Ocular surgery, whether reconstructive, cosmetic, palliative, or otherwise, is highly patient specific. Even though most surgery patients have the same basic ocular architecture, every eye has its own set of specific features and dimensions that in certain cases may be significantly different from those of expected norms. As a result, surgeons must rely upon their individual experience and skills to adapt whatever surgical techniques they are practicing to the individual requirements as determined by each patient's unique ocular structural features and dimensions.
To date, this individualized surgical adaptation has been accomplished essentially through freehand and best guess techniques based upon a pre-surgery examination and evaluation of the individual patient's ocular region. This examination may include preliminary measurements as well as the surgeon making reference markings directly on the patient's ocular tissues with a pen or other form of dye or ink marking. Then, after the patient has been prepared and placed in position for surgery, typically in a supine or prone position as opposed to the often vertical positioning of the patient during the pre-surgery examinations, the surgeon adapts the placement and configuration of the initial surgical incisions to the actual physical dimensions and circumstances found in the patient as the surgical procedure progresses. As a result, many initial measurements or reference markings on the patient's ocular tissues are at best a general guide as to where to begin the procedure and have limited accuracy and influence on subsequent aspects of the procedure or on the overall outcome of the surgery.
Further complicating matters, ocular tissues are not conducive to pre-surgery reference markings or measurements. This is particularly true because most ocular tissues have wet surfaces and internal physical structures that cannot be accessed for direct measurement or marking prior to surgery.
Additionally, pre-surgical rinsing, sterilization, or drug administration to the ocular tissues may dissolve, alter or even remove reference markings prior to the initiation of surgery. Similarly, subsequent wiping and contact with fluids, including the patient's body fluids, during the surgical procedure may remove or distort any remaining reference markings. As a result, even the most accurate surgical reference markings may lose any practical effectiveness beyond the initial stages of the surgical procedure.
As such, there is a continuing need for effective surgical reference indicia properly aligned with a particular axis, particularly when proper alignment of pre-surgical data is pivotal to satisfactory patient outcome. For instance, proper alignment of pre-surgical data, particularly the true vertical axis of an eye, with the ocular surgery is highly advantageous with intraocular lens (IOL) implantation and orientation of the IOL within the posterior chamber of the eye.
The implantation of an IOL is a highly sophisticated surgical procedure that, in the past, has been performed based on partially accurate or even inaccurate visual measurements and estimated alignment with the vertical or horizontal axis of a patient's eye. Past procedures have commonly relied on the measurement of an eye's vertical or horizontal axis prior to surgery and the subsequent inaccurate translation of that measurement to the IOL implantation procedure where the positioning of the measured axis of the eye may have changed. As a result, it is not uncommon for the IOL placement to be improperly aligned with the true vertical axis of the eye, resulting in such side effects as poor visual acuity, double vision, and halos under low ambient light conditions.
Accordingly, in spite of the ongoing development and the growing sophistication of contemporary ocular surgery, there is a continuing need for the provision of effective surgical reference indicia including information about or which track a patient's natural vertical axis or other important axis of orientation.