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Measurement of Accommodation of eye:
Amplitude, Facility,
Relative Accommodation, Fatigue, Lag,
Dynamic Retinoscopy
Presentation Layout:
-Introduction to accommodation of eye
-Mechanism
-Components
-Measurement of accommodation of eye
- Amplitude
- Facility
- Relative accommodation
- Lag
-Dynamic Retinoscopy
Accommodation
-dioptric adjustment of the crystalline lens of the eye
- to obtain clear vision for a given target of regard
-process by which the refractive power of eye is altered
- to ensure a clear retinal image
For further reading
-Clinical Procedures in Optometry by J.D. Bartlett, J.B. Eskridge, J.F. Amos
-Primary Care Optometry by Theodere Grosvenor
-Borish’s Clinical Refraction by W.J. Benjamin
-Clinical Procedures for Ocular examination by Carlson et al
-American Academy of Ophthalmology
-Optometric Clinical Practice Guideline by American Optometric Association
-Internet
Follow me to get in touch with optometric and ophthalmic updates
Presbyopia/ Methods of Presbyopic Addition Determination (healthkura.com)Bikash Sapkota
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Presbyopia and techniques of measurement
A fantastic presentation in the topic "Presbyopia and techniques of measurement"
A detailed information about presbyopia, techniques of presbyopic add determination and different correction methods.
Informative slide presentation on presbyopia for ophthalmology residents, ophthalmologists, optometrists, ophthalmic assistants, ophthalmic technicians, ophthalmic nurses, medical students, medical professors, teaching guides.
Presentation Contents:
--Introduction to presbyopia
-Types of presbyopia
-Risk factors
-Symptoms and signs
-Refractive error and presbyopia
-Methods of determining near add.
-Management of presbyopia
In a nutshell..
- The evaluation and management of presbyopia are important because significant functional deficits can occur when the condition is left untreated
- Undercorrected or uncorrected presbyopia can cause significant visual disability and have a negative impact on the pt.'s quality of life
- Finally, every tentative addition should be adjusted according to the particular needs of the patient
For Further Reading:
-Clinical Procedures in Optometry by J.D. Bartlett, J.B. Eskridge, J.F. Amos
-Primary Care Optometry by Theodere Grosvenor
-Borish’s Clinical Refraction by W.J. Benjamin
-Clinical Procedures for Ocular examination by Carlson et al
-American Academy of Ophthalmology
-Optometric Clinical Practice Guideline by American Optometric Association
-Internet
Follow me to get in touch with optometric and ophthalmic updates.
Detailed instumentaion and use of manual Lensometer and just a outline of automated lensometer.
I have used the picture of manual lensometer with out the parts describtion because i have explained orally by showing the picture..
Hope u all like it and may help you in learning better. :)
To know Humphrey visual field analyser
To know about various types of perimetry
To identify field defect
To recognize that field defect is due to glaucoma or neurological lesion
To know that field defect is progressive or not
Interpretation of HVFA
Presbyopia/ Methods of Presbyopic Addition Determination (healthkura.com)Bikash Sapkota
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Presbyopia and techniques of measurement
A fantastic presentation in the topic "Presbyopia and techniques of measurement"
A detailed information about presbyopia, techniques of presbyopic add determination and different correction methods.
Informative slide presentation on presbyopia for ophthalmology residents, ophthalmologists, optometrists, ophthalmic assistants, ophthalmic technicians, ophthalmic nurses, medical students, medical professors, teaching guides.
Presentation Contents:
--Introduction to presbyopia
-Types of presbyopia
-Risk factors
-Symptoms and signs
-Refractive error and presbyopia
-Methods of determining near add.
-Management of presbyopia
In a nutshell..
- The evaluation and management of presbyopia are important because significant functional deficits can occur when the condition is left untreated
- Undercorrected or uncorrected presbyopia can cause significant visual disability and have a negative impact on the pt.'s quality of life
- Finally, every tentative addition should be adjusted according to the particular needs of the patient
For Further Reading:
-Clinical Procedures in Optometry by J.D. Bartlett, J.B. Eskridge, J.F. Amos
-Primary Care Optometry by Theodere Grosvenor
-Borish’s Clinical Refraction by W.J. Benjamin
-Clinical Procedures for Ocular examination by Carlson et al
-American Academy of Ophthalmology
-Optometric Clinical Practice Guideline by American Optometric Association
-Internet
Follow me to get in touch with optometric and ophthalmic updates.
