Dry Eye evaluation

1. TEAR FILM EVALUATION
Raju Kaiti
Optometrist
Dhulikhel Hospital, Kathmandu University Hospital

2. STRUCTURE OF TEAR FILM
 It is approximately:
 7 micrometre thick
 7microliter in volume
 Wolff (1946): Precorneal layer
Three layers
• Outer lipid layer
• Intermediate aqueous layer
• Inner mucous layer
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3. Non Invasive Techniques
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 NIBUT
 Lipid layer evaluation
 Interferometry
 Inferior tear meniscus evaluation
 Tear prism height
 Infrared Thermography

4. NIBUT
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 Non Invasive Break Up Time
 The time elapsed from the last blink to appearance of the
first random dry spot on the ocular surface
 Techniques
 Keratometry
 Modified keratometry
 Tearscope TM
 Assesses pre-corneal tear film stability
 NIBUT < 10 seconds
 A marginally dry eye that may be prone to contact lens
intolerance.
 NIBUT of 10 – 20 seconds
 Borderline marginally dry eye, may be more prone to lens
deposits than normal
 NIBUT > 20 seconds
 Stable tear film, normal.

5. Assessment of inferior tear
meniscus 5
 Tear Meniscus Height (TMH)/Tear Prism Height
(TPH)
 Indicates the tear volume
 Normal meniscus height 0.3mm
 Debris in tear meniscus
 Techniques
 Thin optic section
 Primary gaze
 Middle of lower lid margin
 Minimize light intensity
 Normal blinking

6. Interferometry
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 Interference patterns
 Tear film interference patterns
(colored fringes)
 Indicate the different
thicknesses of the component
layers
 Lipid layer
 Colored fringes

7. 7  Clinical observation
 Lipid layer patterns commonly colorless
 Layer too thin for interference (<60 nm)
 Pre-lens colored fringes probably due to thinning aqueous

8. The typical marmoreal pattern seen in the
lipid layer is absent in the dry eye
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9. Infrared Thermography
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 The rate of change of corneal temperature, an analogue of the tear
film evaporation rate is measured
 Evaporation produces cooling
 Infrared thermograms confirm:
 Dry eyes have lower evaporation rates
 Corneal temperature fluctuates between blinks (an effect of
evaporation)
 Dry eyes have slower between-blink cooling (reduced
evaporation)

10. Blink evaluation
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Blink Movement and Blink Rate
 Twitch blink
 Incomplete blink
 Forced blink
 Normal blink
 Average blink rate : 12.5 / min
 During concentrated = 3 / min
 Free conversation = 29 /min

11. Invasive Techniques
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 Schirmer’s Tear test
 Schirmer’s tear test 1
 Basic secretion test
 Schirmer’s test 2
 Tear Break Up Time
 Phenol Red Thread Test
 Fluorescein Staining
 Rose Bengal Staining
 Conjunctival Impression Cytology

12. Schirmer’s Tear test
 Test for tear quantity (aqueous level)
 Based on wetting length of the strip 5x35mm Whatman 41 filter paper
 Placed in the lower fornix 2/3rd from medial canthus and 1/3rd
 from lateral
 2 variations
 Schirmer’s test I
 Measures total tear secretion (basic and reflex)
 Open eye technique
 Normal
 10-30 mm at the end of 5min
 If wetting >30mm before 5 min
 Reflex tearing overactive/ insufficient tear drainage
 Value < 5mmHyposecretion
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13.  Basic Secretion Test
 Variant of Schirmer's test I measures basal tear secretion
 Topical anesthetic is applied
 Cul-de-sac is dried out before the strip is inserted
 Difference between Schirmer's I and BST
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 Schirmer’s 1 reading gives reflex secretion also
 Normal value > 10mm
 Basic Secretion of 3mm or less Abnormal
 Schirmer’s Tear test II
 Measures reflex tear secretion
 Irritate nasal mucosa by rubbing it with cotton swab or smelling ammonia
 Measure wetting after 2min
 Wetting < 15mm Failure of reflex secretion
 Parasympathetic supply

14. Fluorescein Staining
Fluorescein dye is used to detect epithelial defects on the anterior surface
of the eye.
Penetrates only the corneal epithelium at sites of interrupted continuity of
the epithelial surface.
Is enhanced with the use of cobalt blue filter that blocks extraneous light
and highlights staining patterns.
Tear Break Up Time
Tear film Break Up Time in cobalt blue filter
Interval between the last blink & the first appearance of black spot in the
fluorescein-stained tear film (No rn & Ham il 1 9 7 3 )
A black island in the sea of green fluorescein
Assessment of tear film stability
>10 sec Normal
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15. Rose Bengal Staining
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Devitalized cells on the cornea and conjunctiva and mucus in the tear film
detected using 1% rose bengal; highlighted by red punctate staining
0 to 3 graded scale
•Three regions of the interpalpebral ocular surface are assessed
– the triangular wedge of the nasal interpalpebral conjunctiva,
– the corneal surface
– the wedge of the temporal conjunctiva
•The grade of each region is summed, and a score greater than 3.5 is
considered indicative of dry eye

16. Conjunctival Impression Cytology
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 Millipore filter paper of cellulose acetate (with 0.02-μm pores) can
be employed to assess conjunctival goblet cell density.
 The filter paper is cut into strips approximately 5 x 5 x10 mm in size.
After instillation into the inferior cul-de-sac of one drop of
proparacaine or a similar anesthetic, with the aid of a forceps, the
pieces of filter paper are pressed against the nasal, temporal,
inferior, and superior bulbar conjunctiva.
 Pressure is applied to the paper for 2 to 3 seconds.
 The filter paper is then fixed for 10 minutes in a mixture of 70%
ethyl alcohol, 37% formaldehyde, and glacial acetic acid in a
proportion of 20:1:1.

17. Conjunctival Impression Cytology
 Each paper is stained, using periodic acid–Schiff (PAS),
hematoxylin and eosin, and Papanicolaou.
 Under the light microscope, the epithelial cells are evaluated for
morphology and density.
Nelson (1988) classified impression cytology of the conjunctiva in
grades:
 Stage 0: normal cellular structure
 Stage 1: early loss of goblet cells without keratinisation
 Stage 2: total loss of goblet cells with slight enlargement of
epithelial cells
 Stage 3: early and mild keratinisation
 Stage 4: moderate keratinisation
 Stage 5: advanced keratinisation
Grades 1 and 2 are considered normal.
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18. THANK
YOU !!!!!!
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