Alternatives To PK

1. Alternatives To PK • Lecture 16 • Liana Al-Labadi, O.D.

2. Alternatives? • Problems with PK: • Risk of rejection • High degree of irregular astigmatism • Cataract & glaucoma: long time steroid use • Problems eliminated/lessened by leaving a portion of the host cornea in place • PK is a risky procedure • Difficult to develop predictable alternatives that provide visual outcomes equivalent to those of PK

3. Alternatives? • Percentage of full-thickness corneal transplant procedures continues to decline • In 2008, over one-third of all cornea grafts were endothelial keratoplasties • Number has tripled since 2006 • Some surgeons are doing lamellar grafts in more than 90% of their corneal transplant patients • Lamellar Keratoplasties= Sutureless corneal transplants • Less risk of rejection & other complications • Eliminate only the diseased layers of the cornea only • Eliminates surface incisions & suture related complications • Surface irregularities are avoided • Recent development in technique result in visual outcome more comparable to those of PK • The result: faster wound healing, smoother topography & greater visual stability

4. Surgical Options • Penetrating Keratoplasty (PK) • Deep Anterior Lamellar Keratoplasty (DALK) • Posterior Lamellar Keratoplasty (PLK) • DLEK • DSEK • DSAEK • DMEK • Keratoprostheses • Intacs • Collagen Cross Linking

5. DALK • Deep Anterior Lamellar Keratoplasty (DALK) • Endothelial layer is the most immunogenic corneal layers • The most significant source of risk of rejection in PK procedures • In cases where the disease or damage is limited to the stroma • The affected portions of the anterior cornea can be removed, saving the endothelial layer • Initial DALK problems • Poor visual outcome due to irregularity of the dissected surfaces • Scarring in the tissue interfaces • DALK has evolved to the point where visual outcomes were comparable to those of PK • Technique was complex & tedious...limiting its use

6. DALK • Indication • In almost any situation where endothelium & Descemet’s membrane are healthy but overlying stroma or bowman’s membrane is damaged resulting in decreased vision • Keratoconus • Corneal scarring • Corneal dystrophies • OSD that leads to corneal damage

7. DALK • Techniques • Pre-Descemetic • Do not remove all the stroma • Descemetic: Those that fully reach descemet’s membrane • Used for optimal visual results • Main concern: increased risk of perforation with going as deep as possible • Initial DALK problems • Poor visual outcome due to irregularity of the dissected surfaces • Scarring in the tissue interfaces • DALK has evolved to the point where visual outcomes were comparable to those of PK • Technique was complex & tedious...limiting its use

8. DALK • Statistical evidence increasingly supports DALK as a better procedure for certain patients: • Risk of rejection is lower in DALK than in PK • Risk of glaucoma is lower in DALK than in PK • Endothelial cell density is better for those undergoing DALK • Less keratometric astigmatism with DALK than PK • Some suggest results are comparable • DALK also allows for the use of less robust tissue • Higher endothelial cell counts are not required for this procedure

9. DALK • Current disadvantages: • Learning curve for surgeons • Risk of perforation: may require conversion to a full PK • Interface opacification • Non resolving creases in Descemet’s membrane • This requires a back-up grafts: demand on eye bank! • DALK also allows for the use of less robust tissue • Higher endothelial cell counts are not required for this procedure

10. Posterior Lamellar Keratoplasty • Posterior Lamellar procedures: • DLEK • DSEK • DSAEK • DMEK • Indications: • Endothelial layer diseases • Bullous keratopathy • Iridocorneal Endothelial (ICE) Syndrome • Fuch’s corneal dystrophy • Posterior polymorphous dystrophy • Failed graft with an otherwise good refractive outcome

11. DLEK • Deep Lamellar Endothelial Keratoplasty (DLEK) • Original attempts at endothelial transplants involved: • Creating an anterior flap of tissue • Trephining the damaged endothelium out • Suturing the donor tissue in • DLEK preserved the preoperative corneal surface in an attempt to maintain a normal K topography • Problem with original technique • Visual outcome generally in the 20/40 to 20/50 range • DLEK was not the long-term solution for endothelial keratoplasty • Began moving corneal surgery in the direction of increasingly less invasive & more anterior cornea-sparing techniques • DLEK has been displaced for the majority of cases by DSEK/DSAEK

12. DSEK • In 2003: • Dr. Melles prposed a procedure for stripping Descemet’s membrane from the back of recipient K • In this procedure, Descemet’s is stripped in much the same fashion as a capsulorhexis is done in CE, and is often referred to as a Descemetohexis • Advantage vs. DLEK • Smoother recipient interface with the new tissue • Stripping descemet’s membrane from the posterior stroma leaves a smoother surface than dissecting the stromal layers • This procedure is known as Descemet’s stripping endothelial keratoplasty (DSEK)

13. DSAEK • Further evolution of procedure: • Utilizes a microkeratome for separating the posterior layers of the donor (not recipient) cornea • Providing a smoother interface than manual dissection • Translates to better visual outcome: DSAEK is preferred by a majority of surgeons • The only difference between DSEK & DSAEK • The manner in which the donor cornea tissue is prepared for transplantation • Manually in DSEK & via keratome in DSAEK

14. DSAEK • Advantages to DSAEK over PK • Reduced risk of rejection • Much more rapid visual recovery- weeks vs. months • Minimal induced astigmatism • No significant disadvantages • DSAEK & DSEK can cause hyperopic refractive shifts due tot he retained stromal tissue • Ideal candidates • Patients with diseased endothelium for nearly any reason, with an otherwise normal cornea

15. DSAEK • Contraindications • Chronic hypotony • Anterior corneal opacities • Keratoconus • AC IOL patients • Risks (not associated with PK) • Graft dislocation • Interface between the graft & host can account for a reduction in BCVA to the 20/20 or 20/30 level

16. DMEK • Descemet’s Membrane Endothelial Keratoplasty (DMEK) • Most recent development in posterior lamellar keratoplasty • Hold the potential for better visual outcomes than even DSAEK • Involves removing the diseases posterior K in a similar fashion to DSEK/DSAEK • Descemet’s membrane & endothelium are transplanted with little or no posterior stroma • IN DSEK/DSAEK: up to 150um of posterior stroma is often transplanted • Eliminating posterior stroma enables surgeons to achieve better visual outcomes • Technique has not been completely perfected at this point • Graft dislocation rates remain high • More challenging for surgeons than DSAEK

17. Summary • DALK • Useful particularly in parts of the world where high-quality grafts are less frequently available than others • It may also be a preferable procedure for patients whose risk of rejection may be higher or where optimal postoperative care is not as readily available • DSEK & DSAEK • Widely accepted as preferred procedures for patients with posterior corneal disease & no other complicating factors • May be approaching 50% of all corneal grafts by 2011 • DMEK • While in the development stages, pushes visual outcomes to their highest current potential • Offers fast recover