Detailed instumentaion and use of manual Lensometer and just a outline of automated lensometer.
I have used the picture of manual lensometer with out the parts describtion because i have explained orally by showing the picture..
Hope u all like it and may help you in learning better. :)
To know Humphrey visual field analyser
To know about various types of perimetry
To identify field defect
To recognize that field defect is due to glaucoma or neurological lesion
To know that field defect is progressive or not
Interpretation of HVFA
Convergence insufficiency is one of the most frequently encountered binocular vision problem in children and adults. It is often associated with a variety of symptoms, including eyestrain, headaches, blurred vision, diplopia [double vision], sleepiness, difficulty concentrating, movement of print while reading, and loss of comprehension after short periods of reading or performing close activities. Have your doctor diagnose and treat this significant visual problem.
Techniques of refraction is the process of calculation of glass power.drbrijeshbhu
Refractive errors are most common cause of ocular morbidity. It affects all age groups, and ethnic profiles. There is no g nder discrimination. Most common symptoms are blur vission along with pain in eye ,headache and tiredness. Refraction is process of determination of eye and currect it with power glass power or contact lens power. It can subjective or objective.
Passive Therapy in Management of Amblyopia (healthkura.com)Bikash Sapkota
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Passive Therapy in Management of Amblyopia
. Passive Therapy
The patient experiences a change in visual stimulation without any conscious effort
- Proper refractive correction
- Occlusion
- Penalization
Active Vision Therapy in Management of Amblyopia (healthkura.com)Bikash Sapkota
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In the request of my viewers, I have compiled my works here in a website. Visit this website (healthkura.com) to freely download this presentation along with other tons of presentations. Some useful links are given here.____Remember___healthkura.com
Active Vision Therapy in Management of Amblyopia
- Pleoptics
- Near activities
- Active stimulation therapy using CAM vision stimulator
- Syntonic phototherapy
- Role of perceptual learning
- Binocular stimulation
- Software-based active treatments
- Exposure to dark
- Pharmacological Therapy
Interventions to Reduce Myopia Progression in Children (Journal Club) (health...Bikash Sapkota
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Interventions to Reduce Myopia Progression in Children (Journal Club)
Objectives:
- To discuss about the different interventions to reduce myopia progression in children
- To determine the effectiveness of different interventions to slow down the progression of myopia in children
Interventions to Reduce Myopia Progression:
Environmental Considerations
- Time Spent Outdoors
- Near-Vision Activities
Spectacles & Contact Lenses
- Gas-Permeable Contact Lens Wear
- Bifocal & Multifocal Spectacles
- Soft Bifocal Contact Lenses
- Orthokeratology
Pharmacological Therapies
- Antimuscarinic Agents: Atropine & Pirenzepine
Under Correction of Myopia
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Data Collection (Methods/ Tools/ Techniques), Primary & Secondary Data, Assessment of Qualitative Data, Qualitative & Quantitative Data, Data Processing
Presentation Contents:
- Introduction to data
- Classification of data
- Collection of data
- Methods of data collection
- Assessment of qualitative data
- Processing of data
- Editing
- Coding
- Tabulation
- Graphical representation
If anyone is really interested about research related topics particularly on data collection, this presentation will be the best reference.
For Further Reading
- Biostatistics by Prem P. Panta
- Fundamentals of Research Methodology and Statistics by Yogesh k. Singh
- Research Design by J. W. Creswell
- Internet
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Vision Training/ Vision Therapy (Active/ Passive Vision Therapy)/ Sports Vision/ Computer Vision Syndrome
Contents:
-Vision Training
Overview
Misconception
Tips for success
Office Vision Training
Home Vision Training
Conditions treated by vision training
Sports Vision Training
Computer Vision Syndrome
Controversy
Summary
Summary
• Vision training is active therapy as it requires conscious participation by the pt.
