DALK vs. PK

[piper]

OK.....I'm no expert, some of you are. How long will a PK take to heal vs a DALK? Is it true that the PK will give me better visual accuity in time? How much real risk of rejection is there with the PK?

I drove to work today, first time since October. Believe me, I drove carefully, unlike some of the other drivers on the road. The trip in was not bad. Coming home was tough as the sun was low and right behind several intersections with oncoming traffic and ended up right behind several traffic control lights. So, I'll walk out again tomorrow and let my faithful wife drive me back to the sweat-shop for the next year or so...

Please, any other discussion or facts, opinions, info etc on DALK vs PK will be appreciated.

Piper

[jayuk]

Hard to say with DALK as theres still not enough data...however...here is another peice of data that was released few weeks back whic also has Moorefields involved, the aim was to compare PK and DALK outcomes...another reason WHY....alot of the outcome does depend on the Consultant and how he performs the procedure....

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* Ardjomand N,
* Hau S,
* McAlister JC,
* Bunce C,
* Galaretta D,
* Tuft SJ,
* Larkin DF.

Cornea and External Diseases Service, Moorfields Eye Hospital, London, United Kingdom; Department of Ophthalmology, Medical University Graz, Graz, Austria.

PURPOSE: To compare visual function after deep anterior lamellar keratoplasty (DALK) with visual function after penetrating keratoplasty (PK) for keratoconus and correlate this with corneal thickness. DESIGN: Retrospective case series. METHODS: Twenty-three patients (32 eyes) with unilateral or bilateral DALK or PK for keratoconus were analyzed for visual quality after suture removal. Evaluation included measurement of visual acuity, contrast sensitivity, and higher order aberrations (HOAs) (WaveScan((R)); Visx, Santa Clara, California, USA). Readings were performed with both spectacle and rigid contact lens correction of refractive error. Total and residual stromal thickness after DALK was measured using optical coherence tomography (OCT) and correlated to visual quality. RESULTS: Eyes after PK had better visual acuity than eyes after DALK (P = .018). Subgroup analysis of DALK eyes revealed that the level of visual acuity was related to the thickness of residual recipient corneal stroma. Eyes with a recipient corneal bed thickness of <20 mum had visual acuities similar to eyes with a PK, whereas those with a recipient thickness of >80 mum had a significantly reduced visual acuity (P = .0009). Contrast sensitivity was similar in DALK and PK eyes. There was no significant difference in HOAs between eyes with DALK or PK. CONCLUSIONS: These data suggest that the main parameter for good visual function after DALK for keratoconus is the thickness of residual recipient stromal bed. An eye with a DALK with a residual bed of <20 mum can achieve a similar visual result as a PK.

[John Smith]

Piper,

My understanding (in simple terms) is this:

* A DALK graft is significantly less likely to have a rejection episode (say 1-3% DALK, 10% PK).

* A DALK graft with freeze-dried donor tissue will not reject, as there are no live cells being implanted. (As far as I know, Chad Rostron is the only consultant performing these grafts in the UK).

* A DALK graft will take longer to heal optically, and may not give quite as good results as a PK, but the difference is slight.

* A DALK graft will heal much quicker medically meaning less time off work. It will also be physically stronger in the future.

[Sajeev]

Nicely put John,

The reason to some of the differances is that with a DALK (compared to a pk) is that there are now two optical surfaces, which effects vision slightly more, but that has greater advantages in another way.

The frozen DALKS sounds neat!

[John Smith]

Thanks Sajeev,

The frozen DALKs do indeed sound neat, but in my case I'm finding the extra optical healing time (because of a lack of epithelium) a little tedious.

[GarethB]

John,

Do you know if the tissue used in frozen dalk is frozen at the eye bank or is it a fresh donour material that goes through freezing immediatly before surgery?

I only ask because my left eye was a PK with tissue that was from the eye bank (presumable frozen) and the results were better by far than the right eye which was also PK using fresh donour material.

Fully aware that the results can be quite large from graft to graft, but to me it seemed this variability could no explain the differnt results enough.

[John Smith]

Sorry Gareth, I have no idea. All I know is that in John Dart's conference presentation he mentioned that Chad Rostron was the only person using that technique, which was possible because "he has his own eye bank"

[GarethB]

I'll ask the next specialist guest speaker at either Brum meet or the AGM

For me, I'd like to have a money bank rather than an eye bank

[jayuk]

John

Was/is the healing time for the epith expected? Have others that have had the DALK in this manner, experienced the same?

J

[John Smith]

Jay,

Yes, the epithelium healing time is pretty much as expected. I was initially (pre-op) told 6-12 months... I'm just into that window and almost there. I was told 12 months post-op, and now he's saying that the epi won't be at it's best whilst the stitches are there, and that will be the 12 month point when they're removed.