This lecture is based on post-graduate students of Ophthalmology (DO, DCO, MCPS, FCPS, MS) and optical principle of LASER, construction of laser and laser tissue interaction has cover the lecture
Polarization and it's application in OphthalmologyRaju Kaiti
Polarization, types of polarization, mechanisms to produce polarization, Applications of polarization, precautions with polarizing sunglasses, ophthalmic uses of polarization
Polarization and it's application in OphthalmologyRaju Kaiti
Polarization, types of polarization, mechanisms to produce polarization, Applications of polarization, precautions with polarizing sunglasses, ophthalmic uses of polarization
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation
Aberration in optics refers to a defect in a lens such that light is not focused to a point, but is spread out over some region of space, and hence an image formed by a lens with aberration is blurred or distorted.
This belongs to Physical Chemistry portion and it contains most of
things about laser working and principles.
By Aaryan Tyagi's Group
M.Sc. Applied Chemistry (1 Sem)
Amity University, Noida
These lectures has prepared for postgraduate student (Ophthalmology) according to the curriculum of Bangladesh College of Physician and Surgeons (BCPS) and Bangabondhu Sheikh Mujib Medical University (BSMMU) Bangladesh
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation
Aberration in optics refers to a defect in a lens such that light is not focused to a point, but is spread out over some region of space, and hence an image formed by a lens with aberration is blurred or distorted.
This belongs to Physical Chemistry portion and it contains most of
things about laser working and principles.
By Aaryan Tyagi's Group
M.Sc. Applied Chemistry (1 Sem)
Amity University, Noida
These lectures has prepared for postgraduate student (Ophthalmology) according to the curriculum of Bangladesh College of Physician and Surgeons (BCPS) and Bangabondhu Sheikh Mujib Medical University (BSMMU) Bangladesh
spectrophotometer.pptx,DNA/RNA Quantification,clinical diagnosis, protein ana...Parthvi Soni
Spectrophotometry is a powerful analytical technique that plays a crucial role in scientific research and industrial applications. By measuring the absorbance of light by a sample, spectrophotometers provide valuable information about the concentration and characteristics of substances. Understanding the principles, components, and applications of spectrophotometry enables scientists and professionals to utilize this technique effectively for a wide range of analyses. As technology advances, spectrophotometry continues to evolve, offering greater precision, versatility, and efficiency in the pursuit of scientific knowledge and innovation.
These lectures has prepared for postgraduate student (Ophthalmology) according to the curriculum of Bangladesh College of Physician and Surgeons (BCPS) and Bangabondhu Sheikh Mujib Medical University (BSMMU) Bangladesh
This lecture is based on medical students those are preparing for postgraduate degree namely FCPS/MS/MD/ any any subject coz hypertension is a systemic disease and by seeing the ocular fundus we can asses the general condition of blood vessels in major organ.
This lecture is based on post-graduate students of Ophthalmology (DO, DCO, MCPS, FCPS, MS) and optical principle of GAT has to know for a student to use the instrument friendly
This lecture is based on post-graduate medical students of all subject those who are students MS/MD/FCPS of different subject on Central Tendency and Dispersion.
This is the 5 th lecture on "Research Methodology through zoom. The lecture was based on postgraduate Medical students those are different courses of FCPS/MS/MD/PhD (any Specialty)
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists Saeid Safari
Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
ASA GUIDELINE
NYSORA Guideline
2 Case Reports of Gastric Ultrasound
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
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
Factory Supply Best Quality Pmk Oil CAS 28578–16–7 PMK Powder in Stockrebeccabio
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Hot Selling Organic intermediates
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We specializes in exporting high quality Research chemical, medical intermediate, Pharmaceutical chemicals and so on. Products are exported to USA, Canada, France, Korea, Japan,Russia, Southeast Asia and other countries.
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.
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
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.
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
Title: Sense of Taste
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 structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
2. Laser vs Light
Laser Light
Stimulated Emission Spontaneous emission
Monochromatic Polychromatic
Highly energized Poorly energized
Parallelism Highly divergence
Coherence Non Coherence
Can be sharply focussed Can’t be sharply focussed
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3. History of Laser
• 1960: The first laser was built by Theodore Maiman using a
ruby crystal medium.
• 1963: The first clinical ophthalmic use of Laser in human
• 1968: L Esperance developed the Argon Laser
• 1971: Neodymium Yttrium aluminum garnet (Nd:YAG) and
Krypton Laser develop
• 1983: Torkel developed the Excimer Laser
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4. What is laser?
