UPDATE ON CORNEAL TRANSPLANTATION

Frank S. Hwang M.D.

Assistant Professor

Cornea, External Disease and Refractive Surgery

OBJECTIVES

• Types of corneal transplantation

• Donor Selection of corneal tissue

• Penetrating keratoplasty

• Anterior Lamellar Keratoplasty

• Endothelial Keratoplasty

CORNEAL TRANSPLANTATION

• Cornea: immunologic privilege , first

successfully transplanted solid tissue (1905)

• In the USA, ~ 40,000 corneal transplantations vs.

~ 12,000 other solid-organ transplantations.

• Penetrating keratoplasty (PK or PKP):

full-thickness, gold standard

• Lamellar keratoplasty: partial-thickness

• Anterior lamellar keratoplasty (ALK):

• Superficial ALK (SALK)

• Hemi-automated lamellar keratoplasty (HALK)

• Deep ALK (DALK)

• Posterior lamellar keratoplasty or endothelial

keratoplasty (EK)

• Descemet stripping and endothelial keratoplasty

(DSEK)

• Descemet’s membrane endothelial keratoplasty

(DMEK)

53% 5% 35%

DONOR CORNEA CONSIDERATION

• Donor corneas: stored in Optisol-GS

• Exclusion criteria: unknown cause of death,

systemic infections, CNS infection, leukemia,

ocular hx (infection/inflammation, malignancy,

prior refractive sx), Hep B/C, HIV, etc

• Certain considerations: endothelial cell density

(ECD) >2000/mm2, death-to-preservation time,

donor age, tissue storage time

PENETRATING KERATOPLASTY

• Indications: any stromal or endothelial corneal

pathology i.e. keratoconus, failed graft, post-cataract

edema, corneal dystrophies/degenerations

• trephination of donor tissue,

0.25-0.50 mm larger

• trephination & excision of host

cornea

• suture (interrupted, continuous,

or combined)

PK COMPLICATIONS

• Intraoperative: lens/iris damage, poor graft/donor

centration, iris/vitreous incarceration, damage to

donor endothelium, hemorrhage

• Postoperative: wound leak, flat chamber, glaucoma,

endophthalmitis, persistent epi defect, recurrent

primary disease, epithelial ingrowth, primary graft

failure, infected sutures, graft rejection,

regular/irregular astigmatism (most common)

THE CORNEA DONOR STUDY (CDS)

• Designed as a prospective, double-masked, controlled trial to

determine:

• The role of donor age in long-term corneal graft survival

• The effect of ABO blood type matching on corneal graft

survival

• The effect of donor age on long-term donor endothelial cell

density

• Patient enrollment 2000-2002: 40 to 80 years old, and in ‘‘moderate-

risk’’ corneal transplant categories, mostly endothelial diseases,

Fuchs’ dystrophy 675 (61%), Pseudophakic/aphakic corneal

edema 369 (34%)

• Donor Baseline characteristics: 1101 donor corneas, age 10-75,

ECD 2300 to 3300/mm2

• Preoperative management, surgical technique (PKP), and

postoperative care, including prescription of medications, were

provided according to each investigator’s customary routine

THE CDS RESULTS – FIVE YEAR

Graft failure, defined as a re-graft or a cloudy cornea

that was sufficiently opaque as to compromise vision

for a minimum of 3 consecutive months.

ABO incompatibility does NOT increase the risk of

transplant failure

CDS 5-year result

Donor age

(yr)

12-65 66-75

Graft survival 86% 86%

Median cell

loss

69% 75% *

Median ECD 824

cells/mm2

654 cells/mm2

*

THE CDS RESULTS – TEN YEAR

• When analyzed as a continuous variable, higher donor age was

associated with lower graft success beyond first 5 years (P<0.001)

• The 10-year success rate was relatively constant for donors aged 34 to

71 years (75%). The success rate was higher for 80 donors aged 12 to

33 years (96%) and lower for 130 donors aged 72 to 75 years (62%)

CDS 10- year result

Donor age

(yr)

12-65 66-75

Graft survival 77% 71%

Median cell

loss

76% 79% *

Median ECD 628

cells/mm2

550 cells/mm2

*

Anterior Lamellar Keratoplasty (ALK)

• Indicated in corneal conditions where the endothelium is still functional, such as

ectatic disorders, superficial scars, and various dystrophies.

