Variable power intraocular lens and method of implanting into the posterior chamber

A posterior chamber intraocular lens (34) is provided that can be utilized in a human eye. The posterior chamber intraocular lens (34) includes a fluid-expandable sac (40) for containing a fluid (42). The fluid expandable sac (40) includes a lens portion (36) and a valve portion (38) that extends through the sclera (16) of an eye (10) when the posterior chamber intraocular lens (34) is inserted into the eye (10). In an alternate embodiment, the fluid (42) is a liquid crystal material (52) that is used in combination with an electrode (54) and a microprocessor (56) for changing the index of refraction of the posterior chamber intraocular lens (48) and responds to the desired accommodation.

TECHNICAL FIELD 
This invention relates to intraocular lenses. More particularly, this 
invention relates to posterior chamber intraocular lenses having variable 
power. 
BACKGROUND ART 
Intraocular lenses have been heretofore successfully implanted in human 
eyes. For example, anterior chamber lenses have been implanted directly 
behind the cornea, but such a lens is sometimes considered undesirable in 
that it is positioned very close to the cornea and in some cases may 
result in traumatization of the endothelium. In order to minimize the 
problems of anterior chamber lenses, various iris-clip and iridocapsular 
lenses have been developed. 
There have been many other designs of intraocular lenses and the latest and 
most popular intraocular lens involves the use of posterior chamber 
lenses. The reason for the popularity of the posterior chamber lens is 
predominantly because many that are skilled in the art believe that 
breaking or incising the posterior capsule of the lens results in a higher 
incidence of retinal detachment and cystoid macula edema. These 
complications appear to be decreased in any type of extracapsular cataract 
extraction whether it is done in the standard manner or by the procedures 
of lensectomy or phacoemulsification. 
However, one of the present problems with intraocular lenses is that it is 
necessary to decide on the power of the lens preoperatively. This can be 
accomplished, for example, by performing an ultrasound scan and/or 
evaluating the patient's refraction preoperatively and then making a 
clinical estimate of the proper power of the lens in order to determine 
proper refraction of the eye. 
Accordingly, there is a need for a posterior chamber lens having a variable 
power of refraction. 
DISCLOSURE OF THE INVENTION 
In accordance with the present invention, a posterior chamber intraocular 
lens for a human eye is provided that includes a fluid-expandable sac that 
is constructed of a flexible transparent material for containing fluid. 
The sac is dimensioned for occupying the posterior chamber of an eye in 
place of the natural lens and contains a fluid when implanted in the 
posterior chamber of an eye for providing the desired correction, the 
fluid forming the interior portion of the posterior chamber intraocular 
lens of the present invention. The sac which forms the exterior portion of 
the intraocular lens further includes a neck portion that serves as a 
valve and extends through the sclera of an eye when inserted therein. The 
valve allows fluid contained in the sac to be withdrawn or replaced to 
change the index of refraction of the lens, and/or, change the thickness 
of the lens and thereby change the power of the lens. 
In accordance with the surgical procedure provided, the posterior chamber 
intraocular lens of the present invention is implanted into the eye by 
inserting a needle through the sclera of the eye and into the posterior 
chamber. Thereafter, the fluid-expandable sac, constructed of a flexible 
transparent material is inserted through the needle in a collapsed 
condition and into the posterior chamber. A fluid is then instilled into 
the sac thereby expanding it and isolating the vitreous face from the 
natural lens. Thus, the insertion and expansion of the sac dissects the 
attachment of the vitreous face from the posterior natural lens capsule. A 
pressure relief aperture is formed in the cornea of the eye so that 
pressure produced on the interior portion of the eye as fluid is instilled 
into the sac is relieved. The natural lens is then extracted from the eye, 
and may be removed through the pressure relief aperture, by any suitable 
manner known to those skilled in the art, such as by cryoextraction, 
extracapsular extraction or phacoemulsification. 
In accordance with another embodiment of the posterior chamber intraocular 
lens of the present invention, the fluid-expandable sac is filled with a 
liquid crystal material. The accommodation of the eye is monitored and to 
provide an input signal to a microprocessor that is capable of producing 
an output voltage proportional to the desired accommodation. The output 
voltage is transmitted to and applied across the liquid crystal material 
contained in the sac for providing an index of refraction that is required 
to achieve the power necessary for the desired accommodation.

