An inverse linear correlation exists between the refractive state of the eye and spherical aberration induced within the range of laser vision correction. Small values of spherical aberration do not worsen visual acuity or depth of focus, but positive spherical aberration may induce night myopia. In addition, the changes in spherical refraction when the pupil constricts may worsen near vision when positive spherical aberration is induced or improve it when spherical aberration is negative. [J Refract Surg. 2017;33(7):470-474.].
We present a series of 5 consecutive cases in which a small-aperture corneal inlay (Kamra ACI7000PDT) was uneventfully implanted in a corneal pocket created at a depth between 200 μm and 250 μm. Three months after surgery, all patients had good visual results, normal corneal surfaces, and adequate stromal healing. Between 6 months and 19 months after surgery, visually significant refractive changes appeared in the form of a hyperopic shift in 4 cases and a myopic shift in 1 case. Topical steroids were ineffective. In 2 cases, the inlay was explanted. Among the adverse events reported in the 2015 approval of the small-aperture corneal inlay was a low incidence of late refractive changes. Recently, we have encountered a relatively higher frequency of these adverse events. Thus, we evaluated the hypothesis that a relationship between these late refractive changes and the decreased diffusivity of nutritional fluid to the anterior stroma accentuated by a lower depth of implantation is the cause.
MIOL can present a refractive or diffractive optics design [3]. Diffractive MIOL are characterized by optical platforms with a multitude of concentric rings with a specifi c separation and height which results in steps that favor and cause the diffraction of the wave front, which allows to focus at different distances [4].
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