1. The tear film consists of three layers - an outer lipid layer, intermediate aqueous layer, and inner mucin layer. The lipid layer prevents evaporation while the aqueous layer nourishes the cornea and washes away debris.
2. Tears are produced both through basal secretion by accessory glands and reflex secretion by the main lacrimal gland in response to irritation. The tear film forms on the cornea through spreading of layers.
3. Diagnosis of dry eye involves tests like tear film break-up time (BUT), Schirmer's test, and Jones tests to evaluate tear production and drainage. Multiple factors can contribute to dry eye and tear film instability.
The tear film is a complex mixture of substances secreted from multiple sources on the ocular surface, including the lacrimal gland, the accessory lacrimal glands, the meibomian glands, and the goblet cells.
The tear film is a complex mixture of substances secreted from multiple sources on the ocular surface, including the lacrimal gland, the accessory lacrimal glands, the meibomian glands, and the goblet cells.
The tear film constitutes Three layers :- An outermost lipid (oily) layer An aqueous (watery) layer that makes up 90% of the tear film volume; and A mucin layer that coats the corneal surface.
3. To form smooth optical surface on cornea. To keep the surface of cornea & conjunctiva moist It serve as lubricant It transfer oxygen Provide antibacterial action Wash debris out It provides a pathway for WBC in case of injury
4. Functions of lipid layer Retards evaporation of tear film Prevents the overflow of tears
5. Function of Aqueous Layer Flushes, buffers and lubricates the corneal surface Delivers oxygen and other nutrients to the corneal surface Wash out debris Delivers antibacterial enzymes and antibodies such as lysozyme.
6. Functions of Mucin Layer Spreads tears over corneal surface. Protects the cornea against foreign substances . Makes corneal surface smooth by filling in surface irregularities
Each eyelid contains a fibrous plate, called a tarsus, that gives it structure and shape; muscles, which move the eyelids; and meibomian (or tarsal) glands, which secrete lubricating fluids. The lids are covered with skin, lined with mucous membrane, and bordered with a fringe of hairs, the eyelashes.
The tear film constitutes Three layers :- An outermost lipid (oily) layer An aqueous (watery) layer that makes up 90% of the tear film volume; and A mucin layer that coats the corneal surface.
3. To form smooth optical surface on cornea. To keep the surface of cornea & conjunctiva moist It serve as lubricant It transfer oxygen Provide antibacterial action Wash debris out It provides a pathway for WBC in case of injury
4. Functions of lipid layer Retards evaporation of tear film Prevents the overflow of tears
5. Function of Aqueous Layer Flushes, buffers and lubricates the corneal surface Delivers oxygen and other nutrients to the corneal surface Wash out debris Delivers antibacterial enzymes and antibodies such as lysozyme.
6. Functions of Mucin Layer Spreads tears over corneal surface. Protects the cornea against foreign substances . Makes corneal surface smooth by filling in surface irregularities
Each eyelid contains a fibrous plate, called a tarsus, that gives it structure and shape; muscles, which move the eyelids; and meibomian (or tarsal) glands, which secrete lubricating fluids. The lids are covered with skin, lined with mucous membrane, and bordered with a fringe of hairs, the eyelashes.
With a knowledge of anatomy, diseases of eyelids cannot be dealt with. Here we submit our presentation on anatomy of eyelids which will be helpful to all ophthalmogists, and students.
It explains the secretion of the tear film,its importance and the pathologies that can happen when its not being secreted well and as well as the pathophysiology of.It also addresses the different layers of the tear film and the various ways that it can lead to the different diseases of the eye
the paper addresses the different scretory pathways and it speaks about the regulation of the production of the tear film in that the various
The lacrimal apparatus (Tear System)
It's a group of glands, sacs and ducts that makes new tears and drains old ones away. consists of two divisions. The first is the secretory part, which is responsible for the production of tears, and the second is the drainage part. The secretory part contains the main lacrimal gland, which is lodged in a fossa in the lateral part of the roof of the orbit, and two accessory lacrimal glands of Krause and Wolfring. The latter are present near the fornix.
Dry eye disease is a common condition that occurs when your tears aren't able to provide adequate lubrication for your eyes. Tears can be inadequate and unstable for many reasons. For example, dry eyes may occur if you don't produce enough tears or if you produce poor-quality tears. This tear instability leads to inflammation and damage of the eye's surface.
