Various ophthalmic surgical procedures require prolonged and/or exact dilation of the iris. Such procedures include phacoemulsification, which is the process of removing the lens due to cataracts or glaucoma. In such procedures, the iris must be held at an optimum dilation in order to insert surgical instruments into the eye through the pupil. In many cases, it is sufficient to provide a mydriatic, such as tropicamide into the eye to achieve sufficient pupil dilation. In some instances, either because the eye is too small, the pupil is too small, the eye is simply incapable of dilating sufficiently or because of the presence of complication from other medications, such as floppy iris syndrome, various mechanical devices have been fabricated to maintain a correct retraction of the iris.
Currently, there are a number of devices designed for expanding or dilating the iris during surgery. These devices include iris hooks, expansion rings, partial rings and instruments which include fixed tension rings on the end. However, all of these devices are limited by their ease, or lack thereof, of insertion and removal. For example, iris hooks require a separate incision through the cornea for each hook and an individual attachment of the iris for each hook. Thus, as at least four hooks are needed to retract the iris during a procedure, and the risk of damage to the eye is concomitantly increased.
Expansion rings require only a single incision for insertion, however, the main disadvantages of such technologies include their bulkiness and rigidity, making them difficult to insert, remove, and manipulate inside the iris through a small incision. Expansion rings are designed to fit inside the pupil and support the iris in an open position. However, they function because they ultimately provide a rigid or semi-rigid device which, in effect, “props” the iris open during surgery. Unfortunately, the need to provide a rigid or semi-rigid bulwark inside the eye makes the insertion and removal of such devices potentially harmful to the eye. Further, such devices are difficult to position if the anterior chamber is shallow or the pupil is less than 4 mm wide. Thus, various size rings are used depending on the size of the patient's eye. However, in some cases, a small size ring is first inserted only to have the iris continue to dilate or to be affected by “Floppy Iris Syndrome” and the ring becomes useless requiring removal before or during surgery. This, too, can result in damage to the eye.
For example, published U.S. patent application 2008/0269888 to Malyugin, discloses a spring-like device contained within an applicator. When deployed, the applicator is inserted through an incision in the cornea and the ring is ejected into the anterior chamber of the eye. Upon ejection, the ring springs open to resemble a square or rectangular wire frame with loops at each corner. In use, a portion of the rim of the patient's iris is inserted into the loops to be clasped thereby. Due to its latent energy, the act of deploying the ring in the eye provides some risk. Further, the use of spring loops to grasp discrete sections of the iris provides opportunities to tear or damage the iris both during insertion and during removal. In addition, even after the portions of iris tissue have been removed from the grasp of the spring loops, the Malyugin ring (now in its extended form) must be removed from the eye using the same small incision. This process sometimes results in the ring being simply cut into pieces to afford its more convenient removal providing further risks due to smaller debris now taking its place.
Similarly, U.S. Pat. No. 6,620,098 to Milverton describes a device for dilating a pupil comprising a discontinuous ring that is deformable so as to be ejected from a catheter or other injection device in a linear form but then re-form its circular shape once deployed in the anterior chamber. The device described by Milverton also has scalloped flange portions on either side of a connecting body portion, the combination defining a space in which the iris is positioned. When deployed, the surgeon extrudes the device into the anterior chamber and then threads the device around the iris which is held in place by the opposing scallops. Those of skill in the art appreciate that the ability to securely hold the iris in the desired position with the device of Milverton is a function of the passive recoil of the device versus the tension of the iris. If the iris is small and the tension is large, the device may not have the recoil to provide proper dilation. If the iris is too big or the patient suffers from floppy iris syndrome, the device will not be able to maintain contact with the iris and the device will be useless.
Due to the difficulty of insertion, difficulty of retraction and risk of damage to the eye of current devices for iris expansion, it would be beneficial to provide an iris expansion device that is easier to insert, does not require latent kinetic energy to insert and is able to expand to multiple sizes without having to use different size expansion rings.