• The achievement of the final goal occurs slowly and progressively
• VT is not a substitute to lenses or surgical therapy, it is an additional treatment
• Variety of BSV related conditions can be treated with VT
• The underlying neuropsychophysiological mechanisms affected by VT are still
under intense investigation
• VT is the most controversial subject in eyecare profession
Current Trend in Management of Amblyopia (Amblyopia Therapy)/ Amblyopia Treat...Bikash Sapkota
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Current Trend in Management of Amblyopia. Latest as well as old methods of amblyopia management which include active and passive therapies. Amblyopia Therapy/ Amblyopia Treatment
What would be the perfect amblyopia therapy?
Effective
Good compliance
Acceptable to pts. and parent
Quick
Safe
Easy to administer
Cost effective
Well maintained
..............
Summary
Amblyopia occurs due to abnormal visual experience early in life
Proper optical correction alone is necessary for short period of time (6-8 weeks)
before initiation of other therapy
Part time occlusion of better eye is mainstay of treatment since 18th century to till
now
For severe and moderate amblyopia, 6 hrs and 2 hrs of patching is advised
respectively
Atropine is also used in children with poor compliance
Trial of patching can be given in patients as old as 17 yrs
Perceptual learning and pharmacological manipulation have shown areas of
amblyopia treatment beyond the critical period of visual development
Binocular stimulation, software based treatments and other methods do not have
promising result to replace the patching therapy till date
Most of the active therapy methods have good results when used together with
patching therapy
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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
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Retinoscopy and Objective Refraction and Subjective Refraction in spherical ametropia and astigmatism
Retinoscopy (Principle & Techniques of Retinoscopy) and objective refraction, Subjective Refracition
Best presentation about retinoscopy and objective refraction techniques, and basis of subjective refraction. If you want to master the technique of retinoscopy, this presentation can be your guidance and partner in your journey to retinoscopy, objective refraction and subjective refraction.
Presentation Layout:
Retinoscope, types of retinoscope and uses of retinoscope
-Introduction to retinoscopy and objective refraction
-Retinoscopy
- In spherical ametropia
- In astigmatism
- Others: strabismus, amblyopia, pediatric pt.,
cycloplegic refraction
-Static and Dynamic Retinoscopy
-Problems seeing reflex during retinoscopy
-Errors in retinoscopy
Objective of retinoscopy and objective refraction
-To locate the far point of the eye conjugate to the retina
- Myopia or hyperopia
-Bring far point to the infinity by using appropriate lenses
- Determines amount of ametropia by retinoscopy and objective refraction
References:
-Clinical Procedures in Optometry by Eskridge, Amos and Bartlett ,
-Primary Care Optometry by Grosvenor T.,
-Borish’s Clinical Refraction by Benjamin W. J.,
-Theory And Practice Of Optics And Refraction by AK Khurana
-Retinoscopy-Student Manual by ICEE Refractive Error Training Package (2009)
-Clinical Optics and Refraction By Andrew Keirl, Caroline Christie
-Clinical Refraction Guide - A Kumar Bhootra
-Clinical Procedures in Primary Eye Care by David B. Elliott
-Internet
Follow me to get in touch with optometric and ophthalmic updates.
Direct Download Link ❤❤https://healthkura.com/antibacterial-agents/❤❤
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Antibacterial Agents/ antibiotics (Ocular Pharmacology)
PRESENTATION LAYOUT
Introduction to antimicrobial drugs
Classification of antimicrobial drugs
Antibacterial drugs:
- Classification
- Indications
- Side effects
Antibacterial Resistance
Antimicrobial drugs are chemotherapeutic drugs
Two categories: – Antibiotics : Antimicrobial drugs produced by microorganisms
– Synthetic drugs : Antimicrobial drugs synthesized in the lab
..............................................
