Masked intraocular lens and method for treating a patient with cataracts

A masked intraocular lens for implantation into a human eye is presented. The mask, which blocks only part of the lens body, together with the pupil of the eye, defines a small aperture in the eye when the pupil is constricted, thereby increasing the depth of focus, as a pinhole camera does. When the pupil of the eye is dilated, additional light is allowed to pass through the pupil around the mask and to reach the retina to allow a person to see in dimmer light conditions. In one embodiment, the mask defines a small circular aperture and a larger exterior annulus; the small circular aperture has an additional power intermediate between that needed for distance and close vision. Also provided is a method for treating a patient with cataracts comprising replacing the patient's lens with the lens of the invention.

BACKGROUND OF THE INVENTION 
This invention relates to an intraocular lens for the human eye, and, more 
particularly, to a masked intraocular lens of the type which can be 
positioned in the anterior chamber, the posterior chamber, or partially in 
either the anterior or posterior chamber of the eye. The invention also 
relates generally to postcataract patient care and vision improvement by 
implanting a masked intraocular lens to replace the removed natural lens. 
As a person ages, occasionally a person's eye lens gets cloudy. When this 
occurs, a person is said to have cataracts. The cataracts eventually cloud 
the lens so that a person cannot see clearly. When this happens, removal 
of the lens is required. Commonly, thick glasses have been used for 
correcting the vision of postcataract patients. However, the glasses have 
obvious disadvantages associated with the size and weight of the glasses. 
An intraocular lens (IOL) may be implanted to replace the human lens; 
however, these lenses generally are only in focus at one focal distance. 
The present invention circumvents the need for a traditional IOL augmented 
by bifocal or trifocal spectacles by implanting an intraocular lens which 
can focus continuously from near to far and in most light conditions. 
Attempts to produce an intraocular lens that is focusable at both near and 
far distances have not been completely successful. In the normal eye the 
crystalline lens is self-biased toward a spherical shape, that is, toward 
maximum refraction; for example, for distance viewing it is radially 
tensioned, and thereby flattened, by relaxation of the ciliary body. 
However, once the lens is removed, a replacement lens cannot function in 
this manner. Thus, intraocular lenses that allow the patient near and far 
focusability must work on a different principle. 
In U.S. Pat. No. 4,409,691, entitled "Focussable Intraocular Lens", an 
intraocular lens that achieves accommodation in response to contraction 
and relaxation of the ciliary body is disclosed. This lens works on the 
same principle as a lens in a camera. It achieves adjustment of the focal 
distance by adjustment of the spacing between the lens and the fovea. The 
intraocular lens is spring biased towards its distance focus position 
where it remains so long as the ciliary body remains relaxed. When the 
ciliary body contracts, it compresses the spring bias, moving the lens 
away from the fovea to provide accommodation for near viewing. This lens 
has not been completely successful as it requires precise implantation 
into the eye. Furthermore, implantation of this device is a more complex 
procedure than implantation of standard intraocular lenses. In addition, 
such a lens requires precise quantification of ciliary muscle body power. 
However, the capability of ciliary muscle is unknown, especially for 
elderly patients. 
A second technique to try to achieve focusing for near and far vision in an 
intraocular lens implant is disclosed in U.S. Pat. No. 4,636,211, entitled 
"Bifocal Intra-ocular Lens". This patent discloses an intraocular lens 
that focuses for near vision in the central portion of the lens and 
focuses for far vision by a coaxial ring around the central portion. This 
lens is not completely successful as, when one focuses on a near object, 
it is slightly fuzzy around the edges due to the far vision coaxial ring. 
This creates fuzziness for the viewer. 
U.S. Pat. No. 4,605,409 entitled "Intraocular Lens With Miniature Optic 
Having Expandable and Contractible Glare-Reducing Means", teaches an IOL 
with masking means for reducing the glare associated with an intraocular 
lens of small dimension. The masking means of that invention does not 
overcome the problem associated with standard IOLs, that is, it does not 
improve focusability. 
