FIELD OF THE INVENTION 
     This invention relates to speculums for opening, and maintaining in an open position, eyelids, and, more particularly, to speculums having arrangements for being retained at specific opened positions. 
     DESCRIPTION OF THE PRIOR ART 
     Speculums are known in the prior art for opening, and maintaining in an open position, eyelids during ocular procedures or surgery. U.S. Published Patent Application No. 2011/0098538, which published on Apr. 28, 2011, to the inventors and assignee herein, discloses a unitarily formed speculum having an adjustable position retaining arrangement. With this speculum being formed of plastic material, the ability to permit adjustment of the position retaining arrangement and provide secure retention thereof at a desired portion is limited. Memory of the constituent material is relied upon to provide the retentive force; however, excessive deformation and other factors may undermine the material&#39;s inherent memory. 
     SUMMARY OF THE INVENTION 
     A speculum is provided herein which includes first and second arms, each having a channel formed thereon adapted to the shape of an eyelid. A hinge connects the first and second arms which permits the first and second arms to selectively rotate about an axis of rotation. The selective rotation causes the first and second channels to selectively move closer and farther apart. First and second elements are respectively located on the first and second arms, with the first and second elements being configured to cooperatively retain the first and second arms in select rotational positions with interfering interengagement between the first and second elements limiting rotation of the first and second arms. A slot is defined in the second arm to partially separate a first portion of the second arm from a second portion of the second arm with the first portion being displaceable away from the second portion. The second element is located on the first portion. Advantageously, with this arrangement, the first portion acts as a spring-loaded hinge which applies not only biasing force to the second element for retention, but also permits the second element to be separable from the first element. The subject invention provides a mechanical feature beyond the inherent memory of the material for operation of the speculum. 
     These and other features of the invention will be better understood through a study of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a speculum formed in accordance with the subject invention; 
         FIGS. 2 and 3  are, respectively, front and back elevational views of a speculum formed in accordance with the subject invention; 
         FIG. 4  is a top plan view of a speculum formed in accordance with the subject invention in a pre-use state; 
         FIGS. 5 and 6  show the opening of a speculum formed in accordance with the subject invention; 
         FIGS. 7-9  show the closing of a speculum formed in accordance with the subject invention; and, 
         FIG. 10  shows a maximum inward position of a speculum formed in accordance with the subject invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The subject invention relates to speculums which are useable for opening, and maintaining in an open position, eyelids during ocular procedures or surgery. Furthermore, the subject invention is directed to speculums formed from thermoplastic material, including, but not limited to, unitary, one-piece speculums. The subject invention provides improvements over such known designs. U.S. Published Patent Application No. 2011/0098538 A1, to the inventors and assignee herein, discloses various embodiments of such speculums. U.S. Published Patent Application No. 2011/0098538 A1 is incorporated by reference herein in its entirety. 
     With reference to the Figures, a speculum  10  is shown which includes first and second arms  12 ,  14  which are connected by a hinge  16 . The first and second arms  12 ,  14  each include a distal end  18  having formed thereon a channel  20  adapted to the shape of an eyelid. Also, the first and second arms  12 ,  14  each include a proximal end  22 , located opposite the distal end  18 . In a preferred embodiment, as shown in the Figures, the hinge  16  is located at a mid-point of the first and second arms  12 ,  14  between the distal and proximal ends  18 ,  22 . The first and second arms  12 ,  14  may be rotated about an axis of rotation, designated by reference numeral  24  ( FIG. 4 ), to selectively cause the distal ends  18 , and, hence, the channels  20 , to come closer or further apart as need be. The axis of rotation  24  preferably coincides with the hinge  16  ( FIG. 4 ), but, alternatively, may be spaced therefrom. Preferably, the speculum  10  is formed of thermoplastic material, such as high impact polystyrene (HIPS). Also, it is preferred that the speculum  10  be unitary. The speculum  10  may be formed by injection molding. 
