Major Review
 
Implants in Anophthalmic Sockets
 
Ruchi Kabra,1 Nitin Trivedi2, Deepak Mehta3
1 Assistant Professor,Orbit & Oculoplasty unit, M&J Western Regional Institute of Ophthalmology, Civil hospital,
Ahmedabad.(Gujarat)
2 Past President All India Oculoplasty Society of India.
AssociateProfessor, Orbit & Oculoplasty Unit, Nagri Eye Hospital and Research Foundation, Ahmedabad.
3 Professor & Director, M&J Western Regional Institute of Ophthalmology, Civil hospital, Ahmedabad.


Corresponding Author
: .

Abstract

Enucleation and Evisceration still remain the definitive treatment in end stage eye diseases where nil visual prognosis is the expected outcome. Implants in anophthalmic sockets mark the beginning of a new era in anophthalmic socket surgery. The marked improvement in aesthetic outcome ddresses the important issue related to psychological trauma the patient undergoes postenucleation. In this article we review, in short, the history of introduction of implants in anophthalmic sockets, the evolution of newer material, designs, and major complications associated with them.

HISTORY

Since long removal of eye in intractable painful blind eye, traumatic disfigured eyes and intraocular malignancy has traditionally been the definitive treatment of choice. The removal of eye for treatment of ocular disease was first described by George Bartisch in 1583[
1]. This procedure was done without anesthesia and has been described as the most severe and repulsive operations in surgery[2]. This painful and crude procedure proceeded with little change for 265 years. The socket thus left behind was unsuitable for any implant. It was in 1885 when Philips Henry Mules introduced a glass sphere after evisceration with satisfactory result[3]. Frost in 1887 introduced a similar hollow glass sphere in tenon’s capsule post enucleation[4].

Introduction of implants in orbit was a major breakthrough in anophthalmic socket surgery. This was the beginning of a new era in anophthalmic socket surgery where the problems of cosmesis could be addressed. Mules sphere began to be used extensively and silmentaneous search for better material continued. This implant though replaced the lost orbital volume but it had a tendency to migrate within tissues and even sometimes extruded out of the cone. Implants progressed from nonintegrated to partially integrated to integrated implants. Rudeman in 1941 introduced the first exposed integrated implant and an acrylic prosthesis [
5].

Cutler developed a partial exposed integrated implant similar to Iowa implant. These implants did have excellent motility but infection and extrusion finally occurred and these implants fell into disrepute. The high extrusion rates upto 90% with these partially integrated implants emphasized the need for epithelization of wound to decrease extrusion and infection. Attention again was then directed to bury implants. Then it was Allen who discovered a buried nonspherical polymethylmethaacrylate (PMMA) implant[
6]

NEWER IMPLANTS

It was Perry in 1985 who introduced the hydroxyapatite (HA) implant after enucleation and evisceration[
7]. HA was a coral derived natural substance mainly comprising of calcium phosphate and had pores resembling Harvesian system of normal lamellar bone[8]. Porous implants favour fibrovascular ingrowths and this decreases the late extrusion and migration of implants [12,14]. HA soon became popular as they gave good motility even after being integrated implants. A good structural framework also supported pegging. Till 1992 HA accounted for 56% of implants and became the material of choice[2]. Synthetic HA implants with slightly different pore uniformity and interconnectivity was also introduced. Due to the rough surface HA implants needed different wrapping material .Various materials used for wrapping are the polygalactin mesh, donor sclera, fascia lata, temporalis fascia. Even though HA had a brittle nature HA was also used as secondary implants in orbits[8]. The next major introduction was the porous polyethylene implants. This material was used in craniofacial reconstruction. These implants were porous in nature and had smoother surface. The pore size varied from 150-400 micron and muscles could be directly sutured to the implant hence decreasing the need for wrapping material as in HA [10,15]. These implants can be carved according to shape required. This implant incites less fibrosis and tissue reaction than HA[13].

