Removal of an eye is known as enucleation and is generally carried out when a patient has suffered a severe trauma, particularly where the eyeball or globe has been ruptured and it's unlikely that sight will be recovered. There may also be concerns about a rare condition called sympathetic ophthalmia, where the good eye becomes inflamed after the affected eye is damaged.
In some cases, enucleation is recommended if a large eye cancer cannot be removed or destroyed, or where treating the cancer leaves the patient with little or no sight and a permanently painful eye.
Removing the contents of an eye only, which leaves the outer coating of the eye attached to eye socket muscles, is called evisceration.
Implants are used to replace either the entire eye or to fill an eviscerated eye.
There are two types of eye implant, integrated and non-integrated.
Non-integrated implants are usually made of a solid material, such as polymethylmethacrylate (PMMA), which is a type of acrylic plastic — Perspex is made from a type of PMMA.
When a non-integrated implant is fitted into the socket, the eyeball muscles and soft tissues surround it. After healing, a prosthetic or artificial eye, which looks like a big contact lens, is placed over the implant. When the muscles move the implant, the artificial eye moves too. Nowadays, non-integrated implants are wrapped in a mesh, to which the muscles are attached, reducing the risks of drifting or rejection (known as extrusion or being pushed out of the socket).
Integrated implants are made of permeable material, such porous polyethylene. These allow the tissue in the eye socket to grow into the implant, which effectively makes it part of the body.
One of the most interesting types of integrated implant has been developed from coral. The mineral in coral is processed to match human bone and is called hydroxyapatite, or HA. This means that the body accepts it as part of itself.
The eye muscles are attached to an HA implant using a mesh that slowly dissolves as the muscles bond to the implant. Newer HA implants are being developed that do not need mesh — the muscles are sewn directly onto the surface. After healing, the artificial eye (or prosthesis) is fitted and inserted. The artificial eye can also be pegged on to the orbital implant, which allows them to move more than they otherwise would. However, many patients are happy without pegs. Disadvantages of pegging include potential complications such as infection. In some cases, a pegged implant can make a clicking noise when the eye moves. Pegging is carried out approximately a year after an HA implant has been inserted. HA implants with well-fitted artificial eyes can be so good that they are almost indistinguishable from real eyes.
Integrated implants tend not to extrude or be rejected by the body and have a low risk of drifting. They may, however, have a greater likelihood of being exposed because of a breach of the lining of the sock (the conjunctiva) and if so, will require further surgery, ranging from a patch graft or even temporary removal. They can be used to replace other forms of implant, at enucleation or afterwards.
Integrated implants are more expensive than other types of implant and may not be suitable for patients with severe contractions of socket tissue caused by serious infection or injury, or whose sockets have been damaged by radiotherapy.
Regardless of the type of implant, the tissues in the socket tend to shrink over time. This is rectified by using larger artificial eyes but these can give the wearer less eye movement and lead to drooping of the eyelids, or ptosis. As a result a few — less than ten percent — of patients ask for additional surgery to improve the look of their eye.
An orbital implant is placed in the orbital cavity when the eye is removed and the tissues are closed over the implant. A temporary plastic disc (a clear conformer) is fitted on top of the implant for a month after surgery to prevent the socket shrinking.
Two months or more later, the patient sees an ocularist, also known as a prosthetist, who will create a detailed artificial eye or prosthesis that matches the natural eye.
If further eye movement is wanted, Mr Malhotra can peg the artificial eye to the implant. Less than ten per cent of patients choose pegging. The procedure is performed in an operating theatre as day surgery under local or general anesthetic.
In this simple, optional procedure, a hole is made in the implant and a peg is inserted into the hole. Your ocularist then modifies the back of the artificial eye to accept the head of the peg and create a ball-and-socket joint. The procedure takes about 30 minutes. At first, a temporary peg is used. A permanent peg is put in place at another fitting. This may requite a general anaesthetic.
The peg-fitting procedure can only be performed after the implant has had time to fill with tissue from the orbital cavity — usually a year after insertion of the implant.