Polyprismatic lens for enhancing human ocular motility

A device for enhancing the range of vision of a person with low eye motility which includes a plurality of parallel or concentric prisms with bases disposed paracentrically on a transparent medium. The prisms cooperate to enhance the angle of vision of the person as he moves the eye over a small angle, and simultaneously improves the aesthetic appearance of the person by increasing the apparent movement of the eye, as seen by an observer of persons with an artificial eye, which moves less than normally.

BACKGROUND OF THE INVENTION 
a. Field of Invention 
This invention pertains to a polyprismatic lens and, more particularly, to 
a lens having a plurality of parallel prisms. The power of the prisms is 
increased from a central portion of the lens towards the periphery. The 
lens is useful for enhancing the actual or apparent effect of eye movement 
of a wearer. 
b. Description of the Prior Art 
The motility of an eye (the ability of a person to move his/her eye) is 
frequently affected by various pathological causes such as extra-ocular 
muscle disease or by motor nerve innervational deficiency. Persons having 
this problem have in effect a reduced range of eye movement and have 
trouble directing the affected eye toward objects which do not lie 
directly in front of them. In most situations, these persons must turn 
their heads in order to bring the objects into their central vision. 
Furthermore, if this condition affects only one eye, the affected person's 
face and appearance becomes unsymmetrically and aesthetically displeasing. 
This latter factor is also applicable to people who lost an eye and must 
wear a prosthesis. Usually, because of either retained extra-ocular muscle 
dysfunction or cicatricial restrictive reasons, the prosthesis device may 
be hard or impossible to move beyond a small angle. 
Until the present invention, there were no devices which could enhance 
small eye movement satisfactorily. For example, in U.S. Pat. No. 
3,423,151, E.B. White discloses a pair of glasses with a prism secured to 
the frame for extending the field of vision of the wearer. However, this 
approach is useful only for a small number of patients because it requires 
the ability to look sideways. Furthermore, it does not improve the 
aesthetic appearance of the wearer. 
OBJECTIVES AND SUMMARY OF THE INVENTION 
An objective of the present invention is to provide a device which 
increases the effective range of eye movement of a wearer. 
A further objective is to provide a device which may be mounted on or 
incorporated into eye glasses already worn by a person, thereby reducing 
overall expenses. 
A further objective is to provide a device which improves the aesthetic 
appearance of a person by enhancing his apparent eye movement. 
Other objectives and advantages of the invention shall become apparent from 
the following description of the invention. Briefly, a device constructed 
in accordance with this invention comprises a plurality of prisms disposed 
on a transparent medium such as a lens. The prisms are preferably disposed 
paracentrically with respect to a neutral central portion of the lens. The 
power of the prisms is gradually increased from the center outwardly, 
thereby enhancing the eye movement of a wearer and increasing his 
effective arc of scanning. The prisms may be disposed in parallel to each 
along an axis extending in a preselected direction, such as a vertical or 
horizontal direction. Prisms oriented along different axes may be 
optically superimposed. Alternatively, the prisms may be arranged 
concentrically around the neutral region of the lens.

