A Review of Presbyopia Treatment with Corneal Inlays

Abstract

The prevalence of presbyopia continues to increase every year. The therapeutic approaches to presbyopia cover the spectrum of non-surgical to surgical techniques. With recent advances in biocompatible materials, corneal inlays make a strong case for their place within the treatment spectrum. This article takes a closer look at three of the current corneal inlay models: KAMRA, Raindrop, and Presbia Flexivue Microlens. Each design approach and mode of action is described with data from key clinical trials. Furthermore, the ability to choose the most suitable corneal inlay is presented by comparing each model and identifying their similarities and differences. The article then concludes by touching on the future of corneal inlays, looking at associated conditions and complications and how to manage them, as well as an expert’s personal point of view of enhanced ideas for continuing the growth and success of corneal inlays in the market.

Presbyopia: Effectiveness of correction strategies

“…Another approach to defining presbyopia has been to adopt a more physiological approach, describing presbyopia as an age-related progressive decline in the crystalline lens' ability to accommodate, resulting in the inability to focus on near objects (Abdelkader, 2015;Arines et al, 2017;Benozzi et al, 2012;Fedtke et al, 2017;Moarefi et al, 2017). While both objective (Anderson and Stuebing, 2014;Leon et al, 2016) and subjective measures (Cobb, 1964;Donders, 1865;Turner, 1958) of accommodation indicate that to the accommodative response starts to decrease in the early teens, there is only a concurrent drop in accommodative gain by the fifth decade, reducing near image quality and resulting in the apparent acceleration of symptoms in early presbyopes (Almutairi et al, 2017).…”

“…Currently marketed corneal inlays have either a pinhole design to extend depth-of-focus (Dexl et al, 2015), a thin 'lens' which reshapes the anterior corneal surface creating negative spherical aberrations (Whang et al, 2017;Whitman et al, 2016a;Whitman et al, 2016b) or attempts to create corneal multifocality (distance vision through a plano central zone surrounded by rings of varying additional power; Table 3). Previous large and impermeable inlays disrupted the cornea's natural state by hindering natural metabolic functions, hence modern inlays are thin, of small diameter and are made of biocompatible materials that have high fluid and nutrient permeability (Moarefi et al, 2017). These characteristics allow them to be implanted relatively deep in a femtosecond laser cut flap or pocket, the latter preserving more nerves and, therefore, theoretically having less impact on corneal sensitivity and the homeostasis of the tear film (Moarefi et al, 2017).…”

Diffractive Corneal Inlays: A New Concept for Correction of Presbyopia

“…The major difference between both models relies in the corneal asphericities (Q ) that induce different values for the spherical aberration (SA) in each eye. In these model eyes, both DCIs and the SACI have been inserted virtually at a distance of 200 μm from the anterior surface of the cornea, simulating the surgical procedure of the SACI [5]. In the simulation in ZEMAX, the inlays have been introduced as .uda (user-defined aperture) files.…”

“…Currently, all CIs are implanted monocularly in the nondominant eye producing a modified variant of the monovision system, which consists in using the dominant eye for distance vision and the nondominant one for intermediate-near vision. Commercial examples of CIs are the Flexivue Microlens® (Presbia Cooperatief, UA, Irvine, CA, USA) [1,4,5], the Raindrop® (ReVision Optics, Lake Forest, CA, USA) [1,5,6], and the small-aperture corneal inlay (SACI) whose trade name is KAMRA® inlay (Acufocus, Inc., Irvine, CA, USA) [1,5,[7][8][9][10]. The principle of operation of each model is different.…”

“…Surgically, it is introduced at a depth of 200 μm. The SACI is the most successful commercial CI and has been widely studied both clinically and theoretically [1,5,[7][8][9][10]. However, it has certain drawbacks.…”