Fit Char Flashcards
Sag GREATER: (steeper/flatter), (tighter/looser) (stable/unstable)
-how about when sag is decreased?
steeper; tighter; stable (but suction cup!)
decreased: flatter, looser, unstable (rocking effect!)
T/F: it is possible to match sagittal depth with the corneal surface (an ideal fit)
false. Aspheric corneas don’t match spherical sags - close as possible is the only option
U____ distributed tear thickness gives the greatest adhesional forces
uniform - IDEAL tear-lens thickness = 5-10microns
flat = LESS curved = (longer/shorter) radius of curvature
LONGER - remember; they’re inverse!
What is the most stable fitting relationship?
alignment
STEEP fit results in a (thicker/thinner) tear layer in the central portion of the lens
thicker centrally - edges and pushing it up!
if the patient is tearing excessively, how will that affect the lens fit?
will make it fit LOOSER than actual; give ‘em proparacaine to decrease reflex tearing
T/F: if a LA fit is desired, it’s ok to let the lens rest slightly superior to the upper limbus (since it’s under the upper lid anyway)
FALSE. Lid attachment should only be attempted with the upper lid actually covers the sup limbus slightly in NORMAL straight-ahead gaze. Should position superior, but not THAT superior
Movement - interpalpebral - describe it.
What’s the difference w/ LA mvmt?
interpalpebral - down w/ blink, up a LITTLE when completely closed, pulled up w/ opening, slight drop when completely open (centers itself)
LA - follows the motion of the lid. Down on downgaze, STAYS down w/ complete closure, follows it up on upgaze
T/F: lens is still acceptable if it goes slightly past limbus on lid closure w/ a LA fit
true - as long as it’s not excessive
Lens should move (with/against) motion of eye when moving laterally. What happens in a tight fit?
AGAINST (slightly)
- too tight? lens isn’t falling behind slightly
which way does the lens usually ROTATE when blinking? (compare temporal to nasal)
-what aspect of lens characteristics is rotation an issue?
temporal aspects move DOWN, nasal move up. RE goes CC when looking @ pt, LE goes clockwise
bifocals, torics (rotation matters!)
Does the lens rotate more with the upper or lower lid? In which way does it rotate w/ lid closing? Opening?
LOWER lid - upper contributes very little (inf lens edge moves w/ lower lid)
Closing - inferior edge moves nasal
opening - inf. edge moves temporal
Which type of dynamic stability is usually observed with novice GP wearers?
KICK - eye lid twitches and kicks it down
other types: normal (static position), loose (inferior drop or to the sides - fix it)
moderate to high ____ lenses tend to automatically want to lid attach
-what’s a pseudo-lid attachment? What does it indicate?
minus (minus lenticulars) - most comfortable initially
lens stays up when UL pulled away (should fall). Indicates a) flat lens or b) WTR cornea
