CL Flashcards
characteristics of loose/flat CL
- excessive CL movement with blink
- poor CL centration
- lens edge bubbles
- lens edge stand off
- superior eyelid irritation
characteristics of TIGHT contact lens
- minimal CL movement
- indentation around limbus
-injection around limbus - corneal edema
- complains of discomfort
how to adjust flat lenses
- increase sagittal height
- steeper base curve
-inc diameter
how to adjust steep lenses
- flatten sag height
-flatter BC - reduce diameter
steep CL creates ___ lacrimal lake/tear film. Add __ to adjust power on lens.
steep CL creates POSITIVE lacrimal lake/tear film. Add MINUS to adjust power on lens.
Flat CL creates___ lacrimal lake/tear film. Add __ to adjust power on lens.
Flat CL creates MINUS lacrimal lake/tear film. Add PLUS to adjust power on lens.
CL equation
Tear lens:
CL equation
Tear lens: base curve - keratometry
CL equation
mm to diopter conversion:
CL equation
mm to diopter conversion: 337.5/D
CL equation
vertex equation:
CL equation
vertex equation: CL power= spect power/ 1-h(power of spect)
CL equation
CL power:
CL equation
CL power: CL power+ over refraction + lacrimal lens power
CL equation
residual astigmatism:
CL equation
residual astigmatism: total astigm. of eye - corneal astigm
CL equation
SAM FAP:
CL equation
SAM FAP: steeper add minus, flatter add plus
CL equation
LARS (toric lenses):
CL equation
LARS (toric lenses): left add, right subtract (based on doc POV)
condition when flexure happens
-RGP distorted while on the cornea , but assumes normal shape when off the cornea
- caused when RGP is thing so shape is easily contorted
- measure astigmatism with topography/keratometry when RGP is on the eye
warpage happens when
RGP is distorted on and off the cornea.
-caused by rubbing RGP too much when cleaning
- measure astigmatism with RGP on cornea or off the cornea
- confirm with radiuscope
wetting angle determines how well a CL ___
wetting angle determines how well a CL remains wet/ how likely CL is to stay dry
a low wetting angle (less than 90 degrees) indicates:
a low wetting angle (less than 90 degrees) indicates: contact able to wet well with even spread of fluid
a high wetting angle (greater than 90 degrees) indicates:
a high wetting angle (greater than 90 degrees) indicates contact does not spread fluid well and will have many dry sports
Mucin balls:
Location:
appearance:
cause:
Mucin balls:
Location: posterior surface of CL
appearance: small, white, pearl like debris. (-) staining
cause: silicone hydrogen CL that are too flat with extended wear purpose
Treat: keep pt in same lens but re-fit into steeper BC
– or reduce wear time, use wetting drops
Dimple veiling
Location:
appearance:
cause:
Dimple veiling
-Location/appearance: circular indentation on cornea surface
-cause: GP that is fit too steep traps CO2 which leave indentation on corneal surface
-Treat: flatten BC or decrease overall lens diameter
Protein deposit
location:
appearance:
cause:
Protein deposit
location: contact lens surface
appearance: white, slightly translucent deposition
cause: can become integrated in the lens matrix of high water content lenses
other: irritate upper eyelid and cause GPC
jelly bumps
location:
appearance:
cause:
jelly bumps
location: front surface of CL
appearance: small, white, gray deposit
cause: soft CL wear and made of calcium protein complex. Lenses that are hydrophilic more prone.
- lenses that are scratched, have ridges, or have polishing errors
- At risk of jelly bumps: pt with parathyroid disorder, hypercalcemia, (+) oral contracept use, oral antibodies, high doses hormone, breastfeeding
