Spherical Orbital Implants Research Articles

Changing the geometry of polymer spherical orbital implants

BACKGROUND: Over the past decades, various polymer implants have been actively used in the rehabilitation of patients with anophthalmos to form a volumetric support stump and improve the results of cosmetic prosthetics.
 AIM: To assess clinical symptoms and features of the X-ray picture in patients with anophthalmos after implantation of polymeric spherical endoprostheses with a modified geometry.
 MATERIALS AND METHODS: The study is based on the analysis of 30 patients with anophthalmos after enucleations (23) and eviscerations (7) performed using various methods of procedure and insertion into tissues of an implant made of domestic polytetrafluoroethylene. All patients underwent a multispiral computed tomography (MSCT) of the eye sockets according to the same algorithm.
 RESULTS: On the basis of the performed studies, the fact of making a change in the geometry of the implanted spherical implants was revealed, while the parameters of the modified part of the spheres were different and ranged from 14 to 18 mm of final diameters with the initial diameters of the spheres ranging from 18 to 20 mm. A decrease in the volume of spheres with modified geometry from 0.114 to 0.651 cm3 was revealed with initial diameters ranging from 18 to 20 mm.
 CONCLUSIONS: Changes in the geometry of the orbital spheres do not improve the results of cosmetic prosthetics in patients, increase the percentage of implant exposure at different times after surgery, and increase the manifestations of anophthalmic syndrome.

Amplitude of movements with conical or spherical implants in anophthalmic socket

ABSTRACT Purpose: To evaluate the amplitude of movement in anophthalmic sockets reconstructed with conical or spherical orbital implants with and without an external ocular prosthesis (EOP), and whether the fornix depth could play a role. Methods: Prospective observational study involving unilateral anophthalmic sockets evaluated the amplitude of movement with conical (20 subjects) or spherical (16) non-porous orbital implants, with and without an EOP, having the contralateral eye as the control group. Standardized photographs were obtained in the four gaze directions and measurements were performed using the Image J software. The upper and lower fornix depths were measured using rulers. Results: Compared to the contralateral eye, the median movement amplitude without EOP was smaller with conical implants in supraduction (−0.88 mm, p=0.008), abduction (−2.26 mm, p<0.001) and adduction (−0.91 mm, p=0.008). Spherical implants had reduced movement only in abduction (−2.63 mm, p<0.001). Conical and spherical implants had similar amplitudes of movement in all versions, and were always smaller compared to the control. The median movement amplitude with the EOP was −3.05 mm (p=0.001) than without the EOP in abduction and −2.07 mm (p=0.020) in adduction, regardless of implant format. The fornix depth did not affect the orbital implants or EOP movement amplitude’s median. Conclusion: Conical and spherical implants provide similar amplitude of movement and fornix depth did not have an influence on it. The amplitude of movement was significantly limited compared to the contralateral eye and was even more reduced if the EOP was in place with conical or spherical implant formats.

Artificial eye amplitudes and characteristics in enucleated socket with porous polyethylene spherical and quad-motility implant

To compare artificial eye amplitudes in enucleated socket with porous polyethylene either spherical or quad-motility implant and study the characteristics of artificial eyes fit with the two orbital implants. A total of 21 patients were prospectively studied who underwent enucleation because of an intraocular melanoma and the randomization defined a porous polyethylene either spherical or quad-motility orbital implant. Measurements of the amplitude of the artificial eye were obtained with prism and digital photos. The software Scion Image analyzed the digital photos (www.scioncorp.com) and the quantitative data were allocated to groups. The measurements (height, length, thickness) and weight of the 21 artificial eyes were analyzed. Student's t-test was performed to determine the significance of difference between groups (p<0.05). There was no statistically significant difference of the artificial eye amplitude analyzed by means of prisms between both orbital implants (p>0.05 for all directions). On analyzing the digital photos, the artificial eye with spherical implant showed higher artificial eye amplitude downward (p=0.009) among patients older than 55 years old, rightward (p=0.036) and downward (p=0.008) among the 9 patients with enucleated right eye. Height and length were similar in the 21 artificial eyes but those artificial eyes fit with quad-motility orbital implants were statistically significant thicker (p<0.001) and heavier (p=0.001). The similar amplitude of movement of artificial eyes was observed with both spherical and quad-motility orbital implants. Artificial eyes fit with quad-motility orbital implant are significantly thicker and heavier than those fit with spherical orbital implant.

Factors affecting orbital abnormal development and its relevant treatments

Orbital development is associated with the growth of the eyeball. During the development period, congenital or acquired changes of volume of the eyes and radiation treatment in ocular region influence the development of the orbit. Abnormal development of the orbit influences craniomaxillofacial growth and person's overall aesthetics of the face afterwards. Reconstruction of contracted sockets and shrunken orbits poses significant difficulties and obstacles that often results in universal frustration and disappointment results. Various methods have been used to improve these abnormalities. There are substantial different opinions regarding which method offers the best outcome. Traditional methods involve using progressively enlarging conformers, static spherical orbital implants, demis-fat grafts, and inflatable balloon expanders for orbital enlargement. Recently, the self-expander hydrogel tissue expander is available that expanders our option. This article reviews the influence of ocular abnormalities on the development of the orbit, as well as the advantages and disadvantages of various treatments for promoting the development of the orbit.

