Intracorneal Inlays – Special Focus on the Raindrop

US Ophthalmic Review, 2014;7(2):123–30 DOI:


Presbyopia remains the last frontier for refractive surgeons. With increased demand for spectacle independence at all ages, ophthalmologists are exploring different approaches for presbyopia correction. The idea of adding synthetic material to the cornea for the management of presbyopia has come a long way since its inception. The Raindrop® (ReVision Optics®), KAMRA™ Inlays (AcuFocus™) and the Flexivue Microlens™ (Presbia™) are three very different inlays that attempt to reverse presbyopia through different mechanisms. The Raindrop changes the curvature of the anterior cornea in the plane of the pupil, the Kamra uses the principle of the pinhole to increase depth of focus, while the Flexivue is a refractive annular add lenticule that creates a paracentral zone for near vision. The decreased incidence of complications, ease of insertion, reversibility and potential applicability to patients with various refractive statuses make inlays a powerful addition to the armamentarium in the management of presbyopia.

Keywords: Corneal inlays, presbyopia, Raindrop, review
Disclosure: José L Güell and Omar A Barrada have no conflicts of interest to declare. No funding was received in the publication of this article.
Received: January 10, 2014 Accepted March 19, 2014
Correspondence: José L Güell, Director, Cornea and Refractive Surgery Unit, Instituto Microcirugia Ocular of Barcelona, C/ Josep Mª Lladó 3, 08035 Barcelona, Spain. E:

Patient demand for spectacle independence is growing. The advances in laser and non-laser technology have allowed ophthalmologists to offer their patients the freedom to choose between depending on their glasses, or to go spectacle free. Presbyopia, defined as the age-related loss of the ability to clearly accommodate onto near objects, has become the last frontier for refractive vision correction.

The complexity and illusiveness of presbyopia necessitates the ophthalmologist to tackle its pathology in different ways. Corneal, lenticular and even scleral approaches have been previously explored in an attempt to reverse this age-related phenomenon. Corneal monovision and presbyopic laser-assisted in situ keratomileusis (presbyLASIK) procedures give conflicting results. Monovision gives the patient near vision on the expense of far and binocular vision; while presbyLASIK requires further development in its nomogram in order to achieve consistent postoperative results.1–3 Conductive keratoplasty, a technique in which the cornea is moulded into a new shape using radiofrequency waves, has also been studied as an option for presbyopia treatment, with patients usually experiencing a large overcorrection followed by a significant regression of their refractive outcome overtime.4

Other procedures described in the management of presbyopia include scleral expansion and anterior sclerotomy techniques.5,6 Lens surgery with implantation of multifocal or accommodating intraoperative lenses (IOLs) have also shown to reduce dependence on reading glasses;7 however, risks associated with intraocular surgery, difficulty in lens exchange, biometric errors, patient dissatisfaction and loss in contrast sensitivity and photopic phenomena make them far from perfect.8 Also, there is an age bracket (40–50 years old) where patients might be experiencing presbyopia symptoms but still had not developed cataract, and in these patients lens surgery is probably less than ideal. Pseudophakic patients with monofocal IOLs are also not eligible for secondary lens implantation, and in these patients an intracorneal inlay might be a good option.

One of the earliest proposed methods for presbyopia correction is additive refractive keratoplasty. This term refers to procedures in which a foreign material is added to the corneal tissue to modify the refractive condition of the eye. Albeit this method is not new, recent advances in technology, its potential for reversibility and ease of application has made it a subject of great interest to ophthalmologists in recent years.9

As mentioned, intracorneal inlays are far from being a novel idea. José I. Barraquer performed experiments with corneal implants as early as 1949, although with unsatisfactory results.10 Since then, this refractive technology has undergone a series of improvements.

Early inlays were composed of flint glass and plexiglass for the correction of aphakia and high myopia. Earlier trials attempted to use poly(methyl methacrylate) (PMMA) and polysulfone inlays to treat high myopia.11 High index polymers were an optically attractive material choice; however, poor permeability limited their use. As a result, Barraquer developed human donor stromal lenticules for inlays (keratophakia) and onlays (epikeratophakia). Claes H Dohlman was the first to describe the use of a permeable lenticule in 1967.12 Hydrogel inlays were developed so as not to impede metabolic gradients across the stroma including nutrient flow to the anterior cornea. Although semipermeable hydrogel polymers allow free nutrient flow, they have a relatively low index of refraction and are therefore limited in optical power.

Past inlay designs include the Kerato-Gel™ (Allergan, Inc., Irvine, California), which was designed for aphakia and was composed of lidofilcon A. The Chiron inlay® (Bausch + Lomb, Rochester, New York) was a meniscus hydrogel optical lens that ranged from 1.50 to 3.50 diopter (D) in add power with a diameter ranging from 1.8 to 2.2 mm. The PermaVision Intracorneal Lens® (Anamed, Lake Forest, California) was composed of a hydgrogel-based material called Nutrapore with a water content of 78 %. This lens, measuring 5.0 to 5.5 mm in diameter with a central thickness of 30 to 60 μm, intentionally altered the anterior surface curvature. This was followed by the IntraLens (now ReVision Optics®, Inc., Lake Forest, California) in the evolution of space-occupying lenticules that intentionally altered the surface curvature to create a kind of multifocal cornea for the treatment of hyperopia and presbyopia. These technologies served as the precursor for the Raindrop inlay (formerly the Vue+ and PresbyLens, ReVision Optics, Inc.). The Intracorneal Microlens™ (BioVision AG, Brüggs, Switzerland) was a 3 mm diameter, 20 μm thick hydrogel annular add inlay with a central opening free of optical power that also allowed nutrient flow to the anterior central cornea. This inlay was designed for placement in a stromal pocket with a mechanical microkeratome pocket maker. The Microlens went on to be known as the InVue™, the precursor to the Flexivue inlay™ (Presbia Coöperatief UA, Amsterdam, the Netherlands ).13

