in one embodiment , an iol may provide accommodating capability by forward movement in the eye , varying the distance of the iol or lens optic from the retina , and / or curvature change of the lens optic . to achieve these affects , the iol may make use of the forces of zonule tension from ciliary muscle contractions . in addition , vitreous forces may act upon the iol . vitreous forces are also reliant , at least in part , on ciliary muscle contractions wherein such contractions result in posterior bulking within the eye , which decreases the volume of the vitreous cavity . since the vitreous volume is fixed , the pressure on the contraction of the ciliary muscle cause vitreous movement wherein the peripheral vitreous is pushed back and the central vitreous moves oppositely and , therefore , forwardly . consequently , the movement of the vitreous may push the lens optic forward in the eye . it appears that forward movement of the lens optic must be significant in order to adjust the lens power for example to provide near vision . however , minor curvature changes on the lens optic appear to change the lens power significantly . an iol providing accommodation by forward movement in the eye and / or curvature change of the lens optic is shown in fig1 a and 1c to 1 e . in one embodiment , an iol 10 a includes a lens optic 12 a and a haptic 14 a . as is known , lens optic 12 a provides for the corrective refraction of light for focusing to the retina , while haptic 14 a is a supporting structure for mounting the optic in the capsular bag . haptic 14 a includes mounting points 18 a , which engage against the capsular bag . the lens optic is secured to the haptic through flexible , elastomeric membranes 16 a . membranes 16 a together at least substantially encircle optic 12 a . each membrane has a flexibility greater than that of the surrounding materials . in particular , each membrane 16 a has a flexibility greater than that of either lens optic 12 a or haptic 14 a . flexibility may be achieved by selection of materials or , as in the illustrated embodiment , by selection of the thickness of the membrane relative to the surrounding parts . for example , the membranes may be formed thinner and possibly much thinner than the haptic to render it more flexible than that part . while two membranes are shown , it is to be understood that one substantially circular membrane may be employed , if desired . alternately , further membranes may be positioned such that they together encircle optic 12 a . for example , with reference to fig1 b , an iol is shown including four membranes 16 b about optic 12 a . the membranes are able to flex to permit movement of optic 12 a relative to haptic 14 a , in response to the application of force to optic 12 a . the membranes , however , are resilient such that they are biased towards their original form as the application of force is diminished or discontinued . haptic 14 a may be formed in various ways to mount the iol in the posterior chamber or the anterior chamber of an eye and to support the membranes 16 a and therethrough lens optic 12 a . while other haptic forms can be used as desired , in the illustrated embodiment , haptic 14 a is a plate haptic including an upper half 20 a ′ and a lower half 20 a ″. the haptic includes a membrane support ring formed of segments 21 . in particular , each of the upper half and the lower half of the haptic includes a ring segment 21 that extends the haptic upwardly around the optic to support membranes 16 a . in the illustrated embodiment , ring segments 21 frame the membranes 16 a to offer support for the membranes at their outer edges . ring segments 21 may be formed as a part of the haptic or sepearately therefrom with a connection to the haptic . membranes 16 a may be mounted at or close to the optic &# 39 ; s largest diameter side edges 23 ( see fig4 ) and each membrane extends along a section of the circumference about the optic such that membranes 16 a together substantially encircle the optic . the membranes may be independent from each other , for example in one embodiment separated by slits or gaps 22 . in the illustrated embodiment , the iol includes two membranes 16 a about the optic , with each membrane being continuous between its ends and extending substantially about one half the optic circumference . the membranes are spaced apart at each of their ends to form gaps 22 therebetween . the gaps may , for example , be positioned on the sides of the iol between the haptic mounting points 18 a . haptic 14 a may also be discontinuous , for example by forming the upper half 20 a ′ separate from the lower half 20 a ″, for example , at a split or gap 24 adjacent to gaps 22 between membranes 16 a . gaps 22 and 24 reduce stiffness and resistance to bending for the iol wherein only the optic provides stiffness between the upper half and the lower half of the haptic . as such , when the ciliary muscle contracts to change the zonule tension and increase the vitreous pressure , the iol can easily bend between gaps 22 and 24 . furthermore , where gaps 22 , 24 are used that space the surrounding parts , the gaps can allow for greater range of motion to facilitate depth movement of the optic as the parts do not readily bear against each other . gaps 22 , 24 also permit dimensional expansion of the iol wherein the diameter d r of the iol at rest ( fig1 c ) may be extended to diameter d e wherein the iol is expanded about gaps 22 , 24 ( fig1 d ). the expansion to diameter d e facilitates travel of optic 12 a to thereby facilitate accommodation . in