Peg Placement Procedure
Placing the Motility/Support Peg
Creating the hole for the motility/support peg is performed under retrobulbar or general anesthesia. It is important that the hole be created 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. 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 created. The template is placed into the socket, and the area where the hole is to be created is marked on the conjunctiva with a pen. The template is then removed before creating the hole.
The area is prepared and draped in the usual fashion for a sterile procedure. The socket is sterilized with copious irrigation of Betadine and a lid speculum is placed between the eyelids.
The implant is stabilized by grasping the soft tissue anterior to the implant with two toothed forceps held 180 degrees apart. The implant can also be stabilized with an implant ring stabilizer or a Thornton ring.
A pilot hole is created at the designated spot using a 20-gauge hypodermic needle. By twisting the hypodermic needle, held in the fingers, the needle should penetrate about 5mm into the implant. Then remove the ring stabilizer and/or forceps and access the position of the needle. The position of the needle should be perpendicular to the frontal plane of the patient. It should not be angled up or down or to the right or to the left. If this is not the position of the needle, remove the needle and start a new hole in the proper direction. Again, check the position of the needle after penetrating the implant 5 mm. If the needle is in the proper position, re-stabilize the implant and twist the needle so that it goes into the implant 8 to 10 mm. Again, remove the stabilizing instrument and assess the position of the needle. If not in a good position, start again. If the position is good, continue twisting the needle until you are completely through and through the implant. You will feel the resistance change when you are completely through the implant. Gradually enlarge the pilot hole with an 18 gauge, then 16 gauge, then 14-gauge needle. If the implant has been in the patient for a year or more, there may be new bone growth near the center of the implant. This new bone may be difficult to penetrate with a 20-gauge needle. Enlarge the pilot hole as deep as you can with an 18 gauge, then 16 gauge, then 14-gauge needle. You will then need a power drill to complete the through and through hole. Use a foot-controlled power drill with a 1.75 mm drill bit (5/64ths of an inch). Do not use a round cutting burr.
You are now ready to insert the threaded sleeve into the implant. Place ophthalmic antibiotic ointment on the end of the sleeve driver and on the notched end of the threaded sleeve. Place the end of the sleeve driver down the shaft of the threaded sleeve. The ointment will hold the sleeve onto the sleeve driver. Place the threaded sleeve into the drilled hole of the implant and turn the sleeve driver in a clockwise rotation to screw it into the implant. You should feel some resistance as you screw the threaded sleeve into the implant as the threads on the threaded sleeve cut into the hydroxyapatite implant material. Screwing the threaded sleeve to the proper depth is important. The sleeve should be screwed into the implant until the top of the sleeve is 2 to 3 mm above the level of the conjunctiva after the edema of the conjunctiva has resolved. You must factor in the edema of the conjunctiva when deciding how deep to place the threaded sleeve. The final position of the top of the threaded sleeve after the conjunctiva edema has resolved should be 2 to 3 mm above the conjunctiva. The conjunctiva will form a chemical bond with the titanium oxide which exists on the surface of the threaded sleeve, therefore producing a true attachment of the conjunctiva to the titanium threaded sleeve.