• Superficial ALK (SALK): pathology limited to anterior third

• Hemi-automated lamellar keratoplasty (HALK): 50% thickness

• Deep ALK (DALK): deeper stroma

• Dissections were achieved freehand or automated by a microkeratome or

femtosecond laser

• Stroma-to-stroma interfaces, as in

SALK, can degrade visual acuity over time

• Stroma-to-DM interfaces, as in DALK, provide higher quality vision

• HALK: donor cornea prepared with microkeratome, recipient cornea prepared freehand

ANTERIOR LAMELLAR KERATOPLASTY (ALK)

• Advantanges: Extraocular procedure resulting in a low risk of

many complications, including transplant rejection and failure.

Less topical steroid use than PK or EK. Early suture removal

safe.

• Disadvantages: Usually more technically demanding than PK.

Fails unless host endothelium is healthy. Regular and irregular

astigmatism the same as for PK.

• Most common intraocular complication is Descemet’s

performation and conversion to PK.

12-mo DALK (28) PK (28)

BCVA logMAR 0.39 (20/50) 0.31 (20/40)

Endothelial loss 12.9% 27.7% *

Spherical equivalent -2.02 -2.30

Endothelial rejection 0 3

(Micro)perforation of the Descemet’s membrane occurred in 32% of the

DALK eyes, and 18% of the patients required conversion to PK

• Indicated in endothelial dysfunctions such as pseudophakic/phakic

bullous keratopathy, Fuch’s dystrophy, Posterior Polymorphous

dystrophy, and Iridocorneal Endothelial syndrome

• DSEK/DSAEK: DM & endo with a thin layer of posterior stroma

• DMEK/DMAEK: only DM & endo, no stroma; 748 DMEK performed in

2012

• “A” stands for “automated”: using keratome to dissect

• Eye banks now provide pre-cut tissue for DSAEK and DMEK

Endothelial Keratoplasty (EK)

• Descemet stripping and endothelial keratoplasty

(DSEK)

• Descemet stripping automated endothelial

keratoplasty (DSAEK)

• Descemet’s membrane endothelial keratoplasty

(DMEK)

• Descemet’s membrane automated endothelial

keratoplasty (DMAEK)

ENDOTHELIAL KERATOPLASTY (EK)

DSAE

K

DME

K

ENDOTHELIAL KERATOPLASTY (EK)

• Advantages: No induced astigmatism resulting in

early visual recovery and better visual outcomes.

Fewer suture and wound related complications. Lower

risk of other complications.

• Disadvantages: Suboptimum visual result unless

corneal stroma is relatively free of opacity; reduced

vision due to interface opacity or transplant folds in

some cases

• Complications: Detachment in 5–30% of cases. Can

be re-attached by re-injecting air. Possible pupil

block following air tamponade

DSAEK VS DMEK • Potential advantages of DMEK: faster visual rehabilitation, better visual

outcomes, and lower rejection rates.

COMPARISON OF PK, ALK & EK PK

Can be used for any

indication

Potentially best optical

result

Relatively undemanding

technique

ALK

Minimal requirement for

donor material

Extraocular procedure

Low risk of rejection

Less topical steroid use

Early suture removal safe

EK

Better globe integrity

Fewer wound cx

Faster recovery

No suture-related issues

Less post-op astigmatism

Higher rejection rate

Many complications

Astigmatism common

Graft-host interface limit VA

Astigmatism similar to PK

Dependent on endo quality

Technically more difficulty

Graft-host interface limit VA

Rejection rate similar to PK

Dependent on epi/stroma

quality

Long term survival unknown

FUTURE DIRECTIONS

• Descemetorhexis Without Endothelial Keratoplasty (DWEK)

• Rho Kinase Inhibitors

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