For Further Reading
oTextbook of microbiology by Ananthanarayan & Paniker
o Essentials of Medical Pharmacology KD Tripathi
o Basic & Clinical Pharmacology by Bertram G. Katzung
o Ophthalmic Drugs by Graham Hopkins and Richard Pearson
o Internet
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anatomy of optic nerve and its blood supply and clinical corelation
Presentation Layout: optic nerve anatomy
Embryology of optic nerve
Introduction
Parts of optic nerve
Blood supply
Clinical significance
For Further Reading
Wolff’s Anatomy of the eye and orbit by Bron, Tripathi and Tripathi
Anatomy and Physiology of eye by A.K. Khurana 2nd edition
Comprehensive Ophthalmology by A.K. Khurana 5th edition
AAO- Fundamentals & Principles of Ophthalmology : sec 2
Walsh and Hoyt’s Clinical Ophthalmology
Internet
Polarization of Light and its Application (healthkura.com)Bikash Sapkota
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polarization of light & its application.
PRESENTATION LAYOUT
Concept of Polarization
Types of Polarization
Methods of achieving Polarization
Applications of Polarization
POLARIZATION
Transforming unpolarized light into polarized light
Restriction of electric field vector E in a particular plane so that vibration occurs in a single plane
Characteristic of transverse wave
Longitudinal waves can’t be polarized; direction of their oscillation is along the direction of propagation.............
For Further Reading
•Optics by Tunnacliffe
•Optics and Refraction by A.K. Khurana
•Principle of Physics, Ayam Publication
•Internet
- 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
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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
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
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
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
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
3. • Dioptric adjustment of the crystalline lens of the eye
- to obtain clear vision for a given target of regard
• Process by which the refractive power of eye is altered
- to ensure a clear retinal image
Accommodation
4. • In an emmetropic eye
- parallel rays of light coming from infinity are brought to
focus on retina being accommodation at rest
- eyes can also focus diverging rays coming from near
object on retina to see clearly due to ACCOMMODATION
5.
6. Mechanism of Accommodation
As a result
Allowing near object to be
focused clearly on retina
Ciliary muscle contracts Ciliary ring shortens
Increase in
dioptric power
Lens becomes spherical i.e.
convexity increases
Tension in capsule is relievedZonules are relaxed
Equator of lens move forward
7.
8. With Age
lens fibers & lens
capsule lose elasticity
the size & shape of
the lens increase
reduction of
accommodative amplitude
onset of presbyopia
10. Ocular changes in Accommodation
• Slackening of zonules – due to contraction of
ciliary muscles
• Change in curvature of lens
- almost no change in posterior surface (6 mm)
- anterior surface radius of curvature
(from 11 mm to 6 mm)
11. • Anterior pole along with iris moves forward
- shallowing of anterior chamber in centre
• Pupillary constriction and convergence of eyes
- near triad
• Choroid moves forward
• Ora serrata moves by 0.05mm forward with each
diopter of accommodation
15. Reflex Accommodation
• The normal involuntary response to blur which
maintains a clear image
• Largest and most important component
• Automatic adjustment of refractive state to obtain
clear retinal image
• Occurs for small amount of blur, upto 2.00 D, beyond
which voluntary effort is required
Voluntary Accommodation
16. Vergence Accommodation
• Induced due to action of disparity (fusional) vergence
• Gives rise to convergence accommodation/
convergence ratio(CA/C) =0.4 D per meter angle in
young
• Second major component of accommodation
17. Proximal Accommodation
• Due to influence or knowledge of apparent nearness
of object
• Stimulated by targets located within 3m of the
individual
• Tertiary component of accommodation
18. Tonic Accommodation
• Revealed in absence of blur, disparity, and proximal
inputs as well as any voluntary or learned unusual
aspects
• Reflects baseline neural innervation from the
midbrain
• In young adults, ranges from 0 to 2 D
19. Depth of Field and Depth of Focus
When an object is accurately focused monocularly,
often the objects somewhat near and somewhat
farther away are also seen clearly without any change
in accommodation
This range of distance from the eye is depth of field
The range at the retina in which an optical image may
move without impairment of clarity is depth of focus
20. Measurement of Accommodation
A full clinical examination includes assessment