Dry eyes feel uncomfortable. If you have dry eyes, your eyes may sting or burn. You may experience dry eyes in certain situations, such as on an airplane, in an air-conditioned room, while riding a bike or after looking at a computer screen for a few hours
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
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June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
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Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
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It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
1. TEAR FILM
Dr Md Ferdous Islam
Department of Ophthalmology
CMH, Dhaka
2. THE TEAR FILM
The main role of lacrimal system is to establish &
maintain a continuous tear film over the ocular
surface
Pre-corneal tear film was 1st demonstrated by
Fischer in 1928.
Rollet described it as the most superficial 6th layer
of cornea.
3. STRUCTURE OF THE TEAR FILM
Wolff
Coined the term ‘PRE-CORNEAL FILM’.
Tear film consists of 3 layers.
1)Outer Lipid layer
2)Intermediate Aqueous layer &
3)Inner mucin layer
4.
5.
6. LIPID LAYER
Outer most layer.
0.1um thick
Formed from the secretions of Meibomian, Zeiss &
Moll glands.
Contents 1)low polarity lipids-wax & cholesterol
esters 2)high polarity lipids-TG, FFA ,phospholipids.
Functions 1)prevents the overflow of tears.
2)prevents evaporation.
7. AQUEOUS LAYER
Middle layer.
Formed by secretions from the main & accessory lacrimal
glands of Krause & Wolfring.
Constitutes the main bulk of tear film.
thickness over the cornea 10um.
Film covering the cornea is thinner than over the
conjunctiva.
Contents inorganic salts, glucose, urea, enzymes, proteins
& glycoproteins.
Buffering capacity of the tear film is d/t HCO3 ions & protein
Functions 1)provides O2 to corneal epithelium.
2)washes away debris & irritants.
3)contains antibacterial sub- lysozyme &
betalysin.
8. MUCOUS LAYER
Innermost layer.
Secreted mainly by the conjunctival goblet cells
30um thick.can be demo in living eye by alician blue drops
Functions 1)plays a vital role in the stability of the tear film.
2)converts the hydrophobic corneal epithelium to a hydrophilic
one.
3)lubricates the ocular & palpebral surfaces.
4)provides a slippery coating over the foreign bodies; thereby
protecting the cornea & conjunctiva against the abrasive effects of
such particles as they move about with blinking.
5)absorps various organic compounds in tears
9. NEW TEAR FILM MODEL
Recent observation--
mucins exist as a network
distributed in the aqueous
body of the tear film.
Glycocalyx emanate as
transmembrane molecules
into the aqueous & are
anchored at the cell
membrane.
Membrane associated
proteins-MUC1,4&16 as
well as secretory mucins-
MUC5AC &MUC7 have
been identified at the
ocular surface.
10. PHYSICAL PROPERTIES OF TEAR FILM
Property
Thickness 4-8um
Volume 4-13ul
Rate of secretion 1.2ul per min
Turn over rate* 18% per min
Refractive index 1.357
Ph of tears* 7.3-7.7
Osmotic pressure* 0.90-0.95%
Temperature 30’c at cornea and 35’ at limbus
Oxygen tension 40-160 mm hg
11. TEAR FULID COMPOSITION
Mainly composed of 3 protein factors-albumin,globulin
and lysozyme
IgA is the most prominent Ig.
IgE levels increase in patients with allergic
conjunctivities.
IgM increases in patients with acute infections.
Lysozyme constitutes 20% all tear protiens,highest in
conc among all body fluids
Electrolytes Na,K and Cl higher concetrations in tears
than in blood
12.
13. FUNCTIONS OF TEAR FILM
Makes corea a smooth optical surface
Wets cornea and conjunctiva and prevent from drying
Flushes out debris and organisms
Bactericidal properties (presence of lusozyme,lactoferrin
and betalysin)
Ig’s and specific Ab in tears defend the eye against
infections
Lubricating action
Enables anti inflammatory cells to reach injured cornea
and conjunctiva
Provides epithelial cells with O2 ,Glucose and Growth
Factors
14. NEURAL ASPECTS
The trigeminal v1 (fifth cranial) nerve bears the sensory
pathway(afferent) of the tear reflexes.
