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HAND CRAFTED OCULAR PROSTHETICS
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The human eye is one of the hardest organs to simulate. It is an extremely complex part of the body and is often referred to as the "window of the soul". For over 30 years, Cos-Medic Pty Ltd has been working on ways to achieve the very best cosmetic results for an artificial eye. To do this, we must first study the human eye and it's structure.

The eye begins developing in an embryo on the second week of pregnancy. The eye will weigh about 15 mg in the 10th week, and this will double within the next two weeks. At the end of a full term pregnancy, the eye will weight 2800mg.

After birth, the eye will grow quite fast and be at adult size by the age of two years. Over this period of time, the iris will change colour and usually darkens slightly. The new born baby will have sight and this will become increasingly sharper over the next four months and should have a reading of 20/20 by the age of three.

PUPIL AND IRIS.

The Iris is a very complex shutter mechanism that will open and close similar to a camera lens. The open section of the iris is the pupil and is controlled by nerve impulses. The function of the iris is to regulate the opening of the pupil to prevent excessive light entering the retina so it can provide clear images. There are two muscles that affect the size of the pupil (the dilator and the sphincter muscles) the dilator will increase the amount of light to the retina, as the sphincters will decrease the light. The pupil is constantly adjusting its size.

The human eye will vary from race to race. Pigmentation and the pupillary membrane remnants are unique in each person although most Caucasians will be born with blue eyes though lack of pigment colour. People with blue eyes are less tolerant of bright light as pigment is an absorber of light. We find that the Australian Aboriginal usually has quite a large amount of yellow pigmentation in the sclera (the white of the eye). If a large amount of pigment is present within the iris this will usually produce a brown eye.

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THE GLOBE AND EXTRAOCULAR MUSCLES.

The fully-grown eye will be approximately 2.5 cm in diameter but only one-sixth will be visible externally. The sclera is the protective housing for the globe. This sclera will change colour over the years with tints of grays or yellow and in some cases blood vessels or capillaries will dilate and give the eye a reddish look. To give the globe / sclera motility, it has six muscles attached (four Rectus and two Oblique). These muscles undergo simultaneous relaxation and contraction to move the eyes in tandem with the companion eye.

THE OPHTHALMIC SURGEONS AND COS-MEDIC.

Here are many parts of the human eye that will not be covered at this time, as we will now concentrate on reproducing this complex organ with the teamwork of the ophthalmic surgeon and the ocularist.

When an eye is to be removed by the ophthalmic surgeon it can be done in one of two ways, evisceration (surgical removal of the contents of the eye with retention of the cornea and sclera) or enucleation (complete surgical removal of the eye). With either operation, an implant is usually inserted to replace the lost orbital volume of the socket after the removal of the eye or it's contents.

If the surgeon elects to operate with an enucleation, the motor muscles (recti muscles) will be attached to the implant or it's rap, for mobility of the inserted implant.

Cos-Medic will generally see the client from four to six weeks post op to allow for any swelling of the orbit to settle. The ocularist will then produce a custom fit for the new prosthetic eye to match the socket and the companion eye. This shape will be simular to a large contact lens that will fit over the ball implant. Cos-Medic will generally produce a thin shell eye when a ball implant has been inserted. There will be a small air volt in the posterior of this shell, which will sit just off the implant and will provide an airlock. This airlock will retain the prosthesis in the socket and will give maximum mobility.

The thin shell will be produced by way of the modified empirical fitting technique, rather then a fully impression fitted prosthesis normally used by other ocularist's. It is Cos-Medic's view that the impression method can produce a heavy prosthesis that can result in reduced movement and can dislodge due to this excess weight of the prosthetic eye.

After the size of the prosthetic eye has been determined, the iris is then produced using an iris button that is machined to the diameter of the companion iris. Acrylic paints are placed onto the button to recreate the colours and the pupillary membrane found in the human iris. There can be up to twenty coats of paint and clear sealer applied to achieve a more natural appearance to the prosthetic eye. The pupil is added, and then a scleral blend is produced (the limbus, a soft smoky edge) by way of the white acrylic sclera overlapping the periphery of the button.

Blood vessels (cotton) are added along with scleral tints. The prosthetic eye is then ready to be coated with clear acrylic, and polished for the final fitting.

We must always remember that the human eye is an amazing living organ and impossible to reproduce, but with the skills of the ophthalmic surgeons and Cos-Medic we can achieve an extraordinary result..