Orbit, 2014; 33(3): 229–233 ! Informa Healthcare USA, Inc. ISSN: 0167-6830 print / 1744-5108 online DOI: 10.3109/01676830.2014.881395
REVIEW
Fabrication Techniques for Ocular Prostheses – An Overview
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Marcelo Coelho Goiato1, Lisiane Cristina Bannwart1, Marcela Filie´ Haddad1, Daniela Micheline dos Santos1, Aldie´ris Alves Pesqueira1, and Glauco Issamu Miyahara2 1
Department of Dental Materials and Prosthodontics and 2Department of Pathology and Propedeutic Clinic, UNESP, Univ Estadual Paulista - Arac¸atuba Dental School, Brazil
ABSTRACT The goals of treatment with ocular prostheses are to restore facial aesthetics and self-esteem to anophthalmic patients. Fabricated in acrylic resin, artificial eyes should be aesthetically pleasing, scratch-resistant, and adequately polished. Use of a prosthesis without such characteristics can lead to psychological damage, as well as infection and inflammation due to the accumulation of microorganisms and other substances on an irregularly shaped prosthesis. The present literature review describes the different techniques for fabricating ocular prostheses. Reproduction of the iris color and color stability are important factors that promote adequate aesthetics. The fabrication of an individual ocular prosthesis in acrylic resin provides satisfactory aesthetic results because the impression process establishes the defect contour. Additionally, the iris and sclera can be individually characterized. As the techniques, materials, and manufacturing methods for ocular prostheses continue to evolve, the aesthetics and functionality of prostheses will also improve. Keywords: Artificial, eye, paint, sclera
INTRODUCTION
variety of maxillofacial materials that are available, the aim of the current literature review was to overview the different techniques of fabricating ocular prostheses, in order to aid maxillofacial prosthodontists in choosing the most suitable technique, in terms of aesthetics, functional outcomes, and patient satisfaction.
Facial features are the most important non-verbal means of communication. Loss of any part of the face can cause severe mental trauma, affecting the patient’s social and professional life.1–4 Aims of treatment with an ocular prosthesis include repairing deformities of the eyeball, recovering facial aesthetics, protecting the anophthalmic cavity, restoring the lachrymal direction, and preventing accumulation of lachrymal fluid in the eye cavity.5,6 However, the presence of movable tissue layers may affect the quality of ocular prosthesis retention and cause irritation of the tissue layers.1,2,7,8 Many materials and implant types have been used to restore orbital volume and, to some extent, prosthetic mobility.9 Porous orbital implants have become increasingly popular with enucleation, evisceration, or secondary implant surgery.10 Considering the difficulty in obtaining natural facial prostheses and the
METHODS The PubMed and Bireme databases were searched for articles related to techniques used to fabricate ocular prostheses. The databases were searched with the terms ‘‘artificial eye,’’ ‘‘ocular prosthesis,’’ and ‘‘paint’’ for in vitro studies, clinical reports, and literature review articles published from 1985 to 2010. Articles dealing with other types of rehabilitation not involving ocular prosthesis fabrication were excluded.
Received 29 November 2011; Revised 7 November 2013; Accepted 6 January 2014; Published online 20 February 2014 Correspondence: Marcelo Coelho Goiato, UNESP – Arac¸atuba Dental School, Department of Dental Materials and Prosthodontics, Jose´ Bonifa´cio, 1193, Arac¸atuba – SP, Brazil, 16015-050, Tel: 55-1836363287, Fax: 55-1836363245, E-mail: [email protected]
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CONSIDERATIONS IN OCULAR PROSTHESIS DESIGN
conjunctiva and Tenon’s capsule, or even complete implant exposure, could occur.14–17
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History of the Ocular Prosthesis The development of different techniques for fabricating ocular prostheses began in the Roman and Egyptian civilizations, and continued through the Renaissance period with Ambroise Pare´.11,12 From the 18th century, prostheses were fabricated in glass.12 The technical and artistic development of such prostheses continued in France, Italy, and Germany, where Ludwig Muller Uri was considered an icon in manufacturing ocular prostheses.11,12 During World War II, the import of glass-based ocular prostheses from Germany was interrupted. Because dentures were being fabricated in methylmethacrylate with good tolerance by patients, researchers began to use this material to manufacture ocular prostheses.13 In addition, because of the extreme difficulty in fabricating ocular prostheses from glass, use of the latter material became increasingly restricted.12,13
