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Corneal Inlays to Correct Presbyopia

Dr. Ravi Singh | 29 May 2017
Presbyopia affects all individuals at some point in their lifetime and traditionally, spectacles have been used to manage the condition. Corneal inlays are novel devices implanted within the corneal stroma to surgically correct presbyopic symptoms.

Monovision has commonly been used to maximise spectacle independence for presbyopic patients – with either a contact lens, laser refractive surgery or lens extraction surgery. While often effective, the induced anisometropia is not always tolerated by patients and can be associated with loss of stereoacuity and binocularity.1,2 Lens extraction surgery with multifocal intraocular lens implantation (in all of its platforms) is also an effective option but involves more invasive surgery and potential symptoms from glare, haloes and loss of contrast sensitivity.3,4,5 Multifocal contact lens wearers experience similar problems as well as other limitations, in addition to the risks associated with contact lens wear.6

This has led to the development of corneal-based approaches to presbyopia correction, which reduce or eliminate the need to create potentially intolerable anisometropia as with monovision, and avoid intraocular surgery.

Corneal Inlays

Corneal inlays are devices implanted within the corneal stroma. Their aim is to modify the optical properties of the cornea to create uniocular multifocal vision while maintaining binocular vision. They are typically implanted unilaterally in the non-dominant eye while having the dominant eye emmetropic for optimum distance clarity.

In Australia, there are three commercially available inlays for correcting presbyopia, all with differing optical principles. The KAMRA Vision (Acufocus Inc., Irvine CA, USA) has been available for the longest duration and been most studied. It relies on pinhole optics for correcting near vision. Raindrop (ReVision Optics Inc., Lake Forest, CA, USA) creates a hyperprolate central cornea, which acts as a near add, with the cornea peripheral to this zone focusing distance images on the retina. The Flexivue Microlens (Presbia Cooperatief U.A., Amsterdam, Netherlands) is a bifocal lens implanted within the cornea. All devices are implanted within the corneal stroma under a laser assisted keratomileusis (LASIK) flap or inside a corneal stromal pocket, at varying depths, all created with a femtosecond laser.

KAMRA Vision

The Acufocus KAMRA Vision device is a polyvinyl disc measuring 5µm thick with a diameter of 3.8mm and a central 1.6mm aperture (Figure 1 and 2). The surrounding skirt has 8,400 laser etched perforations to allow diffusion of nutrients within the corneal stroma.7

The pinhole aperture increases depth of focus for the eye, allowing clarity of image over a range of distances, including near vision. The implants were originally implanted under a LASIK flap at a depth of 150–200µm but later transitioned to being implanted with a femtosecond laser-created pocket at a similar depth for added refractive stability. A refraction in the implanted eye of –0.75 dioptres was recommended to be ideal for optimum near focus without compromising distance vision.

Clinical Results

There have been a number of publications on KAMRA efficacy and safety. The largest study by Waring et al (n=507, age range 45–60yrs) in emmetropic eyes was multicentre with follow up at 18 months of 99 patients. Mean uncorrected near visual acuity (UNVA) improved from J8 to between J2–J3 at 18 months. Mean intermediate visual acuity (MIVA) improved from 20/35 to 20/26 at 18 months. Mean uncorrected distance visual acuity (UDVA) was reported to be 20/20 in the implanted eye at 18 months but this was recorded as reduction compared with preoperative UDVA. No implants were explanted. Contrast sensitivities were found to be reduced in the implanted eyes but reported to be within normal limits.8

The second largest study by Tomita et al involved 223 eyes (mean age 52, range 41–65) and reported simultaneous LASIK for ammetropia and KAMRA implantation targeting –0.75D in the implanted eye and plano in the dominant eye. Mean UNVA improved from J8 to J2 at six months follow up.9 No significant complications were recorded. A patient questionnaire for daily tasks also showed improvement in patients’ level of function for near tasks.

Igras et al reported a series of 132 ammetropic eyes, which were treated with LASIK as needed, targeting plano in the dominant eye and -0.75D in the non-dominant eye (200µm flap thickness), and implanting the inlay just prior to flap repositioning. Median age was 56 years (range 44–68). Mean UNVA improved from J13 preoperatively to 97 per cent achieving UNVA J3 or better at 12 months, with mean UDVA of 20/25 at 12 months. Two implants were explanted, one for lack of visual adaptation to the implant, the other from hyperopic shift.10

Hyperopic shift due to interface oedema in the pocket has been reported to occur and is usually treatable with topical steroid therapy. There was no loss of vision seen from the above implant-explanted eyes.

The author of this review reported (unpublished data) 29 eyes implanted with KAMRA under a LASIK flap with simultaneous LASIK and target refraction of -0.75D. At follow up, 97 per cent UNVA was greater than J5, 75 per cent greater than J3 and 50 per cent greater than J2. Three implants were explanted, two for maladaptation and one for persistent hyperopic shift not responsive to topical steroids. No loss of CDVA occurred. (Data presented at the Australasian Society of Cataract and Refractive Surgeons meeting 2015).