     It is preferred that the speculum  10  be provided with a position retaining arrangement, whereby the first and second arms  12 ,  14  may be retained in a particular relative position. With reference to the Figures, complementary first and second elements  26 ,  28  are formed on the first and second arms  12 ,  14 , respectively. Preferably, the first element  26  includes a series of teeth  30 , each defining a peak  32 . By way of non-limiting example, the teeth  30  may be saw-tooth shaped, but other shapes are possible. Recesses are defined between adjacent pairs of the teeth  30 . The second element  28  preferably includes a pointer  36  formed to nest within the recesses  34  between the peaks  32  of adjacent pairs of the teeth  30 . Two or more of the pointers  36  may be also arranged in series to engage the teeth  30 . 
     Preferably, the teeth  30  are configured to by-pass the pointer  36  over a predetermined range of relative movement between the first and second arms  12 ,  14 . The pointer  36  is formed to restrict movement of the teeth  30  relative thereto. 
     As shown in  FIG. 3 , in a preferred embodiment, a pair of the set of teeth  30  is provided with a channel  38  therebetween. The channel  38  permits the teeth  30  particularly the two sets of the teeth  30 , to straddle a portion of the second arm  14 , in providing stability during interengagement of the complementary elements  26 ,  28 . In addition, a pair of the pointers  36  may be utilized. 
     With reference to  FIGS. 1 and 4 , in the initial pre-use state, the first and second elements  26 ,  28  are preferably separated and out of contact. The speculum  10  may be maintained in the pre-use state through inherent memory provided to the speculum  10  during manufacturing. 
     During use, and, as shown in  FIG. 5 , with initial coming together of the proximal ends  22  of the first and second arms  12 ,  14 , and resulting separation of the distal ends  18  in opening the speculum  10 , the first element  26  is caused to engage the second element  28 , particularly with the teeth  30  by-passing the pointer  36 . Preferably, the first and second arms  12 ,  14  may be engaged between the hinge  16  and the distal ends  18  to cause opening of the speculum  10 . Alternatively, or in addition, the proximal ends  22  may be engaged to cause opening of the speculum  10 . The pointer  36  imparts resistance against separation of the distal ends  18  due to interfering interengagement with the teeth  30 . A threshold amount of force allows such resistance to be overcome to permit adjustment of the teeth  30  relative to the pointer  26 . 
     With the pointer  36  nesting between adjacent pairs of the teeth  30 , as shown in  FIG. 6 , the relative positions of the first and second arms  12 ,  14  may be adjusted and maintained as needed. Thus, the states shown in  FIGS. 5 and 6 , adjusted from the pre-use state of  FIG. 4 , may be achieved and maintained. 
     The speculum  10  is used to open the eyelids of a patient and to maintain that opened state. The degree to which the eyelids are opened may be adjusted as described above. It is noted that the eyelids may impart a reactionary closing force against the speculum  10 . The threshold level of resistance against relative movement generated by the first and second elements  26 ,  28  must be greater than the closing force applied by the eyelids. 
     The force of retention to maintain the interengagement of the first and second elements  26 ,  28 , such as in the state shown in  FIG. 6 , is imparted at least in part by the inherent memory of the constituent material of the speculum  10 . To enhance the retentive force, a slot  40  is defined in the second arm  14  to partially separate a first portion  42  of the second arm  14  from a second portion  44  of the second arm  14  with the first portion  42  being displaceable away from the second portion  44 . The second element  28 , which may be in the form of the pointer  36 , is located on the first portion  42  of the second arm  14 . A connecting portion  46  extends between, and connects, the first and second portions  42 ,  44 . 
