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Presbyopia technologies compete for front-runner status
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NEW ORLEANS — Several promising refractive surgical procedures are vying for front-runner status in the competition for a safe and effective treatment of simple presbyopia. However, as is often the case with multiple competing technologies, no single method is completely effective. These technologies were discussed at the American Academy of Ophthalmology meeting here.
Australian refractive surgeon Noel Alpins, MD described the three principal techniques currently in either U.S. or international clinical trials.
“The first involves scleral expansion techniques such as anterior ciliary sclerotomy with refinements such as silicone or titanium expansion plugs that are sutured into place to reduce regression over time,” he said. “The second, laser presbyopia reversal (LAPR), is a technique analogous to the incisional technique with the ablative properties of the laser creating incisions under lifted conjunctival flaps. Finally, the mode of action of intrascleral segment surgery as described by Schachar is also purported to be by scleral expansion. All these techniques claim to improve accommodation by relative movement of the ciliary body that changes zonular tension in one way or another,” he said.
In November, Presby Corp. (Dallas) received Food and Drug Administration (FDA) approval to conduct expanded clinical trials of the scleral expansion band procedure (SRP). The expanded FDA study follows Presby’s FDA feasibility clinical trial surgeries conducted at six major universities during the past year, according to a press release. The SRP uses the Scleral Expansion Band (SEB), which is inserted just below the surface of the sclera while remaining well outside of the cornea. The SEB is injection molded from PMMA.
Observations on presbyopia
Many U.S. ophthalmic surgeons rely on monovision for presbyopia correction. “At present, with current U.S. limitations, monovision is my principal approach,” said Roger F. Steinert, MD, at the AAO Subspecialty Day Refractive Surgery meeting.
Dr. Steinert reported that a review of data from his LASIK patients older than 45 showed that 67% selected monovision and have been successful with it. “The principal downside to monovision is an increased rate of enhancement procedures in the distance eye, because the monovision patients are entirely dependent on that one eye for their distance vision and therefore are very critical of the quality of their LASIK result in the distance-corrected eye,” he said.
“As a cataract surgeon, one notices a proportion of patients who seem to gain near vision with a monofocal lens and coexisting emmetropia. The potential for a lens with enhanced ability to flex at the optic-haptic junction, such as C&C Vision’s AT-45 silicone lens with polyamide haptics, would seem to have the greatest potential to aid pseudophakia-induced presbyopia,” Dr. Alpins said.
Theoretically, ciliary muscle contraction reduces the volume available to the vitreous body, initiating the lens optic’s forward movement, aided by a hinge at the optic/haptic junction. “The mechanism would favor the likely forward movement of the lens by less than 1 mm. An implant of average power of about 20 D for a pre-cataract emmetropic eye would be needed to achieve an effective 2 D addition for near vision,” he said.
According to Dr. Alpins, the accommodative pseudophakic implant has many advantages over monofocal vision, including better depth perception.
“As the surgery is incorporated in conventional small-incision cataract surgery, it is likely to have the most rapid uptake of refractive cataract surgeons and the widest acceptance if it is shown to be consistent and effective. The procedure depends on stability of the haptics in the bag with established fibrotic reaction, with an optic well situated posteriorly in the capsular bag,” he said. Outcomes have been tracked for more than 1 year with promising results, Dr. Alpins said.
“The Allergan (Irvine, Calif.) SI18 looped lens acts on a similar principle to the AT-45. The progressive multifocal Array lens has multifocal properties but does not exploit the process of anterior movement of the lens on attempted accommodation. The patient can encounter difficulties with halos and night vision,” he said.
Phakic IOLs
According to Christopher Freeman, OD, and Paul Karpecki, OD in the November 2001 issue of Primary Care Optometry News, there are three major players in the game of phakic IOL implantation: the Bausch & Lomb (St. Louis) Nuvita lens, the Ophtec (Boca Raton, Fla.) Artisan (Worst-Fechner iris claw) lens and the Staar Surgical (Monrovia, Calif.) ICL (implantable contact lens).