The motor pathway is autonomic (involuntary), &, in
general, uses the pathway of the facial (seventh) nerve
in the parasympathetic division via pterygopalatine
palatine ganglion, as efferent pathway.
Applied A newborn infant has insufficient development of
nervous control, so she/he "cries without weeping”.
15.
16.
17. APPLIED ASPECTS
Crocodile tears syndrome/ Bogorad's syndrome"
uncommon consequence of nerve regeneration
subsequent to Bell's palsy or other damage to the facial
nerve in which efferent fibers from the superior salivary
nucleus become improperly connected to nerve axons
projecting to the lacrimal glands (tear ducts), causing one
to shed tears (lacrimate) during salivation while smelling
foods or eating.
Presumed that one would also salivate while crying due to
the inverse improper connection of the lacrimal nucleus to
the salivary glands, but less noticeable.
18. TEAR FILM DYNAMICS
Secretion of tears
Formation of tear film
Retention & redistribution of tear film
Displacement phenomenon
Evaporation from the tear film
Drying & break up of tear film
Dynamic events during blinking
Elimination of tears
20. BASAL SECRETION
In the human eyes the cornea is
continually kept moist & nourished by
basal tears.
• They lubricate the eye & help to keep it
clear of dust.
• Secreted by accessory lacrimal glands
21. •
REFLEX SECRETION
•Results from irritation of the
eye by foreign particles,
bright light,hot & peppery
stimuli to the tongue.
•These reflex tears attempt
wash out irritants that may
have come into contact with
the eye.
•Secreted by main lacrimal
gland
22. Applied If lacrimal gland is damaged in
surgery or other failure of lacrimal
function occur, it is not a serious matter,
for the accessory glands are enough for
general secretion
23. 2.FORMATION OF PRE OCULAR TEAR FILM
Conjunctival mucus spreads on to the
cornea by the action of the lids.
On this new surface- aqueous layer is
spread spontaneously.
Over this the superficial lipid layer
spreads; probably contributing to its
stability & retarding evaporation b/w
blinks.
24. 3.RETENTION & REDISTRIBUTION
The outer most layer of corneal
epithelium+mucopolysaccharides leads to
retention.
Precorneal film is stagnant. Redistribution
occurs in the form of bringing of new tear
fluid by way of marginal strip where there
is constant flow of tears
25. 4.DISPLACEMENT PHENOMENON
Demo that cornea is covered by a film which
has stability, compressibility, elasticity &
unaffected by gravity
Demo by upward movement of particles in the
film on displacing lower eyelid upwards over
eyeball
This phenomenon is possible due to presence
of thin monomolecular layer on the surface of
cornea
26. 5.EVAPORATION
All lipid films including wax esters & cholesterol
esters retard evaporation of water
Important in low humidity & turbulent air flow
near cornea, such as exists in a windy & arid
climate
Evaporation from tear film = 10% of production
rate, so, evaporation = 0.12ul/min (as tear
production = 1.2ul/min)
27. 6.STABILITY, DRYING & RUPTURE OF TEAR FILM
Tears has to cover entire preocular surface to function
properly
It is re-established completely after a blink , but has short
lived stability
It takes 15-40 secs for tear film to rupture & dry spots to
appear, when blinking is prevented
Drying of corneal surface cannot be a result of evaporation
of water alone, as it takes at least 10 mins to eliminate
whole tear film by drying alone.
28. 7.ELIMINATION OF TEAR FILM
HOLLY & LEMP’S MECHANISM
Initially all the tear film thins uniformly by evaporation.
When thinned out to critical thickness, some lipid
molecules attracted by the mucin layer & migrate
down to this layer.
When the mucin layer is sufficiently contaminated by
lipid from the top, the mucin becomes hydrophobic &
the tear film ruptures
Blinking repair this and restore aqueous layer
29.
30. 8.DYNAMIC EVENTS DURING BLINKING
As the upper lid moves downwards, the superficial
lipid layer is compressed b/w the lid edges
This will contaminate the mucus & this lipid
contaminated mucus is rolled up in a thread like
shape & dragged into lower fornix
When the eye opens, at 1st the lipid spreads in the
form of a monolayer against the upper eye lid
Then spreading of the excess lipid follows & in
about 1 sec multimolecular lipid layer is formed
The spreading lipid drags some aqueous tears with
it thereby thickening the tear film.