DETAILED DESCRIPTION 
In accordance with the present invention, a posterior chamber intraocular 
lens together with a surgical method for the implantation thereof in a 
human eye is provided. Unlike previous intraocular lenses, the posterior 
chamber intraocular lens of the present invention is a nonrigid lens that 
permits the corrective power of the lens to be changed after implantation 
thereof into an eye. 
Referring to the figures generally, and particularly to FIG. 1, there is 
depicted a horizontal cross section of a human eye, partially broken away 
and generally referred to by reference numeral 10. Eye 10 includes a 
cornea 12, limbus 14, a sclera 16, conjunctiva 18, an iris 20, an anterior 
chamber 22, a posterior chamber 24, a natural lens 26, ciliary body 28, 
suspensory ligaments 30 and a vitreous chamber 32. The function and 
interrelationship of these components of the eye are well known and for 
that reason a detailed explanation of each component is not provided 
herein. 
A posterior chamber intraocular lens 34 in accordance with the present 
invention is shown in position in eye 10 in FIG. 3. Posterior chamber 
intraocular lens 34 includes a lens portion 36 and a valve portion 38. 
Lens portion 36 preferably occupies the entire posterior chamber taking 
the place of natural lens 26. Valve portion 38 extends through sclera 16, 
generally about 2.5 millimeters posterior to limbus 14 of eye 10. The 
exterior of posterior chamber intraocular lens 34 is a fluid-expandable 
sac 40 that is constructed of a transparent material compatible with the 
eye. For example, fluid-expandable sac 40 may be constructed of 
polypropylene, polyethylene or silicone. Lens portion 36 of 
fluid-expandable sac 40 is preferably a biconvex shape, as depicted in 
FIG. 3, when filled with fluid. Alternatively, lens portion 36 of 
fluid-expandable sac 40 can be a plano-convex shape or any other desired 
shape. Preferably, lens portion 36 of fluid-expandable sac 40 has a 
diameter of approximately 13.5 millimeters when the desired amount of 
fluid is instilled therein so that the peripheral portions of 
fluid-expandable sac 40 contact ciliary body 28, or may be smaller and fit 
within the capsule of the lens following an extracapsular cataract 
extraction. 
As shown in FIG. 3, fluid-expandable sac 40 contains a fluid 42 for 
providing the desired index of refraction for posterior chamber 
intraocular lens 34. Fluid 42 may be either a gas or a liquid. Preferably 
fluid 42 will be a liquid since generally the desired index of refraction 
of lens portion 36 is more easily attainable, since liquids have a greater 
range of indices of refraction than various gases. Alternatively, the sac 
may be made so that the walls have optical power and the total optical 
power of the intraocular lens is altered by varying the distance between 
the walls of the sac by filling the sac with different amounts of fluid. 
For example, fluid 42 may be an aqueous saline solution. Alternatively, 
fluid 42 may comprise a liquid having a higher index of refraction than 
water, such as an oil, including silicone oil. However, the use of such a 
material should be carefully evaluated prior to use in a human eye since 
leakage of some materials from fluid-expandable sac 40 could be 
deleterious to eye 10. 
Thus, fluid-expandable sac 40 isolates posterior chamber 24 from the 
anterior chamber 22. This facilitates removal of the natural lens as will 
be hereinafter described. Further, fluid-expandable sac 40 prevents any 
intrusion into vitreous chamber 32 and maintains the normal vitreous 
volume without disturbance of the relationship of vitreous chamber 32 to 
the macula (not shown). 
