Assessing Oxidative Stress And Inflammatory Response In Porcine Corneas Post Laser-Induced Refractive Index Change (Liric)

Laser-Induced Refractive Index Change (LIRIC) is a novel, non-invasive method to correct ametropia by altering the refractive index using a femtosecond laser with a high repetition rate and lower energy compared to conventional refractive laser surgery methods. This study investigates whether porcine corneas treated with LIRIC exhibit less oxidative stress and inflammation compared to controls or porcine corneas undergoing oxidative stress induction.

Laboratory investigation, Experimental Eye Research Institute at University Eye Hospital, Ruhr-University Bochum, Bochum, Germany.

LIRIC treatment was applied to the stroma of explanted porcine corneas using a 140 fs-laser with two different energy settings (10 and 35 nJ). Additional corneas were cultivated with 100 or 200 mM H₂O₂ for 24 hours to induce oxidative stress. Untreated corneas served as controls. RT-qPCR was performed on corneas from all five groups (n=4/group) to analyze markers for inflammation (IL1B), oxidative stress (HIF1a), superoxide dismutase (SOD1, SOD2), angiogenesis (VEGF, VEGFC), and tight junctions (TJP1).

The IL1B inflammatory response was significantly upregulated in corneas subject to oxidative stress (p<0.05), while corneas treated with LIRIC at both energy settings showed no signs of inflammation (10 nJ: p=0.36; 35 nJ: p=0.73). Also, a significant downregulation of HIF1A was observed in corneas treated with 35 nJ LIRIC (p=0.03), with no changes noted in the other groups. Both SOD1 and SOD2 were downregulated in LIRIC-treated corneas (p<0.05). VEGF levels decreased in both LIRIC groups (p<0.05) but were upregulated in corneas treated with 200 mM H₂O₂ (p<0.001). Additionally, VEGFC expression was lower after LIRIC treatment but higher in the H₂O₂ group. A significant upregulation of TJP1 was only observed in the H₂O₂ groups (p<0.050).

LIRIC treatment in porcine corneas demonstrated no induction of inflammation and a notable reduction in oxidative stress markers. These results indicate that LIRIC is a promising non-invasive technique for correcting ametropia, with minimal adverse effects on corneal health. Given its potential, further clinical studies are essential to evaluate the long-term outcomes and explore the broader clinical applications of LIRIC in refractive surgery.