Laser is the acronym of
• L: Light
• A: Amplification by
• S: Stimulated
• E: Emission of
• R: Radiation
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5. Laser physics
• Laser as electromagnetic waves emitting radiant energy in tiny
package called quanta/photon. Each photon has a characteristic
frequency and its energy is proportional to its frequency
• Three basic ways for photons and atoms to interact.
i. Absorption
ii. Spontaneous Emission
iii. Stimulated Emission
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7. Properties of laser
1) Laser is monochromatic
2) A particular laser has single wavelength
3) This depends on the medium used
4) It cannot be white
5) It is always coloured, i,e green, blue-green etc
6) It is coherent, i,e each wave (photon) is in the same phase as
the next.
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8. Properties of laser
7) It is collimated, i, e rays (photon) are exactly parallel
8) Polarization: The photons vibrate in the same plane
9) It produces bright light
10) It produces intense heat & energy at short distance
11) Laser can burn, coagulate, evaporate & disrupt
12) It can be concentrated in a very small area
(Ref: Manual of Optics & Refraction PM Mukherjee Page: 2.3.4)
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9. Properties of laser
• The light emitted from a laser is monochromatic, that is, it
is of one wavelength (color). In contrast, ordinary white light
is a combination of many different wavelengths (colors).
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10. Properties of laser
• Lasers emit light that is highly directional. Laser light is
emitted as a relatively narrow beam in a specific
direction. Ordinary light, such as coming from the sun, a light
bulb, or a candle, is emitted in many directions away from the
source.
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11. Properties of laser
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The light from a laser is said to be coherent, which
means the wavelengths of the laser light are in phase
in space and time
13. Different issues to know to understand laser
In order to understand the basic principle of a
laser, it is
instructive to first consider a
passive resonator ("cavity"),such as an
arrangement of mirror that creates a closed path
for a light beam.
The simplest configuration is made with only
two mirror, one being flat and one being curved.
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14. Different issues to know to understand laser
However, its optical power will decay, as some energy is lost in
every resonator round trip. A so-called gain medium can now be
inserted that, when supplied with energy ("pumped").
If the gain g is lower than the resonator losses l, the power
decay is only slowed down. For g = l, the optical power stays
constant; and for g > l, the power rises with each round trip.
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15. Different issues to know to understand laser
• The latter condition can not be maintained
forever; sooner or later, the high intra cavity
intensity will saturate the gain.
• In the steady state, as reached after some time,
the gain will be exactly sufficient to compensate
for the resonator losses. We then have
continuous-wave laser operation with constant
optical power and g = l.
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16. • For extracting a laser beam as a useful
output of the device, the left mirror, for
example, acts as an output coupler,
transmitting some percentage (say 10%)
of the intra cavity power.
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17. Different issues to know to understand laser
1.Spontaneous absorption- electron will move from
low energy level to high energy level by absorbing
photon
2.Spontaneous radiation- electron will move from
high energy level to low one by releasing photon
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22. Three basic components of Laser
A Laser medium
• e,g solid, liquid or gas
Exciting method
• Light or electricity
Optical cavity (Laser tube)
• Around the medium acts as a resonator
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23. Construction of Laser
• Laser consists of a cylinder that may be solid or
hollow; latter is filled with gas, liquid or a
combination.
• These substances should have ability to absorb
energy in one form and emit a new type of more
useful energy. The energy can be thermal,
mechanical, light or electrical. The process of
conversion is called lasing.
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24. Construction of Laser
A cavity of the cylinder has two concave
mirrors at each end. One of them is fully
reflective. The mirrors are coated with thin
film of dielectric that reflects light close to
the wavelength of the laser light. The other
mirror is located on the other of the tube.
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25. • The focal length of each mirror almost
coincides with the centre of the tube The
second mirror is partially reflective and is
considered to be leaky.
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26. Construction of Laser
There are two slanting windows that close
each end of the tube.
The cavity or the rod is surrounded by
source of energy that raises the energy
level of the atoms within the cavity to a
high level in a very unstable state.
This is called population inversion.
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27. The next step is spontaneous decay of the
energized atom to a lower energy level.
This phenomena is the basis behind the
release of high energy in the form of light
that is converted to suitable wavelength.
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28. Construction of Laser
• Thus, to summarized, there are 2 steps:
1) Population inversion in active medium
2) Amplification of appropriate wavelength.
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29. The energy stored in the laser material, i,
e, gas, liquid or solid, is released in a
narrow beam of monochromatic light.
This light is a source of high thermal
energy, which is used in ophthalmology
for various purposes.
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30. Previously, we discuss that one mirror is
partially transparent, some of the light is
allowed to leave the tube.
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31. • This light will be coherent (the wave fronts in
phase),
• monochromatic (one wave length) and
• collimated (all the rays parallel).
Light is produced continuously, and such a laser
is said to be operating in continuous-wave (CW)
mode.
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32. Laser mode
Laser light is generally regarded as being
coherent, as a practical level not all the light
waves are preciously parallel as they resonate
between the two mirrors of the Laser tube.
