Researches showed that classic corneal collagen crosslinking (CXL) can effectively control the progression of keratoconus and corneal ectasia, but its adverse responses and complications are common due to the de-epithelial procedure. A transepithelial riboflavin-ultraviolet CXL surgery has applied in ophthalmology, but its effectiveness and safety evaluation is less.

This study was to evaluate the effectiveness and safety of rapid transepithelial riboflavin-ultraviolet CXL for keratoconus.

A prospective self-controlled study was designed. Forty-six eyes of 28 keratoconus patients scheduled to receive the rapid transepithelial riboflavin-ultraviolet CXL in Beijing Tongren Hospital from March to October in 2014 under the approval of this hospital and informed consent with a follow-up duration for one year. The spherical equivalent (SE), astigmatic power, central corneal thickness (CCT), endothelial cell count, corneal topography parameters, the parameters from the anterior segment optical coherence tomography (AS-OCT) and corneal biomechanical parameters were examined before surgery and 1 week, 1 month, 3 months, 6 months and 12 months after surgery, and the results were compared among different time points to assess the effectiveness of transepithelial riboflavin-ultraviolet CXL for keratoconus. The postoperative irritation symptoms and adverse response were observed to evaluate the safety of surgery.

No intraoperative complication and serious adverse postoperative infection were found in all the operated eyes. Slight irritation symptoms occurred in operated eyes 1 day after surgery and disappeared 3 days after surgery. A little reducing was seen in the spherical equivalent 1 month later, without significant difference among various time points (F=0.722, P=0.614). However, a significant reducing was found in astigmatic power in 12 months after surgery compared with before surgery (t =3.242, P=0.004). No considerably differences were seen in corneal endothelial cell (CEC) density, variation coefficient of CEC area and hexagonal CEC ratio among different time points (F=0.246, 0.465, 0.981; all at P>0.05). The corneal thickness values in postoperative 3 and 6 months were (467.86±52.92)μm and (468.51±52.96)μm, which were insignificantly higher than (453.91±45.78)μm in preoperation (t=0.236, 0.469; both at P>0.05), however, the corneal thickness value in postoperative 12 months([488.67±51.44]μm) was significantly increased in comparison with preoperation (t=3.681, P=0.002). The maximal corneal curvature value (Ks), minimal corneal curvature value (Kf) and average corneal curvature value (Avek) were not significantly lower 3, 6 and 12 months after surgery than those before surgery (F=0.592, 0.897, 1.029, all at P>0.05). High reflective light band of corneal stroma was found in OCT images in 39 eyes (84.78%) with the mean depth of (214.38±31.92)μm. No significant differences were found in corneal hysteresis (CH) and corneal resistance factor (CRF) before and after surgery (F=1.268、0.894, both at P>0.05).

Rapid transepithelial riboflavin-ultraviolet CXL for keratoconus can increase corneal thickness, flatten corneal curvature and therefore arrest the development of keratoconus corneas. In addition, this therapy does not alter the shape and function of corneal epithelial and endothelial cells with mild irritation to eyes.

[Key words] Keratoconus/drug therapy; Photochemotherapy/methods; Photosensitizing agents/therapeutic use; Riboflavin/therapeutic use; Ultraviolet rays; Biomechanics, corneal; Accelerated transepithelial riboflavin-ultraviolet corneal collagen crosslinking