     The first portion  42  is initially in an unstressed rest state as shown in  FIGS. 1 and 4 . The connecting portion  46  acts as a fulcrum for permitting rotation of the first portion  42  relative to the second portion  44  in displacement of the first portion  42  from the rest state and away from the second portion  44 . In addition, with displacement of the first portion  42  from the rest state and away from the second portion  44 , the connecting portion  46  acts as a “living hinge” which generates a reactive biasing force applied to the first portion  42  which urges the first portion  42  towards the rest state. This biasing force acts to provide additional retentive force to the second element  28  against the first element  26  in counteracting at least a portion of the reactionary closing force generated by the eyelids during opening of the speculum  10 . 
     With the first and second elements  26 ,  28  being in interengagement, e.g., as shown in  FIG. 6 , it is preferred that the first portion  42  be in the rest state. Alternatively, the first portion  42  may be in a state displaced from the rest state (away from the second portion  44 ) with the first and second elements  26 ,  28  being in interengagement. This causes the connecting portion  46  to apply a biasing force to the first portion  42  which urges the first portion  42  towards the rest state. This biasing force provides additional retentive force to the second element  28  against the first element  26 . In addition, displacement of the first portion  42  away from the second portion  44  allows for separation of the first and second elements  26 ,  28  ( FIG. 8 ). 
     It is preferred that displacement of the first portion  42  relative to the second portion  44  be limited. In particular, it is preferred that the connecting portion  46  not be over stressed so as to cause yielding or plastic deformation thereof. It is desired to maintain the deformation of the connecting portion  46  within limits of elastic deformation. 
     To limit the range of displacement of the first portion  42  relative to the second portion  44 , it is preferred that a stop member  48  be provided which extends from the second portion  44  and is configured to limit rotation of the first portion  42  about the connecting portion  46  in being displaced away from the second portion  44 . The stop member  48  is configured to physically contact, and limit movement of, the first portion  42 , as shown in  FIGS. 8 and 9 , within a predetermined range of motion based on the material characteristics of the constituent material of the speculum  10 . It is preferred that the stop member  48  limit the movement of the first portion  42  inside of the elastic range of motion of the connecting portion  46  with avoidance of approaching any yielding or plastic deformation thresholds. 
     With reference to  FIGS. 7-9 , the speculum  10  may be closed after a procedure so as to be released from a patient&#39;s eyelids. To cause closing, the proximal ends  22  may be caused to move apart. As a result, the distal ends  18 , and hence the channels  20 , move closer together. The interengagement of the first and second elements  26 ,  28  may be forcibly overcome, whereby the pointer  36  is caused to traverse the teeth  30  in a ratcheting fashion. The connecting portion  46  may permit responsive movement of the second element  28  in and out of interengagement with the first element  26  during such adjustment. Alternatively, and more preferably, the first portion  42  is caused to be displaced away from the second portion  44  with the second element  28  coming out of interengagement with the first element, as shown in  FIG. 8 . This separation allows for the first and second arms  12 ,  14  to be rotated to the closed position with no or minimal resistance generated between the first and second elements  26 ,  28 . As shown in  FIG. 9 , the first and second elements  26 ,  28  may be caused to be separated and spaced apart in a closed state of the speculum  10 . 
     It is noted that the teeth  30  may be configured to be generally one-way passable having ramped surfaces  30   a  facing the pointer  36  and having steep surfaces  30   b  facing away from the pointer  36  ( FIG. 5 ). This arrangement allows for the pointer  36  to ride over and by-pass the ramped surfaces  30   a  in opening the speculum  10 . However, the steep surfaces  30   b  are configured with little or no angle relative to the pointer  36  so as to inhibit or limit reverse movement of the pointer  36  relative to the teeth  30  in the closing direction. Displacement of the first portion  42  to separate the pointer  36  from the teeth  30  may be relied upon to permit reverse adjustment of the pointer  36  relative to the teeth  30 . With this arrangement, the teeth  30  and the pointer  36  may be configured to have tight interengagement which further enhances the retention generated therebetween. 