Another emerging implant is the Aluminum oxide implant also referred to as the bioceramic implant as it is made of ceramic biomaterial similar to that used in orthopedics and dentistry[
13]. Expandable implants with osmotically active gel which expand in vivo and stimulate orbital growth were recently introduced especially for congenital anophthalmos. The latest implant introduced is the Alpha Sphere.It is the first poly-Hema (2-hydrooxyethyl metha acrylate) implant. The majority of alpha sphere composition is water and this closely resembles that of natural globe. The long term result of this porous implant is awaited. With the use of various implants over the years, now motility of implants and prosthesis has also become an important issue.

The first prosthesis or artificial eyes as they were then called were developed by Venetians around 1580 and these were very thin glass shells .In 1880 Snellen developed the modified eye design which was hollow glass with rounded edges.It was only in late 1960,the modified impression method was developed by Allen. This method accurately duplicated shape of individual sockets as well as addressed the anterior lid problems due to prosthesis placement. Motility of prosthesis which is a very important issue depends on various factors as prosthesis-implant interface, weight of prosthesis, state of fornices, stability and muscle attachment to implant, placement and coupling of peg to the prosthesis. The most common material used in pegging is polycarbonate and titanium.

COMPLICATIONS

With the long term use of implants complications gradually surfaced and came to light.The published rate of complications vary from one series to another[18]. Reported complications include exposure, conjunctival thinning, cyst formation, discharge, pyogenic granuloma formation, migration and extrusion of implant[18]. Serious complications like infection and extrusion may call for implant explantation. Surgical technique, materials used in implants, size of implant, hygiene of the sockets, pegging all determine the ultimate success rate of surgery. Proper assessment of the size of an orbital implant along with proper placement is a very important step towards the success of surgery. We recommend preoperative BScan of the eye and the use of orbital sizers intraoperatively to determine the exact size of implant to be placed. Prosthesis is generally placed 4-6 weeks later after the edema subsides and the socket hygiene is taken care off. It is not the motility of implant that is the main problem now,it is the transfer of this motility to the prosthesis that is the main concern now- a- days. To peg or not to peg is absolutely surgeon's decision as pegging though definitely improves motility but invites their own series of complications. In our cases we donot generally peg the implant because in our experience though by not using peg system there is definitely a compromise on the motility aspect but most certainly the chances of infection,irritation and exposure of the implant also decrease.








The journey of implants in anophthalmic sockets have gone through various stages like from solid to hollow spheres, from nonintegrated to integrated, from plain to porous, from nonpegged to pegged implants.In general an ideal implant is being sought for which should have the following characteristics. It should be lightweight, nonantigenic, inert, biocompatible, affordable. It should mimic the motility of the normal globe, and should have minimum complications like infection, extrusion and migration. Presently all implants are broadly classified as nonintegrated, semi- integrated, fully integrated,biogenic.

Nonintegrated implants are the ones which are nonporus and are not integrated and have no direct muscle attachment.

Examples are the silicon and acrylic implants. Semiintegrated implants allow attachment of muscle in tunnels on anterior surface for better motility. Examples include Allens, Iowa

BioIntegrated implants-these allow fibrovascular ingrowth in the porous channels and result in direct biological integration with orbital contents. Examples include HA, porous polyethylene implants, aluminium oxide, alpha sphere.

Biogenic implants- An autograft or allograft of natural tissue with direct biological integration with orbital structures but not prosthesis. Examples include dermis fat graft, mucous membrane graft.

The most difficult aspect in finding an ideal orbital implant and prosthesis is that it has to match a fellow eye which is not static and has constant dynamic motion. It is still a matter of debate as to which implant is best suited for anophthalmic sockets. In our experience porous implants are presently the material of choice as vascularisation leads to integration of implants. But porous implants are significantly more expensive than acrylic and silicon implants. Younger cosmesis oriented patients may be the most ideal patients for implants in anophthalmic surgery. Aesthetic results have definitely improved with the use of orbital implants but still patients have to be cautioned about the likelihood of problems and potential need for additional surgeries. Proper implant selection and a well executed technique helps a lot in restoring cosmesis and decreasing complications in patients.It seems that the journey of using implants in anophthalmic sockets is to continue and its scope for use in anophthalmic sockets is to be limited only by the innovative capabilities of its surgeon.

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