Pinholes have been used in pinhole cameras to bring distant objects, near 
objects, and everything in between into continuous focus. Pinholes are 
used by ophthalmologists to assess retinal function; the pinhole acts as a 
sort of universal lens, correcting all refractive errors, including 
astigmatism and spherical aberration. Although it has been known that the 
pinhole acts in this useful way, pinhole contact lenses and pinhole IOLs 
(such as is described in Choyce, Intra-Ocular Lenses and Implants, London. 
H.K. Lewis, 1964. pp. 21-26) made in the past did not work in dim light 
conditions. In adequate light the pinhole contact lenses and the pinhole 
IOLs functioned as expected, allowing the patient to see in the distance 
as well as read a book. However, in dim light, where the pinhole fails to 
admit enough light into the eye, image quality declined. Essentially it 
was like wearing dark glasses indoors. 
An earlier study of pinholes indicated that pinholes might be useful for 
solving vision problems caused by refractive errors if the problem of 
vision in dim light could be overcome. (Miller et al., "A Crossed 
Polaroid-Pinhole Device," Ann. Opthalmol., 1986, Vol. 18, 212-15. That 
study also indicated that a pinhole diameter of 1.6-1.8 would provide 
better than 20/40 vision even in the face of artificially induced 
refractive errors of up to 3 diopters. Miller and Johnson also studied the 
pinhole effect with the hope of solving vision problems. (Miller and 
Johnson, "Quantification of the Pinhole Effect," in "Perspectives in 
Refraction," Rubin, ed., Survey of Opthalmology, 1977, Vol. 21, 347-50.) 
They found that pinholes were useful for overcoming artificially induced 
refractive errors, and, in particular, that pinholes with a 1.0-2.0 mm 
diameter were most useful. They revealed a soft contact lens which was 
dyed black except for a 1.5 mm aperture and which maintained 20/40 vision 
even in the face of a 6 diopter error, but which constricted peripheral 
vision. They also revealed a soft contact lens with a clear 1.5 mm pinhole 
defined by a blackened annulus with an outer diameter of 4.5 mm which was 
surrounded by an outer clear ring to improve peripheral vision. The 
present invention takes advantage of the focusing power of the pinhole 
while at the same time getting around the problem of dim illumination in 
low ambient light conditions. 
SUMMARY OF THE INVENTION 
The present invention is a masked intraocular lens (IOL) that keeps most of 
the world in focus in most light conditions. In normal light conditions 
the pupil of the eye is approximately 4 mm in diameter. The masked IOL 
further reduces the opening available for light to pass to the retina to 
approximately 1-3 mm, so that all the light that reaches the retina comes 
through a 1-3 mm pinhole. At this point the eye is working like a pinhole 
camera and there is a sharp image on the retina for near, intermediate, 
and far objects. In lower ambient light conditions, the pupil of the eye 
dilates. This dilation increases the area through which light may pass and 
reach the IOL. The masking on the IOL is configured so that, in turn, more 
of this available light may reach the retina by passing around the edges 
of the mask on the IOL. At this point, the eye is no longer working as a 
pinhole camera, but the masked IOL allows enough light to reach the retina 
so that an image is maintained thereon, albeit somewhat blurry. In an 
important embodiment of the present invention, the IOL is manufactured 
with an intermediate added power in the center of the IOL. This added 
power moves the range of depth of focus from infinity to a close distance 
while maintaining a high contrast image. 
An object of the present invention is to provide a masked intraocular lens 
for postcataract patients which eliminates the need for heavy, 
uncomfortable glasses, or a contact lens or an IOL and reading glasses or 
bifocals. 
Another object of the present invention is to provide the postcataract 
patient with an intraocular lens which enables the patient to achieve 
near, intermediate, and far vision with clarity. 
