BLOG: The impact of cross-linking on corneal transplants
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Key takeaways:
- Patient registries have shown that PK rates for keratoconus decreased after the introduction of cross-linking.
- It can take a long time for a new treatment paradigm to be fully adopted.
Penetrating keratoplasty is an effective procedure that can restore sight for patients. However, it is not without significant risks and burdens, especially for young people who may need a second or even third graft during their lifetime.
Since the approval of iLink (Glaukos) corneal cross-linking in the U.S. in 2016, I’m happy to say I have been performing far fewer PKs for keratoconus (KC) than I used to, but it has been hard to pin down precise numbers for the impact of cross-linking on PK rates in the U.S. Data from countries with national health systems and large patient registries provide an opportunity to answer this question objectively.
Image: Sumit “Sam” Garg, MD
Researchers from Oslo University Hospital, which provides corneal transplantation services to about half of Norway’s population, recently published a study showing that cross-linking has had a major impact on corneal transplantation rates at their institution. The number of PKs performed for KC between a 2-year period (2005-2006) just before the 2007 introduction of cross-linking there and a more recent 2-year period (2021-2022) when cross-linking was widely available decreased dramatically.
Between those two periods of time, the number of PK procedures performed for KC decreased from 55 (40% of all keratoplasties in 2005-2006) to 11 (3.1%), an 80% decline over 15 years (Figure 1). The number of transplants in patients younger than 30 years old decreased from 26 in 2005-2006 to just one in 2021-2022. The mean age of patients undergoing PK for KC increased over time from 34.6 years to 44.3 years. Most of the patients (90.9%) undergoing PK in the 2021-2022 period were deemed to be in stage 4 KC. One of the patients who underwent a transplant had previously had epi-on cross-linking after being diagnosed with advanced KC at age 17. While the fact that patients were mostly undergoing PK as a very last resort makes sense, it also underscores the importance of early diagnosis and treatment to avoid progressing to the later stages of the disease.
Even while the number of keratoplasties for KC was declining, the overall rate of corneal transplants more than doubled, so the decrease in PKs for KC was not due to unwillingness or inability to perform transplant procedures, COVID-related delays or a lack of cornea tissue. Moreover, there is no evidence that the prevalence or incidence of KC in Norway decreased in 2021-22, suggesting that the decline in PK procedures is truly due to changes in patient care after the introduction of cross-linking in 2007. Improved scleral contact lens technology likely also played a role.
The same group of authors had previously reported a 50% decrease in transplant rates for KC rates 8 years after the introduction of cross-linking, and researchers in the Netherlands reported a 25% reduction in PKs 7 years after the introduction of cross-linking there. But it may simply take a long time for new treatment paradigms to be fully adopted. Indeed, the Norwegian authors surmised that 7 to 8 years was “too short to be able to ensure that [cross-linking] treatment is offered to all patients with progressive KC.”
In the U.S., we have had access to cross-linking for less than 8 years. Already, there are reports from the IRIS Registry that about 30% of newly diagnosed KC patients in 2020 underwent cross-linking. I am optimistic that the treatment rate for appropriate candidates will continue to rise, and with it, we will see a large decrease in the need for corneal transplantation for KC here, as well.
References:
- Godefrooij DA, et al. Acta Ophthalmol. 2016;doi:10.1111/aos.13095.
- Hagem AM, et al. Cornea. 2024;doi:10.1097/ICO.0000000000003401.
- Sandvik GF, et al. Cornea. 2015;doi:10.1097/ICO.0000000000000460.
- Syed ZA, et al. Ophthalmology. 2024;doi:10.1016/j.ophtha.2024.01.036.
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