Age analysis of KAMRA patients’ results showed that all age groups benefited from KAMRA implantation but satisfaction was especially high in the 60–65 year age group, likely representing their long standing dependence of reading glasses.11 Additionally, pupil size was not found to affect the clinical outcomes of surgery.12 Normal visual fields post implantation, and adequate retinal examination, have also been demonstrated following KAMRA implantation.13

Raindrop

Raindrop is a space occupying meniscus shaped hydrogel lens that is implanted in the visual axis in the superficial corneal stroma (Figure 3). It has the same refractive index as the corneal stroma. It induces a hyperprolate central cornea that acts as a near add while the area around this acts as an intermediate vision zone and the peripheral cornea acts for distance vision. It is implanted in a cornea under a LASIK flap at the midpoint of the light constricted pupil (Figure 4) at a depth of 150µm where a residual bed thickness of 300µm is available. Where the corneal thickness is 500-600µm, it is implanted at one-third the corneal depth.

Clinical Results of Raindrop

One year Food and Drug Administration (FDA) data for 373 emmetropic presbyopic patients with mean age 51.3±4.3 having undergone Raindrop implantation have been published.14 UNVA was 20/25 or better in 93 per cent of patients, UIVA was 20/32 or better in 97 per cent of patients and 95 per cent had UDVA of 20/40 or better. Contrast sensitivity loss was seen at the higher spatial frequencies but not observed binocularly. No patients lost two or more lines of Snellen visual acuity.

In terms of glare and haloes, 95.9 per cent of patients reported them to be mild or absent. The satisfaction score for unaided near vision tasks preoperatively was 56±26 (0=complete dissatisfaction, 100=complete satisfaction) and was 83±22 postoperatively at follow up.

Central corneal haze anterior to the implant was detected in 14 per cent of patients and resolved, with or without topical steroids, in all but one patient who had their inlay explanted with final corrected vision of 20/25. Haze development was seen more frequently in less deep implantation depths. A total of 11(2.9 per cent) of inlays were removed. Other reasons for removal were vision dissatisfaction in six patients (1.6 per cent), inlay misalignment in two patients and LASIK flap epithelial ingrowth in two patients. Vision recovered in the explanted eyes to 20/25 or better in all patients.

Another study performing simultaneous LASIK and Raindrop implantation in hyperopic presbyopic eyes showed similar improvements in near vision.15

Flexivue Microlens

The Flexivue Microlens is made from biocompatible acrylic material with an ultraviolet filter (Figure 5). It is transparent, 3.2mm in diameter, and has an edge thickness of 15µm. It has a central 0.51mm diameter hole to aid diffusion of nutrients, water and oxygen within the corneal stroma. The central 1.6mm has no power add (used for distance vision) while the peripheral zone has a different refractive index giving rise to a power add, ranging from +1.50 to +3.50D in 0.25D increments, customised for the patient (Figure 6).

The lens is implanted through a corneal pocket at a depth of 300µm and centered over the pre-marked visual axis.

Clinical Results

One study on 47 emmetropic eyes (mean age 52±4 years, range 45–60) found UNVA 20/32 or better in 75 per cent of eyes with 81.25 per cent of patients reporting high satisfaction at 12 months and 93.75 per cent independent of reading glasses.16 Mean UDVA however, decreased significantly from 20/20 preoperatively to 20/50, though binocularly UDVA was maintained. Higher order aberrations (HOA) were noted to increase in the operated eye and with this, contrast sensitivity reduction was also measured. No cases of corneal reaction were seen.

A more recent larger study of 81 emmetropic presbyopic eyes (mean age 50 years, range 44–63) found UNVA to be 20/25 in the treated eye at 36 months,17 UDVA worsened slightly from 20/20 preoperatively (logMAR 0.02 ±0.6) to 20/25 (logMAR 0.16+/0.08) at 36 months, though CVDA was maintained and binocular UDVA was also maintained compared with preoperative measurements. Loss of two lines of Snellen UDVA was seen in 19 per cent but no loss of CDVA was seen. No corneal stromal reaction was observed around the implant. Six implants (12.8 per cent) were explanted for bothersome glare, haloes or reduction in UDVA. Overall 9 per cent reported mild glare and 91 per cent reported nil glare symptoms. Of the patients who maintained their implant at 36 months, all reported satisfaction with their near vision.

A statistically significant reduction in contrast sensitivity was seen at higher spatial frequencies as well as in increase in HOA, including spherical aberration.

Conclusion

Corneal inlays are a safe and effective surgical modality for managing presbyopic symptoms. They represent another option to monovision or intraocular lens surgery. They are especially attractive for patients who are intolerant of monovision and do not want to undergo intraocular lens surgery. Presbyopic emmetropes may also benefit from the minimal loss of UDVA in their non-dominant eye.

