Term
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Definition
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Term
| NaFL is an ion of weak acid so it does what? |
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Definition
| Allows no pentration of an intact epithelium - It pools in areas where the epithelium is deficient |
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Term
| NaFL absorbs ____ light and emits ____ light. |
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Definition
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Term
| What filter would it be best to use in order to visualize NaFL stain? |
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Definition
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Term
| Tear break up time (TBUT) measures what? |
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Definition
| It measures the integrity of the tears. It measures the interval between the last complete blink and the first random 'dry' spot |
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Term
| What is a normal TBUT? The TBUT is considered clinically important if it is less than how long? |
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Definition
15-45 seconds
less than 10 seconds |
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Term
| When is the tear film the thickest? |
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Definition
| Immediately after a blink |
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Term
| What is the normal tear break up pattern? |
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Definition
| Tears break inferiorly first, the split upward, and then flatten outward |
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Term
| What is the theory for why the tear film layers break up? |
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Definition
| Instability and eventual rupture of mucin layer secondary to Van der Waals forces. The aqueous ruptures over the hydrophobic epithelium |
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Term
| The primary thought of why the tear film breaks is explained in the Holly-Lemp mechanism which states that what? |
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Definition
| The aqueous layer of the tear film starts to evaporate, causing the outer lipid layers to get closer and closer to the mucin layer, eventually contaiminating it. The mucin layer becomes hydrophobic, the aqueous layer continues to become thinner and the tear film eventually ruptures over this area |
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Term
| What is the McDonald-Brubaker mechanism of TBUT? |
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Definition
| It states that the suction by the meniscus (due to negative pressure) thins the aqueous resulting in bands of thinned tear film. When the lids open, the tensile strength of the thinned tear film lessens the suction, leading to rupture of the film |
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Term
| Can contamination of the lipid layer with debris (makeup, blepharitis etc) lead to a decreased TBUT? |
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Definition
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Term
| Dry spots may develop from immature ______ where new squamous epithelium is establishing. |
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Definition
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Term
| The NaFL clearance test looks at what? What is a normal value? |
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Definition
Looks at tear turnover
Minimal NaFL remains in a normal eye after 5 minutes |
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Term
| Describe Schirmer's Test 1. What are the sensitivity and specificity rates? |
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Definition
Wet a thin paper strip and place one end in the cul-de-sac of the lower lid. This can be done with or without anesthetic.
The sensitivity is low (25%) - may miss many dry eyes
The specificity is high (90%) - most caught are truly dry eye |
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Term
| What is the problem with using an anesthetic on Schirmer's Test 1? |
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Definition
| Using an anesthetic causes decreased corneal sensitivity and thus the cycle of new basal tear secretions. It compromises the neural signal |
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Term
| What does Schirmer's 2 test? |
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Definition
| Nasal mucousal stimulation - shows if problem with stimulating reflex tears |
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Term
| During the thread test (or zone-quick test or phenol red test) a 0.2 mm thread is placed with one end inside the lower lid. The phenol red turns yellow when wet due to its pH sensitivity. What is one good aspect of this test and one bad aspect? |
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Definition
| Good because it is much more comfortable than Schirmer's thick paper. Bad because it doesn't correlate well with other tests |
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Term
| In an inflammatory allergic response a touch tear microassay is specific for important protein in tears? |
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Definition
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Term
| Testing of the pH and osmolarity of tears is not done clinically even though it is what? |
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Definition
| Osmolarity is the most specific and sensitive test for measuring dry eye in patients |
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Term
| What is the most common of the goblet/mucin tests? What does it show? |
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Definition
Impression cytology
It shows goblet cell density and its capacity to make mucin |
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Term
| What are two ways to measure tear film thickness? |
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Definition
| Laser interferometry and confocal microscopy |
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Term
| A normal tear film meniscus is 0.2 to 0.5 mm in size and looks like a thin line across the lid margin. A poor quality or quantity of tear meniscus looks like what? |
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Definition
| Instead of it being a thin symmetrical line it appears to be scalloped |
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Term
| What are some non-invasive techniques for examing the tear film? |
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Definition
Slit lamp evaluation
Reflect grid pattern (placido disk) from cornea
Keratometer evaluation of mire distortion
Tear scope (NITBUT) |
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Term
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Definition
JP Guillon designed
permits observation and grading of lipid and aqueous layers, tear meniscus, BUT, and blink sequence
It is live (in vivo) and non invasive
It uses colored interference fringes, dark zone, other patterns to interpret
Problem - requires acquired skill level to interpret |
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Term
| Although the tear scope has problems (difficulty analyzing patterns) it is good for measuring TBUT because.... |
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Definition
| You can see the break easier because it shows a full view of the cornea and you don't have to scan around with the slit lamp beam to see the tear break up |
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