of accommodative function in five parameters
o Amplitude of accommodation
o Lag of accommodation
o Accommodative facility
o Relative accommodation
o Accommodation fatigue
21. Amplitude of Accommodation
• Punctum Remotum
- The farthest point at which the objects can be seen
clearly
- Infinity for emmetropic eyes
• Punctum Proximum
- The nearest point at which objects can be seen clearly
22. • Range of accommodation
- Distance between near point and far point
• Amplitude of accommodation
- The dioptric difference between near point and far
point
(A= P-R)
Amplitude of Accommodation
24. Push Up Method
- To determine maximum amount of accommodation that
eyes are capable of producing individually or together
- Done by RAF Rule, Livingstone Binocular Gauge,
Prince Rule
Measurement of Amplitude of Accommodation
25. Royal air force rule
Wing like support that fits over
nose and rests against lower orbital
margins
Test chart
Metal rod
1st side : divided into cm for NPA
2nd side : divided into diopter(NPA in D)
3rd side : age
Prince Rule
26. Procedure
• Near visual acuity chart placed on near point rod
• Direct patient’s attention to 20/20 line of letters on
near point card
• Patient left eye occluded
27. • Near point card brought closer to patient (2-3 inches
per second)
• Patient instructed to keep the letters as clear as
possible and report when it blurs
• Prompt the patient to clear the target
28. • Stop when patient can no longer clear the print within
2 to 3 seconds of viewing
• Record the dioptric points on the near point rod that
corresponds with the blur
• Procedure repeated for left eye
29. Hofstetter formulae for expected amplitude as a
function of age (using the data of Donders,
Duane and Kaufman)
• Maximum amplitude = 25 - 0.4(age)
• Probable amplitude = 18.5 - 0.3(age)
• Minimum amplitude = 15 - 0.25(age)
Formula to determine Amplitude of Accommodation
30. Example :
• For 20 years old patient
Minimum AA is given by :
15 – 0.25 *age= 15 – 0.25 *20
= 10 DS
NPA = 1 /10
= 0.1m
= 0.1 *100 cm
= 10 cm
31. Minus lens method/ Sheard’s method
• Each eye is tested monocularly first
• Then tested binocularly
• Full refractive correction worn by patient
32. • Pt. asked to fixate 6/60 target at 6m
• Minus lenses added progressively till the target can be
seen clearly or patient first reports blur
• Power of concave lens = AA in diopter
33. • If amplitude of accommodation is insufficient for age
Accommodative Insufficiency
• What does the patient complain ?
“ The letters become blurred while reading
and it becomes difficult to see near objects”
• So, the patient should be treated with push up
therapy of Hart-Chart Rock
34. Accommodation insufficiency & presbyopia
AI PRESBYOPIA
Accommodative power is
significantly less than the
normal physiological limit
for the patient’s age
Physiological insufficiency
of accommodation is
normal for age
Asthenopic symptoms are
more prominent
Symptoms of decreased
near VA is more
prominent
35. Amplitude of accommodation and age
The amplitude of accommodation declines throughout life
until at about 50 or 60 years of age when it becomes zero
36. • Rule of 4’s
Amplitude= 4x4-(Age/4)
Example:
Age of 20,
Amplitude = 16-20/4
= 11 diopters
Amplitude of accommodation and age
37. o Subjective measurements overestimate true
accommodative amplitude
o Reasons why subjective measurement of accommodation
should be avoided
# The endpoint of the subjective push-up test requires a
subjective evaluation of best image focus by the subject
and this endpoint varies between individuals
Subjective measurement of AA: Weak points
38. # Subjective evaluation influenced by depth of focus, visual
acuity, contrast sensitivity of the eye, and contrast of the
image
For example
- A dimly illuminated reading chart may provide a poor
stimulus to accommodate
- Different levels of illumination alter pupil diameter and
therefore depth of focus of the eye thus influencing the
near point of clear vision
39. # Measurements confounded by the increasing angular
subtense of the object
- As a reading chart is brought closer to the eye, this results
in an increased retinal image size and hence increased
legibility of the letters
# Inaccurate because of the lag of accommodation
- Accommodative response of the eye lags behind the
stimulus and that this lag increases as the stimulus
amplitude increases
40. Provide a true measure of accommodative amplitude
of the eye
Can be done statically or dynamically
Autorefractors, refractometers or aberrometers are
suitable instruments
Objective Methods of Measuring AA
41. Provide a measure of the refraction of the eye as the eye
changes focus between a distant and a near target
The accommodative response amplitude is then