The inlay procedures would appear to be safe and reversible in the small percentage of patients’ eyes that did not adapt to them. They are a promising technology and represent another tool for surgically managing presbyopia. The choice of implant will likely come down to surgeon preference and experience as all appear to be similar in efficacy and safety. As ever in refractive surgery, there may be more than one surgical approach for patients wishing to undergo refractive surgery and each patient will need to have their options carefully explained and tailored individually to them.

Dr. Ravi Singh MBBS (Syd) FRANZCO is an Ophthalmologist based in Newcastle, Australia. His principal areas of clinical interest are cataract, refractive and cornea surgery as well as eyelid surgery. He graduated from Medicine at the University of Sydney and undertook Ophthalmology training at the Sydney Eye Hospital. He then undertook a Cornea and Refractive Fellowship in the UK under Professor Harminder Dua in Nottingham,UK  followed by an Oculoplastic Surgery fellowship with Dr Jane Olver in the London, UK.
In addition to  private practice he is a VMO and Unit Director for Ophthalmology at the John Hunter Hospital and Senior Lecturer in Ophthalmology at the University of Sydney where he tutored in Refractive Surgery. Dr. Singh is also a board member of the Hunter Postgraduate Medical Institute, the peak teaching body in the Hunter area.

References
1. Ito M, Shimuzu K, Amano R, Handa T. Assessment of visual performance in pseudophakic monovision. J Cataract Refract Surg 2009;35:710-14
2. Finkelman Y, Ng J, Barrett G. Patient satisfaction and visual function after pseudophakic monovision. J Cataract Refract Surg 2009;35:998-1002
3. Wilkins M, Allan B, Rubin G et al. Randomized trial of multifocal intraocular lenses versus monovision after bilateral cataract surgery. Ophthalmology 2013;120:2449-55
4. van der Linden J, van Velthoven M, van der Meulen I et al. Comparison of new generation sectoral addition multifocal intraocular lens and a diffractive apodized multifocal intraocular lens. J Cataract Refract Surg 2012;38:68-73
5. van der Linden J, van der Meulen I, Mourits M, Lapid-Gortzak R. Comparison of hydrophilic and a hydrophobic apodized diffractive multifocal IOL. Int Ophthalmol 2013;33:493-500.
6. Kollbaum P, Dietmaier B, Jansen M, Rickert M. Quantification of ghosting produced with presbyopic contact lens correction. Eye Contact Lens 2012.;38:252-9.
7. Ostrin L, Glasser A. Accommodation measurements in a presbyopic population. J Cataract Refract Surg 2004;30:1435-44.
8. Waring GO 4th. Correction of presbyopia with a small aperture inlay. J Refract Surg 2011;27:842-5.
9. Tomita M, Kanamori T, Waring GO 4th et al. Small aperture corneal inlay implantation to treat presbyopia after laser in situ keratomileusis. J Cataract Refract Surg 2013;39:898-905.
10. Igras E, O’Caoimh R, O’Brien P, Power W. Long term results of combined LASIK and monocular small aperture corneal inlay implantation. J Refract Surg 2016;32(6): 379-384
11. Tomita M1, Waring GO 4th2. One-year results of simultaneous laser in situ keratomileusis and small-aperture corneal inlay implantation for hyperopic presbyopia: comparison by age. J Cataract Refract Surg. 2015 Jan;41(1):152-61.
12. Tomita M, Kanamori T, Waring GO 4th, Huseynova T. Retrospective evaluation of the influence of pupil size on visual acuity after KAMRA inlay implantation. J Refract Surg. 2014 Jul;30(7):448-53.
13. Seyeddain O, Hohensinn M, Riha W, et al. Small-aperture corneal inlay for the correction of presbyopia: 3-year follow-up. J Cataract Refract Surg 2012; 38:35–45.
14. Whitman J, Dougherty P, Parkhurst G, Olkowski J. Treatment of presbyopia in emmetropes using a shape changing corneal inlay. Ophthalmology 2016;123:466-475.
15. 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.
16. Limnopoulou AN, Bouzoukis DI, Kymionis G et al. Visual outcomes and safety of a refractive corneal inlay for presbyopia using femtosecond laser. J Refract Surg 2013;29:12-18.
17. Malandrini A, MArtone G, Menabuoni M, Catanese et al. Bifocal refractive corneal inlay implantation to improve near vision in emmetropic presbyopic patients. J Cataract Refract Surg 2015;41:1962-1972.

  • Figure 2. Size of KAMRA compared to a standard soft contact lens
  • Figure 3. Raindrop in situ: a faint outline of the implant is visible in the central pupil area
  • Figure 4. Cross section and picture of Raindrop implant under a LASIK flap
  • Figure 5. Slit lamp picture of Flexivue lens insitu
  • Figure 6. Diagram of dimensions and layout of flexivue lens
  • Figure 1. Schematic diagram of KAMRA implant showing laser etched perforation in skirt and central clear pinhole.

' In Australia there are three commercially available inlays for correcting presbyopia, all with differing optical principles '