Dry eye disease

Question 1

what is dry eye disease

Answer 1

dry eye is a multifactorial disease of the ocular surface characterised by a loss of homeostasis of the tear film , and accompanied by ocular symptoms in which tear film instability , hyperosmatlorty, ocular surface inflammation and damage and neurosensory abnormalities play etiological roles

Question 3

what are the two types of dry eye disease

Answer 3

evaporative dry eye (dysfunction of lipid layer)

aqueous deficient dry eye - aqueous dysfunction

Question 4

how does covid 19 affect dry eye

Answer 4

covid 19 and therefore increased green time and online learning were associated with worsening pre-existing ocular surface diseases

Question 5

what is evaporative dry eye due to

Answer 5

typically due to some type of meibomian gland dysfunction

Question 6

what are causes of evaporative dry eye

Answer 6

anterior blepharitis

contact lens wear

seborrheic dermatitis

allergic eye disease

psoriasis

Question 7

what are causes of aqueous deficiency dry eye

Answer 7

typically due to reduced lacrimal secretion

causes include

Sjogren syndrome dry eye systemic - autoimmune disease

rheumatoid arthiritis

systemic lupus erythematosus

stevens johnson syndrome /TEN

trigeminal nerve in jury

refractive surgery

Question 8

how is tear hyperosmolarity related to dry eye disease

Answer 8

tear hyperosmalirty and tear film instability are the core drivers of dry eye disease

regardless of how its initiated patients end up in a vicious cycle where tear hyperosmolarity occurs which causes inflammatory proteins to activate and recruit other inflammatory mediators to affect the Hglycocalayx and cause epithelial cell apoptosis and goblet cells

the loss of glycolaxyl musician (exists between mucin and corneal layer) joins tear film and cornea probably ACCOUNTS FOR SOME OF THE CORNEAL STAINING WE SEE AND LEADS TO REDUCE CORENAL WETTING WHICH contributes to reduced tear break up time (uchino 2018)

Question 9

how does tear film become damaged

Answer 9

a normal tear film consists of a lipid layer and aqueous layer in this order from the ocular surface

in dry eye the tear film is collapsed sometimes with decreased expression of membrane muffins in epithelial cells and disordered or lost epithelial cells

Question 10

how to differentiate between evaporation dry eye and aqueous dry eye disease

Answer 10

to differentiate between the two causes history will need to be taken and a careful examination of the lids on slit lamp

aqueous dry eye disease tends to be worse during the day whereas evaporation dry eye is worse on waking

however there is often little correlation. between signs and symptoms

the usual symptoms of dry eye disease include ocular discomfort (gritty eyes) light sensitivity and epiphora

Question 11

what is the first line of treatment for dry eye disease

Answer 11

first line of treatment is non pharmacological and is aimed at identifying any modifiable lifestyle factors

the aim of treatment should be to re - establish and maintain the ocular surface homeostasis that has been damaged by the vicious circle outline previously

Question 12

what are signs of dry eye disease

Answer 12

reduced tear film break up time (without fluroscein is preferred)

schemers test (a test of the production od tears)

tear osmolarity not usually done in the nos clinic but is the most reliable indicator of dry eye disease

values greater than 308mOsm/litre (milie - osmole - is a measure of saltiness per litre are Indicative of dry eye disease as are asymmetries between the values od the two eyes

examination of the corneal epithelium using stains/dyes e.g. flurocein and lissamine green (staining goblet cells in the conjuctiva)

Question 13

how are artificial tear preparations used

Answer 13

they are available but there is a wide variation of options and not all options are available at all local formularies

reviews have found that no single preparation is more effective than others

hyaluronic acid has been shown to be effective in a range of patients and across a range of severities. Optimal drop concentration = between 0.1 and 0.4% and optimal drop frequency is still lacking evidence