Hydroxypropyl Methylcellulose (HPMC) Lubricant Facilitates Insertion of Porous Spherical Orbital Implants

The insertion of an orbital implant in the posterior Tenon's space or in the eviscerated sclera must be smooth, without entrapment or dragging of adjacent soft tissue. Anterior Tenon's fascia and conjunctiva must be closed without undue tension that could lead to subsequent postoperative implant exposure. Current methods to prevent tissue drag include passing the implant via a cut "thumb" from a surgeon's glove, the use of a prepackaged rigid plastic funnel, or a specialized orbital implant introducing forceps, e.g., Carter sphere injector. We recommend also coating the porous implant with an inert semisynthetic viscoelastic polymer, thus enabling easy placement. We illustrate this in a typical case.

Use of self-expanding, hydrophilic osmotic expanders (hydrogel) in the reconstruction of congenital clinical anophthalmos

Rehabilitation of the congenitally anophthalmic orbit is frustrating to both the parents and physician. Traditional methods involve using progressively enlarging static acrylic conformers to expand the conjunctival socket, followed by placement of conventional static spherical orbital implants, dermis-fat grafts, or inflatable balloon expanders for orbital enlargement. Limitations of these methods typically result in less-than-optimal cosmetic outcomes, with retardation of bony orbital and overlying soft tissue growth adversely affecting midfacial growth and symmetry. Recent advances in tissue expansion technology may offer additional, novel alternatives to conventional therapies. Hydrogel tissue expanders were recently adapted for use in congenital anophthalmia. The expanders are placed in their dry, contracted states, and expand gradually to their full size via osmosis of surrounding tissue fluid, with up to a 10-fold increase in volume. Offering the benefit of predictable and controllable self-expansion, hydrogel expanders may offer yet another alternative or adjunctive therapy to the early rehabilitation of the contracted socket. Separate appliances are used for conjunctival and orbital reconstruction. Initial results appear promising. Tempering the enthusiasm for their use, however-particularly in terms of implanted orbital expanders-is the recent spate of long-term complications reported from previous uses of hydrogels as scleral buckling material. Self-expanding hydrogel tissue expanders appear to offer an intriguing reconstructive alternative to the frustrating condition of congenital anophthalmia. Long-term safety of the material as an orbital implant has not yet been demonstrated, but early results are promising.

Safety of unwrapped spherical orbital implants.

To determine the exposure rate of unwrapped spherical orbital implants after enucleation surgery. Retrospective review of consecutive case series. All patients undergoing orbital implantation during enucleation surgery from October 1999 to September 2003 were included. Charts were reviewed for preoperative diagnoses, type and size of implant, use of a wrapping material, and complications. Twenty-six consecutive patients underwent enucleation surgery without wrapping material. Nineteen patients received porous polyethylene, 5 patients received polymethylmethacrylate, and 2 received hydroxyapatite. Mean implant diameter was 21.03 mm. Mean follow-up was 17.1 months (range, 2 to 43 months). There were no complications of implant extrusion, exposure, infection, or migration. The use of unwrapped spherical orbital implants may be associated with a low rate of early exposure. Careful choice of implant type may help reduce the risk of implant exposure.

Hydroxyapatite and calcium phophate coatings on aluminium oxide orbital implants

Background: Hydroxyapatite and calcium phosphate have been used as bone graft substitutes as they facilitate and promote tissue ingrowth. We carried out a study to examine uncoated and coated aluminium oxide (alumina) spherical orbital implants and assess whether the coatings influence fibrovascular ingrowth.Methods: The aluminium oxide spheres (three coated with hydroxyapatite, three coated with calcium metaphosphate and three uncoated) were manufactured at the School of Materials Engineering, Yeungnam University, Kyongsan, Kyongbuk, Korea. The implants were examined macroscopically and with scanning electron microscopy and were analysed chemically by means of x-ray powder diffraction and x-ray fluorescence spectrophotometry. Implantation of three hydroxyapatite-coated, three calcium metaphosphate-coated and three uncoated aluminium oxide spheres was done in nine adult male New Zealand albino rabbits. Implant vascularization was evaluated at 4, 8 and 12 weeks by means of histopathological sectioning.Results: All three types of implant had multiple interconnected pores. The coatings increased the size of the trabeculae from 150 μm to 300 μm. As a result, the pores appeared slightly smaller but still ranged in size from 300 μm to 750 μm, compared to 400 μm to 800 μm in the uncoated implants. The coatings also increased the weight of the implants slightly. The implants were all strong mechanically. They were made up primarily of aluminium oxide. The coated implants contained significant amounts of calcium oxide (a contaminant). There was no clinical difference in the socket response between the three groups. Histopathologically, fibrovascularization occurred uniformly throughout each implant at 4, 8 and 12 weeks after implantation.Interpretation: The hydroxyapatite and calcium metaphosphate coatings did not appear to facilitate or inhibit fibrovascular ingrowth at 4, 8 and 12 weeks. Longer-term studies are need to determine whether the coatings play a role in long-term acceptance and retention of the implants.

