Comparative Results Between “Epi-Off” Accelerated and “Epi-Off” Standard Corneal Collagen Crosslinking-UVA in Progressive Keratoconus – 7 Years of Follow-Up

Abstract

The purpose of the present study was to assess the long-term efficiency and safety of the "epi-off" accelerated CXL (9 mW/cm 2 for 10 minutes) in comparison to the standard "epi-off" CXL (3 mW/cm 2 for 30 minutes) in terms of topographical and keratometric parameters, refractive data and visual outcomes at 7 years of follow-up, in progressive keratoconus. Material and Method: A retrospective and comparative study was performed. A total of 183 eyes from 183 patients with documented progressive keratoconus were included in the study. The patients were divided in two groups: 93 eyes from 93 patients underwent "epi-off" standard cross-linking technique (3 mW/cm 2 for 30 minutes) (S-CXL group) and 90 eyes from 90 patients underwent accelerated "epi-off" corneal CXL technique (9 mW/cm 2 for 10 minutes) (A-CXL group). Results: Improvements in uncorrected distance visual acuity (UDVA) were statistically significant compared to baseline values in both groups at each time-point visit (p=0.0421 at 1 year, p=0.0411 at 7 years for A-CXL and p=0.0375 at 1 year, p=0.0389 at 7 years for S-CXL). At 7 years there was a statistically significant increase in CDVA (p=0.039 in the A-CXL group and p=0.0343 in the S-CXL group at 7 years). Statistically significant reduction was noticed in Ksteep (p=0.0411 in A-CXL group and p=0.0224 in S-CXL group), Kflat (p=0.0198 in A-CXL group and p=0.008 in S-CXL group), K mean (p=0.0106 in A-CXL group and p=0.0193 in S-CXL group) and Kmax (p=0.0413 in A-CXL group and p=0.054 in S-CXL group) at 7 years, compared to baseline values, in both groups, but without any statistically difference between the two procedures, at all time-point visits (p>0.05). Conclusion:The long-term outcomes of "epi-off" accelerated corneal collagen crosslinking-UVA (9 mW/cm 2 for 10 minutes) are similar to standard "epi-off" corneal collagen crosslinking procedure in the treatment of progressive keratoconus.

Long-term outcomes of corneal crosslinking

“…Of the 9/18 (50%) of studies reviewed with reported progression criteria, follow-up ranged from 3 to 13 years and post-CXL progression rates ranged between 0.8 and 33% [26,31,40,44 One study had one participant with a persistent epithelial defect [31]. Microbial keratitis was found in 2.6% of patients in one manuscript [40], while persistent corneal haze or scarring was found in & ] while in the 18 that examined best corrected visual acuity (BCVA) or corrected distance visual acuity (CDVA), eight of 18 (44.4%) identified no significant change [23,25,39,40,42,45,49 ,50] and 10 of 18 (55.6%) documented statistically significant improvements at 2-10 years…”

“…Long-term data on CXL for progressive pediatric KCN suggest that overall SDP and newer techniques do not successfully halt progression as effectively as in adults, while visual and topographic outcomes vary significantly between studies. postprocedure [22,26,31,33,41,43,44…”

“…Similarly, topographic parameters were commonly assessed in patients undergoing SDP for progressive KCN. All 18 of 18 studies examined Kmax, the steepest anterior corneal curvature, and 13 of 18 (72.2%) noted a significant improvement over time [22,23,25,26,31,33,[39][40][41]43 ,50] compared to three of 10 (30.0%), which noted no significant change [33,42,44].…”

“…Various safety concerns with SDP have been noted since its inception, including infectious keratitis, integrity of limbal epithelial cells, anterior corneal haze or scarring, sterile infiltrates, endothelial toxicity, corneal nerve damage, excessive hyperopic shift, and excessive pain [15]. Alternate methods of CXL including accelerated and transepithelial ("epithelium-on") approaches have been tested recently to address the shortcomings associated with this protocol with mixed results [16][17][18][19][20][21][22][23][24][25][26][27]28 && ,29-31,32 && , [33][34][35][36]. The use of CXL in corneal ectatic disorders has been rapidly expanding since the early 2000 s [37 & ].…”

Independent-effect comparison of five crosslinking procedures for Progressive Keratoconus based on Keratometry and the ABCD Grading System using Generalized Estimating Equations (GEE)

“…The most commonly used method in clinical practice is the standard Dresden protocol for corneal crosslinking (S-CXL). However, S-CXL is time-consuming, and although prior studies report comparable efficacies of accelerated CXL (A-CXL) and S-CXL [ 4 , 5 ], some clinical centers do not currently use conventional S-CXL to treat keratoconus. Moreover, removal of the corneal epithelium may cause pain, discomfort, temporary vision reduction, and decreased corneal clarity (haze), and can increase the risk of infectious keratitis [ 6 – 8 ].…”