Still another object of the present invention is to provide a pinhole 
intraocular lens that allows enough light to reach the retina in low 
ambient light conditions. 
A further object of the present invention is to provide an improved method 
for treating a cataract patient whose natural lens must be removed without 
requiring the patient to wear heavy glasses and without causing 
significant loss of vision as compared to a normal person. 
These and other features and objects of the present invention will be more 
fully understood through the following detailed description in which 
corresponding reference numerals represent corresponding parts throughout 
the several views.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
At the outset, the invention is described in its broadest overall aspects 
with a more detailed description following. In its broadest overall 
aspects, the intraocular lens of the present invention operates on a 
principle similar to the focusing arrangement of a pinhole camera. In a 
pinhole camera the aperture is small enough so that only a thin bundle of 
light rays, i.e., a small blur circle, passes through the pinhole to 
ultimately produce a sharp image on the film. By properly masking the 
intraocular lens implant all the light entering the eye is in a thin 
bundle, which is perceived as a sharp image by the retina; therefore, more 
of the world is in focus. This effect works well when there is plenty of 
light; however, when there is little ambient light a pinhole does not 
allow enough light to reach the retina. The IOL of the present invention 
is masked in some areas by black opaque material. In bright light the 
pupil constricts, and the mask allows only a pinhole of light into the 
eye. 
The pinhole defined by the mask has a diameter of 1-3 mm. This forms a 
sharp pinhole image on the retina. In dim light, the pupil dilates. When 
the pupil is dilated, light can pass through the pupil and the pinhole in 
the IOL, but also around the edges of the mask away from the pinhole 
increasing the number of light rays which reach the retina. Thus, a 
greater percentage of available light enters the eye in low light 
conditions allowing a person to see. 
In one important embodiment, the area of the IOL defined by the mask as a 
pinhole has an added power. In this embodiment, the dioptic power of the 
central IOL region (diameter between 1-3 mm) is slightly higher (0.5 to 
2.5 diopters higher) than the base IOL power. This added power is not as 
strong as bifocal IOLs now being tested which have powers to approximately 
3 diopters. Yet, this "intermediate add" helps the pinhole focus up close 
while at the same it does not produce the decrease in contrast seen with 
higher power adds. Also this intermediate add does not disturb distance 
vision when the pupil is constricted around the add in bright light 
conditions. The power of the lens peripheral to the opaque mask is that 
needed for distance vision. Thus, the lens can have two powers 
(intermediate and distance), separated by an opaque area. 
Referring to FIG. 1, the masked intraocular lens is indicated generally by 
10. The mask is indicated by 11. The transparent part of the lens 10 is 
indicated by 12. As can be seen from FIG. 1, the pupil 13 of the eye 25 
has constricted so that there is an approximately 4-4.5 mm diameter 
opening x which allows light through the eye 25 to the retina 18. The 
masking 11 of the intraocular lens 10 reduces this 4-4.5 mm diameter x to 
approximately 1-3 mm as is shown by bracket y. The eye 25 in this 
situation acts as a pinhole camera, and the image 16 on the retina 18 is 
sharp for near objects, far objects, and everything in between. 
Shown in FIG. 2 is a schematic drawing of the eye 25 with the implanted 
intraocular lens 10 of the present invention and the optics of the eye and 
IOL lens in low light conditions. Here, the pupil 13 has dilated to 
approximately 5-7 mm (x') in diameter due to the low light conditions. 
With this dilation, the pupil 13 allows much more light to reach the IOL 
10 and allows light to reach the unmasked portion 12. The diameter of the 
area of the transparent portion 12 of the IOL 10 through which light 
passes is now the enlarged diameter represented by the bracket y' in FIG. 
2. Thus, more rays of light reach the retina 18. The eye 25 in this 
situation no longer acts as a pinhole camera, but the intraocular lens 10 
allows enough light to reach the retina 18 so that an image 16 is 
maintained although it may be slightly blurry. 
