Previous Corneal Collagen Crosslinking Does Not Affect Outcomes of DALK

MOSCOW, RUSSIA – AUGUST 15, 2019: An assisting ophthalmic surgeon prepares patients for an operation at Veterans’ Hospital 2. Alexander Shcherbak/TASS (Photo by Alexander ShcherbakTASS via Getty Images)
A history of CXL will not affect bubble formation or increase surgical complications, according to a report.

Previous corneal collagen crosslinking neither affects bubble formation success nor increases intra- or postoperative complication in deep anterior lamellar keratoplasty (DALK) surgery for keratoconus, according to research results published in Cornea. 

In patients with and without a history of previous corneal collagen crosslinking, researchers conducted a retrospective, nonrandomized comparative study to evaluate both the surgical outcomes and intraoperative and postoperative complications associated with big-bubble DALK. 

The total study population included 77 eyes from 77 patients with keratoconus. Those with corneal collagen crosslinking (CXL)-DALK included 27 eyes and a median patient age of 24 years. The DALK group included 50 eyes and a median patient age of 25 years. In the CXL-DALK group, the mean interval between CLX treatment and DALK surgery was 45.6±21.07 months. 

Twenty-four eyes in the CXL-DALK group — 88.9% of patients — achieved a cleavage plane (big bubble), while 3 eyes (11.1%) required layer-by-layer stromal dissection. In the DALK-group, these rates were 90% and 10%, respectively. A type 1 bubble was obtained in 22 eyes, while a type 2 bubble was obtained in 2 eyes, compared with 42 and 3 eyes, in the CXL-DALK and DALK groups, respectively. No eyes experienced type 3 bubbles. 

At all postoperative visits, corrective distance visual acuity (CDVA) mean logMAR significantly improved in both groups. Seven eyes had a preoperative CDVA of 20/100 or better, compared with 20/40 or better in all eyes during the second postoperative year. No statistically significant between-group difference was seen in either uncorrected visual acuity or CDVA at any postoperative visit. Mean maximum keratometry, keratometric astigmatism, and spherical equivalent refractive error values were all also significantly improved in both patient groups. 

Mean endothelial cell losses were 10.2%±3.1 and 10.9%±5.4 at 2 years in the CXL-DALK and DALK groups, respectively.

Mean suture removal completion time was 17.89±2.54 months and 17.86±2.35 months in each group, respectively. At 2 years, all grafts were clear, and no graft rejections occurred. Four eyes in the CXL-DALK group experienced persistent epithelial defect, compared with 2 eyes in the DALK group, within 6 postoperative months. One eye in each group experienced a traumatic graft detachment. 

Study limitations include the retrospective, nonrandomized nature of the research. 

“This study is the largest case series comparing big-bubble DALK outcomes between keratoconus patients with and without a history of previous CXL treatment,” according to the study. “Our results show that previous CXL does not increase intraoperative or postoperative complication rates of DALK surgery when compared with noncrosslinked eyes.” 

“According to the comparative results of this study, corneal surgeons can perform big-bubble DALK surgery as needed in patients with keratoconus with a history of CXL treatment without big concern.”


Sari ES, Kubaloglu A, Koytak A, Oglugolu AN, Sahin G. Effect of previous crosslinking on intraoperative and postoperative outcomes and complication rates of big-bubble deep anterior lamellar keratoplasty for keratoconus: A comparative study. Cornea. Published online May 27, 2021. doi:10.1097/ICO.0000000000002760