Referring to FIG. 2, there is illustrated posterior chamber intraocular 
lens 34 of the present invention being inserted into eye 10. Natural lens 
26, illustrated in FIG. 2, generally has some type of physical damage, 
such as a cataract. This necessitates removal of natural lens 26 which is 
replaced by posterior chamber intraocular lens 34 of the present 
invention. Fluid-expandable sac 40 of posterior chamber intraocular lens 
34 is placed in posterior chamber 24 of eye 10 in accordance with the 
following procedure. A peritomy of conjunctiva 18 is performed so that a 
portion of sclera 16, generally about 2.5 millimeters posterior to limbus 
14, is uncovered. Thereafter, an insertion member, such as a hollow needle 
44, for example, is inserted into and through that portion of sclera 16 
that has been uncovered by the peritomy of conjunctiva 18, preferably in 
the area of the pars plana. Hollow needle 44 is then inserted into 
vitreous chamber 32. Preferably, hollow needle 44 generally protrudes 
between about 1 and 2 millimeters into posterior chamber 24. Hollow needle 
44 is dimensioned to permit insertion of fluid-expandable sac 40 into the 
hollow portion thereof. Collapsed fluid-expandable sac 40 of posterior 
chamber intraocular lens 34 is then inserted into and through hollow 
needle 44. Fluid-expandable sac 40 is then expanded with a fluid 42 
causing fluid-expandable sac 40 to spread out and fill posterior chamber 
24 to isolate the vitreous from natural lens 26. In this manner, the 
vitreous face of vitreous chamber 32 is dissected from the posterior lens 
capsule of natural lens 26 by fluid-expandable sac 40. Prior to instilling 
fluid 42 into fluid-expandable sac 40, a pressure relief aperture 46 is 
formed in cornea 12. Since instilling fluid 42 into fluid expandable sac 
40 increases the interior pressure of eye 10, which could cause 
deleterious effects, this pressure is relieved by allowing fluid to exit 
through pressure relief aperture 46. Pressure relief aperture 46 can be 
formed before hollow needle is inserted through sclera 16. 
FIG. 4 illustrates fluid-expandable sac 40 being transported through hollow 
needle 44 in a collapsed state. Fluid pressure can be utilized to force 
fluid-expandable sac 40 through hollow needle 44 or an instrument, such as 
a rod, dimensioned to be inserted within hollow needle 44, can be used for 
this purpose. When fluid-expandable sac 40 is filled with fluid 42 with 
natural lens 26 removed, posterior chamber intraocular lens 34 occupies 
posterior chamber 24 as shown in FIG. 3. Preferably, posterior chamber 
intraocular lens 34 occupies the entire volume of posterior chamber 24. 
The peripheral portions of fluid-expandable sac 40 can be ribbed or can 
incorporate small pins (not shown) so that posterior chamber intraocular 
lens 34 is restrained from movement within posterior chamber 24 of eye 10. 
After posterior chamber intraocular lens 34 has been inserted in position 
in posterior chamber 24 such that the vitreous face of vitreous chamber 32 
is separated from natural lens 26, natural lens 26 is then removed. 
Natural lens 26 can be removed by any manner known to those skilled in the 
art, such as lensectomy, phacoemulsification, cryoextraction, or 
extracapsular extraction. Further, entire natural lens 26 may be removed 
including all of, portions of or none of suspensory ligaments 30. 
Alternatively, the sac of natural lens 26 can remain with only the 
crystalline portion of lens 26 being removed. In an alternate embodiment 
(not shown), fluid-expandable sac 40 can be placed within the sac of 
natural lens 26 after the crystalline portion thereof is removed. The 
removed portions of natural lens 26 can be removed through pressure relief 
aperture 46, if desired. 
As shown in FIG. 3, valve portion 38 of fluid-expandable sac 40 forming the 
exterior of posterior chamber intraocular lens 34, extends through sclera 
16. This has the effect of maintaining posterior chamber intraocular lens 
34 in a predetermined relation with respect to eye 10. The aperture formed 
in sclera 16 by hollow needle 44 is closed leaving valve portion 38 
therein. Preferably, valve portion 38 protrudes slightly from sclera 16 
and is covered with conjunctiva 18 after injection of fluid 42. Thus, it 
is a relatively simple procedure if it is desired to change the index of 
refraction of posterior chamber intraocular lens 34, since it is necessary 
only to add or withdraw fluid 42 from lens 34 or replace fluid 42 with 
another type of fluid having a different index of refraction. 
