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Vladimir G Lemberg, Hong Fu, James E Hill; Femtosecond laser assisted keratopigmentation for presbyopia correction. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3939.
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One of the presbyopia correction methods is to insert a ring-like inlay (KAMRA Inlay, AcuFocus, Inc.) into the corneal stroma of the non-dominant eye. The purpose of this work is to explore the concept of using femtosecond laser assisted keratopigmentation for presbyopia correction. In particular, we evaluate the ability of the iFS® laser to create the intricate corneal features and the feasibility to produce a pigmented aperture in a femtosecond laser ring cut. This method of presbyopia correction is expected to eliminate foreign body sensation and the impact of inlay on nutrients flow. It enables precisely controllable aperture centration and eliminates potential corneal inlay displacement.
Experimentally, we used the iFS® laser (Abbott Medical Optics Inc.) to create the intracorneal ring cut in porcine corneas, then filled the channel with opaque ink. The ring cut was created at a depth of 200 microns in the cornea. The inner ring diameters tested were 1.0 and 1.5mm, respectively, and the outer ring diameters were 3, 4, and 5mm, respectively, and the laser pulse energy ranged from 0.3 to 1.5μJ. The diameter of the anterior side cut was 3.7mm, and the energy was 1.4μJ. The ring cut is injected with a biocompatible dye to create an aperture, which has been proven safe and durable in corneal tattooing. Four different dyes were tested. Two types of needles were tested for injecting the dye. Theoretically, we analyzed the blur and image quality as a function of defocus and pupil sizes.
The femtosecond laser produced complete ring cut on the porcine corneas. We injected the dye into the ring cut through the anterior side cut. In all samples the injected dye spread to cover the ring area and formed an aperture. We observed that the dye spreading resulted in a tendril type pattern at the inner and outer edges. The theoretical analysis shows that an up to 3 diopters depth of focus can be gained with reasonable aperture sizes.
The intricate corneal features created by the iFS® femtosecond laser enabled keratopigmentation for presbyopia correction. The keratopigmentation is expected to have several advantages over a ring-like inlay. Preliminary feasibility to produce a pigmented aperture with femtosecond laser ring cut is demonstrated. Further research is needed to address the reversibility of the keratopigmentation.
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