Lecture 6 - preliminary evaluation Flashcards
what is the normal blink rate?
10-15 per minute
why is the lid positioning important to measure/observe?
some lenses are balanced on the eye using lid forces (toric lenses)
how do you assess lid tension?
pull upper lid outward - grade resistance (3+ = very tight and -3 = very loose)
what is the LIPCOF grading scale?
the lid parallel conjunctival folds - if patient has long term dry eyes, the conjunctival becomes loose
what grade on the LIPCOF scale is considered dry eyes?
grades 3 and 4 (1 and 2 = no dry eyes)
if the patient has 1 or more folds but are shorter than the tear meniscus height, what is the LIPCOF grade?
grade 1 (if same height = 2 and if higher than meniscus = 3)
why can an iris iridectomy be a concern?
it creates a second pupil if lids don’t cover hole
what are some invasive techniques to assess tear film?
TBUT, schirmer, phenol red, rose bengal, lissamine green and tear osmolarity test
what are some non-invasive techniques to assess tear film?
NITBUT, tear prism/meniscus height, tear viscosity and lipid layer evaluation
what is a normal TBUT?
more than 10 sec (abnormal = less than 10 sec)
what is a normal schirmer test? how long are strips left on eye?
5 minutes
normal = greater/equal to 10mm (abnormal less than 10mm)
what is the phenol red thread test testing?
tear volume (basal) and pH
how does the phenol red test for pH?
color changes from yellow - red when pH is 6.6 to 8.2
how long is the phenol red test and what is normal?
15 seconds
normal = greater/equal to 20mm (abnormal less than 20mm)
what does the rose bengal stain?
dead and devitalized epithelial cells and mucus (mucins and other tear film components block staining)
what does Lissamine green stain?
dead and degenerated cells - not healthy epithelial cells
what is a dry eye tear osmolarity result?
values > 308 mOsms/L (higher salt concentration in dryness)
what is the NITBUT test?
non-invasive TBUT - use diffuse white light and observe mire stability/tears
what is a normal tear prism/meniscus height?
0.2-0.4mm (abnormal = less than 0.1mm)
what do you look at when assessing the viscosity of tear film?
movement of bits of debris in the tear prism - how rapidly they move in the pre-ocular tear film (POTF)
what are you looking at during the lipid layer evaluation?
superficial lipid layers - different interference patterns are formed and each correspond to a lipid layer thickness
what is the thickest lipid layer formation? what is the thinnest?
color fringes = thickest
amorphous
flow pattern
meshwork = thinnest
what is a normal lower lid position? Upper lid position?
lower lid = -1.0 to +2.0
upper lid = -0.5 to -2.0mm
what is a normal tear viscosity?
2-3 = normal (5 = ver viscous and 1 = watery)