  1. Epstein RL, Gurgos MA, Presbyopia treatment by monocular peripheral presbyLASIK, J Refract Surg, 2009;25:516–23.
  2. Braun EH, Lee J, Steinert RF, Monovision in LASIK, Ophthalmology, 2008;115:1196–1202.
  3. Alió JL, Amparo F, Ortiz D, Mopreno L, Corneal multifocality with excimer laser for presbyopia correction, Curr Opin Ophthalmol, 2009;20:264–71.
  4. Ehrlich JS, Manche EE, Regression of effect over long-term follow-up of conductive keratoplasty to correct mild to moderate hyperopia, J Cataract Refract Surg, 2009;35:1591–6.
  5. Malecaze FJ, Gazagne CS, Tarroux MC, Gorrand JM, Scleral expansion bands for presbyopia, Ophthalmology, 2001;108:2165–71.
  6. Qazi MA, Pepose JS, Shuster JJ, Implantation of scleral expansion band segments for the treatment of presbyopia, Am J Ophthalmol, 2002;134:808–15.
  7. Maxwell WA, Waycaster CR, D’Souza AO, et al., A United States cost-benefit comparison of an apodized, diffractive, presbyopia-correcting, multifocal intraocular lens and a conventional monofocal lens, J Cataract Refract Surg, 2008;34:1855–61.
  8. Woodward MA, Randleman JB, Stulting RD, Dissatisfaction after multifocal intraocular lens implantation, J Cataract Refract Surg, 2009;35:992–7.
  9. Barraquer JI, Modification of refraction by means of intracorneal inclusion, Int Ophthalmol Clin, 1966;6:53–78.
  10. Barraquer JI.Queratoplatica Refractiva.Estudios e informaciones, Oftalmologicas,1949;2:10.
  11. Deg JK, Binder PS, Histopathology and clinical behavior of polysulfone intracorneal implants in the baboon model. Polysulfone lens implants, Ophthalmology, 1988;95:506–15.
  12. Dohlman CH, Refojo MF, Rose J, Synthetic polymers in corneal surgery: glyceryl methacylate, Arch Ophthalmol, 1967;177:52–8.
  13. Waring GO, IV, Santhiago MR, The evolution of corneal inlays—Exploring the development of intrastromal inlays for the treatment of presbyopia, Cataract & Refractive Surgery Today, December 2011. Available at: crstodayeurope/2011/12/article.asp?f=the-evolution-ofcorneal- inlays (accessed March 27, 2014).
  14. Dohlman CH, Refojo MF, Rose J, Synthetic polymers in corneal surgery: glyceryl methacylate, Arch Ophthalmol, 1967;177:52–8
  15. Funderburgh JL, Mann MM, Funderburgh ML, Keratocyte phenotype mediates proteoglycan structure: a role for fibroblasts in corneal fibrosis, J Biol Chem, 2003;278:45629–37.
  16. Tanihara H, Inatani M, Koga T, et al., Proteoglycans in the eye, Cornea, 2002;21:S62–S69.
  17. Larrea X, De Courten C, Feingold V, et al., Oxygen and glucose distribution after intracorneal lens implantation, Optom Vis Sci, 2007;84:1074–81.
  18. Harvitt DM, Bonanno JA, Re-evaluation of the oxygen diffusion model for predicting minimum contact lens Dk/t values needed to avoid corneal anoxia, Optom Vis Sci, 1999;76:712–9.
  19. Hill RM, Fatt I, Oxygen uptake from a reservoir of limited volume by the human cornea in vivo, Science, 1963;142:1295–7.
  20. Yilmaz OF, Bayraktar S, Agea A, et al., Intracorneal inlay for the surgical correction of presbyopia, J Cataract Refract Surg, 2008;34:1921–7.
  21. Mulet ME, Alio JL, Knorz MC, Hydrogel intracorneal inlays for the correction of hyperopia: outcomes and complications after 5 years of follow-up, Ophthalmology, 2009;116:1455–60
  22. Seyeddain O, Riha W, Hohensinn M, et al., Refractive surgical correction of presbyopia with the acufocus small aperture corneal inlay: two-year follow-up, J Refract Surg, 2010;26:1–9.
  23. Yilmaz Ö, Alagöz N, Pekel G, et al., Intracorneal inlay to correct presbyopia: long-term results, J Cataract Refractive Surg, 2011;37:1275–81.
  24. Limnopoulou AN, Bouzoukis DI, Kymionis GD, et al., Visual outcomes and safety of a refractive corneal inlay for presbyopia using femtosecond laser, J Refract Surg, 2013;29:12–18.
  25. Chayet A, Barragan Garza E, Combined hydrogel inlay and laser in situ keratomileusis to compensate for presbyopia in hyperopic patients: one-year safety and efficacy, J Cataract Refract Surg, 2013;39:1713–21.
  26. Barragan Garza E, Gomez S, Chayet A, Dishler J, One year safety and efficacy results of a hydrogel inlay to improve near vision in patients with emmetropic presbyopia, J Refractive Sur, 2013;29:166–72.
Keywords: Corneal inlays, presbyopia, Raindrop, review