K reading - ANSWERAnterior corneal curvature measurements obtained using
keratometer
Lacrimal lens - ANSWERThe lens that is formed by the tears that collect between the
base curve of a contact lens and the anterior cornea.
Plus lacrimal lens - ANSWERSteeper BC than "k" results in..
Minus lacrimal lens - ANSWERResults from BC being flatter than "k"
Corneal astigmatism - ANSWERAll astigmatism found in the curvature of the cornea as
determined by the k readings
What is the corneal astigmatism?
"K" readings= 45.00D @.00 @ 90 - ANSWER2.00D of corneal astigmatism
With the rule astigmatism - ANSWERthe vertical corneal meridian has the steepest
curvature
What is the type of astigmatism?
"K" readings= 46.00D @.25D @ 90 - ANSWERWith the rule astigmatism.
Against the rule astigmatism - ANSWERthe horizontal meridian (2nd k reading) has the
steepest curvature
What is the type of astigmatism?
"K" readings= 46.00D @.25D @ 90 - ANSWERAgainst the rule
Residual astigmatism - ANSWERAstigmatism discovered during the refraction that is
not located on the cornea. May also be known as lenticular astigmatism
What is the type of astigmatism?
Spec Rx: 2.50 -1.75 x 165
"K" readings= 43.00D @.00D @ 90 - ANSWERResidual. Cyl does not match
the difference in k readings
, Apical clearance philosophy (central cornea) - ANSWERFitting technique where the
lens is designed w posterior lens curve. (BC) steeper than flattest corneal meridian.
Used with "against the rule" astigmatism
Corneal alignment philosophy (lid attachment) - ANSWERThis fitting technique lens is
designed w BC flatter than meridian. Used with "with the rule" astigmatism
Back toric design - ANSWERHigh corneal astigmatism over 3.50D. Corrected with toric
surface on the posterior curve
Front toric design - ANSWERUsed for residual astigmatism correction
Bitoric design - ANSWERCorrection for both corneal astigmatism on posterior curve and
residual astigmatism on anterior curve
Steps of rigid contact lens fit - ANSWER1. Transpose spec rx to minus cyl
2. Compensate for vertex distance change ( D^2 x d)/1000 . Add and subtract from sph
3. Calculate residual astigmatism ( difference of cyl and k reading difference)
4. Determine flattest corneal meridian (lowest k reading)
5 determine base curve (337.5/ Diopter= ___mm)
6. Compensate rearm film - S.A.M VS. FAP (steeper add minus = +sph power, flatter
add plus= -sph power)
LARS rule - ANSWERLeft add (lens rotates left 'clockwise' & add amount of rotation to
the spec axis; right subtract (lens rotates right 'counter clockwise' & subtract amount of
rotation to the spec axis)
slit lamp - ANSWERAn instrument composed of a magnifying lens combined with a light
source; used to provide an examination of the eye's anatomy
Pt wears a lens with.. BC:42.50 POWER: -2.25. OVERREFRACTION: -.75 . fitter refits
with BC 43.00. Power of new lens should be:
A. -2.75
B. -3.00
C. -3.50
D. -4.00 - ANSWERC
To use the slit lamp with retro illumination, the light beam is bounced or reflected off the:
A. Ciliary body
B. Macula
C. Cornea
D. Iris - ANSWERD. Iris
A contact lens was ordered with a CPC of 43.00 D. Verification reveals that the lens
received is actually 42.00D. In comparison to the lens ordered, the lens received is:
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