1 Blinking orbital prosthesis Client: Gregory Gion Medical Art Prosthetics, LLC Advisor: Professor William Murphy Team members: Team leader – Hallie Kreitlow BSAC – Ryan Kimmel BWIG – Joel Gaston Communications – Allison McArton Date: May 12, 20082 Table of Contents Abstract………………………………………………………………………………. 3 Problem Statement Problem motivation.………………………....………………..………………. 3 Background..………………………………………………………...………... 3 Client Requirements…….………………………………………………….… 4 Team Goals……………………………………………………………...…….. 4 Competition……………………………………………………………………. 4 Alternative Design Descriptions Actuator movement..………………………………………………………….. 5 Repelling Magnetic field.……………………………………………………... 6 Attractive Magnetic field……………………………………………………… 7 Memory Metal Circuit…..…………………………………………………….. 8 Design Matrix …………………………………………………………………………...9 Proposed Design….………………………………………………………………...…. 10 Final Design….………………………………………………………………...……… 12 Testing and Results….………………………………………………………………..... 13 Future Work and Conclusion.……..…………………………………………...……… 18 Appendices A: Product Design Specifications …...………………………………...….. 19 B: References………………………………………...……………………….. 243 Abstract An orbital prosthesis is an artificial eye that closely mimics a person’s natural eye. Although they provide the patient with a more natural appearance, the prosthesis is easily noticed because it cannot blink. The goal of this project is to create a mechanism which allows an orbital prosthesis to blink. The two major parts include the mechanism for movement of the eyelid and the use of an infrared sensor for an automated system that relies on the movement of the naturally blinking eye. The focus of this prototype is devoted to the mechanics of the blink, and not the synchronization with the natural eye. Through designing and testing, a final design was chosen, which employs the use of a motor to open and close the eyelid. Problem Statement Motivation Patients have requested that orbital prostheses impart more life-like qualities, including the ability to blink. Each year 11,000 incidents occur in the United States alone that leave patients with a large facial gap where the eye had been previously located (Lee,1998). The client alone sees 20 patients a year for an orbital prosthetic (Gion, 2008). Despite the realistic look and feel of our client’s prostheses, the current prosthesis does not blink, which reveals that the eye is not authentic. Background Orbital prostheses are used when a person suffers a tragic circumstance (injury or disease) that damages the eye and surrounding area beyond repair. Specifically, orbital prostheses are used to make a patient appear more normal, drawing less attention from the general public. Despite the life-like appearance, a prosthetic does not serve the same function as a healthy eye and can never be used to regain lost sight.4 Client Requirements The size of the orbital cavity is limited to approximately 16.4cm3. In addition to limited space, the prosthesis must be able to operate at 37° C and atmospheric pressure. Most importantly, it must be safe for everyday patient use. Any external components must be small enough so future researchers can work on a complete enclosure. Team Goals Our goal is to design and create an actual size model of a blinking orbital prosthesis. Through testing, the average rate of a human blink will be quantified and imitated with our prototype. Due to our client’s cost constraints, we need to keep the overall cost under $1000. Competition Currently, there is no mass-marketed model for a blinking prosthesis. Researchers have developed a way to detect a blink from the orbicularis oculi muscle on the unaffected eye (Honda, 1999). This technology, however, is very invasive due to the insertion of sensors into the body. In addition to this model, researchers have also developed a robotic eye (Wired, 2000). The main focus of this prototype was movement of the eyeball, rather than the blinking movement of the eyelid. In spite of this, the project incorporated external sensors to detect movement of a natural human’s eyes. This particular prototype could be incorporated into future work of detecting an eye blink.5 Alternative Design Descriptions The adequate budget supplied by the client, and the fact that the only requirements were that the prosthesis fit in the cavity and be safe for use, allowed for a great deal of creativity in the design process. The initial brainstorming sessions produced several conclusions, most notably the fact that some sort of electrical impulse would be needed to make the eyelid blink. From this basic train of thought four designs were developed including closing the eyelid using an actuator, generating a repelling magnetic field to close the eyelid, producing an attracting magnetic field to keep the eyelid open, and using a memory metal circuit to close the eyelid. Actuator movement The first solution presented is an actuator connected to an op amp that would drive the eyelid up and down, causing a blink to occur. The op amp's input will be received from two electrodes connected to the contralateral eye muscle, with an addition electrode used as a reference, effectively creating a differential amplifier. This design has several advantages, the most notable being the fact that that it will work regardless of the environment outside the eye (i.e. in front of the face). This is important in situations like poor weather, or under certain research conditions. This solution does have several major flaws, however. First and foremost, this design is highly invasive,
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