Refocus Group, Inc.

PresVIEW™ and Presbyopia - For Professionals

Refocus Group's Mission is to Become a Surgical Standard of Care for the Treatment of Presbyopia

Note: Refocus Group’s primary product, the PresVIEW™ Scleral Implant is an investigational device and is not yet approved for sale or use in the United States or Canada.  However, the product is currently approved for sale in the European Union.

What Causes Presbyopia?  New Research...

Today, there remains a large number of theories regarding the cause of Presbyopia (the progressive loss of accommodation with aging), primarily because there continues to be a lack of agreement in both the mechanism of accommodation in the human eye and the root cause of presbyopia itself.  However, among all the theories of accommodation there is agreement on certain tenets.  These are that in the emmetropic eye the ciliary muscles are at rest during distance vision focus and are activated during near vision focus.  The activation of the ciliary muscles during near focus affects the lens by causing a steepening of the anterior and posterior surface.  There is an accompanying miosis of the pupillary aperture.

The most commonly held mechanism of accommodation in the human eye and theory of presbyopia was described by Helmholtz in the nineteenth century.  Briefly stated, Helmholtz described the human lens as being stretched around the equator by zonular fibers emanating from the ciliary muscles.   The ciliary muscles, according to Helmholtz, are in a constant state of tension keeping the curvature of the crystalline lens relatively flat for distance vision.  When the ciliary muscles contract during accommodation, they release tension on the zonules, which allows the lens to “round-up” (become more convex increasing the len’s refractive power) due to the len’s natural elasticity.   Increasing or decreasing the tension on the zonules thus provides a dynamic range of near vision.  Helmholtz blames progressive hardening of the lens with age for diminishing the ability of the lens to round up when tension from the zonules is released.   This then is the main cause of presbyopia per Helmholtz, which is still embraced by many researchers today.

At the same time, ophthalmologists have been aware of numerous inconsistencies in the Helmholtz’ theory such as the measured decrease of spherical aberration with accommodation, the lack of uniform “hardening” of the lens for a given individual in a particular age group, and delay in any significant hardening of the lens for all individuals until their late 50’s and 60’s, while accommodative ability decreases in a linear fashion starting in the early 20’s.   Helmholtz also ignores the fact that the lens, which is made of ectodermal tissue, continues to grow by 20 microns per year, especially in its anterior and posterior surfaces causing the lens to become more convex with age.  While this should make the patient’s vision more myopic, older patient’s actually become more hyperopic – the “lens paradox”.  There is also the well proven fact that the distance between the outer edge of the lens and the ciliary body decreases on a linear basis with age.   This would naturally diminish tension on the zonules over time, again causing the lens to round up and become more convex according to Helmholtz, providing a bias towards myopia, even without accommodation.   Once again, this has not been supported by evidence from clinical observations.

Because of the many inconsistencies in the Helmholtz theory, over the course of the last three decades a number of new theories have been developed regarding the causes of presbyopia.

Radial Tension On The Zonules During Accommodation, Not After

Dr. Ron Schachar developed a novel and highly innovative theory of accommodation in the 90’s based on the ectodermal origin of the lens and a radial pulling of the lens to increase the curvature during accommodation    Dr. Schachar believes that when the eye is attempting to see at near, the radially oriented ciliary muscles cause the equatorial zonules to pull outwardly on the periphery of the lens, which is the opposite of the mode of action proposed by Helmholtz.   As described by structural deformation equations and as demonstrated in models by Dr. Schachar, this pulling at the equatorial plane of the lens causes a flattening of the peripheral lens but a steepening of the central portion of the anterior and posterior lens surfaces, thereby decreasing the spherical aberration in the accommodated state.