Question 14

what are the types of artificial tears

Answer 14

hypromellose

carbomers

hydroxythycellulose

polyvinyl alchol

sodium hyaluronate (hylaruynoic acid)

carmellose

trehalose

Question 15

what is the next line of treatment if artificial tears are not responsive

Answer 15

if disease severity is unresponsive got artificial tear supplements than further treatment options include a course of steroids to reduce the corneal inflammation and try and stop the vicious circle

further options include the use of cicilosporin eye drops or analogous serum eye drops but these need referral to the doctors

in cases of ADDE punctual plugs can be used to try and increase the tear reservoir

Question 16

what structures are involved in the production of normal tear film

Answer 16

lacrimal gland is located underneath the eyebrow (innervated by the facial nerve which is the seventh nerve , tears are also produced by the meibomian gland

Question 17

is the lacrimal gland under parasympathetic or sympathetic innervation

Answer 17

parasympathetic ally innervated

lacrimal gland involved primarily in the production of reflex tears

Question 18

where is the meibomian gland located

Answer 18

located in the upper and lower lids

Question 19

what do meibomian glands produce

Answer 19

they produce meiobom

prevents tear evaporation tear evaporation can cause dry spots on the cornea

Question 20

in what other glands are the lipid layer produced in

Answer 20

• the glands of ziess and moll

Question 21

where is the aqueous layer of tear film produced

Answer 21

the glands of Krauser and wolfring and are located in the tarsal plate

these are acessory glands and they are producing normal levels of aqueous

Question 22

where is the mucin layer produced

Answer 22

goblet cells of the conjuctiva

mucin is composed of heavy weight molecules called glycoproteins

Question 23

what is the role of mucin layer

Answer 23

increases wet ability of the tear film

if there was no mucin there would just be aqueous next to the cornea and it would not be dispersed out across the corneal surface - so the mucin layer is essential for a normal tear film

Question 24

how are the structures that are responsible for the different tear film components neurally regulated

Answer 24

neural regulation is ongoing

there are neurosensory mechanisms that are undergoing constantly from the cornea and conjuctiva that influence the production of mucin , lipid and aqueous , constantly regulated and controlled , when the regulation and feedback breaks down and the glands become diseased/dirsupted gives rise to dry eye disease

Question 25

what muscles control blinking

Answer 25

obicularis oculi controlled by cranial nerve e7 (facial nerve)

Question 26

what opens the lid ( parasympathetic)

Answer 26

levator muscle and is innervated by the third

Question 27

what opens the lid (sympathetic control)

Answer 27

mullers muscle e.g. if someone is given too much phenelephrin

Question 28

what is a characteristic symptom of dry eye disease

Answer 28

gritty eyes (suggestive of something affecting the tear film) and in the absence of infection it will be dry eye disease

Question 29

what is hyperosmolarity

Answer 29

osmolarity= a measure of the salt concentration hyperosmolarity refers to an increase in the salt concentration there are machihienes that get measure the osmolarity of the tear film as a result of hyperosmolarity e.g. high conc of salt in the tear film it draws water from the corneal epithelium resulting in epithelial apopotisis

Question 29

what happens if epithelial apoptosis occurs due to hyperosmolarity

Answer 29

these epithelial cells are responsible for the normal regulation of tear film , if we are killing these neurosensory cells then it will feedback into the system and correct tears will not be produced chain of events - hyperosmolarity - neurosensory abnormalitties- tear film instability - crappy tears

Question 30

what part of the tear film is affected with aqueous deficient dry eye

Answer 30

something is wrong with the aqueous layer - not producing the correct amount of aqueous

Question 30

what part of the tear film layer is affected with evaporative dry eye

Answer 30

something is wrong with the tear film layer and therefore tears are evaporating

Question 31

what happens to blink rate as you look close up

Answer 31

you blink less

Question 32

what is anterior blepharitis

Answer 32

inflammation of the lids and crusting

Question 33

how is sjogrens syndrome related to dry eye

Answer 33

shortens syndrome is a systemic disease which is a autoimmune condition that inside of lacrimal glands

Question 34

why is refractive surgery associated Wirth aqueous deficiency dry eye

Answer 34

in order to get to the cornea you have take off the epithelium - have to cut itnto neurosensory fibres which regulate tear production

