Intracorneal inlay for presbyopia yields promising early results
A new implant prototype reduced spectacle dependence and did not adversely affect distance vision.
Donald T.H. Tan
A new intracorneal implant for presbyopia achieved promising clinical outcomes and high patient satisfaction in initial commercial implantations in Singapore, according to a study.
At a joint symposium of the ESCRS, APACRS, ASCRS and LASCRS at the European Society of Cataract and Refractive Surgeons meeting in Barcelona, Donald T.H. Tan, MBBS, FRCSG, FRCSE, FRCOphth, OSN Asia-Pacific Edition Board Member, described initial implantations of the KAMRA intracorneal inlay, formerly the AcuFocus intracorneal inlay, in 15 patients in Singapore in June.
The take-home message is that our studies and results in commercial patients have established an excellent safety and efficacy profile with KAMRA, which is also borne out by the other study sites, Prof. Tan told Ocular Surgery News in a subsequent interview. Our patients have high satisfaction, and we believe that KAMRA today represents one of the best means of presbyopia correction currently available, especially with regard to potential upgrading and reversibility of the technology. Of course, more long-term data and more patients are needed as we progress in our goal to solve presbyopia.
The intracorneal inlay device retained 20/20 distance visual acuity in all patients within a few days after implantation. It was easily implanted using current bladeless LASIK technologies and did not adversely affect distance visual acuity in the implanted eye. All patients maintained stereopsis after implantation.
I believe this device and technology is in pursuit of perfection, Prof. Tan said at the meeting.
Indications and specifications
The device may be implanted alone in the nondominant eye or in combination with refractive surgery. It is implanted through a femtosecond laser-created pocket or LASIK flap. It achieves presbyopic correction through a pinhole effect. At only 5 µm thick, equal to a corneal endothelial cell, the device stays in place, Prof. Tan said. It can be removed and potentially upgraded.
Indications for simultaneous bilateral LASIK and unilateral intracorneal inlay implantation are presbyopia with myopia and/or astigmatism and spectacle dependence.
Although we have not performed this in hyperopes yet, as we have far less hypermetropia in Asian eyes, we do intend to perform this on hyperopes as well, Prof. Tan told OSN. The clear advantage will be almost complete independence from spectacles.
Contraindications include forme fruste keratoconus and dry eye, the customary contraindications for corneal refractive surgery. Intracorneal inlay implantation is performed in accordance with LASIK flap thickness and corneal thickness protocols, he said.
For combined cases with LASIK, we still respect the absolute residual stromal bed depth of at least 300 µm, as in normal LASIK, and as the flap required for KAMRA implantation is in the region of 190 µm to 200 µm, that provides an additional corneal thickness limit accordingly in the eye to be implanted with KAMRA, Prof. Tan said.
Benefits and potential risks
Early results showed improvements in near visual acuity, Prof. Tan said. Preoperatively, mean near vision was J8. Postoperatively, mean near visual acuity was J3 at 1 week and J2 at 1 month. Distance acuity remained unchanged, Prof. Tan said.
Improving visual outcomes in the early postoperative period may be attributed to neural adaptation and the need to adjust to reading with the nondominant eye only. Additionally, almost all patients found that the implant did not impede binocular distance vision, as they still retained good distance vision in the implanted eye, Prof. Tan said.
Most importantly, we have seen that all patients maintain binocularity and stereoscopic vision, unlike monovision, he said. As one can expect from these results, patient satisfaction remains high, especially as we explain the initial period of adaptation required.
In September, three additional patients with myopia, astigmatism and presbyopia underwent implantation in a combined procedure. Patients underwent a simultaneous bilateral femtosecond LASIK treatment in conjunction with unilateral implantation of the intracorneal inlay device in the nondominant eye.
I was able to review them at 1 day postop, and the most important early parameter was distance vision, and all of them were 20/20, Prof. Tan said during his presentation.
Potential complications of intracorneal inlay implantation include intermediate or long-term haze, Prof. Tan said.
We havent seen any of that, fortunately, with this newer version of the device, he said.
Other potential disadvantages include postoperative dry eye, but the femtosecond laser-created pocket reduces some potential effects of dry eye, Prof. Tan said.
No intraoperative or postoperative complications have occurred in commercially treated patients, including those with combined LASIK and implant surgery, he said. by Matt Hasson and David W. Mullin
- Donald T.H. Tan, MBBS, FRCSG, FRCSE, FRCOphth, can be reached at Corneal and External Eye Disease Service, Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore 168751; +65-6227-7255; fax: +65-6323-1903; e-mail: firstname.lastname@example.org. AcuFocus has funded previous clinical trials run by Prof. Tan but not the one discussed here.