determined as the difference between the refraction
when looking at a distant target and the refraction when
looking at a near target
42. If a negative powered trial lens is placed in front of one eye
while viewing a distant letter chart, the consensual
accommodative response can be measured in the contralateral
eye
Also by muscarinic agonists (pilocarpine)
- The resulting accommodative response measured
periodically over 30–45 minutes using an autorefractor until the
maximal accommodative response is attained
Methods of Stimulating Accommodation
43. The magnitude of the accommodative response depends
on drug concn, intraocular pharmacokinetics, iris
pigmentation and other non-accommodative factors that
influence how much drug or how quickly the drug reaches
the ciliary muscle
44. Accommodation facility
• Aka inertia of accommodation
• Tests the ease of accommodative response to the
change in stimulus
• Testing accommodative facility provides an index of
how quickly accommodation can change
45. • Measured in cycles per minute
• Can be tested by two methods
Near – Far Test
Flipper Lens Test
Accommodation facility
46. Near-Far test
• To determine flexibility of accommodative system
• Rapidly alternates viewing distance
• Done under monocular and binocular conditions
• Not appropriate for moderate AA i.e. <4.50 DS
or absolute presbyopia
47. • Place a series of 20/25 to 20/30 high contrast letters on
wall 6m away
• Patient holds near VA chart at distance corresponding with
no more than 2/3rd of patient’s AA
• Appropriate distance correction worn
Procedure
48. • Occlude patient’s left eye
• Tell patient to switch focus
back and forth between letters on wall and near chart
after making letters clear
(This is done for 30 seconds)
• Procedure repeated for left eye for 30 seconds
Procedure
49. • Record the number of cycles per minute
1 cycle = 2 jumps (jump from far to near and back to
far again)
Expected
Monocularly : 15 cycles per minute (minimum)
20 cycles per minute (average)
Binocularly : 12 cycles per minute(minimum)
16 cycles per minute (average)
50. Flipper Lens Test
Flipper lens
- Two plus and two minus lenses mounted in same holder
- Available in powers of :
+/- 0.50, 1.00, 1.50, 2.00, 2.50, 3.00
51. • Purpose
To determine the ability of accommodative system to
respond to lens created blur with a monocular stimulus
presentation
Note : In the binocular presentation, the ability of both
accommodative and vergence systems to interact is
tested
Flipper Lens Test
52. • Patient holds near-point VA chart with
20/25 letters at 40 cm
• Direct light from overhead lamp
• Distance correction worn
• Left eye occluded
• Flipper lens placed in front of right eye(usually minus
side first)
Procedure
53. • As soon as letters on acuity chart
becomes clear, it is flipped to other
side i.e. plus side
• As letters become clear with plus
side flip back lens to minus
• Continue the procedure for 30 seconds
• The process repeated for left eye for 30 seconds
54. Record and interpretation
• Record no. of cycles in a minute
1 cycle = plus to minus and back to plus again
Expected
Monocularly minimum = 12 cycles per min
average = 17 cycles per min
Binocularly minimum = 10 cycles per min
average = 13 cycles per min
55. • Decreased accommodative facility
Accommodative Infacility
What does the patient complain of ?
“It becomes difficult to focus for near activities
after distance viewing and vice-versa”
• Patient requires therapy with Hart Chart Rock near-
distance method or with flipper lens
56. Fatigue of Accommodation
• Aka ill-sustained accommodation
• Measures ability of the eye to adequately sustain
sufficient accommodation over an extended time period
• Can be tested by RAF rule or flippers
57. • With RAF rule, amplitude of accommodation is
measured repeatedly
• AA initially sustained with considerable effort,
overtime it cannot be maintained
• So, decrease of AA on repeated testing suggest
Fatigue of accommodation
58. • Patient complains of
“letters become blurred after reading for sometime”
• Treat patient with push up therapy or flipper lens therapy
59. Relative Accommodation
• The amount of accommodation to be exerted under
fixed convergence is called relative accommodation
• Two types
Negative relative accommodation
Positive relative accommodation
60. Fig: The relation between (PRA), (NRA), and (PC). The dotted
lines in the Figure describe the point the accommodation is focused to when a plus
lens (for NRA) or a minus lens (for PRA) is added without changing the
convergence stimuli. The positive relative movement (PRM) and negative relative
movement (NRM) describe the direction of the different dioptric focus change
movements of the PRA and the NRA in relation to the PC.
