A recent study demonstrated that topography-guided, photorefractive intrastromal crosslinking (PiXL) provides similar safety with significantly greater keratometry flattening when compared with standard corneal crosslinking (CXL). The customized procedure also provided more regular corneas, as customizing the fluence application in keratoconic eyes allows significant visual rehabilitation apart from halting the disease process, according to the study.

With 32 eyes in each group, PiXL eyes received 30mW/cm2 pulsed irradiance with a total fluence ranging from 5.4J/cm2 to 15J/cm2, in concentric circles centered on the posterior float maximum, while standard CXL eyes received homogenous 9mm ultraviolet-A irradiation of 9mW/cm2 delivering a total fluence of 5.4J/cm2.

The study noted a significant reduction in maximum keratometry and inferior-superior asymmetry in the PiXL group at both the six-month and one-year post-op visits. Corrected spectacle distance visual acuity improved significantly in the PiXL group, and the researchers observed a greater depth of a stromal demarcation line as well.

The researchers highlighted that using concentric rings of standardized size allowed minimal fluence delivery to at least 7mm corneal diameter while allowing higher fluence over the maximally elevated area of the cone. They believe this can provide treatment in eyes with or without a well-defined posterior float cone, thereby extending the procedures applicability to those with early  ectasia.

Sachdev GS, Ramaurthy S, B S, Dandapani R. Comparative analysis of safety and efficacy of topography-guided customized cross-linking and standard crosslinking in the treatment of progressive keratoconus. Cornea. September 16, 2020. [Epub ahead of print].