This article on corneal inlays by Dr Dan Durrie was featured in this month’s EyeWorld magazine. Dr Durrie describes the evolution of corneal inlays, culminating in the development of the most advanced version, the KAMRA inlay from AcuFocus.

Clarity for KAMRA

by Daniel S. Durrie, M.D.

The KAMRA corneal inlay Source: AcuFocus

The AcuFocus KAMRA inlay for the treatment of presbyopia Source: Perry S. Binder, M.D.
The KAMRA corneal inlay by AcuFocus (Irvine, Calif.) is gaining traction as a great option for treating presbyopia in markets that have access to it, such as Europe, the Middle East, and Asia-Pacific. The inlay works based on the principle of small aperture optics and provides improved depth of focus to improve near vision while having minimal impact on distance vision. The KAMRA inlay is the result of decades of study on corneal inlays. Jose Barraquer is accredited to be the first to experiment with corneal implants in 1949 (1).

A series of improvements took place, but early generations of inlays suffered from poor predictability, loss of acuity over time, haze, corneal thinning, and decent ration.(2-4) The development of new biocompatible materials and experimentation with optimal placement, however, have changed the history of corneal inlays and the treatment of presbyopia. I first started working with hydrogel inlays to correct aphakia in 1985. The porous nature of the hydrogel material made these well tolerated by the cornea, whereas inlays made out of polysulfone caused corneal thinning and melting due to their poor permeability. This was one of the first indications that in order for an inlay to be tolerated by the cornea, the biological principals of the cornea must be maintained. That includes an inlay of material that allows glucose to go through the cornea and nourish the corneal epithelium.

The KAMRA inlay has gone through six design iterations, starting with the original design that was made from Dacron fabric and was 25 microns thick. Over time, the platform has transitioned to polyvinylidene fluoride, a highly biocompatible material that is used routinely in IOL haptics. Further, the inlay has been reduced in size to just 5 microns thick in the current design. The number of microperforations has increased from 1,600 to 8,400, and these are arranged in a pseudorandom pattern to allow for appropriate nutrient flow and to minimize light scatter. Although melts occurred in a prior generation of inlay and with an earlier procedure, to date there have been no flap melts in the current clinical trial that will be submitted for approval next year.

In addition to the evolution in materials and design, numerous clinical studies over the past 7 years have led to the optimal depth placement in the cornea. Early studies demonstrated that shallow placement of the inlay has the potential to create some stress on the cornea, causing corneal shape change and thinning and ultimately resulting in an explant of the inlay. After performing a series of studies we also found that if the inlay was implanted too deeply, we had much lower visual recovery. The inlay should be implanted at an optimal depth of 200 microns. When kept at this depth, the cornea tolerates the inlay very well.

Development in other areas of ophthalmology has also aided in the advances in the corneal inlay procedure. The femtosecond laser allows surgeons to program what they want, and then it is executed with precision. This permits them to not only control the depth, but also the configuration of the incision. The precision of the laser allows us to make pockets at certain locations in the cornea, aiding with centration.

Another new technology now in use, the AcuTarget System, provides surgeons with real-time inlay placement guidance within 100 microns of the intended placement location, as well as objective placement assessment post-op. This surgical aid has the potential to reduce procedure time, resulting in quieter eyes in the immediate post-op period. In addition to historical data dating back to the 1960s, in-depth, international, multicenter clinical trials have provided evidence of the safety and efficacy of the KAMRA corneal inlay. With the transition from an investigational product for many years to a commercially available product outside of the U.S., there are now over 8,000 inlays implanted in Japan, Australia/New Zealand, Europe, the Middle East, and South America, without any corneal thinnings and with good patient satisfaction.

References

1. Barraquer JI. Queratoplatica Refractiva. Estudios e informaciones Oftalmologicas. 1949;2:10.
2. Deg JK, Binder PS. Histopathology and clinical behavior of polysulfone intracorneal implants in the baboon model. Polysulfone lens implants. Ophthalmology. 1988;95:506-515.
3. Alió JL, Mulet ME, Zapata LF, Vidal MT, De Rojas V, Javaloy J. Intracorneal inlay complicated by intrastromal epithelial opacification. Arch Ophthalmol. 2004;122:1441-1446.
4. Choyce P. The present status of intracameral and intracorneal implants. Can J Ophth.1968;3:295-311.

Editors’ note: Dr. Durrie has financial interests with AcuFocus.

Contact information

Durrie: 913-491-3330, ddurrie@durrievision.com

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The KAMRA Inlay is a breakthrough in correcting the need for reading glasses, and is now our primary treatment for anyone aged 45 upwards. You can read an article from yesterday’s London Evening Standard all about KAMRA. It features Karen who had the Keyhole KAMRA version, where no LASIK-type flap is created, and the inlay is simply inserted into a tiny pocket through a keyhole entrance. Unlike LASIK, there is no significant dry eye and the patient could even rub their eyes afterwards without risk of dislodging anything.

You can see the full article here: www.thisislondon.co.uk/standard/article-24014966-london-clinic-develops-10-minute-operation-to-freeze-failing-eyesight.do

You can learn more about KAMRA and presbyopia here at KAMRAvision.com

Anthony asked:

Hi Dave
I am 67 years old and currently use daily contacts. Left eye D + 1.50 Right D + 1.75, the left eye has a slight astigmatisum. I use + 2 reading glasses. I have been told that due to some mild furring around the edges of the cornea, expected at my age, I will need Intra – Ocular Lenses, one for long distance and one for reading. Also I have some dryness in both eyes, again expected at my age.
Do you think I am too old and would Z-Lasik be able to correct my vision in both distance and reading or just distance. I live in London so travelling to Wimpole Street is not a problem should I decide to have a consultation.

