Researchers measured corneal thickness changes with isotonic riboflavin solution and hydroxypropyl methylcellulose (HPMC) during accelerated corneal collagen crosslinking (CXL) with or without the use of an eyelid speculum.

Study design

Researchers divided 52 eyes (48 patients) with progressive keratoconus into 2 groups. In group 1, an eyelid speculum was removed during 20-minute riboflavin (0.1%) with HPMC (Mediocross M; Avedro) instillation. In group 2, the eyelid speculum remained in place during CXL. All patients underwent accelerated CXL using continuous ultraviolet-A (UVA) light exposure at 9 mW/cm² for 10 minutes; total energy dose was 5.4 J/cm².

Intraoperative ultrasound pachymetry measurements were noted before and after epithelial removal, after riboflavin loading, and after 5- and 10-minute UVA light exposure.

Outcomes

After removal of the epithelium, pachymetry decreased an average of 25 μm and 31 μm in groups 1 and 2, respectively. The thinnest pachymetry in both group 1 and 2 increased after soaking (52.26 μm and 27.88 μm; P < 0.001) but eyelid closure during riboflavin instillation promoted a significantly greater increase in pachymetry readings (P < 0.0001) compared with the speculum group.

Overall, corneal thickness remained stable in both groups during UVA irradiation at 5 and 10 minutes (P > 0.05). However, compared with preoperative pachymetry before epithelial removal, the thickness significantly increased throughout the procedure in group 1 after epithelial removal and remained at preoperative levels in group 2.

Limitations

Reproducibility of this study is important to help ensure the ability to generalize these conclusions to other cohorts.

Clinical significance

Eyelid closure during instillation of riboflavin solution during epi-off CXL further induces corneal swelling. Discontinuation of eyelid speculum during riboflavin loading may improve the safety of procedures performed in thin corneas.