Referring to FIGS. 3 to 5, frontal views of the eye 25 are shown with the 
implanted intraocular lens 10. FIG. 3 shows the IOL 10 in the eye 25 as it 
would appear to a viewer in high light conditions. The contracted pupil 13 
and the mask 11 of the IOL 10 function together to define a pinhole 
aperture 15. At this point the eye 25 is functioning as a pinhole camera. 
In FIG. 4, the ambient light has been reduced and the pupil 13 has dilated 
to compensate for this light reduction. The aperture 15 created by the 
opening in the pupil 13 and the masked IOL 10 is larger than in high light 
conditions. The eye 25 in this condition is still functioning as a partial 
pinhole camera although there may be some fuzziness in the image (not 
shown) received. In FIG. 5, the pupil 13 is fully dilated due to the low 
light condition and the aperture 15 is very much expanded. The eye 25 in 
this case is no longer functioning as a pinhole camera and enough light is 
allowed through the mask 11 to allow a person to see. The area of the IOL 
through which light may pass when the pupil is fully dilated is larger 
than the area of the IOL through which light may pass when the pupil is 
constricted. 
In the preferred embodiment of the invention, it is envisioned that the 
masked IOL 10 will be inserted in the posterior chamber 27 of the eye 25. 
Currently this type of intraocular lens implantation technique is the most 
common in the United States. Shown in FIGS. 1 and 2 is a schematic view of 
the masked intraocular lens 10 containing J-loops 20. It is also 
envisioned that the intraocular lens 10 of the present invention can be 
manufactured with C-loops or circular loops. The IOL of the present 
invention preferably includes a means for attachment to the eye. However, 
a particular means for attachment forms no part of the invention. It is 
envisioned that the masked intraocular lens 10 will be implanted by "in 
the bag" fixation. Further, "in the bag" or ciliary sulcus fixation can be 
used for posterior chamber lens fixation. Of course, the method used to 
implant the IOL of the present invention forms no part of the invention. 
Shown in FIGS. 6 and 7 is a second embodiment of the masked IOL 10 of the 
present invention. In FIGS. 6 and 7, part of the lens 10 is blocked off by 
an opaque annular black mask 11. In bright light, the pupil constricts so 
that only light within the area of the mask can pass through with the mask 
11 allowing only a pinhole of light to pass through the IOL 10, thus 
forming a sharp image 16 on the retina 18. In FIG. 7, in dim light 
conditions, the pupil 13 dilates, and light enters the eye 25, not only 
through the pinhole 15, but also from the circular clear area 17 
surrounding the opaque annulus 11. This results in an enlarged aperture 
that maintains the amount of light entering the eye. Pinhole research 
(Miller et al., supra) has shown that a 1.8 mm pinhole maximally 
accomplishes continuous focusability from reading distances all the way 
out to infinity, equivalent to an accommodation of three diopters. 
However, for the lens of the present invention, the preferred pinhole is 
1-3 mm in diameter, not just 1.8 mm. The preferred outside diameter of the 
opaque annulus 11 is 4-6 mm. The preferred width of the opaque annulus is 
approximately 1.5 mm. The area of the opaque annulus is larger than the 
area of the pinhole. The preferred configurations are shown in Table 1 
below. 