In accordance with another embodiment of the present invention, a posterior 
chamber intraocular lens 48 is provided utilizing a fluid-expandable sac 
50 similar to fluid-expandable sac 40, with fluid-expandable sac 50 being 
filled with a liquid crystal material 52, as shown in FIG. 5. Posterior 
chamber intraocular lens 48 is responsive to achieving a desired 
accommodation by altering the index of refraction of liquid crystal 
material 52. This can be accomplished in a number of ways which are 
hereinafter described. For example, the accommodation of the eye can be 
monitored by measuring the electrical potential generated by ciliary body 
28. An electrode 54 is located in ciliary body 28, as shown in FIG. 5, 
which provides an input signal, that is proportional to the desired 
accommodation, to a microprocessor 56, which can be implanted into sclera 
16 of eye 10 as shown in FIG. 5, or into any other suitable location. A 
suitable power source is provided for microprocessor 56 and could also be 
implanted (not shown). Microprocessor 56 may comprise, for example, Model 
8080 manufactured and sold by Intel Corporation. Microprocessor processor 
56 is programmable in a manner well known to those skilled in the art to 
provide a corresponding output depending on the relative intensity sensed 
by electrode 54 which is proportional to the accommodation of the eye. By 
monitoring the electrical potential generated by ciliary body 28, the 
refractive power of the intraocular lens can be controlled. Alternatively, 
an electrical signal proportional to the location of the eyes can be 
obtained by implanting electrodes in the rectus medialis (not shown) of 
eye 10. Microprocessor 56 is utilized for producing a voltage output for 
providing a voltage potential across liquid crystal material 52 contained 
within fluid-expandable sac 50 to provide the index of refraction that is 
required to obtain the desired accommodation based upon the relative 
position of the eyes. The voltage output of microprocessor 56 is 
transmitted through electrical wires 58 and 60. Electrical wires 58 and 60 
connect to electrodes 62 and 64, respectively for applying a voltage 
potential across liquid crystal material 52. Electrodes 62 and 64 can be a 
thin transparent material forming a coating on the interior of 
fluid-expandable sac. For example, a thin coating of tin oxide and indium 
oxide can be used for electrodes 62 and 64. 
In accordance with another embodiment of the present invention, liquid 
crystal material 52 may comprise a material that darkens on an increase in 
the voltage potential supplied across such a liquid crystal material. A 
small photo electric cell (not shown) is mounted in the conjunctiva of the 
eye for monitoring the ambient light for automatically altering the 
optical density of the liquid crystal material. 
In accordance with another embodiment of the present invention, instead of 
using a photo electric cell to monitor the ambient light, a small 
electrode 66 can be placed in the iris of the eye and the size of the 
pupil or contraction of the iris which occurs under a particular lighting 
condition can be used to monitor the potential generated so that the 
intraocular lens would then become darkened when the pupil started to 
contract with increasing light. It is well known that the pupil contracts 
under two circumstances, when there is increased light and when one is 
reading or looking at a close object. During the reading phase the ciliary 
body also contracts in order to produce normal accommodation and electrode 
54 is provided for sensing ciliary muscle in order to alter the refractive 
index of the liquid crystal for the reading and simultaneous monitor the 
iris contraction. This allows a determination to be made when both the 
iris and ciliary muscle contract to therefore prevent the lens from 
darkening when reading. However, when the eye looks at a bright room it is 
not reading, or looking at close objects, the pupil would be small but the 
ciliary body would not contract and therefore there would be an impulse 
only from the iris so that the lens would then be darkened. By proper 
choosing the type of liquid crystal material, it would be possible to 
control both optical density and index of refraction of posterior chamber 
intraocular lens 48. For example, by utilizing a liquid crystal material 
that darkens under an applied voltage between V.sub.o and V.sub.1, and 
changes its index of refraction under an applied voltage between V.sub.2 
and V.sub.3, where the range of V.sub.0 to V.sub.1 is exclusive of the 
range of V.sub.2 to V.sub.3, both the index of refraction and optical 
density of posterior chamber intraocular lens 48 can be controlled 
utilizing electrodes 54 and 66. 
In another embodiment, the fluid-expandable sac may contain a material 
which, in direct response to increased light, becomes optically denser. 
With this embodiment, it would not be necessary to incorporate electrodes 
to monitor microcontractions and relaxation if the material would 
automatically change its optical density is a direct response to the 
lighting condition. 
While the invention has been described with respect to preferred 
embodiments, it is to be understood that the invention is capable of 
numerous modifications, rearrangements and changes that are within the 
scope of the invention as defined by the appended claims.