RESUMO
PURPOSE: To compare clinical outcomes of customized transepithelial (epi-on) corneal crosslinking (CXL) in high oxygen and customized CXL with epithelial removal (epi-off) in room air for keratoconus (KC). SETTING: Umeå University Hospital, Umeå, Sweden. DESIGN: Prospective, randomized, single-masked, intra-individually comparing study. METHODS: Thirty-two participants with bilateral progressive KC were treated with bilateral customized topography-guided CXL, 30 mW/cm2; 7.2-15 J/cm2 and were randomized to epi-on in one eye (32 eyes) and epi-off in the fellow eye (32 eyes). Uncorrected (UDVA) and best corrected visual acuities (BCVA), maximal keratometry (Kmax), subjective ocular discomfort, low-contrast visual acuities (LCVA) at 10% and 2.5% contrast, ocular and anterior corneal wavefront aberrations, manifest refractive spherical equivalent (MRSE), endothelial cell count (ECC) and adverse events were assessed through 24 months. RESULTS: Both treatments showed improvements at 24 months in UDVA; -0.16 ± 0.24 (p < 0.001) and -0.13 ± 0.20 logMAR (p = 0.006), respectively, BCVA; -0.10 ± 0.11 (p < 0.001) and -0.10 ± 0.12 (p = 0.001), Kmax; -1.74 ± 1.31 (p < 0.001) and -1.72 ± 1.36 D (p < 0.001). LCVA 10% improved for both protocols (p < 0.001), but LCVA 2.5% improved for epi-on CXL only (p = 0.001). ECC was unaltered and no adverse events occurred. The epi-on eyes had significantly less discomfort symptoms during the whole first week posttreatment (p < 0.05). CONCLUSIONS: High-oxygen customized epi-on CXL is a viable alternative to room air customized epi-off CXL, with faster improvements in BCVA and LCVA and less early ocular discomfort.
RESUMO
PURPOSE: To analyse the temperature of the corneal surface in keratoconus during corneal customized crosslinking (CXL) with a preserved epithelium (epi-on) under oxygen flow, and epi-off CXL in room air, and to assess the effect of pre-heating the oxygen. METHODS: This masked, intra-individual comparing randomized study included 14 participants with bilateral progressive keratoconus treated with bilateral CXL: one eye with epi-on CXL under a flow of 2.5 L/min oxygen; the fellow eye with epi-off CXL in room air. In a second setting involving 12 healthy participants, room-tempered oxygen was flushed over one eye and oxygen pre-heated to 37°C over the fellow eye. The corneal surface temperature was assessed with infrared photography. RESULTS: A reduction in corneal surface temperature was seen from the pre-treatment application of topical riboflavin in the epi-off group (-1.1 ± 1.0°C, p < 0.001). The temperature increased during the first half of the CXL treatment in both groups (+0.7 ± 1.2°C, p = 0.041 for epi-on; +0.7 ± 0.9°C, p = 0.023 for epi-off CXL, respectively). In epi-on CXL an overall temperature increase was seen during the treatment (+0.8 ± 1.2°C, p = 0.016). In the second setting, pre-heating the oxygen rendered a surface temperature increase of +1.8 ± 0.2°C (p < 0.001). CONCLUSION: In epi-off CXL, the application of topical room-tempered riboflavin decreases the corneal surface temperature, likely due to increased evaporation. A slight temperature increase is seen during CXL with both epi-on and epi-off CXL, albeit far below the corneal safety limit. The corneal temperature can, however, be increased by applying pre-heated oxygen, a possible approach to modify or augment the treatment effect in CXL.