31.
32. 9.ELIMINATION OF TEARS
Lacrimal fluid over the preocular surfacemarginal tear
stripLacus lacrimalisinner canthus lacrimal
passages nasal cavity
Lacrimal pump mechanism:- fibres of the pretarsal &
preseptal portion of the Orbicularis which arise from the
lacrimal fascia & posterior lacrimal crest.
This LPM operates with the blinking movements of the
eyelids as follows:-
33.
34. DRAINAGE OF LACRIMAL FLUID FROM NLD INTO
NASAL CAVITY
Gravity helps downward flow.
Air currents in nose induce negative pressure within
NLD draw the fluid down the potential lumen of the
duct into the nose.
Hasner’s valve present at lower end of NLD,
remains open as long as the pressure within nose
is less than the NLD, allows the tears to flow from
NLD to nose
35.
36. CHIEF C/O THE PATIENTS WITH TEAR FILM
DYSFUNCTION
Burning or Itching
Fluctuating Vision
Foreign Body Sensation
Grittiness or irritation
Watering or excessive tearing
Sore or tired eyes
History of Styes
Ocular Discharge
Light sensitivity
Contact Lens Discomfort
37. HISTORY FOR A DRY EYE(DE) PATIENT
Duration of reading or computer use
Using contact lens
Living in air conditioned environment
Frequent air traveling
Cigarettes smoking
Exposure to allergans or systemic allergies
Hormonal change
Autoimmune diseases
38. DISEASES RELATED TO DYSFUNCTION IN
TEAR FILM
Evaporative Dry Eye
Oil deficiency- secondary
to obstructive meibomian
gland dysfunction
Defective resurfacing of the
eye by the tear film (result of
poor blinking or abnormal lid-
globe congruity)
39. DRY EYE: MULTIFACTORIAL NATURE
Elderly woman
Contact lens
user
Post
menopausal
Taking
glaucoma
medications
Working for long
hours in front of
computer
Air-conditioned
environment
40. DISEASES RELATED TO DYSFUNCTION IN
TEAR FILM
•Hyper secretion of tear film
C/O Wet eyes
Lacrimation from
excess tearing
Obstructive
epiphoria as a result
of failure of tear
drainage
( Schirmer’s value)
41.
42. TEAR FILM BREAK-UP TIME(BUT)
Difference b/w the last blink and
the first randomly appearing dry
spots
Assessed with fluorescein and
cobalt blue filter in broad beam
Avg of three reading is taken
Suspect Dry Eye when
BUT<10secs
43. CAUSES OF TEAR FILM DESTABILITY
Tear Film rupture occurs when
hydrophobic lipid diffuses from the
superficial layer and contaminates the
underlying hydrophilic mucin layer
Epithelial change
44. SCHIRMER’S TEST
Rate of tear formation is
estimated
Whatman filter paper no 41 is
used
Dimension 5mm X 35mm
5mm tab is folded at one end
The bent end is placed at the
junction of the lateral 1/3rd and
medial 2/3rd of the lower
conjunctival sac
Performed in dim light with fans
and ACs switched off
45. SCHIRMER TEST
Without Anesthesia
Measures Reflex Tear
Secretion (dry eye = < 6mm
wetting)
With Anesthesia
Measures Basal Tear
Secretion (dry eye =< 3mm
wetting)
46. JONES-I (PRIMARY) TEST
Differentiates excessive watering due to blockage in
lacrimal passage with primary hypersecretion of tears
1 drop of 2% fluorescein in instilled in the conjunctival
sac
After 5mins a cotton tipped bud (moistened with
4%proparacaine) is inserted under the inferior turbanate
Fluorescein if recovered from the nose then the
excretory system is patent
Otherwise should go for Jones-II test
47. JONES-II (SECONDARY) TEST
Helps to identify the probable site of partial obstruction
4% xylocaine instilled in the conjunctival sac
residual fuorescein washed out
NLD irrigated with NS
Patient is positioned his/her down by 45deg
+ve –fluorescein stained saline recovered from the nose showing
functional patency of upper lac passage
-ve- unstained saline recovered from the nose shows block in the upper
lac passage or defective lacrimal pump mechanism