Techniques of tear film evaluation by Raju Kaiti

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
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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

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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 2/3
rd
from medial canthus and 1/3
rd

 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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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
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

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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 & Ha m il 1 9 7 3 )
A black island in the sea of green fluorescein
Assessment of tear film stability
>10 sec Normal

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
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.
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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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