Ch 36. Dry Eye / DEWS II Flashcards
What are the pillars of the dry eye’s definition according to DEWS II.
Symptomatic Lacrimal homeostasis disruption due to:
- Lacrimal instability
- Hiperosmolarity
- inflammation
- ocular surface disease
- Neurosensory disfunction
Name the two types of accessory lacrimal glands
Wolfring and Krause
Which are the main neurotransmitters affecting lacrimal gland secretions?
Acetilcholine and noradrenaline.
<em>Secondary analogues are Neuropeptide Y, vasoactive intestinal peptide, substance P, calcitonin gene-related peptide. </em>
describe the histological classification of meibomian glands.
Modified Acinary, Sebatious, holocrine.
Are meibomian gland lipids mostly polar or non-polar?
(95%) Non polar
Which is the main mucin molecule according to size, corneal humectability, and barrier function?
MUC-16
<em>with <strong>2,5MDa</strong> in size and a total potential glycosylated size of <strong>20MDa</strong></em>
what is the normal volume, production rate, and change rate?
7ul total volume
1,02 secretion rate
16% change/min.
Where is the lacrimal osmolarity higher (precorneal tear film or meniscus)
In a normal patient Is higher in the meniscus
In DES it is significantly higher in places of lacrimal instability and tear break.
This is important because the measurement of osm in the meniscus can underestimate its real pre-corneal value.
Through which mechanism can linfoma produce dry eye disease?
Lacrymal gland infiltration
Main differential diagnosis of Sjogren Associated Dry eye in the elderly?
Age-related, Non-Sjogren, acuose-deficient dry eye
What osmolarity can be used in the diagnosis of mild Dry eye disease, and moderate/severe disease?
Mild: >308 mOsm/L
Mod/Sev: > 316 mOsm/L
What is the normal ocular protection index, and how is it interpreted?
TBUT / interblik interval.
Normal value is >1.
A value >1 means that the TBUT is longer than the I-I, which means that the ocular surface is protected from desiccation and hyperosmolarity by the tear throughout the I-I. A value <1 means that the tear breaks before each blink, with a perpetual cycle of hyperosmolarity and surface damage.
What is the Lubricin?
It is proteoglycan 4, an important molecule with a lubrication function in the ocular surface and other frictional surfaces of the body.
It is being studied to be used as a medical treatment for dry eye.
Is the tear a Newtonian or a non-newtonian fluid, what is the clinical importance of this?
It is non-newtonian.
this is important because, in non-newtonian fluids, viscosity is dependent on frictional forces, meaning that in the tear, viscosity drops during the blink (tear are pseudoplastic), therefore its lubrication ability is enhanced during that period of rapid movement
What is the area of meniscus-induced lacrimal shallowing?
an area right on top of the lower meniscus where the lacrimal film has its lower thickness.
It is important because it is presumed to be the area with higher osmolarity, and therefore a hi risk area for epithelial changes in dry eye disease.
What is the Marx line?
An area of staining just under the mucocutaneous junction of the lid, that increases with the age, and inflammatory conditions.
It is presumed to be a zone of high osmolarity (due to higher evaporative forces) therefore, also a zone of higher pro-inflammatory-molecules concentration. Once this line reaches the meibomian ducts, the meibomian glands are exposed to this adverse environment.
