Surgical Correction of Presbyopia

Lenticular, Corneal, and Scleral Approaches

Michael Greenwood, MD; Shamik Bafna, MD; Vance Thompson, MD

Disclosures

Int Ophthalmol Clin. 2016;56(3):149-166. 

In This Article

Corneal Inlays

In general, corneal inlays are placed in the nondominant eye. The current inlays available for the treatment of presbyopia are made out of synthetic materials and have various mechanisms of actions including changing the index of refraction, changing the corneal curvature, and small-aperture optics. The ideal synthetic inlay would be thin, have a small diameter, permit high nutrient and fluid permeability, and be implanted relatively deep within the stroma depending on the intended mechanism of action. Large, impermeable inlays can impede metabolic, catabolic, and/or dehydration processes in the cornea disturbing the cornea's natural state. An inlay implanted superficially can lead to unintended surface changes, or possible extrusion by mechanical forces. Placement depth will vary for each inlay design given different materials and mechanisms. Inlays designed to intentionally alter surface curvature tend to be implanted more superficially. Other inlay designs that utilize a different index of refraction or small aperture are typically implanted deeper to avoid surface curvature changes.

Corneal inlays have several benefits. The inlays are removable and are able to be repositioned, which allows for modifications, if needed. They can also be combined with other refractive procedures, and as the procedures are limited to the cornea, they do not put patients at the same risks as intraocular surgery. Importantly, unlike monovision, the eye with the inlay does not have a significant decrease in distance vision, which allows for good binocular function and therefore little or no decreased stereoacuity.[13,14]

The inlays are placed with the assistance of a femtosecond laser under a flap or into a pocket.[15] The pocket technique offers several advantages.[15,16] A major advantage is that more of the peripheral corneal nerves are preserved when compared with a flap technique, which enables corneal sensitivity to be maintained, reduces the severity of dry eye syndrome, and potentially allows for quicker visual recovery. Theoretically, the pocket procedures may be more biomechanically stable than lamellar procedures as less tissue alteration occurs. Lastly, there is less chance of striae, which can be associated with flaps. When a combination of excimer laser treatment to achieve ametropia plus placement of an inlay is needed, the lamellar flap option is more attractive. The flap allows for easy access in case repositioning or removal is needed. A final option is to use the dual interface technique, in which a pocket is created 120 μm deeper to a previous or sequential LASIK flap if a refractive correction is needed.

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