Background <p>A Phase I/II trial to evaluate the initial safety and performance of a novel corneal crosslinking device, the Corneal Crosslinking Pen in keratoconus patients. This was a prospective exploratory study with 12 months of follow up.</p> Methods <p>Twenty-one eyes of 21 patients aged 14–27 years and diagnosed with progressive keratoconus were enrolled and treated unilaterally. Corneal crosslinking (CXL) following an accelerated epi-off protocol with riboflavin was done using the Corneal Crosslinking Pen. Effectiveness endpoints included changes in astigmatism, maximum keratometry (KMax), and best corrected visual acuity (BCVA) compared to baseline. Safety included adverse events and changes in pachymetry, intraocular pressure (IOP), and endothelial cell count (ECC).</p> Results <p>Astigmatism was significantly reduced at 12 months by a mean (95% CI) of 0.56 (0.10, 1.03) D. KMax was also reduced by a mean of 0.63 D, but this was not significant. BCVA improved significantly by nearly four lines of vision (- 0.38; logMAR). No corneal thinning was observed; pachymetry, IOP and ECC all remained stable across 12 months. Adverse events were infrequent and mild.</p> Conclusion <p>These early results suggest that the Corneal Crosslinking Pen was safe and effective for CXL. Future studies will seek to confirm the large improvement seen for BCVA and elucidate a potential mechanism.</p>