red eye Flashcards
things that cause a CL associated red eye
CHADS
- compliance
- hypoxia
- allergies
- dry eyes
- solution sensitivity
what CL should be ordered for this patient? Ks -OD: 47.00/45.50 @ 090 -OS: 47.00/45.50 @ 090 SUBJ -OD:-6.50 -2.00 x 090 20/20 -OS:-6.50 -2.00 x 090 20/20
-6.00 -1.75 x 090
make sure to do a power cross and use the vertex equation in both meridians and then figure out the Rx
vertex=(P/1-dP)
after the SCLs are placed on the eye, you note the right CL rotes 10 degrees clockwise and the left lens rotes 10 degrees counterclockwise, resulting in BCVA 20/25 each eye. What new CL axis should be ordered in each eye to improve the patient's BCVA? Ks -OD: 47.00/45.50 @ 090 -OS: 47.00/45.50 @ 090 SUBJ -OD:-6.50 -2.00 x 090 20/20 -OS:-6.50 -2.00 x 090 20/20
OD axis 100
OS axis 080
LARS from dr perspective
clockwise=left
counterclockwise=right
LARS only works if the lens consistently rotates to the same spot each time.
which of the following available BCs is most appropriate to use for the initial CL fitting for this patient? Ks -OD: 47.00/45.50 @ 090 -OS: 47.00/45.50 @ 090 SUBJ -OD:-6.50 -2.00 x 090 20/20 -OS:-6.50 -2.00 x 090 20/20 CL RX -OD: -6.00 -1.75 x 090 -OS:-6.00 -1.75 x 090
8.3, 8.6, 9.0, or none of these?
8.3
this patient has a fairly steep K that are best fit with a smaller (steeper) BC (measured in mm). remember that as the radius of curvature increases, the cornea becomes flatter and the K values become lower.
Bercher Twist test
rotate the cyl in the phoropter. if the patient cannot tolerate less than 5 degrees of rotation, he likely will not be successful in a soft toric CL
DK
refers to oxygen permeability of a CL material. a higher DK results in greater oxygen permeability. A higher DK is healthier for the eye because it allows more oxygen to be transmitted to the cornea
DK/t
transmissibility. a thicker lens results in a decrease in oxygen transmissibility
hydrogel and DK
DK increases as water content increases
siHy and DK
as water content increases, DK decreases
siHY CLs have Dk values that are greater than traditional hydrogels (>60)
PMMA and Dk
they have 0 oxygen permeability and are no longer RXed
loose lens
flat BC
smaller diameter
decreased sag
tight CL problems
central bubbles
mucin balls
poor comfort on insertion but improved comfort after wearing, improved vision immediately after a blink, and perilimbal injection after many hours of wear
loose CL problems
may show increased drop fo the CL inferiorly on upgrade (>2mm), poor comfort (esp with a blink), and blurred vision immediately after a blink that improves between blinks
SM and hyperopes and aphakes
corrected with + lenses. SM increases as vertex distance increases for a + lens. Mag will be decreased in Cl compared to specs
myopes and SM
corrected with - lenses. SM decreases as vertex distance increases for a mins lens. therefore, in myopes, mag will be increased in CL compared to specs
myopes + CL
more convergence and accommodation
myopes and glasses
gives BI, decreased convergence and accommodation
hyperopes and CL
less convergence and accommodation
solution sensitivity
toxic
- follicles
- infiltrates
- diffuse SPK
- redness
- most common causes: thimerosal and chlorhexidine
saline solution
it is ok for wetting CL, but it does not clean or disinfect
tap water and CL
never use due to acanthamoeba
management for solution sensitivity
- switch to a different MPS as they may be less sensitive to other preservatives
- hydrogen peroxide solutions such as clear care neutralize to saline after 6 hours; therefore no chemicals are present when the CL is inserted on the eye
- dailies worn only for one day before being thrown away, thus eliminating the need for CL solution
GP BC
the curvature of the back surface of the optical zone of the CL. Recall that steepening the BC will results in a steeper CL fit and flattening the BC will results in a flatter CL fit. for every 0.5mm change in BC,the power of the CL should be adjusted by 0.25D to account for the change in the steepness of the fit.
SAM FAP
if the BC is steepened, add minus power, if the BC is flattened, add plus power to the CL