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Combined PRK, CXL associated with loss of corrected distance vision
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In a retrospective study of corneal cross-linking associated with PRK, a substantial loss of corrected distance vision was observed due to haze, leading the study authors to recommend caution in the use of this combined procedure.
Twenty-six eyes of 16 patients with keratoconus underwent PRK followed immediately by CXL. All PRK treatments were performed with the Schwind Amaris laser platform, using either topography-guided or aspheric ablation after mechanical or laser epithelium removal. Mitomycin C was applied in all eyes, and CXL was performed according to the standard Dresden protocol.
Mean uncorrected distance vision and manifest refraction improved significantly compared with baseline measurements, but CDVA decreased, with half of the eyes losing at least one line and more than one-quarter of the eyes losing two or more lines. Patients with atopy had the most significant CDVA loss. In all eyes that experienced CDVA loss, significant haze was observed.
“Haze was intrastromal in all eyes as typically seen after CXL,” the authors noted. In some cases, it was “intense and pre-endothelial,” while no subepithelial haze, as more typically seen after PRK, was observed.
“The results of our study reveal that PRK immediately followed by corneal CXL may not be as safe as previously described,” the authors said.
They hypothesized that the irregular stromal surface resulting from topography-guided PRK in keratoconic corneas might trigger a cascade of biochemical reactions leading to haze. Unknown interactions between MMC, riboflavin and UVA irradiation could also potentiate cell apoptosis, triggering unpredictable wound healing “or even enabling a more profound absence of keratinocytes.”
They recommended approaching the combined procedure with caution, as it may not be as safe as originally thought and may cause severe visual acuity loss. – by Michela Cimberle
Disclosures: Moraes reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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