Question 35

what is a glycocalyx

Answer 35

the glycocalyx is a intermediate layer between the mucin layer and the corneal epithelium related to the corneal epithelium micropilthey acts as join between the tear film and the mucin layer itself , evolved in the wetting and transmission of some of the nutrients , when we see it dissapera then we see formation of dry areas on the cornea and reduced tear break up time

Question 36

what happens if you lose glycolayx

Answer 36

you get cell death , dry spot formation and problems with the glycolayx and mucin layer

Question 37

where does the grittiness in dry eye disease come from

Answer 37

what happens when our patient blinks? - instead of having lubrication of the lid over the tear film there will be contact between the lid and the epithelium so you feel the lid action of the cornea

Question 38

what are factors for evaporative dry eye disease

Answer 38

MGD- mebiomian gland dysfunction anterior belpharitis deficient or unstable tear film lipid layer vitamin a deficiency allergies contact lense wearer these are all disrupters to tear film stability

Question 39

if you have evaporative dry eye disease what happens

Answer 39

if you have evaporative then you have high evaporation of the tears (of the aqueous component of the tears) this leads to the tear hyperosmolarity - leads to high evaporttion which leads to tear hyperosmolarity

Question 40

what are factors for aqueous deficiency dry eye disease

Answer 40

non sorjens dry eye disease KCS- keratoconjuctivits sica (dry eye disease) SSDEautominune (sorjens syndrome dry eye disease) systemic drugs these all affect aqueous input meaning low flow in i.e. not much of the aqueous is going in - compared with losing aqueous in evaporative dry eye disease

Question 41

what is the main driver of dry eye disease

Answer 41

tear hyperosmolarity is the main driver

Question 42

what its acute epitheliel MAPK

Answer 42

these are intermediate signalling molecules - it leads to goblet cell and glycol calyx mucin loss - epithelieel and cell apoptosis this leads to tear film instability because you ar losing the neurosensory control - this leads to tear hyperomsolarity

Question 43

how does DED cause epiphora

Answer 43

reflex tears to the itchiness and grittiness

Question 43

if symptoms are worse in the morning what type of dry eye disease is that

Answer 43

evaporative dry eye disease if worse during evening or morning = aqueous

Question 44

why do you measure tear film break up time without fluroscein if possible first

Answer 44

disrupts tear film

Question 45

what is schimers test for

Answer 45

measuring aqueous production it is a little strip of paper that you hook into the lower fornix and you measure how far along the schirmer strip the tears have progressed

Question 46

what are the aims of dry eye disease treatment

Answer 46

aims are to reduce tear hyperosmolarity using aqueous supplements , to increase tear film stability and to let the cornea recover to redevelop normal neurosensory control

Question 47

what should be considered about artificial free preperations

Answer 47

things that contain preservatives are harmful to the front of the eye in particular benzayl conium chloride so if you have someone with an anterior surface pathology you shouldn't but that preservative free tends to be More expensive

Question 48

what things need to be balanced when considering type of artificial tear preparations

Answer 48

the viscosity and effect on vision vs the treatment efficiency -

Question 49

risk factors of dry eye disease include

Answer 49

age , hormonal disorders. lifestyle, allergies, glaucoma , belpharitis , contact lense wear

Question 50

symptoms of dry eye disease include

Answer 50

dryness, blurry vision, foreign body sensation , photophobia, achiness , pain

Question 51

what inevstigatice techniques can be used to investigate dry eye disease

Answer 51

tear stability, tear volume , ocular surface damage , dermodex

Question 52

what is glycolayx and why is it important

Answer 52

The keratoconjunctival epithelium surface has protruding structures known as microplicae, whose tips include highly expressed membrane mucins that take the form of lawn patterns In patients with dry eye, the MUC16 protein expression decreased, the barrier was broken, and galectin 3, which should otherwise form the glycocalyx, was released into the tear fluid at increased levels. In addition, in cases of severe dry eye with intense barrier collapse,