ABLATION OF THE CORNEA BY USING A LOW-ENERGY EXCIMER-LASER

We describe a new multipurpose method for corneal refractive surgery b y using a focused excimer laser beam, which allows the application of a small, compact low-energy excimer laser. It is possible to ablate an y area desired in the cornea without masking by scanning the focused b eam. The ablation depths in freshly enucleated swine eyes were measure d in relation to the number of laser pulses (at fixed fluence) and the pulse fluence at wavelengths lambda = 248 nm and lambda = 193 nm. The irradiation conditions were investigated to obtain smooth ablation of the corneal material over an area of about 1 cm2. The experiments sho w that smooth ablation is obtained when the ratio of the excimer laser beam spot diameter on the corneal surface and the displacement for on e scanning step is given by a whole number. A simple model based on re ctangular beam profiles is presented to exemplify this.