424B1
1
FINAL PROSPECTUS DATED 08/12/1999
Clinical Trials Results
Myopia. Since 1991, ophthalmic surgeons have utilized Intacs technology for
the treatment of myopia in 1,787 patient eyes in clinical trials conducted in
the United States and throughout the world. KeraVision's clinical trials have
been designed to demonstrate the safety and efficacy of Intacs corneal ring
segments and the safety of the surgical procedure used to insert Intacs. The
safety and efficacy of Intacs corneal ring segments was evaluated using
standard ophthalmic techniques. KeraVision initiated clinical trials using the
initial design of Intacs in 1991 in both the United States and Brazil. In
September 1994, KeraVision completed enrollment of a 90-patient FDA Phase II
myopia trial using the initial design of Intacs. In September 1996, KeraVision
completed enrollment of the group of 150 U.S. Phase II myopia patients with a
modified design of Intacs. In November 1996, KeraVision initiated an expanded
Phase II myopia trial involving 59 patient eyes to evaluate moderate myopia (-
3.5 to -5.0 diopters). In October 1996, KeraVision received FDA approval to
commence a ten-center, 360-patient Phase III clinical trial for myopia in the
United States and began that trial in December 1996. KeraVision completed the
enrollment for the trial in May 1997. Our initial Pre-Market Approval (PMA)
application was based on data from the PMA cohort, a group of 452 patients
enrolled in the Intacs Phase II and Phase III clinical trials. Three
thicknesses (0.25, 0.30 and 0.35mm) of Intacs corneal ring segments were
evaluated. Intacs were successfully placed in 449 eyes out of 454 surgical
attempts. After 12 months of follow-up, data were available for 97.6% of the
PMA cohort patients.
Intacs corneal ring segments have been removed from 39 patient eyes from the
PMA cohort. Intacs corneal ring segments can be easily removed in a brief,
outpatient procedure. The Intacs removal rate for the Phase III trial was 4.3%
as compared to 9.6% from the earlier Phase II trial. Reasons for Intacs
removals included: one for infection, 15 for patient dissatisfaction with
correction achieved (undercorrection, overcorrection or induced astigmatism),
19 for patient dissatisfaction with visual symptoms (glare, halos, difficulty
with night vision, etc.) and four for other reasons. There have been no
clinically significant complications associated with Intacs removal procedures.
The removal results demonstrate that the refractions returned to preoperative
levels by three months following removal, in most instances. Best spectacle-
corrected visual acuity was 20/20 or better in all cases following removal.
The first procedure for the treatment of myopia using Intacs was performed in
1991, and to date more than 1,700 procedures have been conducted using Intacs
corneal ring segment technology in clinical trials. Although KeraVision has
developed eight-year clinical data on the safety and efficacy of Intacs in
correcting myopia, it has limited long-term safety and efficacy data. We cannot
assure you that long-term safety and efficacy data when collected will be
consistent with these clinical trial results and will demonstrate that Intacs
can be used safely and successfully to treat myopia in a broad segment of the
population or on a long-term basis.
All surgical procedures, including the Intacs placement procedure, involve
some inherent risk of complications. For the PMA cohort, five patients
experienced safety-related complications for an overall incident rate of 1.1%.
All five patients recovered with no clinically significant effects. Adverse
events include: one infection, one shallow Intacs corneal ring segment
placement, one temporary loss of 2 lines of best corrected visual acuity and
two corneal perforations. During the 12 months of follow up, there was a 4.5%
incidence of removal and a 0.9% incidence of exchange procedures. Other
complications included: overcorrection, reduction in central corneal sensation,
difficulty with night vision, undercorrection, induced astigmatism, blurry
vision, double vision, halos, glare, corneal blood vessels, and fluctuating
distance vision. No patient has had a lasting injury to the eye or sustained
any material loss of best corrected vision. In many patients, deposits have
been observed in the stromal tunnel next to the Intacs corneal ring segments.
In all cases, the deposits were confined to the stromal tunnel with no effect
on patients' vision. Although KeraVision believes that these deposits are not
complications, we cannot assure you that this will be the case on a long-term
basis.
All of these complications have also been observed in connection with other
refractive surgery techniques. Although KeraVision believes these complications
may be mitigated, KeraVision cannot assure you that these or other
complications will not be serious or lasting or will not impair or preclude
KeraVision from retaining existing regulatory approvals or obtaining regulatory
approvals for our products or the acceptance of these products by patients or
ophthalmologists.