Dr. Schachar believes that presbyopia is caused by the regular continuous growth of the ectodermal lens.  This causes an increase in the equatorial diameter of the lens with aging, which in turn reduces tension on the zonules which are connected to the ciliary muscles.   By the time a person is 50 years old, this aging process eliminates the leverage that the ciliary muscles normally exert on the lens during accommodation, and it becomes impossible for the lens to change shape in response to changes in the ciliary muscle.    In fact, this reduced leverage correlates strongly with the progressive decrease in accommodative ability demonstrated in Donders table of accommodative amplitude.

In order to reverse this loss of zonular tension, Dr. Schachar developed the PresVIEW™ Scleral Spacing Procedure  ("SSP"), which employs four small PMMA implants strategically placed in the sclera over the ciliary muscles - which act as fulcrums creating a vaulting effect.   This restores the natural tension on the zonules in the four oblique quadrants where the implants are placed.     As described below, researchers at the Refocus Group have continued to refine Dr. Schachar’s theory and the application of the Scleral Spacing Procedure with outstanding results.

Recent revisions in the Schachar theory still hold that the reduction in distance between the edge of the crystalline lens and the ciliary body with age create the conditions that cause presbyopia. However, we now believe that the mechanical and physiological improvements provided by the SSP implants relative to their interaction with the zonules and and ciliary muscles, could vary from the original Schachar theory in actual application.  Nonetheless, scleral expansion remains at the core of the positive impact achieved during the surgery, and it is clear that the PresVIEW™ Scleral Spacing Procedure has provided dramatic improvements in near-vision acuity for most patients.

Within the last year many SSP patients in clinical trials have received four to five lines of improvement in Distance Corrected Near Visual Acuity (“DCNVA”) as measured by Sloane visual exams, and many have achieved end points of 20/20 or 20/32.    A majority of patients have received 20/40 DCNVA at a minimum, and most are able to read without glasses or other visual aids.

Can Presbyopia Be Treated?  What Are Today’s Alternatives? Are They Safe?  Are They Reliable?

In addition to the PresVIEW™ Scleral Spacing Procedure  discussed above, the historical treatment for presbyopia has been a prescription for simple reading glasses or in the case of patients with myopia, hyperopia and/or astigmatism, bifocals or trifocals.  Contact lenses may also be used  in connection with reading glasses.   These solutions work well for some people, but all rely on the use of vision prosthetics, which many individuals consider to be inconvenient.   Typically when a person who has never worn glasses requires them for reading, they will have multiple pairs at home and at work.  Contact lenses require a high degree of maintenance and are often less well tolerated by the time a patient becomes presbyopic.  Because presbyopia could be complicated by other common vision conditions like nearsightedness, farsightedness and astigmatism, the specific lenses that would allow a patient to see clearly at near need to be checked regularly – further adding to their inconvenience for the patient.

Monovision – Laser or Surgical Correction

One available alternative to utilizing separate distance to near corrections with visual aid in monovision.  Monovision can be achieved through contact lenses or excimer laser surgery such as LASIK or PRK.   This approach corrects one eye primarily for distance vision and the other eye for near work, allowing the patient to be less reliant on glasses.

There is also a method to reshape one of the corneas using high frequency radio waves to achieve the same monovision effect.  Many patients find monovision to be a satisfactory solution.  However, not everyone can tolerate this approach since it requires an adjustment period to allow the mind to register and incorporate the difference between the two eyes   Also, in the case of the LASIK or high frequency radio waves, the change to the cornea is permanent and in most cases irreversible.

Another method used to correct presbyopia uses static bifocal optics.  While Bifocal contact lenses have had a long history, only a small percentage of patients using them have experienced satisfactory results to date.  Investigational trials of bifocal excimer laser correction, involving laser surgery to the cornea, are underway as well.

Lens Removal And Replacement With Multi-focal or Accommodating IOL’s

Another option, frequently recommended when a patient has a cataract, is the removal of the crystalline lens and replacement with an artificial lens with two focal zones (both near and far – known as a bifocal or multi-focal lens).   With multi-focal lens, the distance and near correction are placed in concentric rings around the center of the lens.  This approach inherently creates a number of compromises, often including a reduction in the quality of the patient’s distance and near vision.

