An ocular prosthesis, commonly referred to as an artificial eye, is a medical device designed to replace a missing natural eye. Its primary function is the cosmetic restoration of the eye socket’s appearance following surgical removal or congenital loss. This custom-made device is a thin shell that sits over an underlying implant, helping to maintain the natural shape of the eyelid and facial structure. A successful prosthesis significantly aids in patient comfort, confidence, and social integration.
Ocular Prostheses Do Not Restore Sight
The most common misunderstanding about an ocular prosthesis is the belief that it can restore vision. This device is purely a cosmetic replacement and cannot sense light or transmit visual information to the brain. Unlike advanced visual prostheses, often called bionic eyes, the artificial eye is a passive, non-electronic shell. It does not connect to the optic nerve, meaning the individual remains blind in the affected eye. The device’s main purpose is to fill the orbital volume, preventing the soft tissues of the eye socket from shrinking or collapsing.
Surgical Foundation for Placement
The placement and function of a prosthetic eye depend entirely on the surgical preparation of the eye socket. The two main procedures are enucleation, which removes the entire eyeball, and evisceration, which removes only the internal contents, leaving the outer white shell (sclera) intact. In either case, the lost volume is replaced with a spherical orbital implant, typically made of porous materials like hydroxyapatite. This implant is surgically placed deep within the eye socket and covered by the patient’s own tissue, such as the conjunctiva.
The orbital implant serves two mechanical purposes: it replaces the lost bulk to prevent a sunken appearance and acts as a new pivot point for movement. During surgery, the extraocular muscles responsible for eye movement are preserved and attached to the surface of this implant. In an evisceration, the muscles remain attached to the preserved scleral shell, which covers the implant, often leading to better movement transfer.
For an enucleation, the surgeon must reattach the six extraocular muscles directly to the spherical implant’s surface. A temporary clear plastic shell, known as a conformer, is then placed behind the eyelids. This conformer maintains the socket’s shape while the tissues heal over a period of six to eight weeks.
The Customization Process
The visible component of the artificial eye is a custom-fitted shell created by a specialized technician known as an ocularist. This process begins with the ocularist taking an impression or mold of the healed eye socket tissue, using a material similar to that used for dental impressions. This ensures the final prosthesis has a personalized fit, which is important for comfort and maximizing the transfer of movement. The shell itself is constructed from medical-grade acrylic, a durable and biocompatible plastic.
The artistry of the ocularist is demonstrated in the detailed, hand-painted customization of the acrylic shell to match the remaining natural eye. The ocularist meticulously paints the iris, pupil, and sclera, often incorporating minute, thread-like red fibers to replicate the delicate vascular patterns. This precision, matching the color, size, and characteristics of the companion eye, allows the prosthesis to blend seamlessly and achieve a lifelike appearance. A custom fit is essential because an improper fit can cause chronic irritation, discharge, and limited movement.
Achieving Coordinated Movement
The prosthetic eye does not move on its own; its movement is entirely passive, relying on the underlying structures. Coordinated movement with the companion eye is achieved through the mechanical transfer of motion from the preserved eye muscles to the orbital implant. When the eye muscles contract, they pull the orbital implant, causing it to rotate within the socket tissue. The custom-fitted acrylic shell then sits directly over the front of this moving implant, much like a large contact lens.
The movement of the implant pushes the prosthetic shell, causing it to move in a coordinated, though restricted, manner with the natural eye. Some patients with porous implants may be candidates for a secondary procedure to receive a pegging or coupling mechanism. This involves placing a titanium pin into the implant, which then locks into a corresponding receptacle on the back of the prosthetic shell. This direct coupling improves the range and fluidity of motion, particularly the rapid movements observed during conversation.