Fl Patterns Flashcards
When is viewing the Fl pattern necessary?
when the fit has been assessed to be undesirable - lower lid fit, lens too loose, etc.
MW of FL?
MW of FluoreSoft dye?
Absorbs what type of light? UV-__ to short ___
Emits what color/wavelength light?
376
710
UV-A, short blue (485-500)
Green (525-530)
What’s the minimum detectable tear thickness?
-What’s the minimum detectable gradation of intensity difference?
.0022mm - any thinner and it’ll look black
.02mm - to see diff b/w shades of green
-green is more intense if thicker
ideal tear film thickness:
centrally:
peripherally:
central: 5-10 microns (dull, trace green haze)
peripheral: 100-180 microns (bright green)
You can view the Fl pattern with either the ____ UV lamp, or the slit lamp with the ___ ___ filter
-enhance pattern w/ Which four filters? [WTSL]
burton UV - not on Boston pdts! (UV filter)
cobalt blue filter- low 10x mag, wide filter
-Wratten 12, Tiffen, Schott, Lee
What’s the problem w/ too MUCH Fl?
-too little?
too much - obscures real pattern
too little - looks like alignment; it’s not
Apical Zone - usually the central __-__ mm
-three ways to define it?
central 7-8mm
Alignment: light green haze throughout
Clearance: excess bright green central
Touch: Dark centrally, brighter green peripheral
Doing what to a lens too much causes it to make bubbles?
steepening too much
Mid-peripheral zone: important for lens p____ and s____
-three ways to define it?
positioning, stability
- alignment: even, light green in mid-peri zones
- clearance: bright green in mid-peri
- touch: most often accompanies apical clearance - lens is steeper than cornea
Mid peripheral clearance is greater with a (steeper/flatter) lens? Most often accompanies what pattern apically?
flatter; apical touch
peripheral zone: how to classify? Which is ideal?
low, medium, high - medium/moderate is ideal (maximize tear flow/comfort balance)
-bubbles may also occur w/ lens too FLAT - get up underneath the edges
Which pattern - static or dynamic - gives the true apical relationship of a lens?
static (when the lens is CENTERED)
-dynamic - when lens is in normal RESTING position
Toricity
- WR: steepest corneal curvature (horiz/vertical), causes clearance (horiz/vertical) - darker (touch) area along the (90/180)?
- AR?
- Obl: band of touch with the longer dimension goes along the (flatter/steeper) meridian
steepest vertically(yes it is - x180 means power is in the 90), clearance vertically, darker band horizontally
-flatter (more touch along longer dimension)
AR corneas will show clearance in what orientation?
180 - horizontal
the larger the OZD is made, the (easier/more difficult) it is to maintain alignment - WHY?
harder as the OZD becomes larger - MORE eccentricity (increase in corneal FLATTENING) as you move away from the corneal apex
A “donut” pattern is revealed when what is too large?
Optic zone
dynamic Fl patterns give a better assessment of the lens to cornea relationship during n___ l___ w___
-what relationships are you looking for here?
normal lens wear
- decentration: lens tilt, companion touch, mid-peripheral arcuate pooling, Fl pattern changes
- tear flow dynamics
Which fits/cornea types will cause mild decentration?
flat fits, lid attachment fits, toric corneas
Lens tilt causes the lens to tilt (toward/away) from the direction of decentration.
I.e. Lens tilted superiorly. Where will you see clearance/touch?
TOWARD direction of decentration
superior touch, inferior clearance (like a see-saw)
companion touch occurs in the direction of decentration and causes what shape to appear w/ clearance?
oval/crescent IN THE DIRECTION OF DECENTRATION - that part of cornea is flatter (because it’s the peripheral cornea) and causes lots of dye to get up in there
what is mid peripheral arcuate pooling?
area of clearance b/w the area of companion touch and the apex
With good tear exchange, fluorescein should appear under the lens within __-__ blinks
2-3.
