Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Eye prosthesis – Intraocular lens
Reexamination Certificate
2001-10-02
2004-06-29
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Eye prosthesis
Intraocular lens
C623S006490
Reexamination Certificate
active
06755860
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an intraocular lens designed to be inserted in a capsular sac in an eye.
Intraocular lenses are designed to correct aphakia during an operation for a cataract. A cataract is characterized by the progressive loss of vision because the cornea in the patient's eye becomes opaque. A surgical operation is performed to extract the opacified cornea and to replace it with an artificial cornea called an intraocular lens. The intraocular lens may be placed in the anterior chamber in front of the iris or in the posterior chamber behind the iris, in a ciliary seat or in the capsular sac of the eye. The lens is composed of two parts, an optical part enabling vision that may be single-focal or multi-focal, and a support or haptic portion that will interact with the tissues by mechanical thrust and cellular growth and hold the lens in position in the eye. There are two types of implants used to replace the natural cornea at the present time, namely “rigid” implants and “flexible” implants.
Polymethylmethacrylate (PMMA) is usually used for rigid intraocular lenses. The flexible implant can bend and be inserted through a very small cornean or scleral incision about 3 millimeters long, after extraction of the natural lens nucleus from the capsular sac. This technique reduces residual astigmatism. Many intraocular lenses made of flexible material have already been proposed. For example, these lenses may be made from polysiloxanes, or flexible hydrophobic or hydrophilic acrylic polymers (copolyhema). Intraocular lenses made of co-polyhema are made by machining in the dry state, and the material will then be hydrated to make it flexible.
A flexible single piece intraocular lens disclosed in French Patent Application FR 2 766 699, is designed to prevent movement of the lens optics along the optical axis when the lens is being put into place. This lens is shown in FIG.
4
. In order to achieve this purpose, closed haptic portions
410
having legs
411
,
412
that are not radial are used. Thus, in theory, forces transmitted through the legs
411
,
412
onto the optical part
401
when the lens is in position in the capsular sac of the eye do not have a radial component. Consequently, the optical part
401
should not move or be deformed. However, note that according to
FIG. 4
, the longitudinal axes of the legs
411
,
412
for each haptic portion
410
intersect at a point S′ that is in the angular section with center O and with an arc defined by the contact portion
414
of the haptic portion joining the free ends of the legs
411
,
412
. Once the lens is in position, centripetal forces will be applied to each haptic portion
410
. Considering the geometry of each haptic portion defined above, these forces will induce a rotation moment on each leg
411
,
412
. According to
FIG. 4
, these two rotation moments will have opposite signs. If the values of these two moments are the same, then the haptic portion will simply be compressed, which will necessarily cause buckling of legs. If the sum of the moments is not zero, the leg with the smallest moment will be compressed and the haptic portion will pivot towards the direction of the highest moment. Thus, in all cases, at least one leg will be compressed. This compression phenomenon is also illustrated in
FIG. 5
a
in which the shape of a hapic portion as illustrated in
FIG. 4
is shown. In this figure, the compression C exerted on the haptic portion when the lens is in position causes a centripetal component Fc
1
and a tangential component Ft
1
to be applied to each leg
411
,
412
. Due to the particular geometry of the haptic portion of the lens, the signs of these tangential components Ft
1
are opposite and are in opposite directions. Depending on the value of these forces, the phenomena described above will be applied to each leg
411
,
412
. These phenomena will generate an accumulation of stresses that will result either in random deformation of the leg(s) causing instability in the position of the optical part, or an additional pressure exerted on the peripheral tissues of the capsular sac that can cause complications for the patient. These phenomena may also occur when the geometry of each haptic portion is such that the two legs are facing inwards instead of outwards as shown in
FIG. 5
b
. In this case, the tangential components Ft
2
will be towards each other.
SUMMARY OF THE INVENTION
The purpose of this invention is to overcome the disadvantages of prior art by proposing an intraocular lens in which the haptic portions do not cause any displacement of the optical part along the optical axis, or stress accumulation on the optical part or on the peripheral tissues.
This objective is achieved by an intraocular lens comprising an optical part approximately in the shape of a disk and a support part or haptic portion comprising two closed pairs of haptic portions laid out symmetrically about a first diameter of the optical part, the haptic portions in each pair being symmetrical with each other about a second diameter approximately perpendicular to the first diameter, characterized in that each haptic portion is provided with two arms or side segments in which a first end is fixed to the periphery of the optical part and, for each haptic portion, the longitudinal axes of the side segments intersect at a point that is not included in an angular sector with the same center as the optical center of the optical part, and in which the arc consists of a contact portion joining the second ends of the side segments of the same haptic portion.
REFERENCES:
patent: 4657546 (1987-04-01), Shearing
patent: 6461384 (2002-10-01), Hoffmann et al.
Stamper et al., Intraocular Lens Data, Ophthalmology—Instrument and Book Supplement 1984, pp. 179-180.
Delage Denis
Liffredo Renato
Biotech
Lowe Hauptman & Gilman & Berner LLP
Willse David H.
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