TABLE 1 
______________________________________ 
Width of Pinhole 
Pinhole Diameter 
Plus Masked Annulus 
IOL Diameter 
______________________________________ 
1 mm 4 mm 6-7 mm 
2 mm 5 mm 6-7 mm 
3 mm 6 mm 7 mm 
______________________________________ 
Shown in FIGS. 8, 9, and 10 are front views of an eye with one embodiment 
of the masked IOL 10 of the present invention implanted as it would appear 
to a viewer. FIG. 8 shows the eye in bright light conditions where the 
pupil 13 has constricted to a diameter x of approximately 3.5 mm around 
the mask 11 of the IOL 10 such that only a pinhole of light is allowed 
through the IOL 10. The pinhole diameter y, may be 1-3 mm. In FIG. 9 the 
ambient light has decreased to moderate conditions and the pupil 13 of the 
eye is dilated to a diameter x' of approximately 4.5 mm so that light is 
let in through the pupil 13 and past the clear region 17 between the outer 
edge of the annulus 11 and a remainder of the IOL not blocked by the pupil 
13. Of course, light also passes through the center of the masked IOL 10 
on to the retina. The area of the aperture through which light passes is 
that of a circle having a diameter of 4.5 mm minus the area of the annulus 
11. In FIG. 10, where ambient light has decreased further, the pupil has 
dilated even more to a diameter x" of approximately 5.6 mm, thus allowing 
a bigger ring of light to pass through the clear region 17. The area of 
the aperture through which light passes is that of a circle with a 
diameter of 5.6 mm minus the area of the annulus 11. In the drawings, the 
iris is indicated by 22. 
In order to compensate for the slight pinhole enlargement over 1.8 mm, the 
lens power of the central region may be enhanced slightly, by 0.5-2.5 
diopters. This intermediate add helps the pinhole to focus from far away 
to up close, while at the same time not producing the decrease in contrast 
seen in the bifocal IOLs with approximately 3.0 diopter adds now being 
tested. In addition, by not using a full 3.0 diopter add, the patient can 
see far distances with a constricted pupil on a sunny day. 
Shown in FIG. 11 is a model eye for conducting experiments to determine the 
effectiveness of the masked IOL of the present invention. A model eye was 
constructed as shown in FIG. 11. In this figure, an illuminated Snellen 
Chart 35 is shown which represents the outside world at reading distance. 
Also shown is a model cornea 36, a model pupil 37 and a model masked IOL 
38. The cornea is simulated with an appropriately powered spherical convex 
lens 36 as is the masked IOL 38. The pupil is simulated with a variable 
aperture 37 and the retina is simulated by a screen 39 upon which an image 
is projected. This "retinal" image was photographed using a non-contrast 
enhancing film by the camera 30. 
The results of the model eye testing are shown in FIGS. 12 through 14. In 
FIG. 12, the model eye was compared using a standard IOL and a masked IOL 
in accordance with the present invention as represented by 38 of FIG. 11. 
The model eye was set up to look at an object at a reading distance 
through an average size pupil (3.4 mm). The masked IOL, as shown in FIG. 
12, produces a clearer image 40 than the image 42 produced by a standard 
IOL. The masked IOL has overcome the large refractive error and has 
brought the near image 40 into sharp focus. 
In FIG. 13, the model masked IOL in accordance with the present invention 
as represented by 38 of FIG. 11 was tested to determine its performance 
with different sized pupils. With an average sized pupil, diameter x of 
3.4 mm as shown in FIG. 13, the quality of the image 44 is very good, as 
would be expected from the pinhole 15. As the pupil 37 dilates to a 
diameter x' of 4.5 mm and then to a diameter x" of 5.6 mm, and more light 
is admitted to the eye, the images 46, 48 achieved degrade although not 
significantly. 
In FIG. 14, it is shown that the masked IOL also corrects for astigmatism. 
Cataract extraction introduces a certain amount of post-operative 
astigmatism in most patients and refractive correction is often needed. On 
the left of FIG. 14 is an image 50 produced by an astigmatism of +1.5 
diopters. This degree of astigmatism is not uncommon on post-operative 
cataract patients. On the right is an image 52 of the same astigmatism, as 
seen through the masked IOL 38. As can be seen from FIG. 14, the image 52 
is much clearer. 
Decentration of the IOL is a problem in post-operative cataract patients. 
Recent epidemiological data has shown that 84 percent of all IOLs show 
decentration of less than 1.1 mm. Larger decentrations are a rare event. 
