Update on four technologies moving through phase III trials

Boston-With a host of studies reporting positive results for the surgical correction of presbyopia, optometrists can start to see these options become more widely available in the next decade, according to Steven H. Linn, OD. Dr. Lin reported on these emerging studies at the American Academy of Optometry's annual meeting.

Surgical methods for correcting presbyopia target different tissues and include scleral expansion techniques, LASIK procedures, femtosecond laser corneal and lens procedures, novel multifocal and accommodating pseudophakic IOLs, multifocal piggyback IOLs, and corneal inlays. Dr. Linn reviewed all of these technologies, but highlighted the following four as the ones to watch because they are farthest along in U.S. clinical development: PresView Scleral implant (Refocus Group), the Kamra corneal inlay (AcuFocus), the Synchrony dual-optic accommodating IOL (Abbott Medical Optics), and the Tetraflex accommodating IOL (Lenstec).

The PresView scleral implant employs the Schachar theory of presbyopia and accommodation. It aims to restore physiological conditions necessary for accommodation by expanding scleral tissue around the lens to increase the circumlental space. The circumlental space decreases with age as the crystalline lens increases in size. Enlarging this space surgically reduces crowding of the ciliary muscle around the lens to enable translation of a greater accommodative effect when the ciliary body contracts with near-focusing effort.

The implant, which acts as a spacer, is about the size of a grain of rice and elevates the sclera. The surgeon places this precisely into scleral tunnels created in four quadrants at a depth of about 400 µ in a procedure using a proprietary on-eye fixation system that acts as a guide for the scleratome. Each implant consists of two parts that lock into place.

A phase III trial of PresView is underway, with an estimated completion date of January 2013, Dr. Linn said. The phase II trial showed the average patient gained 3 lines of near acuity after 6 months and many benefited with a 5-line near vision improvement; 90% of patients reported their near vision was better or significantly better than at baseline, according to Dr. Linn. Data from the phase III study show 84% of patients achieved 20/40 near vision (J4 to J5) at 6 months, he noted.

"Scleral expansion approaches in general have benefits of providing true restoration of accommodation without affecting central vision or topography," Dr. Linn said. "They may decrease IOP to benefit glaucoma patients, and this technique involving implants is reversible. However, cosmesis is an issue because of the conjunctival hemorrhages, which take time to heal after the implant procedure."