Keratoconus Progression Can Be Halted With Corneal Crosslinking  

Corneal crosslinking appears safe and effective for stopping progressive keratoconus; however, extreme corneal flattening associated with loss of corrective distance visual acuity may occur.

Keratoconus progression can be halted with strong overall success after a corneal crosslinking (CXL) procedure, according to a long-term follow up study published in Clinical Ophthalmology. Extreme corneal flattening can be a complication of the procedure and may require corneal transplantation or rigid contact lens, according to the report. 

Researchers retrospectively analyzed 45 eyes with progressive KC that underwent corneal crosslinking with epithelial removal between June 2006 and September 2011 at the Oftalmosalud Institute of Eyes in Lima, Peru. The research team performed data analysis at preoperative evaluation, 1 year postoperatively, and at least 10 years or more postoperatively. The mean follow-up time was 11±1.07 years (range, 10–13 years).

The study defined keratoconus progression as an increase in steep keratometry (Ks) of 1.5D or higher between 2 examinations and defined extreme flattening effect as a decrease in K values equal to or greater than 5 diopters (D). 

Overall, the rate of keratoconus progression was 2.22% (1/45) among the cases, which is similar to that previously reported after 10 years of follow-up, the study authors explain. Extreme flattening effect was observed in 15.5% (7/45) of the eyes. 

“Extreme corneal flattening associated with loss of CDVA is a complication of CXL to be aware that may require corneal transplantation or rigid contact lens.

Extreme flattening was associated with a loss of corrected distance visual acuity (CDVA) in 4.44% (2/45) of the eyes and 1 eye with corneal flattening of 11.5 D lost 7 lines of CDVA and required corneal transplantation. However, the researchers emphasize that excessive keratometric flattening is not always a complication of corneal crosslinking, and it is more frequently associated with an improvement in CDVA and uncorrected distance visual acuity (UDVA) (5/7 eyes) rather than a decrease in CDVA (2/7 eyes). 

There was a significant improvement in Ks, UCVA, CDVA, and spherical equivalent during the last visit, the report shows.  

“In conclusion, our study demonstrates that corneal crosslinking is a safe and effective procedure to stop the progression of KC, providing an excellent visual outcome for the vast majority of eyes,” according to the researchers. “Extreme corneal flattening associated with loss of CDVA is a complication of CXL to be aware that may require corneal transplantation or rigid contact lens.”

Study limitations include the small sample size and patients with good outcomes may have been selectively lost to follow-up.  


Henriquez MA, Perez L, Hernandez-Sahagun G, Rojas RP, Stulting RD, Izquierdo L JR. Long term corneal flattening after corneal crosslinking in patients with progressive keratoconus. Clin Ophthalmol. Published online July 3, 2023. doi:10.2147/OPTH.S409009