Long-term follow-up of the Allen implant : 1967 to 1991

The objectives of this study are to determine the incidence of superficial tissue breakdown and/or exposure of the Allen implant, to identify potential risk factors for superficial tissue breakdown and/or exposure of the Allen implant, and to provide a comparison for future studies of other orbital implants. The authors retrospectively studied 186 consecutive patients managed with enucleation and Allen implant placement from January 1967 through December 1991. Information was obtained from a review of the patients' records and from telephone and letter surveys. 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 allen implants (1.1%) became exposed 5.3 and 11.5 years, respectively, after initial implant placement and were subsequently replaced by dermis fat grafts. Superficial tissue breakdown without implant exposure occurred over four additional Allen implants (2.2%); the patients satisfactorily were treated medically or surgically without the need for removal or replacement of the Allen implant. Most prostheses have horizontal and vertical excursions of 30 degrees or more. The satisfactory motility, the low incidence of superficial tissue breakdown, and the even lower incidence of exposed Allen implants observed in our long-term follow-up study provide evidence that the Allen implant is a satisfactory choice to replace the enucleated eye. The absence of implant exposure occurring before 5 years of follow-up underscores the need for long-term follow-up to properly evaluate newer orbital implants.