61. Negative Relative Accommodation
• To test patient’s ability to decrease accommodation
while maintaining convergence at 40 cm
• A reduced Snellen’s chart with 20/20 letters at 40 cm
• Place patient’s distance correction in trial frame
62. • Add plus power in 0.25 steps every 2 seconds until
patient reports first blur
• Normal values : +1.75 to +2.00 DS
Value of Negative Relative Accommodation
63. Positive Relative Accommodation
• To test the patient’s ability to increase accommodation
while maintaining convergence at 40 cm
• Add minus power in 0.25 steps every 2 seconds until
patient reports first blur
• Normal values : -2.25 to -2.50 DS
Value of Positive Relative Accommodation
64. • Time lapse between the presentation of an accommodative
stimulus and occurrence of the accommodative response
• Average time
- Far to near accommodation is 0.64 seconds
- Near to far accommodation is 0.56 seconds
Lag of accommodation
65. • Accommodative response
- Measure of actual accommodation that is present
• Accommodative stimulus
- Measure of accommodation exerted by target or stimuli
Lag of accommodation =
Accommodative stimulus – Accommodative response
66. - Normal lag: +0.50 or +0.75D
- High lag: +1.00D or higher
- Decreased lag: +0.25D or less
• Assessed clinically by
Dynamic retinoscopy
Binocular cross cylinder test
67. Dynamic Retinoscopy
• Objectively determines the point that is conjugate to the
retina when the pt. is viewing a particular target
• Goal is to determine accommodative Response
• Also helps to determine the most appropriate near
prescription with testing conditions
68. Techniques to perform dynamic retinoscopy include
- Interposing additional lenses into line of sight to
achieve neutrality
- Moving retinoscope in space to the point that is
conjugate to the retina
69. Methods of Dynamic Retinoscopy
• Monocular Estimation
Method (MEM)
• Nott retinoscopy
• Bell retinoscopy
• Cross method
• Sheard’s method
• Tait’s method
• Low neutral and high
neutral method
• Stress Point retinoscopy
• Book (Getman)
retinoscopy
70. Monocular Estimate Method (MEM) Retinoscopy
• Gives an estimated measure of the spatial positioning of
accommodation with regard to convergence
• Cognitive demand is moderate
• Done by interposing additional lenses in front of eyes
71. Materials
• Series of cards with a central aperture mounted on a
retinoscope
• Cards can have printed letters, or words, or pictures that
range in size from 20/160 to 20/30 arranged around the
aperture
72. Procedure
• Pt. instructed to keep the targets clear
• Sweeps the retinoscope beam
• Observe the motion of the retinoscopic reflex
• Quickly interpose a trial lens at the spectacle plane
(starting from +0.25 and increasing in 0.25 steps)
73. Interpretation
• “lag of accommodation” is the amount of plus lens that
neutralizes the reflex
Example
If the retinoscopic reflex is neutralized by +1.75D then lag
is +1.75
ADD = +1.75 – (+0.75)
= +1.00
74. Nott Dynamic Retinoscopy
• Main purpose is identical to the MEM method
• Cognitive demand is moderate
• Done by moving retinoscope in space to the point that
is conjugate to the retina
76. • Pt. wears the compensating distance lenses
• Pt. directed to read the letters
• Performs retinoscopy by moving farther from the plane
of regard until the motion is neutralized
Procedure
77. Interpretation
• Dioptric difference between these two distances equals
the lag of accommodation
Example
Distance from the target to spectacle plane = 40cm
Distance from retinoscope to spectacle plane = 50cm
Lag of accommodation = +2.50D – 2.00D
= +0.50D
78. Bell Retinoscopy
• Evaluate the performance of the accommodative system
under moving & real life conditions in free space
• Cognitive demand is low
79. Materials
• Three dimensional viewing target
• A small, highly reflective bell dangling from String
- replaced with a Wolff Wand (½ inch diameter, metal
ball mounted on the end of a rod)
80. • Wand is held by the
examiner
• Moved closer to and
farther from the patient
- slower than 2
inches/sec
Procedure
81. • Retinoscope is positioned at a fixed distance of 50 cm
(20 inches)
• Patient fixates the target and the examiner notes the
direction of the reflex
Procedure
82. • Target is moved closer to the patient there will be a point
where the motion changes from “with” to “against’’
• Target is again moved away from patient until with motion
is observed
Procedure
83. Interpretation
• Distance between the retinoscope and the target, when
the motion change occurs, is a physical measure of the
lag of accommodation
84. • “with” to “against” motion is observed at 35 – 42 cm
(14 - 17 inches)
• “against” to “with” at 37 - 45 cm. (15 -18inches)
• Accommodative flexibility can be assessed by
observing how quickly or sluggishly the reflex changes
85. Binocular Cross Cylinder Test
• Method of determining lag of accommodation
• Blur no longer provides a stimulus for accommodation
but disparity vergence is fully functional
86. Procedure
• Use the cross grid on the near point card
• With patient’s distance correction in trial frame, place
cross cylinder with minus cylinder axis vertical (090
degree) in front of eye
• Ask patient “Are ‘up and down’ or
‘across’ lines clearer, blacker,
or sharper ?”
