When keratoconus needs a corneal transplant: DALK and full-thickness grafts

A corneal transplant is considered when keratoconus is advanced and contact lenses no longer give useful vision or cannot be tolerated. Two operations are used, a partial-thickness graft called DALK and a full-thickness graft, and studies show similar vision with each and fewer rejection episodes with DALK.

How often is a transplant needed?

Older estimates put the share of people with keratoconus who eventually need a transplant at about 10% to 20% [1, 2]. Those estimates come from before cross-linking was widely used.

In New Zealand, keratoconus was the leading reason for corneal transplant every year from 1991 to 2015 [3]. By 2019 it accounted for about 28% of transplants and had moved to second place behind repeat grafts [4]. In Auckland between 2000 and 2009, people having a transplant for keratoconus had a mean age of 30, and Māori and Pacific people were over-represented [5].

Is a transplant the only option left?

A Belgian clinic offered scleral lenses to people with very severe keratoconus. Of 51 eyes fitted, 40 were still wearing the lenses about two and a half years later. Eight eyes in the study went on to a transplant because of poor vision with lenses, intolerance or handling problems [6].

A transplant is still needed for some eyes. Reasons given in the literature include advanced disease, lens intolerance and corneal scarring [7, 8].

The two operations

DALK (deep anterior lamellar keratoplasty) replaces the front layers of the cornea with donor tissue. Your own innermost layers, Descemet's membrane and the endothelium, stay in place [9].

A full-thickness graft (penetrating keratoplasty) replaces every layer of the central cornea with donor tissue [9].

In a full-thickness graft the endothelium comes from the donor and can be attacked by the immune system [9]. In DALK it is your own, so that form of rejection cannot occur [10].

In a meta-analysis, about 3% of planned DALK operations had to be converted to a full-thickness graft during surgery [9].

How the two compare

Vision. A Cochrane review found only two randomised trials, with 111 participants. It found no evidence of a difference in vision between the two operations. Follow-up in the trials was at most about three years, and the reviewers rated the evidence as low quality overall [1]. A 2025 meta-analysis of 47 studies and 27,018 eyes also found no significant difference in best corrected vision at one year [11].

Rejection. Both reviews found rejection was less likely after DALK [1, 11]. In the Cochrane review, most rejection episodes in either group were treated successfully with steroid drops [1].

Graft failure. The 2025 meta-analysis found a lower risk of graft failure with full-thickness grafts [11]. An earlier meta-analysis found similar failure rates [9]. The Cochrane review found no evidence of a difference in graft failure between the two operations in its two small trials. One graft failed, and it was a full-thickness graft. The reviewers concluded there was not enough evidence to say which operation gives better overall outcomes [1].

Long-term survival. A French centre followed 502 grafts for keratoconus. Overall, about 97% were still clear at 10 years and about 96% at 20 years, with no significant difference between DALK and full-thickness grafts [10]. The authors note that their single-surgeon results are higher than registry figures [10].

Other differences. In the French study, DALK eyes lost endothelial cells at about half the rate of full-thickness grafts. They were also less likely to need treatment for raised eye pressure [10]. In the Australian graft registry, first DALK and full-thickness grafts for keratoconus now show comparable survival and long-term vision [12]. Across grafts for all conditions in that registry, not keratoconus alone, fewer people with a partial-thickness (lamellar) graft needed glasses or contact lenses than people with a full-thickness graft [12]. An earlier analysis of the same registry had found better survival and vision with full-thickness grafts [13].

Recovery is slow

In the French study, vision improved gradually over the first 30 months as stitches were removed and astigmatism reduced. In that centre, stitches stayed in for at least 18 months [10].

Glasses or contact lenses are often still needed after a transplant [12, 14]. A review reports that astigmatism of more than five dioptres develops after 19% to 38% of full-thickness grafts, more often in keratoconus [14].

Keratoconus can return

A review puts the chance of corneal bulging returning at 6% to 11% by 20 to 25 years after a full-thickness graft [14]. Some studies report higher figures:

• In a Japanese study of grafts that had stayed clear for at least 10 years, 18 of 50 keratoconus eyes (36%) showed recurrence after an average of 27 years [15].
• A 2026 study using corneal mapping found recurrence in about 21% of 136 eyes, with no significant difference between DALK and full-thickness grafts [16].

Definitions of recurrence differ between studies, which partly explains the range.

Among repeat transplants in Auckland, keratoconus was the most common original diagnosis. A first repeat full-thickness graft lasted a median of 12 years, and each later regraft lasted a shorter time [17].

These findings are why people with a graft are followed long term. In the French study, patients were followed with no time limit [10].

Talking to a surgeon

A corneal surgeon can advise which operation, if any, suits your eye. Dr James McKelvie's clinic describes corneal transplantation at Eye Surgeons NZ.

This article is general information. It does not replace an examination or personal advice.

Choosing a surgeon: in the Waikato, corneal cross-linking is offered by Dr James McKelvie at Eye Surgeons NZ, Dr Michael Merriman at Hamilton Eye Clinic and Mr Chris Murphy. You are free to choose any of them, or another surgeon, and we will send your results to whoever you choose.

Care at Rose Optometry is provided by our optometrist team: Jagrut Lallu, Jacqueline Rowe, Emilie Lawson, Jason Shen, Jessica Wood, Stella Wong and Anjali Hira.

References

1. Keane, 2014, Cochrane Database Syst Rev. DOI PubMed 25055058
2. Godefrooij, 2016, Acta Ophthalmol. DOI PubMed 27213687
3. Kim, 2016, Br J Ophthalmol. DOI PubMed 27635063
4. Chilibeck, 2021, Cornea. DOI PubMed 34267061
5. Crawford, 2017, Cornea. DOI PubMed 28257380
6. Koppen, 2018 (online 2017), Am J Ophthalmol. DOI PubMed 29103959
7. De Clerck, 2026, Medicina (Kaunas). DOI PubMed 41901604
8. Czuj-Porębska, 2026, J Clin Med. DOI PubMed 42278940
9. Liu, 2015, PLoS One. DOI PubMed 25633311
10. Borderie, 2024 (online 2023), Br J Ophthalmol. DOI PubMed 37890880
11. Awad, 2025, Semin Ophthalmol. DOI PubMed 39943883
12. Williams, 2022, Clin Exp Ophthalmol. DOI PubMed 35488434
13. Coster, 2014, Ophthalmology. DOI PubMed 24491643
14. Moramarco, 2022, J Clin Med. DOI PubMed 35628805
15. Yoshida, 2018, Graefes Arch Clin Exp Ophthalmol. DOI PubMed 30196480
16. Alkan, 2026, Cornea. DOI PubMed 42228517
17. Lu, 2019, Clin Exp Ophthalmol. DOI PubMed 31268240

This article is general information, not personal medical advice. Most sources were checked against the full published papers in October 2026.