Characteristics of the Anophthalmic Cavity Since the 1940s, techniques and materials for fabricating ocular prostheses have continued to evolve, and the aesthetics and functionality of such prostheses have increased.1 A key consideration in the development of the ocular prosthesis has been the characteristics of the anophthalmic cavity. The natural appearance of the ocular prosthesis is directly related to its movement during use, which is related to the correct adaptation of the prosthesis to the ocular muscles. However, the anophthalmic socket is limited in the degree to which its residual mobility can be transmitted to the ocular prosthesis. Other concerns include the volume of the cavity and risk of implant extrusion. To overcome these limitations, various implant materials have been employed, including hydroxyapatite (HA), polyethylene, aluminum oxide, and silicone, with smooth or rough surfaces. Under normal conditions, however, these materials do not appear in the anophthalmic cavity. Therefore, high rates of extrusion and infection have led to a design of completely buried integrated implants. In the past 11 years, coralline HA has been the most widely used implant material because of its high biocompatibility and anti-inflammation properties.9 However, this material has a high surface roughness; therefore, it is essential that the sclera or fascia be covered for the attachment of the extraocular muscles. This situation may present a risk of infectious disease transmission. Moreover, if the rough surface of the implant were to be uncovered or inadequately vascularized, then erosion of the overlying
TECHNIQUES FOR OCULAR PROSTHESIS FABRICATION Impression of the Ocular Defect To provide a customized ocular prosthesis, an accurate impression of the ocular defect must first be obtained. Compared to prostheses fabricated without an impression, an acrylic resin prosthesis obtained from an adequate impression offers better aesthetics and more precise outcomes because the impression process establishes the contours of the defect. After the impression procedure, the iris and sclera are characterized.9 Dental impression materials, such as irreversible hydrocolloids and silicones, have been successfully used to register the topography of the eye socket.18,19 Numerous ocular impression techniques have been described, and the effectiveness of each method depends on the operator’s expertise and availability of materials. These techniques can be classified into different categories, including: direct impression/ external impression; impression with a stock, modified stock, or custom ocular tray; impression with a stock ocular prosthesis; ocular prosthesis modification; and the wax scleral blank technique.19–21 In some situations, it is necessary to use individual trays, such as when the anophthalmic socket is irregular or stock trays are not available. Another recommended technique involves the reduction of a premanufactured prosthesis on its posterior region, which is then used as a tray.18,19 The impression technique involves selecting an aesthetic stock eye and reducing its peripheral and posterior aspects. The stock eye is lined with a thin mix of ophthalmic alginate, which is inserted to produce a definitive impression [19].
Iris Painting Techniques The first step in painting an artificial iris is a detailed observation of the color, diameter, and morphological elements of the patient’s natural iris under indirect natural light.22–24 Different techniques for obtaining a button eye have been suggested, such as conventional painting and mixing monomer-polymer on the artificial iris,20,25 reverse painting using prefabricated caps, and using digital and hard copy images of the patient’s healthy eye.26 According to the literature, the use of prefabricated caps provides similar physical properties of the ocular prosthesis compared to the use of colorless acrylic resin in the monomer-polymer mixture.23 Orbit
Ocular Prostheses
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Manual iris painting Several factors play an important role in determining the aesthetic outcome of manual iris painting, as described next. Quality of iris paint. The quality of the paint used for iris painting is an important property that impacts whether the painting shows bleaching, stains, and color alterations during and after polymerization as a result of ultraviolet rays on the paint. Depending on the surface, different paints can be applied,2,22 such as varnishes and gouache, acrylic, oil, and automotive paints. Gouache and acrylic paints have been used to color the iris, but both present color alterations. Oil paint has better color stability when exposed to degradation action and environmental agents.21,23,27 Surface on which the irises are painted. Iris painting can be done on paper discs, directly on the acrylic resin sclera, ethyl-cellulose discs, acetate, and the colorless acrylic ocular bottom. An inverse painting technique can be used. For each type of surface, a specific type of paint is indicated.23 Black21 and white27 cardboards and Carmem paper2 can be used as surfaces for iris painting. Some authors do not recommend painting on paper disks, and rather suggest the use of celluloid acetate disks.28 Directly painting on an acrylic disk has been indicated to allow visualization of the color of the disk and its placement in the wax-plastic piece. A painted glass iris provides superior aesthetic results compared to all other techniques.2,22 Digital imaging Another option for artificial iris fabrication is digital imaging.26 The digital image provides acceptable aesthetic results because it closely replicates the patient’s iris with minimal color adjustments and modifications. The technique is simple, decreases treatment time, and requires minimal artistic skills, which are necessary in the iris painting technique. However, special digital photography equipment and settings as well as computer software for image adjustments are required.2,26
Sclera Fabrication The sclera corresponds to the base of the ocular prosthesis. Acrylic resin offers advantages for ocular prosthesis fabrication, such as durability, ease of cleaning, reliable mechanical retention, biocompatibility, and low cost30; therefore, it is the material of choice to manufacture the ocular prosthesis.29 Acrylic resin is composed of a polymer powder of methyl methacrylate and a liquid monomer. It has excellent resistance and is easy to color. However, !
