Cataract surgery and beyond
FSL began its use in cataract surgery in 2008, and it brings increased precision to corneal incisions and the capsulrhexis and allows for the lens to be fragmented with a decrease in phacoemulsification energy.7-9 This decrease in phaco energy results in less endothelial cells loss at one month and in theory may result in a decrease in cystoids macular edema after surgery.10 Limbal relaxing incisions can be made with FSL and are of a precise depth and length, improving refractive outcomes.
FSL LASIK appears to have several advantages over current use of two different lasers. In 2016, the first FSL system (VisuMax, Carl Zeiss) was approved in the United States.
Small-incision lenticule extraction (SMILE) is a procedure where in which a small lenticule of stromal tissue is removed from a corneal incision or flap. The lenticule is of a precise refractive power, resulting in a change in refractive error. SMILE is FDA approved only for the correction of myopia up from -1.00 D to -8.00 D with up to -0.50 D of astigmatism.
Several theoretical advantages of the SMILE procedure are:
• Less disruption of the corneal nerves, which may result in less dry eye
• Less tissue taking, which may improve biomechanical stability of the cornea and lower induction of higher order aberrations.11-14
Currently, two corneal inlays are approved in the United States, and both require FSL to access the corneal stroma.
The two inlays employ very different strategies to correct presbyopia, but the depth of the inlay is critical to their success. Kamra Inlay (AcuFocus) uses a pin-hole technique to increase depth of focus and increase near vision. A deeper (>220 µm) “pocket” created by FSL yields improved outcomes.15
RainDrop Inlay (ReVision Optics) alters the curvature of the central cornea to create hyperprolate shape to the cornea, resulting in improved near vision. FSL is required to make a pocket at 30 percent of the cornea depth (average 160 µm) to allow for the proper reshaping of the cornea.
Penetrating keratoplasty and lamellar keratoplasty use to create a more precise wound and allow for more elaborate wound configuration—resulting in faster and more predictable wound healing.16,17 Research shows there is less residual astigmatism and a trend toward higher endothelial cell count despite similar final best corrected visual acuity between the two groups.18
The objective of these patterns is to increase the surface area between the donor and the host tissue along with moving the surface junction further from the limbus. ODs aim to decrease the risk of rejection while increasing surface area to promote healing.
Deep lamellar keratoplasty removes the anterior, damaged cornea while leaving a healthy endothelium intact. FSL can precisely remove the anterior tissue while leaving the endothelium untouched.
The laser has been experimentally used to perform sclerotomies to treat glaucoma.19 The precision of FSL allows for an exact incision and a smoother healing.
FSL technology continues to evolve and find more applications within eye care.
Related: Preparing your patient for PRK
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