Simultaneous Phototherapeutic Keratectomy And Corneal Crosslinking In Eyes With Keratoconus: A Randomised Clinical Trial (Shark)

To compare visual and refractive outcomes after transepithelial phototherapeutic keratectomy (t-PTK) combined with accelerated corneal cross-linking (CXL) versus accelerated CXL with mechanical epithelial removal in progressive keratoconus.

Prospective randomised clinical trial at Oslo University Hospital, Oslo, Norway.

One hundred eyes of 100 patients with keratoconus were prospectively enrolled between January 2024 and November 2025 and randomised 2:1 to CXL with mechanical epithelial debridement or t-PTK followed by CXL. Patients were examined preoperatively and 6 months after treatment. Primary outcomes were changes in uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA). Secondary outcomes were changes in manifest refraction and different corneal tomographic values. 

No significant changes in UDVA, CDVA or maximum keratometry (Kmax) were observed in the two groups. The t-PTK+CXL group demonstrated a significantly myopic shift (−1.89±1.87 D) and astigmatic reduction (+1.63±1.57 D), whereas minimal refractive change occurred after CXL alone. Between-group comparison confirmed significantly greater spherical and cylindrical change in the combined group (all p<0.001), without differences in UDVA, CDVA or Kmax. In subgroup analysis, eyes with advanced ectasia (Kmax ≥55 D) treated with t-PTK+CXL showed significant improvement in both UDVA and CDVA, whereas no visual improvement was observed in eyes with Kmax <55 D.

Combined t-PTK and CXL resulted in significantly greater refractive change than CXL alone, characterised by astigmatic reduction and a predictable myopic shift. Visual benefit was confined to eyes with advanced keratoconus (Kmax ≥55 D), suggesting that the main advantage of combined treatment lies in the more severe disease.