DETAILED DESCRIPTION OF THE INVENTION 
A set of prisms arranged in accordance with this invention is shown in FIG. 
1. In this Figure, the set 10 includes three prisms 12, 14, 16 disposed 
vertically adjacent to an optically neutral region 18. Preferably, the 
prisms are spaced evenly, and the power of each prism is increased as its 
distance increases from the neutral region. For example, in FIG. 1, prim 
12 may power of 10.DELTA. (diopters), prism 14 a power of 20.DELTA., and 
prism 16 a power of 30.DELTA.. Each prism has a base B around which the 
light is bent by the prism, and an apex A opposite base B. FIG. 2 
illustrates the advantages of this arrangement. Set 10 is mounted on a 
lens 20 which is placed in front of an eye 100 of a person, with neutral 
area disposed substantially along the optical axis 0 of eye 100, with base 
B lying perpendicular to lens 20. Each prism is oriented so its base is 
the closest element of the prism to the axis 0, and apex A is disposed 
away from the axis. In other words, the bases of the prisms face the 
center of the lens 20. FIG. 2 is provided mainly to illustrate the 
invention. Therefore, the lens 20 can be assumed to be a planar lens. 
However, it should be understood that the lens may have other optical 
characteristics selected for correction of defects of the eye 100. Now, if 
the wearer moves his eye 100 to shift his direction of gaze to angle 
.theta..sub.1, light passing through prism 10 is refracted so that his 
direction of looking is increased to intercept objects an at angle 
.theta..sub.1 '. Without prism 12, the angle of gaze of the person is 
limited to .theta..sub.1. Similarly, if the wearer moves his eye more to 
shift his direction of gaze to angle .theta..sub.2, his field of vision is 
increased to .theta..sub.2 ' by prism 16. Because of the increase of power 
of prism 16 compared to prism 12, the angle of scanning is increased 
proportionally. Thus, FIG. 2 illustrates how prism 10 can increase the 
effective range of visual direction of the wearer, and how a relatively 
small eye movement can result in a greater field of gaze then with normal 
lenses. 
Importantly, the arrangement shown in FIGS. 1 and 2 also improve the 
aesthetic appearance of the wearer. When the wearer moves his eye by angle 
.theta..sub.2, with the prisms, it will appear to observers, that the eye 
movement covered an angle of .theta..sub.2 '. Thus, the prisms give the 
appearance that a person moved his eye much more than he actually did. 
This latter effect is especially important for wearers of prosthetic 
artificial eyes, which always move less than the normal amount. As 
explained before, these persons usually have very limited eye movement. 
Preferably, as shown in FIG. 3, the set of prisms includes a second group 
of prisms 10' being arranged symmetrically opposite the first group 10. 
The prisms are arranged in parallel to each other and perpendicular to an 
axis. This axis (Y--Y) may be vertical as shown in FIG. 3, if it is 
desired to enhance the range of eye movement in a vertical plane. The 
prisms are preferably arranged symmetrically with respect to neutral area 
18. Thus, prisms 12 and 12' have lower power (such as 10.DELTA.), prisms 
14 and 14' have a higher power (20.DELTA.) and prisms 16 and 16' have the 
highest power (30.DELTA.) with all prisms arranged with their bases 
directed toward the neutral, central area. It should be understood that 
for purposes of clarity only three prisms are shown for each set, however 
it should be understood that this number can be increased or decreased. 
Alternatively, the prisms may be arranged symmetrically along a horizontal 
axis (X--X) as shown in FIG. 4. This arrangement provides an increased 
amplitude of eye movement in a horizontal direction. 
Two symmetrical sets of prisms arranged along orthogonal axes may also be 
superimposed optically to obtain the arrangement shown in FIG. 5. This 
arrangement not only increases the field of vision along both the 
horizontal and vertical planes but because of the combined effect of the 
two sets of prisms, it also enhances diagonal eye movement, i.e. eye 
movement at an angle with respect to either the horizontal or vertical 
plane. From a mechanical view point, it is difficult to provide orthogonal 
prisms on the same side of a lens. Therefore, it is preferable to have one 
set of prisms 1OA, 10' on one side of the lens and a different set of 
prisms 1OB orthogonal to the first set, disposed on the other side of a 
lens 22. This arrangement is shown in FIGS. 6 and 7. 
In a somewhat preferred embodiment of the invention, instead of being 
parallel, the prisms may be formed as concentric, circular or toroidal 
prisms (FIG. 8) surrounding an optical neutral center 32, about 2mm in 
diameter. In this arrangement each prism of a series has a base 34 
arranged circumferentially to center 32, with a conical slope 36 extending 
away from the center as shown. This arrangement has the same effect as the 
two-dimensional arrangement shown in FIGS. 6 and 7 but, it is simpler to 
make and is disposed on the same side of a lens. 
As previously mentioned, the optical power of each prism is generally 
proportional to its distance from the neutral zone. This optical power may 
range from 5 to 60.DELTA.. If small prisms are used, then the prisms may 
be partitioned in subgroups, each subgroup having a preselected optical 
power. For example, in FIG. 8, prisms 38, 40 and 42 may belong to the same 
subgroup, and have the same optical power. Prism 30 (and other prisms not 
shown for the sake of clarity) belongs to a next subgroup having a higher 
optical than prisms 38, 40 and 42. The optical power of adjacent subgroups 
may be increased in regular increments of, for example 5.DELTA.. 
The prisms may be formed in any well known manner in the art. For example, 
the prisms may be cut simultaneously with the lens. Thus, the prisms and 
the lens may be made of glass, a plastic material or other transparent 
medium. Alternatively, the prisms may be made separately and then secured 
to the lens with an adhesive. 
Obviously, numerous modifications may be made to the invention without 
departing from its scope as defined in the appended claims.