     With reference to  FIG. 10 , inward rotation of the first and second arms  12 ,  14  may be limited by contact between the channels  20  or the distal ends  18 . In addition, or alternatively, stop blocks  56  may be provided on the hinge  16 , as shown in  FIG. 10 , which are configured to come into contact to limit inward motion of the first and second arms  12 ,  14 . Conversely, outward rotation of the first and second arms  12 ,  14  may be limited by contact between the proximal ends  22  of the first and second arms  12 ,  14 . In addition, or alternatively, the first element  26  may be configured to limit or inhibit outward range of movement. For example, the teeth  30  may be arranged to extend over a length coinciding with the desired range of motion. The first element  26  can be configured such that motion of the pointer  36  past the teeth  30  in the opening direction is limited or inhibited, e.g., with the first element  26  being configured to interferingly engage the pointer  36  past the teeth  30  in creating a stop or frictional engagement therewith which inhibits further movement. 
     Preferably, the slot  40  extends from an inner edge  50  of the second arm  14  and the stop member  48  extends from an outer edge  52  of the second arm  14  ( FIG. 4 ). The hinge  16  extends between the inner edges  50  of the first and second arms  12 ,  14 . It is also preferred that the slot  40  be located between the hinge  16  and the proximal end  22  of the second arm  14 . The slot  40  preferably terminates with an enlarged end  54 , past which the connecting portion  46  extends. The enlarged end  54  is preferably circular in shape. The enlarged end  54  acts as a stress relief to limit breaks or cracks propagating from the slot  40 , particularly with displacement of the first portion  42 . 
     The connecting portion  46  is preferably slender in a direction along a longitudinal axis of the second arm  14  to allow for bending thereabout. To provide sufficient inherent memory in the connecting portion  46  to generate the biasing force described above, as shown in  FIG. 1 , it is preferred that the connecting portion  46  be formed with increased thickness in a direction perpendicular to the longitudinal axis of the second arm  14  as compared to surrounding regions of the speculum  10 , particularly regions of the first and second portions  42 ,  44  adjacent the slot  40  and the connecting portion  46 . 
     To facilitate adjustment of the speculum  10 , the proximal ends  22  may be configured to define finger tabs  58 , as shown in  FIGS. 1 and 4 . The finger tabs  58  may be formed solid with a concave or textured surface to enhance frictional engagement therewith. Alternatively, an aperture (not shown) may be formed in the finger tabs  58  which allows for partial or whole insertion of a user&#39;s fingers. 
     In addition, or alternatively, to facilitate adjustment of the speculum  10 , one or more tabs  60  may be formed to extend from the first arm  12  and/or the second arm  14 , as shown in  FIGS. 1-3 . The tabs  60  each include an engagement surface  62  configured to be pressingly engaged to cause the first and second arms  12 ,  14  to be opened. As will be appreciated by those skilled in the art, one of the tabs  60  may be provided on one of the first or second arms  12 ,  14  which would permit relative motion between the first and second arms  12 ,  14 . The tabs  60  may also include secondary engagement surfaces  64 , each disposed to face away from the corresponding engagement surface  62 , formed to be pressingly engaged to cause the first and second arms  12 ,  14  to move towards a closed position. It is preferred that the tabs  60  be located between the hinge  16  and the channel  20  of the respective arm  12 ,  14 . The tabs  60  may be provided on a speculum  10  (formed as described above) which does not include the slot  40 . It is preferred that the tabs  60  be provided on each of the first and second arms  12 ,  14  where the slot  40  is provided.
A speculum is provided herein which includes first and second arms, connected by a hinge, each having a channel formed thereon adapted to the shape of an eyelid. First and second elements are respectively located on the first and second arms configured to cooperatively retain the first and second arms in select rotational positions. A slot is defined in the second arm to partially separate first and second portions of the second arm with the first portion being displaceable away from the second portion. The second element is located on the first portion. Advantageously, with this arrangement, the first portion acts as a spring-loaded hinge which applies not only biasing force to the second element for retention, but also permits the second element to be separable from the first element. The subject invention provides a mechanical feature beyond the inherent memory of the material for operation of the speculum.