describes only the pathological part of dry eye disease

1. Dry Eye Pathology
-DR. PRAVDA CHATURVEDI

2. Dry Eye
In 1995 National Eye institute defined dry eye
as:
“A disorder of tear film due to tear deficiency or
excessive evaporation, which cause damage to the
inter- palpebral ocular surface and is associated with
symptoms of ocular discomfort.”
In 2007, DEWS modified it as:
“Dry eye is a multifactorial disease of the tears and
ocular surface that results in symptoms of discomfort,
visual disturbance and tear film instability with
potential damage to the ocular surface.”

3. Lacrimal Function Unit

4. Lacrimal Function Unit
Tearing apparatus
Production- lacrimal gland, meibomian gland,
gland of wolfring and krause, manz and goblet
cell
Clearance- lacrimal passages
Ocular surface
Conjunctiva
Cornea
Eyelids
Sensory and motor nerve

5. Pre-corneal Tear film
From out wards in, the layers are
o Lipid layer
o Aqueous layer
o Mucous layer

6. Lipid Layer
Lipid layer is secreted by the meibomian
glands & gland of Zeiss.
Their function is:
 To reduce the evaporation of the aqueous
layer.
 To increase the surface tension& assist in
vertical stability of the tear film
 To lubricate the eyelids.

7. Aqueous layer
• The middle layer is secreted by main
and acessory lacrimal glands & has
following functions:
 To supply atmospheric oxygen to the
avascular corneal epithelium
 Anti –bacterial function
 To reduce the irregularities of corneal
surface
 To clean away the debris.

8. Mucin layer
 The inner layer is
secreted by the
conjunctiva goblet cells,
crypts of Henle & glands
of Manz.
 It converts the corneal
epithelium from
hydrophobic to
hydrophilic state

9.  The new concept of
the tear ocular
surface structure
being that of a
metastable tear film
consisting of an
aqueous gel with a
gradient of mucin
content decreasing
from the ocular
surface to the
undersurface of the
outermost lipid layer.

10. Normal tear film
• Volume: 7-10 μl , avoid blinking 20-30 μl
• Thickness : 7microns
• Production : 1.2 μl/min (0.5-2.2)
• Tear evaporation: (0.14 μl/min in 30% humidity)
• pH : 6.5-7.6
• Surface tension : 40.7 dyne/cm
• Refractive index : 1.336
• Osmolarity : 300-310 mOsm/l

11. Pathophysiology
• Aqueous tear deficiency
• Mucin-deficient dry eye
• Meibomian gland dysfunction
• Hormonal imbalance
• Inflammation

12. Factors in the Pathogenesis
of Dry Eye Disease
• Genetic predisposition
• Systemic autoimmune disorder
• Viral infections affecting lacrimal gland
• Neurotrophic keratitis
• Hormonal insufficiency (Age related, Menopause, Androgen insufficiency)
• Age related atrophy of lacrimal gland
• Insufficiency of spread of tears (conjunctivochalasis)
• Iatrogenic (LASIK, Contact lens, Medications—systemic/topical)
• Video display terminal
• Environmental stress.

13. Pathology
 Unstable tear film due to
• Mucin deficiency
• Lipid deficiency
• Inadequate spread due to mechanical damage
 Hyperosmolarity of tear film
 Blink related microtrauma
 Loss of corneal sensation
 Inflammation

14. Environment,
Medications,
Contact Lens,
Surgery
Rheumatoid Arthritis
Lupus,
Sjögren’s,
Graft vs Host Disease
Menopause,
Meibomian Gland
Disease
Symptoms of Ocular Surface Disease
Inflammation
Tear
Deficiency/
Instability
Irritation
Triggers of Dry Eye Disease

15. THE HEALTHY EYE
Stern et al, Cornea. 1998:17:584
NORMAL TEARING
DEPENDS ON A
NEURONAL FEEDBACK LOOP
Secretomotor
Nerve Impulses
Tears Support and Maintain
Ocular Surface
Lacrimal
Glands Ocular Surface
Neural Stimulation

