Surgical Technique

Drilling for the Motility/Support Peg

Drilling of the hole for the motility/support peg is performed under retrobulbar local anesthesia. It is important that the hole be drilled in the proper location since a proper fit and the optimum motility of the artificial eye both depend upon accuracy in placement of the motility/support peg (Kolberg 1991). While it is possible to approximate the correct location of the hole by observing the gaze of the companion eye and marking the conjunctiva overlying the implant based on the gaze of the companion eye, the greatest degree of accuracy is ensured by having the ocularist make a template of the patient's artificial eye, with a through-and-through hole in the area where the peg hole is to be drilled. The template is placed into the socket, and the area to be drilled is marked on the conjunctiva with a pen. The template is then removed before drilling.

The area is prepared and draped in the usual fashion for a sterile procedure. The socket is sterilized with copious irrigation of antiseptic and a lid speculum is placed between the eyelids. The area to be drilled is cauterized and the conjunctiva and soft tissue overlying the implant are grasped with heavy-toothed forceps (0.9 mm or 1.5 mm teeth) to stabilize the implant. It is helpful to have an assistant grasp the tissue at 180° away from the first pair of forceps in order to give two stabilization points.

A hole measuring 3.0 mm in diameter is drilled to a depth of between 10 mm and 13 mm. The drill bit should be of the type in which the cutting blades are confined to the end of the bit, so as to prevent conjunctival tissue from gathering on the shaft during drilling. A temporary flat-headed peg measuring 2.5 mm in diameter and 10 mm in length is then placed in the hole. If the peg head seats well against the conjunctiva, it is removed and the hole is irrigated with an antibiotic solution and then filled with antibiotic ointment. The peg is replaced and the artificial eye is placed over peg. The eye is patched for 24 hours.

After 4 weeks, the hole is inspected for epithelial growth. If the hole is well healed, the patient is sent to an ocularist to receive a ball-headed peg and to have a hemispherical socket created on the posterior surface of the artificial eye. A ball-and-socket coupling is thus achieved and the movement of the Bio-eye HA orbital implant is transferred directly to the artificial eye.

In one variation of the motility/support peg configuration, the peg is mounted directly to the posterior surface of the artificial eye. This may be necessary in cases where the artificial eye must be made too thin to permit creation of the 3.0-mm-deep socket in the anterior aspect of the eye (Kolberg 1991). It should be noted, however, that direct affixation of the motility/support peg to the posterior aspect of the eye makes it more difficult for the patient to insert the eye.

In another variation of the motility/support peg configuration, a semi-permanent acrylic sleeve is inserted into the hole after drilling. The portion of the sleeve shaft that comes into contact with the implant is threaded, in order to bite into the implant material. This threading stabilizes the sleeve and facilitates its orderly removal, if necessary. The threaded sleeve functions like an epithelialized hole, and will accept both a peg attached to the artificial eye and a ball-headed peg. One advantage of this variation is that the sleeve prevents the hole from closing if the peg is removed for a long period of time (Shields 1992). Another advantage is that both ocularists and patients are more comfortable dealing with a plastic-lined hole. The sleeved hole does not exert "suction" on the peg, as does an epithelialized hole, and there is no bleeding associated with removal of the peg.

The most recent innovation in peg design is the locking-socket peg. In this configuration, the head of the peg snaps into a narrowed socket created in the posterior aspect of the artificial eye. This prevents dislodgement of the peg on extreme gaze and lends maximum support to the weight of the artificial eye, which minimizes lower lid sag.