The Bausch & Lomb Nuvita lens is a four-point, angle-fixed anterior chamber IOL designed by Georges Baikoff, MD, and is based on the aphakic design by Charles Kelman, MD. The Nuvita lens is currently undergoing modification from the latest single-piece, flexible loop MA20 model. The new version of the lens will be foldable to allow for decreased incision size, will be composed of one piece, will have little compression of the haptics and should have an incision size of 3.5 mm or less.
The Artisan iris claw lens is a single-piece, anterior chamber IOL comprised of PMMA that is clipped onto the anterior mid-peripheral iris by two opposing claws. This method of placement, while requiring increased surgical skill, allows for centration over the pupil and the possibility in the future for a toric lens that can be centered over the pupil and positioned to correct astigmatism.
The Staar ICL is a posterior chamber IOL available in clinical trials for correction to –20 D and +20 D. The procedure also requires making two iridotomies or iridectomies prior to implant surgery, making a small incision (2.5 to 4 mm), inserting this lens through a Staar Surgical injector into the posterior chamber in front of the crystalline lens and then positioning the lens in place.
The ICL is a single-piece, plate design lens made of porcine collagen/HEMA copolymer — a unique material allowing flexibility, compatibility and good optics in a thin lens.
Laser option
LAPR using the SurgiLight IR-3000 laser is an exciting laser-based option. SurgiLight filed an Investigational Device Exemption with the FDA in early November to allow clinical trials of LAPR using the OptiVision Er:YAG laser (previously called the IR-3000 laser.) The trials would take place at seven U.S. sites and include 350 patients.
Oscar Mallo, MD, of Argentina, described the infrared fiber-coupled laser system as a safe and effective method for correction of presbyopic patients’ near vision with minimum regression. LAPR is based on a hypothesis that attributes increased ciliary muscle functional range to increased elasticity of the scleral ring resulting from the laser ablation.
Dr. Mallo and J.T. Lin, PhD, shared outcomes of an international study of LAPR at the AAO meeting. The patients ranged in age from 42 to 60 years (mean age 53); 17% were men and 83% were women. Of 41 patients and 82 eyes, only four patients did not achieve outcomes as good as expected.
“We believe this is due to either thin scleral thickness or to shallow ablation during our learning stage,” Dr. Mallo said.
Of the 78 remaining cases, postoperatively 74% were J2 or better and 81.5% were J3 or better in near vision without glasses. “Our results improved significantly, if we exclude those patients with thin sclera or shallow ablations,” he said.
Of the 78, 44% are J1 or better, 84% are J2 or better and 93% are J3 or better.
“The general observation is that subjective near-vision improvement was noticed about 2 to 3 days after the procedure. It continued to improve over 2 to 4 weeks. No myopic shift and no regression were noted during the follow-up period, with a maximum of 14 months,” he said.
No significant change in refraction for distance was noted. There was no induced astigmatism. In general, there was a tendency for lower intraocular pressure readings postop, which became normal after a few days to a few weeks, and no significant complications were encountered.
“The advantages of performing presbyopia surgery on the sclera, avoiding the cornea and the anterior segment, consist of unchanged performance on distance visual acuity and contrast sensitivity. Patients who have undergone this technique acknowledge the added benefit of much better vision at the intermediate range, for example, seeing the food while they eat,” Dr. Mallo said.
For Your Information:
- Noel A. Alpins, MD, can be reached at 7 Chesterville Rd., Cheltenham, VIC 3192, Australia; (61) 3-9584-6122; fax: (61) 3-9585-0995; e-mail: alpins@newvisionclinics.com.au. Dr. Alpins has no direct financial interest in the products mentioned, nor is he a paid consultant for any companies mentioned.
- Oscar Mallo, MD, can be reached at Consultorio Oftalmologico, Av. Pueyrredon 2257-PB, (C1119ACF) Buenos Aires, Argentina; (54) 11-4803-6864; fax: (54) 11-4326-7353; e-mail: omallo@fibertel.com.ar; Web site: www.presbicia.org. Dr. Mallo has no direct financial interest in the products mentioned, nor is he a paid consultant for any companies mentioned.
- Roger F. Steinert, MD, can be reached at Ophthalmic Consultants of Boston, 50 Staniford St., Suite 600, Boston, MA 02114; (617) 367-4800; fax: (617) 573-4912; e-mail: rfsteinert@eyeboston.com.