Lecture 11 - Other Contact Lens Applications

Piggyback CLs are a __________ lens on top of a _________ lens

GP on soft

List the 2 purposes of the soft lens in the piggyback lens system

- Improves tolerance to GP

- Corneal protection from GP

What is the purpose of the GP lens in the piggyback lens system

provides optimum vision

List 2 common situations that a piggyback lens system is used

- KCN

- postsurgical fits

What are the 2 fitting approaches to piggyback lenses

- Fit a GP first, then add a low minus soft lens under it

- Fit a soft lens first, then design the GP over it

For the soft lens portion of a piggyback designm (hydrogel/SiHy) is ideal, (hydrogel/SiHy) is okay

SiHy is ideal

hydrogel is okay

In a piggyback fit, when both are on the eye, the lenses should move (together/independently)

independently

In a piggyback fit, the lenses (should/should not) adhere together/become one uni

should not

What adjustment can be made if you notice the two lenses in a piggyback fit are adhering together

flatten GP peripheral curves

(SiHy/Hydrogel) soft lens - can use regular NaF

SiHy

(SiHy/Hydrogel) soft lens - must use high molecular weight NaFl

Hydrogel

(T/F) Piggyback fit must be evaluated with fluorescein on eye

FALSE

can evaluate system with or without fluorescein

List 2 purposes of CL use after corneal surgery

- Provide improved optical correction

- Provide therapeutic ocular surface protection

List 2 cases where CLs are applied to a post surgery cornea as therapeutic ocular surface protection

- persistent epithelial defects

- loose suture

Post-surgical CL fittings are a highly _______________-guided fitting process

Topography

Which 3 graft characteristics can lead to high amounts ofirregular astigmatism and poor VA that can be improved with specialty CLs

- several sutures

- excessive tension

- tissue heaping at graft-hostjunction

Full thickness PKP test to cause high amounts of (regular/irregular) astigmastism

BOTH!

List 2 way surgeons may try to limit the astigmatism result seen in full thickness PKP procedures

- limit use of sutures

- limbal relaxing incisions

What is the goal of Lamellar kKeratoplasty

remove diseased portion of cornea and spare functional tissue

List the different Lamellar Keratoplasty's you may encounter

- Deep anterior lamellar keratoplasty (DALK)

- Descemet's stripping membrane endothelial keratoplasty (DSEK)

- Descemet's stripping automated membrane endothelial keratoplasty (DSAEK)

- Descemet's membrane endothelial keratoplasty (DMEK)

What is the main goal when fitting a GP over sutures

minimal to no interactionbetween sutures and the lens

Some GP lenses fit over sutures are fit with large diameters, why

for clearance at the area of the suture

(ideal fit looks a bit different)

Some GP lenses fit over sutures are fit with small diameters, why

avoid sutures all together

When working with pt with sutures, when using a ___________ lens, the goal is to completely vault the cornea

scleral or hybrid

(T/F) You must wait for sutures to be remoced before you can fit with CLs

FALSE

can begin fit as soon as cornea is stable, regardless if sutures are present or not

Currently, we can fit pt for a CL _____ months after surgery depending on the case

1-3 months

List the 2 major risks/concerns with CL fitting post surgery

- endothelium stress

- graft rejection

How do we limit stress to the endothelium when fitting a post-surgical cornea with a CL

- high Dk material for maximum oxygen transmission

- avoid extended wear

(T/F) Endothelial loss already gradually occurs withoutCL wear

TRUE

A graft rejection must be treated quickly with:

topical steroids

What are the 2 fitting philosophies in GP lens fitting post surgery

- Fit to align with corneal contour

- Fit to vault irregularities and mask corneal contour

What is the first step for GP lens fitting on a post surgical cornea

obtain topography/tomography

necessary for irregularities seen in postsurgical corneas

When attempting tot fit a GP to align with the corneal contour post surgery, you want to use a (small/large) diameter, (>/

large >10mm

__________ corneal shapes are steeper central curvature, peripheral flattening

prolate

__________ corneal shapes are flatter central curvature, peripheral steepening

oblate

KCN tend to has (prolate/oblate) shaped corneas

prolate

Post surgical corneas tend to have (prolate/oblate) shape

oblate

Important to avoid bearing at graft-host junction, list 5 consequences that can occur if you fail to do this

- PEE

- inflammation

- erosion

- scarring

- graft rejection

What is the primary choice of CL style on a post surgical eye

reverse geometry GP

Reverse geometry lenses are recommended to be fit (empirically/diagnostically)

diagnostically

Any lens that has (flatter/steeper) peripheral curve radii than the central base curve radius is a reverse geometry lens

steeper peripheral cruve

In a reverse geometry lenses, there is typically at least __D of difference between central BC and PCR (peripheral curve radii)

4D

In a graft tilt, GP lens will tend to center over (flattest/steepest) portion of graft, this causes __________

steepest

causes decentration

(smaller/larger) diameter lens can help improve centration and limit glare in graft tilt pt

larger

(T/F) Scleral lenses can provide a more successful fit over corneal GPs when graft tilt is present

TRUE

You can fit with soft lenses on post-surgical pt, especially if corneal astigmatism is (regular/irregular)

regular

Why is SiHy material so strongly preferred for post-surgical soft lenses

important to avoid low Dk lenses due to risk of neovascularization and graft rejection

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