Cross-section of laser beam at different points
along its path reveals that it is very slightly
divergent, and that it is more intense at certain
points (called transverse electromagnetic modes)
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33. Transverse mode are not so important when
energy is delivered diffusely (retinal
photocoagulation)
But for photo disruption (YAG) it is important to
have precisely focused energy a greater
disruptive effect and, consequently, the effects of
transverse modes need to be considered.
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34. Units of
wavelength
Unit Symbol Length
Centimeter cm 10-2 meter
Angostrom 10-8 meter
Nanometer nm 10-9 meter
Micrometer μm 10-6 meter
36. The effects of laser energy on ocular tissues
depend upon the:
Wavelength.
pulse duration of laser light and the
absorption characteristic of the tissue in
questions (largely determined by the pigments
contained within it).
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37. Effects of laser energy on tissue
The effects can be
1) Thermal
2) Photochemical
3) Ionizing effect
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38. Thermal effect
Light energy is converted into heat energy if the wavelength
coincides with the absorption spectrum of the tissue pigment
on which it falls and if the pulse duration is between a few
microsecond and 10 s
Melanin in the retina absorb most of the visible spectrum &
xanthophyll strongly absorb blue light, and hemoglobin absorb
blue, green and yellow wavelength.
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39. Thermal effect
In the retina, heat is transferred to the adjacent layers of the
retina to cause a 10-20 degree rise in tissue temp. The result is
photocoagulation and a localized burn.
When visible or infrared light raises the tissue temp to 100 deg
water vaporizes and causes tissue disruption.
Example: Carbon di oxide. Argon laser.
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40. Photochemical effect
When a pulse duration of 10 s or more is required to cause
damage, the mechanism is the formation of free radical ions
which are highly reactive and toxic to cells.
Shorter wavelengths ( blue & UV) causes damage at lower
levels of irradiance and are therefore more harmful.
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41. Ionisation
Photon energy delivered in a nanosecond or less may be
sufficient to strip electrons from molecules to form a collection
of ions and electrons called a plasma.
A plasma has a very high temperature and rapidly expands to
cause a mechanical shock wave sufficient to displace tissue.
Energy released as photons may produce a flush.
Example: Nd-YAG & Argon-fluoride excimer laser
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42. • When the laser energy exceeds the
threshold for causing tissue damage, the
mechanism of any damage depends
largely upon the duration of exposure.
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43. Laser tissue interaction
Laser
Tissue
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Thermal effect
i. Photocoagulation
ii. Photodisruption
iii. Photovaporization
Photochemical
i. Photo radiation
ii. Photoablation
Ionizing
Effect
46. Photoablation
Breaks the chemical bonds that hold tissue together essentially
vaporizing the tissue e,g, photorefractive keratectomy. Argon-
Fluoride (ArF) excimer Laser.
Usually
Visible wavelength: Photocoagulation
Ultraviolet: Photo ablation
Infra red: Photodisruption & Photocoagulation
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47. Photo ablation
• Vaporization of tissue to CO2 and water occurs when it’s temp
rise 60 – 100 deg or greater.
• Commonly used CO2
• Absorbed by water of cells
• Visible vapor (vaporization)
• Heat Cell disintegration
• Cauterization Incision
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48. Photochemical effect
• Photo radiation
• Also called photo dynamic Therapy (PDT)
• Photochemical reaction following visible/infrared light
particularly after administration of exogenous chromophore
Commonly used photosensitizer:
• Hematoporphyrin
• Benzaporphyrin derivatives
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49. Uses of Laser in ophthalmology
Mode Lesion Tissue treated
Photocoagulat
ion
Thermal burn Retina & TM
Photoablation Breakdown of chemical bonds
without thermal change
Cornea
Photodisruptio
n
Breakdown of form plasma
resulting in disruption of tissue
PCO
Photovaporiza
tion
Vaporization of fluid from the
tissue to cut
Small tumor
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50. Commonly used Laser in Ophthalmology
Laser Wave
length
Effect
Argon Laser Green
Argon Laser Blue
514 nm
488 nm
Photocoagulation
Photocoagulation
Nd YAG single frequency
Nd YAG double frequency
1064 nm
532 nm
Photodisruption
Photocoagulation
Diode Laser 810 nm Photocoagulation
Excimer Laser 193 nm Photoablation
Ruby Laser 550 nm Photocoagulation
Krypton Laser Red
Krypton Laser Yellow
647 nm
568 nm
Photocoagulation
Photocoagulation
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51. Modes of Laser Operation
• Continuous Wave Laser: It deliver their energy in a continuous
stream of photons
• Pulse Laser: Produce energy pulses of a few ten of micro to
few mili second
• Q Switches Laser: Deliver energy pulses of extremely shorter
duration (nanosecond)
• A mode locked Laser: Emits a train of short duration pulses
(picosecond)
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