IMPROVING PRESBYOPIA

Implantation of a small aperture cornea inlay (KAMRA, AcuFocus) into a femtosecond laser-created lamellar pocket provides emmetropic presbyopes with near and intermediate vision improvements that are remaining stable through lengthening follow-up, reported Daniel S Durrie MD, at the XXX Congress of the ESCRS. Dr Durrie is an investigator in the prospective, international study evaluating “Pocket Emmetropia KAMRA†(PEK), a presbyopia-correcting procedure for emmetropic patients in which the small aperture corneal inlay is placed in the non-dominant eye. He reported results from follow-up to two years in the study that enrolled 507 patients at 24 sites in the US, Europe and Asia.

The PEK study enrolled patients who were naturallyoccurring presbyopic emmetropes with a spherical equivalent between -0.75 and +0.5 D and no history of refractive surgery. Other inclusion criteria required patients to have near UCVA that was worse than 20/40 and better than 20/100 along with BCDVA of 20/20 or better in both eyes. All patients received the most recent version of the small aperture inlay, which is five microns thick with 8,400 random holes and measuring 3.8mm in diameter with a 1.6mm central aperture. Depth of the pocket for inlay placement was ~200 microns, and all of the procedures were done prior to the availability of technology for intraoperative centration guidance (AcuTarget, SMI). The inlay was positioned based on marking the first Purkinje reflex on the epithelium preoperatively.

Mean near UCVA in the inlay eye was about 20/63 at baseline, improved by an average of 3.2 lines to about 20/32 (J2) at one month and remained unchanged over time. Intermediate vision in the inlay eye was also improved at one month by an average of about 1.5 lines, and the benefit remained stable throughout follow-up, with mean intermediate vision being about 20/25 at 24 months. The procedure resulted in a slight hyperopic shift in mean MRSE (~+0.2 D), and mean distance UCVA in the inlay eye decreased slightly. However, mean distance UCVA remained 20/20 in the inlay eyes at 24 months and was stable in binocular testing at 20/16 throughout follow-up. Mean BCVA was also unchanged throughout follow-up and was 20/20 or better in all inlay eyes and 20/16 binocularly at 24 months.

“Additionally, the gains in near and intermediate vision are stable, with data from some investigators showing the improvements are maintained during follow-up extending to at least four years. This long-term efficacy is a nice advantage of PEK compared with other options for presbyopia correction and may be explained by the inlay’s mechanism. By increasing depth of focus, the inlay can compensate for some of the age-related worsening of near vision, at least for some time,†said Dr Durrie, professor of ophthalmology, University of Kansas Medical Centre, Kansas City, and president, Durrie Vision, Overland Park, KS.

Data for contrast sensitivity testing was available from follow-up at 12 months for 479 eyes and the results showed preservation of function under both mesopic and photopic conditions. “PEK is a straightforward and simple procedure that is accessible to most refractive surgeons using equipment they already have. And for patients, PEK is a unique presbyopiacorrecting procedure that improves near and intermediate vision occur without compromising distance vision, contrast sensitivity or stereopsis,†he commented.

Dr Durrie noted that with its large patient population and some diversity in patient characteristics and equipment used, the PEK study allowed for subgroup analyses to investigate factors predicting outcomes. With eyes stratified by preoperative refractive error, results showed that those with slight myopia, in the range of -0.5 to -0.75 D, had the best results for near as well as for distance vision.

Differences also emerged comparing groups of eyes having pocket creation done using different femtosecond lasers. Three platforms were used across the study sites – the IntraLase FS60 (Abbott Medical Optics), iFS (Abbott Medical Optics), and Femto LDV (Ziemer). Vision results were best in eyes where the pocket was made with one of the more advanced lasers that uses a tighter spot/line separation, either the iFS or Femto LDV, and there was also a benefit for faster vision recovery. The outcomes analyses indicated that the optimal spot/line setting was 6x6 or less. Among eyes operated on with lasers using this setting, mean near UCVA improved from 20/63 at baseline to 20/25 at 12 months and mean distance UCVA was unchanged from the baseline level of 20/20, Dr Durrie reported.

“The smoother surface obtained using the newer generation lasers with the tighter spot/line separation provides better optics that explains the better vision results. This technology also results in less of a wound healing response, which accounts for the faster rehabilitation,†he said.

Pocket vs. flap

A drawback of placing the small aperture corneal inlay into a lamellar pocket instead of underneath a flap is that the pocket procedure does not allow for simultaneous laser vision correction of refractive error. The patients that qualify for the pocket procedure fall into three groups. Plano presbyopes like the patients included in this study, pseudophakic patients that are close to plano and post LASIK and PRK patients who are now developing presbyopia. There are several advantages of using a pocket for inlay placement, said Dr Durrie.

“Cutting of a pocket involves less energy delivery to the cornea, severs fewer corneal nerves, and better maintains corneal strength since there is less extensive corneal fibre dissection. In addition, there is reduced chance for causing topographic changes using the pocket technique, and it also enables more accurate inlay centration by allowing better visualisation of the surface marking of the first Purkinje image,†he explained.