LONG-TERM FOLLOW-UP OF THE ALLEN IMPLANT - 1967 TO 1991

Purpose: The objectives of this study are to determine the incidence o f superficial tissue breakdown and/or exposure of the Allen implant, t o identify potential risk factors for superficial tissue breakdown and /or exposure of the Allen implant, and to provide a comparison for fut ure studies of other orbital implants. Methods: The authors retrospect ively studied 186 consecutive patients managed with enucleation and Al len implant placement from January 1967 through December 1991. Informa tion was obtained from a review of the patients' records and from tele phone and letter surveys. Results: More than half of the patients had follow-up more than 5 years and approximately one third had follow-up of 10 or more years. The mean length of follow-up was 7.8 years. Two A llen implants (1.1%) became exposed 5.3 and 11.5 years, respectively, after initial implant placement and were subsequently replaced by derm is fat grafts. Superficial tissue breakdown without implant exposure o ccurred over four additional Allen implants (2.2%); the patients satis factorily were treated medically or surgically without the need for re moval or replacement of the Allen implant. Most prostheses have horizo ntal and vertical excursions of 30 degrees or more. Conclusion: The sa tisfactory motility, the low incidence of superficial tissue breakdown , and the even lower incidence of exposed Allen implants observed in o ur longterm follow-up study provide evidence that the Allen implant is a satisfactory choice to replace the enucleated eye. The absence of i mplant exposure occurring before 5 years of follow-up underscores the need for long-term follow-up to properly evaluate newer orbital implan ts.