field ERG b-wave
amplitudes can detect toxicity.
Often the first indication of toxicity is
47. Cis-platinum used to treat brain tumors
sometimes reaches ophthalmic vascularization
and causes a reduction in ERG waveform in the
affected eye (OD in this case)
48. Steroid Retinopathy
The fundus photo shows a cherry red
spot in the macula. The ERG response
was diminished in size particularly
following dim scotopic flashes
50. Multifocal erg
Limitation of fferg - Unless 20% or more
of the retina is affected with a diseased
state the ERGs are usually normal.
Erich Sutter adapted the mathematical
sequences called binary m-sequences
creating a program that can extract
hundreds of focal ERGs from a single
electrical signal.
This system allows assessment of ERG
activity in small areas of retina.
mferg allows assessment of ERG activity
in small areas of retina.
51.
52. With this method one can record mfERGs
from hundreds of retinal areas in a
several minutes
55. Small scotomas in retina
can be mapped and degree
of retinal dysfunction
quantified.
61 or 103 focal ERG
responses can be recorded
from the cone-driven retina.
The tested area typically
spans 20-30 degrees to
each side of the fovea
56. Pattern erg
The pattern ERG provides a useful
measure of macular function and
generalized bipolar cell function.
The most common stimulus is a
checkerboard stimulus composed of
white and black squares
PERG generation requires physiological
integrity of anatomically present RGCs
Reduction of PERG amplitude reflect the
reduced activity of dysfunctional RGCs
57. PERG reflects inner retina activity under
light-adaptation.
The PERG should be used in
combination with a traditional light-
adapted luminance ERG to have an index
of outer retina function
PERG represents an important tool to
monitor the onset and the progression of
RGC dysfunction in optic nerve disease.
Example:-
Glaucoma, optic neuritis, ischemic optic
neuropathy, and mitochondrial optic
neuropathy
58.
59. The normal pattern electroretinogram :
N35- a small negative component with a
peak time occurring around 35 ms;
P50- a prominent positive wave emerging
around 50 ms
N95- a wide negative wave around 95 ms
60.
61. perg in Macular diseases:-
The P50 component was shown to be
altered in all patients with retinal and
macular diseases.
perg in Optic nerve disease:-
N95 component was abnormal in 81% of
patients with diseases of the optic nerve.
The P50 component remain normal.
62.
63. ELECTRO-OCULOGRAPHY
Electrophysiological test of function of the
outer retina and retinal pigment epithelium
in which the change in the electrical
potential between the cornea and the
fundus is recorded during successive
periods of dark and light adaptation.
The eye has a standing electrical potential
between front and back, sometimes called
the corneo-fundal potential
64. The potential is mainly derived from the
retinal pigment epithelium (RPE), and it
changes in response to retinal illumination
The potential decreases for 8–10 min in
darkness.
Subsequent retinal illumination causes an
initial fall in the standing potential,
followed by a slow rise for 7–14 min (the
light response).
These phenomena arise from ion
permeability changes across the basal
RPE membrane.
65.
66. The clinical electro-oculogram (EOG)
makes an indirect measurement of the
minimum amplitude of the standing
potential in the dark and then again at its
peak after the light rise.
This is usually expressed as a ratio of
‘light peak to dark trough’ and referred to
as the Arden ratio.
67. The calibration of the signal may be
achieved by having the patient look
consecutively at two different fixation
points located at known angle apart
and recording the concomitant EOGs .
By attaching skin electrodes on both
sides of an eye the potential can be
measured by having the subject move
his or her eyes horizontally a set
distance .
68.
69.
70.
71.
72. Standard method
After training the patient in the eye
movements, the lights are turned off.
About every minute a sample of eye
movement is taken as the patient is
asked to look back and forth between the
two lights .
After 15 minutes the lights are turned on
and the patient is again asked about once
a minute to move his or her eyes back
and forth for about 10 seconds.
73.
74. Typically the voltage becomes a little
smaller in the dark reaching its lowest
potential after about 8-12 minutes, the so-
called “dark trough”.
When the lights are turned on the
potential rises, the light rise, reaching its
peak in about 10 minutes.
When the size of the "light peak" is
compared to the "dark trough" the relative
size should be about 2:1 or greater .
A light/dark ratio of less than about 1.7 is
considered abnormal.
75. Clinical uses of EOG
Retinal diseases producing an abnormal
EOG will usually have an abnormal ERG
too which is the better test for analysis of
scotopic and photopic measures.
A particularly good use for the EOG is in
following the affects of high dosage
treatment with antimalarials such as
chloroquine and plaquenil over the course
of treatment and before the ERG is
affected
76. Most common use of the EOG nowadays
is to confirm Best’s vitelliform disease
Vitelliform lesions represent the
accumulation of lipofuscin in the macular
area. Further effects of retinal pigment
epithelium (RPE) dysfunction include
accumulation of degenerated
photoreceptor outer segments in the
subretinal space.