an iol having more than two membranes , as in fig1 b , gaps 22 a , 24 a may be formed between each membrane 16 b and between each ring segment 21 a . the ring segments 21 a may be extended about the membranes 16 b to support them on their outer edges . the surface area of optic 12 a and membranes 16 a also act to trap vitreous fluid as it is moved within the eye by ciliary muscle contractions . the form of membranes 16 a act to trap the fluid pressure and this creates a force , arrows f , that acts with the flexibility of membranes 16 a to drive forward movement of the optic . in operation , when the ciliary muscle contracts , vitreous pressure will increase and act on the posterior surface area of the lens optic and membranes 16 a to push the lens optic forward as shown progressively from fig1 c where the iol is at rest through the position of fig1 d to the position of fig1 e . in addition , such movement of optic 12 a and membranes 16 a changes the pressure exerted at side edges 23 of the optic by the membranes . this causes the optic curvature to be changed . when the ciliary muscle relaxes , the vitreous pressure is released and the lens optic will return to its original form ( fig1 c ) and position because of material elasticity . a combination of forward movement and lens optic curvature change may provide the eye with significant accommodating power to focus on near objects . the membranes can be formed at an angle to the optic to enhance their effect on optic curvature change when force is applied thereto . in one embodiment , the membranes together form a frustoconical surface formed at an angle α of 5 to 15 degrees or possibly 10 to 15 degrees from a plane defined through the optic side edges 23 . an increase in angle α increases the degree to which optic 12 a can travel . consequently , it may add more positive power for near vision . the iols can be made from various materials , as would be appreciated by a skilled person . for example , the materials for the optic and possibly for other parts are clear and compatible for use in the body . the materials are selected and formed to be sufficiently stiff to retain the iol form and position in the eye , but to be flexible to react to muscle contractions and vitreous fluid pressure . where a foldable lens is useful , foldable materials such as silicone , acrylic , hydrogel , etc . may be used . one - piece construction may also be useful . in the illustrated embodiment a one - piece construction is used wherein the haptic , ring segments , membranes and optic are formed integral . lens optics useful in the present invention may vary , as desired . for example , a liquid form optic , as shown in fig1 a and 2a , or a solid form optic 12 d , as shown in fig1 b , 2 b and 3 a can be selected for the lens optic . some useful optic forms are shown in fig4 . for example , as shown in fig4 a and 4b , a liquid lens optic 12 a may be used . such a lens optic may include an outer capsule 26 forming an inner chamber 28 that may be filled with liquid material such as silicone or other liquid and clear materials . the lens capsule may be thinned centrally with an increasing peripheral thickness , as shown in fig4 b . in other embodiments , a lens optic 12 b may be used wherein the lens capsule 26 a may be more uniformly thick ( fig4 c ), a lens optic 12 c may be used wherein the lens capsule 26 b can include one thicker side ( fig4 d ). capsule design can be selected to control lens optic shape change and thereby curvature changes resulting from application of pressure . a liquid lens tends to have greater flexibility of a solid lens . solid optics may include , for example , an optic 12 d ( fig4 e ) including a form generally symmetrical about its edges 23 or an optic 12 e ( fig4 f ) that is curved assymetrically on either side of its side edges 23 . if a solid optic is selected , soft and flexible materials may be used to construct the optic in order to facilitate curvature change . it is to be understood that while a particular haptic form is shown , other haptic forms may be used as desired such as , for example , as shown in fig2 a to 2d , a frog leg form haptic 14 b , such as is disclosed in applicant &# 39 ; s corresponding u . s . patent application ser . no . 10 / 248 , 917 or a running leg form , also disclosed in the aforementioned patent application . in another embodiment , an alternate plate form , known as a pie shaped haptic 14 d may be used such as is shown in fig3 a to 3d . in an iol having a pie shaped haptic , membranes 16 b are mounted along their outer edges to haptic 14 d . gaps 22 b may be provided between the membranes and gaps 25 may be formed in the haptic adjacent gaps 22 b to provide the flex about gaps described hereinabove . although not shown , a ring may be positioned or formed between membranes 16 b and haptic 14 d , if desired , for additional support of the membranes . it will be apparent that many other changes may be made to the illustrative embodiments , while falling within the scope of the invention and it is intended that all such changes be covered by the claims appended hereto .
an introocular lens includes an optic ; a haptic ; a flexible membrane substantially encircling the optic and connected between the optic and the haptic , the flexible membrane having a flexibility greater than the optic and the haptic . the flexible membrane permits travel of the optic relative to the haptic to permit accommodation in the eye . the flexible membrane my also drive a curvature change in the optic as it travels during accommodation .