Glass-ionomer cement: evaluation as an orbital implant.

To assess the potential of a porous glass-ionomer cement (GIC) as an alternative material for spherical orbital implants, the handling, side effects and rates of fibrovascular ingrowth of this material were compared with those of a synthetic hydroxyapatite (HA) implant. Twenty-one GIC and 8 HA uncovered 14-mm spheres were implanted into the orbits of New Zealand albino rabbits. Postoperative reactions, animal's behaviour, weight increase and socket conditions were monitored. Light and electron microscopy of the exenterated orbits were performed 2, 3 and 6 months after primary insertion. Implanting of GIC was easier than HA. Postoperatively all animals did well. Three HA and 1 GIC implant caused conjunctival dehiscences, but no implant extrusion was observed. Histologically, both materials caused mild inflammation in the surrounding connective tissue capsule, decreasing with time. GIC implants proved to be not truly porous, with only peripheral pores partly occupied by relatively acellular collagenous connective tissue. Free glass particles were observed in both the connective tissue and giant cells, occupying the partly filled pore spaces. HA implants showed extensive ingrowth of vital host tissue from the beginning. Considering the clinical findings and the mild inflammation in the connective tissue capsule surrounding both materials, they would appear to be equally well tolerated at the implant site. The significantly different microstructure and the histological results make GIC, despite better handling, less suitable as an orbital implant.

Porous orbital implants and their behaviour during drilling

The use of porous spherical orbital implants enables ocular prosthesis motility to be improved if necessary by subsequent drilling of the implant and coupling it to the prosthesis with a peg. We compared the effect of drilling at different speeds on hydroxyapatite and porous polyethylene (Medpor) spherical implants. The implants were drilled at fixed speeds of between 15 and 2000 revolutions per minute. The samples were then viewed in an electron microscope and photographed. When hydroxyapatite is drilled the porous structure of the implant is maintained although a precise hole with well-defined walls was not produced. This contrasts with porous polyethylene where the porous structure is lost although a precise drill hole is created. This drilling technique has been used successfully in patients with hydroxyapatite implants, thus making possible stable epithelialisation of the drill hole. Our results confirm that the drilling of porous polyethylene using this technique is unlikely to be successful, as loss of the porous structure would prevent stable epithelialisation of the drill hole, resulting in exposure of the implant.

Complications of Porous Spherical Orbital Implants

Remulla, H. D.; Rubin, P. A. D.; Shore, J. W.; Sutula, F. C.; Townsend, D. J.; Woog, J. J.; Jahrling, K. V.

Complications of Porous Spherical Orbital Implants

To determine the complications observed with using porous spherical orbital implants (hydroxyapatite and porous polyethylene) and the factors leading to their occurrence. A total of 101 cases of porous spherical orbital implantation by five ophthalmic surgeons were reviewed retrospectively. The demographic data, diagnosis, prior surgery, type and technique of surgery, implant characteristics and prosthesis fitting were described in patients with complications. Eleven of the 101 patients had implant exposure. There were six male (1 with bilateral involvement) and four female patients, ranging in age from 2 to 71 years. Preoperative diagnosis included trauma in five patients, nontrauma in five, and tumor in one. Seven had prior eye surgeries. Three patients underwent evisceration, whereas eight underwent enucleation. Eight hydroxyapatite and three porous polyethylene implants were used with diameters of 16 to 20 mm. Three were unwrapped, six were wrapped in sclera, and two were wrapped in preserved fascia. Exposures, which generally occurred within 1 year, were grouped into small (1-5 mm), medium (6-10 mm), and large (> 10 mm). One delayed case occurred after drilling. Small stable exposures were managed conservatively. Larger exposures were managed either by implant revision or replacement. All patients were fit ultimately with a prosthesis. Histopathologic findings of explanted spheres showed fibrovascularization limited to the periphery with moderate inflammatory reaction. Complications were significantly higher in cases of eviscerations than enucleations. Complications occurred in implants either unwrapped or wrapped in homologous grafts. None of the autologous wrapping had exposure. Secondary procedures may initiate exposure when fibrovascular status of implant is inadequate.

Update on enucleation and evisceration surgery.

The best operative results with fewest complications after enucleation surgery can be achieved by following basic principles, some of which are those of conservative tissue excision, using spherical implants placed behind Tenon's capsule into the muscle cone and avoiding surgical techniques that overlap the extraocular muscles (especially the superior rectus) over the front of the implant. The presence of an intraocular tumor demands that an enucleation be done. When the possible development of sympathetic ophthalmia is not present, the surgeon should consider doing an evisceration because of the cosmetic and motility advantages. Mention is made of some developments in enucleation surgery, such as the scleral cap reinforcement, the "baseball" implant technique using donor sclera, the use of liquid nitrogen to freeze intraocular tumors before removal of the eye, the dermis-fat orbital graft, and the use of two spherical orbital implants instead of one.