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Soft Contact Lens Clinical Pearls

This document discusses key clinical pearls about fitting soft contact lenses, including how refractive power changes at different vertex distances, how to determine residual astigmatism, considerations for choosing base curves for spherical lenses, factors that influence success with toric lenses like axis stability, and tips for fitting toric lenses using the LARS method.

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El Min Foro
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262 views2 pages

Soft Contact Lens Clinical Pearls

This document discusses key clinical pearls about fitting soft contact lenses, including how refractive power changes at different vertex distances, how to determine residual astigmatism, considerations for choosing base curves for spherical lenses, factors that influence success with toric lenses like axis stability, and tips for fitting toric lenses using the LARS method.

Uploaded by

El Min Foro
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOC, PDF, TXT or read online on Scribd
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Soft Contact Lens Clinical Pearls

Vivianle Freeman, O.D., F.A.A.O

Effectivity
• Change in refractive power at different vertex distances
• Clinically significant at +/- 4.00 D
• Myopes
– Less minus at corneal plane
– More minus at spectacle plane
• Hyperopes
– More plus at corneal plane
– Less plus at spectacle plane
• Formula:

FCL = Fsp
1- d Fsp

FCL= Power of Contact


Fsp = Power of Spectacle
d = dist between spectacle and CL in meters

Look it up in the Vertex conversion charts

Residual Astigmatism
• Astigmatism remaining after correction with contact lens
– 0.75 D cylinder may be symptomatic
• High myopes tolerate cyl better
• ATR or oblique axis less tolerated
• Variable among patients
• RA = Spec cyl – Corneal Cyl
– WTR : (-) cyl x 180, vertical K’s steeper
– ATR: (-) cyl x 090, horizontal K’s steeper
• Example:
– Spec Rx: pl-2.50X180, K’s: 44.00/46.00 @090
• Spec cyl: 2.50 WTR
• Corneal cyl: 2.00 WTR
• RA = 2.50 WTR -2.00 WTR
• RA = 0.50 WTR or -0.50 x 180
• For WTR cornea:
– Spec Cyl is WTR and equal to corneal cyl à no RA
– Spec Cyl is WTR and greater than corneal cyl à WTR RA
– Spec Cyl is WTR and less than corneal cyl à ATR RA
For ATR cornea, the opposite will be true
Oblique cylinder, RA may be variable if axes do not match
Spherical Soft Lenses
• Base curve: based on average K reading
K≤ 42.00 à Flat BC suggested
K 42.00 to 43.00 à Flat to Median
K 43.00 to 44.00 à Median
K 44.00 to 45.00 à Median to Steep
K > 45.00 à Steep

Toric Soft Lens


• Advised if refractive cyl >0.75D
• Consider toric lens if cylinder > 30% of overall RX
• As cyl increases, axis stability becomes critical
• Perform sphero-cylinder refraction
• Rotate cyl axis until patient definitely notices blur
– Rotation ± 20° à 90% soft toric success rate
– Rotation ± 15° à 90% success with 2 lenses
– Rotation ± 10° à 70% success with 3 lenses
– Rotation ± 5° à patient must accept variable VA with
lenses
• Vertex both meridians
– Spec Rx: -6.50-3.00x180 becomes -6.00-2.50x180
• Choosing a trial lens
– Axis is most important
– Then cylinder power
– Last is spherical
LARS fitting
• Evaluate trial CL of similar power and axis
• Allow for proper lens settling (20 minutes) and evaluate
• Evaluate fit
– Movement, centration, coverage
– Rotation
– Stability of rotation
• Rotation to Left X° à Add X° to spec axis
• Rotation to Right X° à Subtract X° from spec axis
• Note that “Left” and “Right” designate the movement of the inferior edge

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