16. Dry Eye

17. Healthy tears
 A complex mixture of
proteins, mucin , and
electrolytes
 Antimicrobial proteins:
Lysozyme , lactoferrin
 Growth factors &
suppressors of
inflammation: EGF, IL-1RA
 Soluble mucin 5AC
secreted by goblet cells for
viscosity
 Electrolytes for proper
osmolarity

18. Tears in chronic dry eye
 Decrease in proteins
 Decrease in growth
factor concentrations
 Altered cytokine balance
promotes inflammation
 Greatly decreased
soluble mucin 5AC
• Due to goblet cell loss
• Impacts viscosity of
tear film
 Proteases activated
 Increased electrolytes

19. Mechanism of ocular surface
inflammation in dry eye

21. Classification
 International Dry Eye Workshop (DEWS):
• 3-part classification
 Etiology
 Mechanism
 Severity
 Updated by National Eye Institute on basis
of etiopathogenesis:
• Aqueous deficiency state
• Evaporative state

22. Dry eye classification

23. Tear deficient dry eye

24. Sjögren
syndrome
primary
Not associated
with any
disease
secondary
Associated
with
systemic
disease
Rhematoid arthritis
SLE
PAN
Progressive systemic sclerosis
(scleroderma)
Dermatomyositis and
Polymyositis
Primary biliary cirrhosis
Hashimoto thyroiditis
Aqueous deficiency state

25. Non- Sjögren Syndrome
A.Secondary lacrimal gland deficiencies
Lacrimal gland infiltrations
• Sarcoidosis
• Amyloidosis
• Tuberculosis
• Lymphoma
• Hemochromatosis
Lacrimal obstructive disease
• Trachoma
• Ocular cicatricial pemphigoid
• Stevens- Johnson syndrome
• Chemical/thermal injuries
• Post-radiation fibrosis
B. Graft versus host disease (GVHD)
C. Lacrimal gland ablation/ denervation

26. Reflex Hyposecretion:
Reflex Sensory Block-
Decrease reflex induce tear secretion and reduces blink rate
• Neurotrophic keratitis
• Post-infective, e.g: HSV, HZO
• Chronic contact lens wear
• Corneal surgeries, eg: limbal incisions, refractive surgeries,
keratoplasty
Reflex Motor Block-
• Neuroparalytic keratitis

27. Evaporative dry eye

28. Meibomian gland disease
• Reduced number
• Congenital Deficiency
 Meibomian gland dysfunction
•Hypersecretory- Seborrhea
•Hyposecretory- Retinoid Therapy
Obstructive
• Simple- Blepharitis, Atopy, Ichthyosis Etc.
• Cicatricial- Trachoma, Pemphigoid

29.  Low blink rate
• Parkinson’s disease
Disorder of eye lids and lid/globe congruity
• Lid palsy
• Exophthalmos

30. Dry Eye In Contact Lens Users
Contact lens dynamics:
• Alterations in the pre corneal tear film (PCTF)
• Reduction in corneal sensations
• Corneal hypoxia
• Reduced blinking
• Thermal destabilisation.

31. Medications
• Anti-hypertensives
• Anti-androgens
• Anti-depressants
• Anti-arrhythmic Drugs
• Anti-Parkinsonism Drugs
• Anti-histamines
• Anti-cholinergics
• Beta-blockers
• Preservatives in eye drops
• Topical anesthetics

32. Tear film osmolarity
Lacrimal gland disease
Decresed corneal
sensation
Increased palpebral
fissure
Meibomian gland
dysfunction
Decrease sensation
Increased
evaporation
Increased tear
osmolarity
TOXIC TO
EPITHELIUM

35. Final Outcome of Dry Eye
Disease
 Ocular surface related
• Punctate epitheliopathy
• Erosions
• Epithelial defect.
 Patient related
• Visual effects, rapid tear breakup time,
increased blink rate, degradation of image
• Symptom related, subjective distress ultimately
leading to ocular fatigue.