Shielding effect of the smoke plume by the ablation of excimer lasers

BACKGROUND: Shielding and scattering effect of the smoke plume column ejected from the laser ablated material is a well-known phenomenon. Debris evacuation system of the excimer laser equipment removes these particles, but insufficient air flow can result in undesired refractive outcomes of the treatment. The aim of this study was to reveal the effect of the air flow speed on the actual ablation depth. METHODS: SCWIND AMARIS 500E flying spot excimer laser was tested in this study. A 150 μm phototherapeutic keratectomy (PTK) profile with 8 mm diameter was applied to the surface of polymethyl methacrylate (PMMA) plates. The velocity of the air flow was changed with adjustable air aspiration system. Ablation depth was measured with highly-precise contact micrometer. RESULTS: The prediction model was statistically significant, F(1,8) = 552.85, p < 0.001, and accounted for approximately 98.7% of variance of ablation (R(2) = 0.987, R(2)(adj) = 0.986). Lower air flow speed resulted in a weaker ablation capability of the excimer laser. CONCLUSION: Air flow generated by the aspiration equipment is a key factor for the predictable outcomes of refractive treatment. Therefore, manufacturer inbuilt debris removal system should be regularly checked and maintained to ensure proper clinical and predictable refractive results.