Transcript CL PP Week 04

Week 4
Soft lens fitting techniques and care
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From the patient
interview, determine what
type of lens wear schedule
would be best for the
patient.
From the patient exam,
determine if, spherical,
toric or gas permeable is
best for the patient.
Keep in mind, comfort
and visual acuity are
always first priority. Be
sure to ask about
occupational needs and
what they hope to achieve
with the CL’s.
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It is your job to explain
how the CL’s work and
the choices they have.
Take the time to explain
all of the options.
Ask about distance,
intermediate and near
vision issues if the patient
is close to or presbyopic
age.
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Base curve is based on
the “K” readings,
however you must
always evaluate the trial
lens on the eye to make
sure the CL has a good
fit.
Base curves range from
8.0 to 9.2. Most are 8.3
to 8.8. Depending on
the manufacturer, there
are limitations on the
BC and D.
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“K” readings of 42D
and lower are
considered flat. “K”
readings of 46D and
higher are considered
steep.
Base curves for soft CL’s
are specified as steep
(8.0 to 8.3), Median (8.4
to 8.6), and flat ( 8.7 to
9.0).
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Lens power selection is
based on manifest
refraction with a vertex
distance conversion chart,
if necessary. (Effective
power).
A spherical lens can
“mask” a small amount of
astigmatism, but you will
need a thicker lens or a
toric lens to correct
astigmatism.
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To use a spherical lens on
a patient with a small
amount of astigmatism.
You need to convert the
patient’s refraction to
spherical equivalent.
Also CL’s are ALWAYS in
minus cylinder. You will
always need to convert
the plus cylinder Rx into
minus cylinder. Then, do
the spherical equivalent.
This should only be done
if the cyl is 0.75 D or less.
TRANSPOSITION
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+5.00+1.00X90
+6.00-100X180
SPHERICAL EQUIVALENT
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-6.50+0.75X90
-5.75-0.75X180
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-0.75+1.25X110
+0.50-1.25X20
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+4.00+0.75X90
+4.75-0.75X180
+4.50 or +4.25 sph
-3.50+0.50X90
-3.00-0.50X180
-3.25 sph
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Always remember….
Vertex distance is much
farther when refracting a
patient, you must
compensate for this when
fitting with a CL.
This applies to more than
+/- 4.00D.
CAP rule
+8.00 sph = +8.87sph
- 6.00 sph = -5.62 sph
This is based on a 12mm
VD. The VD can vary
from 8-15mm.
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Allow the CL to rest on the
eye for 5 minutes before
evaluating the fit.
If the patient has never worn
a CL before, it will feel like
an eyelash in their eye for
about 5 minutes.
The lens should be centered
on the eye, and re center
after each blink.
The lens should have
adequate movement. There
should be 1mm of movement
after each blink and return to
center over the cornea.
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If there is no movement, the
lens is too tight.
If there is too much
movement, the lens is too
loose.
The VA should be stable and
remain so before, during,
and after each blink.
If the VA is not as clear as
expected, do an overrefraction and check for
residual astigmatism.
Dryness can cause
fluctuating VA or decreased
VA. CL’s may exacerbate
this.
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Check the “K”s with the
CL’s on the eyes. The
mires should be clear
with a proper fit.
The lens diameter
should extend beyond
the limbus by 1 to 1.5
mm and should have an
equal amount of excess
material 360 degrees.
The cornea should
never be exposed after a
blink, this can cause
problems.
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VA unstable with
each blink.
Patient awareness of
the lens.
Poor centering,
especially low fitting.
Too much movement
with each blink.
Edge “stand off”.
(edges do not hug the
eye)
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Lens falls out.
Air bubble under the
lens, especially on the
periphery of the lens.
“K” mires are blurred
after each blink.
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Fluctuating VA, clears
after each blink.
Comfortable at first,
then not.
Circum corneal
injection.
Circum corneal
indentation.
Little or no movement
upon each blink.
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Keratometry mires
distorted, then clear
after each blink.
Air bubbles centrally,
over pupil.
CORRECTING A LOOSE
FIT
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Tighten/decrease the base
curve but keep the
diameter the same.
Increase the diameter and
keep the base curve the
same.
If increasing the diameter,
make sure not to
compromise the 1-1.5 mm
corneal extend. If the lens
is too large, leave the
diameter and adjust the
BC.
CORRECTING A TIGHT
FIT
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Loosen/increase the base
curve, but keep the diameter
the same.
Decrease the diameter and
keep the base curve the same.
If decreasing the diameter,
make sure not to compromise
the 1-1.5 mm corneal extend. If
this causes corneal exposure,
leave the diameter and adjust
the base curve.
Use a thinner lens, same
parameters.
IF THE LENS IS TOO
LARGE
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Decrease the diameter,
but remember….
Decreasing the diameter
may inadvertently effect
the BC and loosen the
lens.
Always recheck your
modifications with a
trial lens.
IF THE LENS IS TOO
SMALL
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Increase the diameter,
but remember…
increasing the diameter
may inadvertently effect
the BC and tighten the
lens.
Recheck the
modification and if
necessary, change the
base curve accordingly.
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Use patient interview to determine lens type.
Use patient ocular exam to fit base curve, diameter
and power.
Use a trial lens to evaluate the lens fit.
Take VA and over-refract if VA is not what was
expected.
Make any modifications to fit and/or VA that may
be necessary.
Use a trial lens to evaluate modifications.
Explain insertion and removal, care and handling
and cleaning to the patient.