The patient may discover that the fixed near focal point may be too close or too far away.  In addition, halos or glare are frequently experienced, especially at night.

Once the surgery has taken place, these visual aberrations can only be corrected by removing the multi-focal lens.

Newer more flexible intra-ocular lenses that provide a small amount of dynamic near vision (known as an “accommodating” lenses) are also available to patients with cataracts that require surgery.  As with multi-focal lenses, accommodating lenses can be good solutions for cataract patients since these patients have typically lost most of or all of their ability to see at near or distance, even with vision correction.    However, for the patient with a healthy lens and good distance vision, the risks associated with any these intraocular lens replacement strategies may offset the benefits.   For example, distance vision could be reduced by both bi-focal or accommodating lenses, as in the case of post refractive laser corneal surgery.   Inaccurate power calculations are not uncommon with bifocal or accommodating lenses.  In addition, there is a risk that removal of the natural lens could result in complications such as bleeding, infection, retinal inflammation, cystoid macular edema, etc.   With the exception of glasses and contact lenses, all of the above procedures are permanent, typically degrade distance vision to some extent and can not be reversed.

Refocus Group Pursues Presbyopia With An Innovative Treatment Option:
The PresVIEW™ Scleral Spacing Procedure

Unlike other presbyopia solutions, The company's PresVIEW™ Scleral Spacing Procedure re-establishes the dynamic focus of the eye by restoring the natural tissue spacing surrounding the crystalline lens — enabling the eye to focus on near objects using the same mechanisms employed before the onset of presbyopia.   This patented technique involves placing four small pieces of inert  plastic made out of PMMA in a circular arrangement in the white part of the eye (the sclera). The small implants stretch and expand the underlying muscle, which can then better manipulate the lens, thereby restoring the ability of the eye to focus at multiple distances. as proven in many recent clinical trials.   This revolutionary procedure was developed by scientists working for Presby Corp in the 1990’s, and is currently being tested in FDA trials in the U.S.

The procedure is minimally invasive and designed to be completed by trained physicians on an outpatient basis in about 20-30 minutes per eye using topical and/or local anesthesia.   Because the surgery occurs in the sclera, it does not affect the visual axis in any way so there are few of the potential risks associated with corneal or intraocular surgery.     After the eye fully heals from the surgery (about three – four weeks), the implants are largely invisible from a cosmetic perspective.    Although rare, should the patient be dissatisfied in any way, the implants can easily be removed.  Based on a history of performing the Scleral Spacing Procedure in well over 1,000 patients over the last ten years, Refocus doctors believe that the Scleral Spacing Procedure is quite safe, and should the implants need to be removed,  no permanent alteration to the eye will occur cosmetically or functionally (however, as with all surgical procedures, some risk of an adverse event is always present).

Participants in clinical trials conducted by Refocus Group to date have reported improved near vision generally no later than 1 to 4 weeks following the procedure, and a large percentage of patients are able to read without glasses or other visual aids by the end of this time.   Because the SSP procedure is designed to restore the natural use of the muscles, as the muscles grow stronger, near vision for most patients will often continue to improve up to twelve months after the surgery.   More importantly, near vision is restored by providing a dynamic range of near acuity, with no glare or halos, no loss of contrast sensitivity (the ability to distinguish shades of grey),  and no potential loss of distance vision.

Availability

In the United States, Refocus Group has completed the first phase of feasibility clinical trials in accordance with Food And Drug Administration (“FDA”) regulations.   Subsequently, Refocus received FDA approval for expanded clinical trials as part of the process required for eventual market approval in the U.S.

Internationally, the  PresVIEW™ Scleral Spacing Procedure has received the CE Mark certification in the European Union, and is anticipated to be available for commercial use in Europe in 2010.