87. • If ‘across’ (horizontal) lines clearer
- Under accommodation
- So, add plus power binocularly until patient reports
equality or vertical lines become clearer
• If ‘up and down’ (vertical) lines clearer
- Over accommodation
- So, add minus power binocularly until patient reports
equality
88. High lag >+0.75D
• Inadequate accommodative response
• As a result of :- Near esophoria
Poor negative vergence
Accommodative insufficiency
Uncorrected hyperopia
Patient is over minused
89. Lead of Accommodation < +0.25D
• Over accommodating
• As a result of :- Near exophoria
Spasm of accommodation
Over plus correction
Inadequate positive vergence
90. References
o Clinical Procedures in Optometry by J.D. Bartlett, J.B.
Eskridge, J.F. Amos
o Theory and Practice of Squint and Orthoptics by A.K.Khurana
o Adler’s Physiology of the Eye by L.A. Levin, S.F. Nilsson
o Borish’s Clinical Refraction by W.J. Benjamin
o Internet
1. Helholth theory of relaxation…..Gulstrand mechanical model
2. Theory of increased tension( Tscherning theory)
3. Schachar’s theory
4. Cotenary ( hydraulic suspension) theory
Afferent: retina to striate cortex, parastriatr cortex,internuncial fibre to pontine nucleus to edinger westphal nucleus
Efferent: 3rd nerve, accessory ganglion, ciliary ganglion,reach sphincter pupillae and ciliary muscle
Definition: The range of object distances for which the circles of confusion are so small that the image is sharp enough to be considered 'in focus' is called the depth of field.
Definition:The range of image distances over which the image of an improperly focused object is acceptably sharp is called the depth of focus.
Definition: The circle of confusion is the area of the retina over which the cells are stimulated by light from a point on an object. The bigger tthe circle, the more blurred the point becomes. The maximum acceptable circle of confusion determines the depth of field and focus of an eye.
Decreasing the pupil size: increases both the depth of field and the depth of focus.
The dioptric difference between the punctum proximum and the punctum remotum is accomodative amplitude
The maximum amount by which the eye can change its power
Accommodation can be stimulated either by moving a test object closer to the eyes or by placing minus lenses in front of the eyes
Donder's push up method
The card should be illuminated by 40 watt incandescent bulb..excessive illumination will greatly increase the depth of focus for some pts. And will therefore results in falsely high amplitude finding
this can be avoided by carefully controlling the
image angular magnification with scaled letter sizes, this is
not done with the subjective push-up test.
-Since accommodation results in a change in the optical
refractive power of the eye, accommodation can readily be
measured objectively
Individuals with light irides showed a stronger accommodative response to pilocarpine than subjects with dark irides.
Use of the words vertical and horizontal can cause confusion
If the pt. accommodates exactly for the target position, the two sets of lines should be equally clear, since the image of the horizontal lines is 0.05 D in front of the retina and the vertical lines will lie 0.05D behind the retina