Ocular socket prosthesis

Details Ocular socket prosthesis Ocular socket prosthesis

1999-11-22

2002-02-12

McDermott, Corrine (Department: 3738)

Prosthesis (i.e., artificial body members), parts thereof, or ai

Eye prosthesis

Globe

C623S004100

Reexamination Certificate

active

06346121

ABSTRACT:

This invention relates to ocular prostheses, and in particular to prosthetic replacements for the eyeball. In one embodiment, the invention provides an eyeball prosthesis of an improved material.
BACKGROUND OF THE INVENTION
It is common for an eye to have to be removed because of severe trauma, infection, congenital abnormality, untreatable painful glaucoma, or the presence of a tumour. After removal of an eye it is desirable to place a prosthetic globe of similar volume within the eye socket cavity. If this is not done in children the orbit orbital bones fail to develop normally, making wearing of a cosmetic shell difficult, and resulting in an unsightly appearance (Soll, 1982; Kennedy, 1973; Berry, 1991). In an adult, although volume replacement is not necessary in terms of bone development, which is already complete, it is vital for orbital volume to be maintained if the patient is to be fitted with an external cosmetic shell and to obtain a natural appearance and “eye” movement. A prosthesis is required for similar reasons if an eye is congenitally absent. Thus there is a widespread need for eyeball prostheses (socket prostheses).
The usual procedure on removal of an eye is to dissect off and preserve the covering conjunctiva, Tenon's capsule (a thicker connective tissue layer which forms the fascial sheath of the eyeball) and the muscles responsible for eye movement. A prosthetic globe is then pushed into the space, the muscles are attached to the prosthesis, and covering tissues are sutured over the outside (Nunery et al, 1993). Once the tissues have healed, an external cosmetic shell can be worn over this surface under the eyelids, and should give reasonable cosmesis and some movement, as it is “carried” by movement of the implanted prosthesis. However, although,in principle an effective prosthesis is possible, major technical difficulties remain to be overcome.
The criteria for an ideal ocular prosthesis are simple; it should be buried in the existing eye socket, and it should be simple, light, smooth and inert (Soll, 1982). In particular, such an ideal prosthesis will not provoke any inflammatory response, and will permit suturing of the ocular muscles directly to the prosthesis so as to provide movement simulating that of the patient's own eye.
It is clear from the literature that the ideal orbital implant has not yet been achieved. Mules appears to have been the first surgeon to place a hollow glass sphere, which he called “artificial vitreous”, within the scleral cavity of an eviscerated eye in human patients with the aim of improving cosmesis; infection-related extrusion was the greatest problem experienced (Mules, 1884). Lang and Frost both developed this idea by using a glass ball as a volume replacement after enucleation; Lang subsequently used celluloid balls to avoid the risk of breakage of a glass prosthesis (Lang, 1887).
Jardon (U.S. Pat. No. 2,688,139) proposed a ball with irregular surface and perforations to encourage tissue ingrowth. Polytetrafluoroethylene, polyethylene, poly(methyl methacrylate) and nylon were suggested as materials.
In recent years simple poly(methyl methacrylate) or silicone spheres have become the norm, in spite of extrusion rates of over 10% in some series (Nunery, 1993). However, it is impossible to attach muscles directly to these materials. Therefore the implant must first be covered with donor cadaveric sclera or with a synthetic material such as Dacron (trade mark), and the muscles are then sutured to the covering layer.
Recently prostheses made of hydroxyapatite have been used in some centres (Perry, U.S. Pat. No. 4,976,731; Dutton, 1991), and these are thought to give a better outcome because, since hydroxyapatite is porous, the surrounding tissues can grow into the ball and help to secure it. However, hydroxyapatite is a hard material and cannot be sutured directly to the tissues; therefore it must still be covered with sclera or Dacron. Furthermore, hydroxyapatite implants are extremely expensive (Dutton, 1991; McNab, 1995) and are thus not routinely available to patients even in many economically developed countries.
Hydroxyapatite implants have gained in popularity in those countries where they are affordable, and several large series have been reported (Dutton, 1991; Shields et al, 1993; Shields, 1992; Shields, 1994). There is evidence that fibrovascular ingrowth into hydroxyapatite does take place, although it appears to be accompanied by a degree of inflammation of the foreign body type (McNab, 1995; Shields et al, 1991; Rosner et al, 1992; Rubin et al, 1994). Moreover, extrusion of the prosthesis can still occur (McNab, 1995; Buettner and Bartley, 1992).
Rubin et al (1994) reported a study in rabbits, in which spheres of hydroxyapatite, 14 mm in diameter, were compared with spheres of porous polyethylene. Vascularisation occurred more quickly in the hydroxyapatite spheres, especially near to the muscle insertions, but both materials showed a low-grade foreign body response.
Girard (1990) has proposed Proplast (trade mark) as both an enucleation implant, citing Neuhaus (1984), and as an evisceration implant, and describes his evisceration technique in the pig in 4 eyes with a maximum of 1.5 years follow-up. This work appears promising, but the results of more extensive trials are awaited. Some studies of keratoprosthesis development have found Proplast to be prone to an inflammatory response and resultant extrusion from the eye (Legeais et al, 1992).
Vachet (U.S. Pat. No. 5,089,021) proposed a ball silicone elastomer covered with porous polytetrafluoroethylene. The porous material is not incorporated into the ball, and is attached either by suturing (like covering a wooden cricket ball with leather) or by adhesives.
Jacob-LaBarre (U.S. Pat. No. 5,192,315) proposed a silicone ball covered with “patches” of porous silicone (for cellular ingrowth) and other porous polymers (for muscle attachment) such as polyurethanes, polyesters, or polytetrafluoroethylene. The means by which the patches are adjoined to the underlying prostheses is not explained. Bare areas between patches are said to enhance mobility by preventing too much tissue attachment.
Goldberg et al (1994) have proposed using porous polyethylene implants which, like Proplast, do not require wrapping, and which allow muscles to be sutured directly to the implant. They reported trying the material in 16 rabbits; there were 2 early extrusions related to infection. Hydroxyapatite spheres used for comparison in 2 rabbits seemed to provoke more inflammation, but fibrous encapsulation occurred with both. The polyethylene showed fibrovascular ingrowth and macrophage invasion; however, the fibrovascular tissue did not reach the centre of the sphere.
De-epithelialized dermal fat grafts have also been used as primary as well as secondary orbital implants (Smith and Petrelli, 1978; Migliori and Putterman, 1991; Smith et al, 1988; Borodic et al, 1989); however, resorption of the fat may occur. Buccal mucous membrane grafts are of use in the contracted socket as a secondary procedure, providing both volume and mucosal surface (Molget et al, 1993). Unless autografts are employed, such fat or mucous membrane graft would entail a risk of graft rejection, as well as a high risk of disease transmission.
Currently the globe prostheses used are generally made of silicone (Nunery et al, 1993; Soll, 1974; Nunery, 1993) in a range of sizes. These prostheses themselves cannot integrate with tissues, or have muscles directly attached to them. They therefore have to be covered before implantation with either donor sclera from a cadaver (Soll, 1974), or with Dacron (trade mark) mesh. Dacron is expensive, and often fails to prevent extrusion, possibly because it does not cushion the prosthesis in any way; if the covering tissues are thin or weak the prosthesis may erode through them. Once such erosion has occurred re-implantation is technically very difficult, and cosmetic appearance and movement are often unsatisfactory. The use of cadaver tissue is undesirable because of the h

Affiliated with

Also associated with

Rating

Ocular socket prosthesis does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Ocular socket prosthesis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ocular socket prosthesis will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2939452