My reply was:
Hi Anthony, Certainly not too old, and I have done blended vision for patients in their 70s. All depends on the condition of your natural lenses and presence of any cataracts. Sometimes IOLs can be the better choice but not always. Your prescription is certainly in range of those I treat for correcting distance and near. Dryness can be assessed and treated if not too bad. If severe, would likely be a block to laser eye correction, but not to IOLs.

We can certainly have a look at consultation with one of my team as a first step. Price wise, the IOLs are the more expensive option, at £2,500-3,000 per eye, the latter being if you opt for multifocal lenses to help with reading and distance. Laser blended vision is £2,200 per eye, again correcting far and near.

Peter asked:

I had laser eye surgery in 1995 for short sightedness. Long distance has become blurred e.g. night driving affected. Will naturally occurring long sightedness change this over time I’m 47?

Peter, you have become somewhat myopic (short-sighted) again, either through progression of your condition (can be associated with high amounts of near work, although that story is not straight-forward), or regression of your treatment, or both combined.
At 47, most people will be showing signs of presbyopia, or age-related loss of near vision. Your myopia will mask those symptoms if you are not wearing glasses or contact lens correction, and so in fact is of some benefit to you. Your presbyopia will have minimal effect on your distance vision though, and will not neutralize it. One option is to get one eye retreated to fix the distance and get a blended vision combination, and so see well for far and near. Will depend on your current prescription though.

Liz asked:

Hello, I do not suffer with headaches etc but I do have to be at least a 12 inches away to be able to for example focus on the smallest words of this website. Any nearer and the words are out of focus but I can read them at a distance. How much would it be for you to correct this to at least 20/20 vision please? Many thanks, Liz.

Liz, you have presbyopia so reading vision is getting blurry, but the distance vision remains clear. This happens to everyone starting in their 40s. Sometimes only one eye needs to be treated if there is no distance glasses prescription, which is about 15% of presbyopic patients. Presbyopic treatments need to be performed very accurately and choice of surgeon (and technology) becomes even more important that in myopia correction (distance vision, short-sight). The cost at Focus is £2,200 per eye. Regards, Dave

Nicholas asked:

Hi Dave, my wife had a consultation about having a laser treatment, because she got fed up of wearing varifocal glasses. She was told that she will still have to wear reading glasses, although they will perform the wavefront laser technique. Her age is 55. They said over the age of 45 you might still need reading glasses. What is your opinion on this please?

Hi Nicholas, LASIK blended vision can correct both distance and near vision, and so reduce or eliminate the need for reading glasses. I know of only two clinics that specifically offer LASIK blended vision. Expect to pay around £2000-2300 per eye. If you only want distance corrected, all laser clinics will offer that.

Gill asked this question about laser eye surgery for varifocal and reading glasses:

Dear Mr Allamby, I was told last year by my optician I would benefit from varifocal lenses, which I hate. My prescription was:
R: Plano (zero) /-2.75 x 180
L: Plano (zero) /-1.25 x 175
Near Add: +1.50D
I am 51 years old. I had a consultation for corrective surgery and told I only need right eye done. Is this correct and how much would this be likely to cost at Focus? Thank you, (brilliant and most helpful blog by the way)
Gill

Hi Gill, You have myopic (short-sighted) astigmatism, with mild astigmatism in the left eye and a moderately higher amount in the right. Additionally, at age 51 you also have presbyopia, which is an age related loss of near vision (itself a form of long-sight). So you have three eye conditions together – myopia, astigmatism and presbyopia, which all need correcting (!) if you want to be pretty independent of glasses. However, correction is certainly possible.

I specialise in correcting these kind of prescriptions, over the last 7-8 years, and have done thousands of cases. I would need to assess which is the dominant eye and correct that eye fully. However, contrary to what the other clinic said, leaving astigmatism in the eye which is to read rarely is successful. So with your prescription I almost always treat both eyes. Of course, everything depends on what we find at the consultation, but this will give you a strong idea of what you likely need.

I charge just under £4,000 for both eyes for wavefront Ziemer Z-LASIK. If you want me personally to do your initial consultation rather than one of my team, add £200. The blended vision presbyopia treatments will be increasing soon, likely to £4,400 for both eyes.

Hope that helps explain somewhat Gill. If you post on the comments below, your reply will also come to me.

Live video of Paul Ross having his laser eye surgery on the ‘This Morning’ TV show.

Fern Britten and Philip Schofield interview Paul Ross and Dr. Dave Allamby about laser eye surgery.

You can see more information in the first featured article above on how laser eye surgery is now used to correction problems with reading vision.

Most people start to need reading glasses after the age of 45 and previously were not eligible for laser eye treatment. All that has changed with advances in technology. FOCUS Laser Vision has been very active in this increasingly popular area of laser eye correction.

TECHNOLOGY that has become available over past two years means that reading vision problems can now be very effectively addressed through laser eye treatment. Although at present only a few clinics specialise in this area, it is the fasting growing section of the laser vision arena.

FOCUS Laser Vision specialises in the correction of loss of reading vision, either through advanced LASIK laser eye surgery or through the use of lenses inside the eye (IOLs)

Several approaches to LASIK are showing promise in the treatment of reading vision problems (presbyopia) for patients with otherwise normal distance vision, or long or short sight, according to studies presented at the 12th Winter Refractive Meeting of the ESCRS.

In research presented by Kenneth A Greenberg MD, all patients achieved good distance vision of 20/25 or better and were able to read telephone directory sized print, 12 months after undergoing customised LASIK treatments. The multicentre study involved 28 presbyopic long-sighted patients with an average age of 56 years.