The range of decentration in 99.5 percent of all cases of IOLs goes from 
0.1 mm to 1.9 mm. In other words, fewer than one-half of one percent of 
the IOLs have decentrations more severe than 1.9 mm. Decentration is 
especially a problem for known bifocal type IOLs. Shown in FIG. 15A is a 
masked IOL 10 centered within the pupil 13. In this case, there is 
obviously no problem because the full aperture, a 2 mm diameter y in this 
example, is exposed. In FIG. 15B there is shown a 1.1 mm decentration. 
This decentration does not effect patient vision with the masked IOL 
design. The aperture area y' is 2 mm by 1.6 mm. Even in FIG. 15C, the 
pinhole is perfectly functional with a 1.9 mm decentration. The aperture 
area y" is 1.8 mm.times. 1.0 mm. Since only one-half of one percent of the 
IOLs would have decentrations greater than that shown in FIG. 15C, the 
masked IOL of the present invention would be functional 99.5 percent of 
the time. 
However, in decentrations of more than 1.9 mm, standard IOLs are often 
removed surgically. The masked pinhole allows one to solve even such a 
large decentration without surgery. In FIG. 16A, a decentration of 2.3 mm, 
which is extremely rare, occurring in less than 0.1 percent of patients, 
is shown. In FIG. 16B, the opaque mask 11 has a preformed cut 55 that aids 
the ophthalmologist in creating a larger opening. As shown in FIGS. 16B 
and 16C, it may be possible to disintegrate the edge of the mask along the 
preformed cut 55 with a Nd:YAG laser 60. The masked IOL has a new larger 
aperture 15 which functions as a pinhole. 
Table 2 below shows a comparison of a new diffractive IOL 62, shown in FIG. 
17, and the masked IOL 10 of FIG. 6 of the present invention. 
TABLE 2 
______________________________________ 
Masked IOL Diffractive IOL 
______________________________________ 
Corrects for Astigmatism? 
YES NO 
Exact Lens Power Critical? 
NO YES 
# of Dioptric Powers 
CONTINUOUS 2 
Decreases Contrast 
NO YES 
Sensitive to Displacement 
NO NO 
Night Glare a Problem? 
NO YES 
______________________________________ 
There are listed six bases of comparison. The masked IOL 10 corrects for 
astigmatism while the diffractive IOL 62 does not. The diffractive IOL 62 
requires the production of the exact lens power needed post-operatively 
which is critical to the functioning of the lens 62 while such is not the 
case for the masked IOL 10. The number of dioptic powers is continuous in 
the masked IOL 10 allowing vision at all distances while the diffractive 
IOL 62 has only two dioptic powers. The diffractive IOL 62 decreases 
contrast which is not the case with the masked IOL 10. The masked IOL 10 
is insensitive to displacement as is the diffractive IOL 62. Finally, the 
diffractive IOL 62 has a problem with night glare (because of light 
scattering from the rings) while such is not the case with the masked IOL 
10. 
In the preferred embodiment of the intraocular lens of the present 
invention, the optic is made of a material such as polymethylmethacrylate 
(PMMA). This material is commonly used for making intraocular lenses. The 
fabrication of the intraocular lens, per se, forms no part of the present 
invention. The mask of the present invention is made of an opaque 
material, such as suture dye. The suture dye is applied to the PMMA to 
produce an opaque pattern on the IOL of the present invention. The dye may 
be applied to either the back or front surface of the lens or both. It may 
also lie within the lens. The important point is that it be applied in 
such a way that that part of the IOL which is to be masked is opaque. In a 
preferred embodiment, the dye will be applied to the back surface so that 
it can be removed with a Nd:YAG laser in the case of decentration as 
described above. 
While the foregoing invention has been described with reference to its 
preferred embodiments, it should not be limited to such embodiments since 
various alterations and modifications will occur to those skilled in the 
art. For example, the mask of the present invention can be a different 
shape than is shown in the figures. All such variations and modifications 
are intended to fall within the scope of the appended claims.