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when used in ocular prostheses, acrylic resin (like other materials) can promote slight discomfort due to its rigidity and small ulcers due to its sharp edges.31–33 To create ocular prostheses, white-pigmented (N1) and colorless acrylic resins are used to mimic the artificial sclera.21–23 The typical resin thickness used for the artificial sclera ranges from 2 to 10 mm; for colorless resin, the thickness ranges from 1 to 3.5 mm.21,22 Different associations between the artificial resin layers can be varied to promote greater translucency, depth, and similarity to the natural eye.22,23 To provide sufficient space for characterizing the sclera and applying additional colorless acrylic resin, the anterior surface curvature of the sclera is trimmed to 1 mm in its thickness. Silk fibers, used to resemble the blood vessels, are applied using tweezers and monomer.5,6 Finally, the colorless acrylic resin is packed over the characterized sclera.
Colorless Acrylic Resin Covering Aesthetic and facial harmonies of the ocular prosthesis are achieved by choosing the appropriate volume and contour of the colorless acrylic resin. A layer of colorless acrylic resin covers the characterized blood vessels and artificial iris, and provides similar brightness when compared to the natural eye. The painted iris is also covered by a layer of colorless acrylic resin, which promotes the visual effect of a magnifying glass under the artificial iris. To overcome this optical effect when painting the iris on paper, the diameter of the artificial iris should be reduced by 1 mm compared to the patient’s natural iris.5,6 The colorless acrylic resin layer varies from 1 to 3.5 mm in thickness. This layer provides translucence, perfect visualization of the artificial iris, and a natural appearance. When inserted into the patient’s socket, the ocular prosthesis is exposed to weather degradation, and the colorless acrylic resin becomes opaque, affecting the aesthetics.5 The polymerization process of the acrylic resin has been modified to enhance its properties. Polymerization by microwave energy provides some advantages, such as reduced polymerization time, high homogeneity of the mixture, and excellent prosthetic fit.24,32–37 Properties of the acrylic resin are affected by the temperature,37 thickness, and quantity of residual monomer, as well as exposure to disinfectants.35,37 The reaction between microwavepolymerized acrylic resins and the paint components is unknown; however, it can be supposed that the direct contact of these components affects the paints’ chemical links, promoting changes of these links during polymerization of the prosthesis. This effect can be increased by the action of ultraviolet rays in a clinical situation.24
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POLISHING PROCESS AND INSERTION The ocular prosthesis should be polished before and periodically after insertion, to avoid the accumulation of microorganisms under its surface. The increased roughness of the ocular prosthesis can promote irritation, hormonal alterations, and, in rare cases, chronic superficial conjunctivitis.24 After insertion of the prosthesis into the patient’s eye socket, its aesthetic appearance should be evaluated. The irises of the natural and prosthetic eyes should be well aligned in the same plane. The eyelids should be similar in shape, and the eyelid openings should be the same. Usually the iris of the prosthetic eye should just touch the lower eyelid and be partially covered by the upper eyelid. The iris colors should match, but the prosthesis will not have the same sheen or sparkle as the natural eye, as the resin will not be completely wetted by lachrymal fluids. Generally, the appearance should improve during the first 2 days.18 The degree of muscle motion can be tested by asking the patient to look in different directions. The ocularist should investigate the surface of the prosthesis to check its regularity and smoothness. He or she should polish the prosthesis, if needed, to provide maximum comfort to the patient. The patient should be instructed on how to remove and insert the prosthesis. Removal consists of pulling the lower eyelid down, gazing overhead, and engaging the lower margin of the prosthesis with one finger, so that it is expelled downward into the hand. The prosthesis should be wetted before insertion, removing and washing it with soap and tepid water once a day, or more often if mucus has accumulated. Patients who have had experience with wearing an ocular prosthesis may require no further treatment, but a new patient should be given a follow-up appointment for possible adjustments.23,24
FINAL CONSIDERATIONS The literature provides several techniques for fabricating ocular prostheses, ranging from stock to custom-made prostheses. Great adaptation and a natural appearance are possible with a personalized prosthesis. Several impression techniques have been proposed, and the professional should choose the most convenient technique. Regarding iris painting, the best long-term outcomes are generally accepted to be achieved with the use of oil paint. Characterization of the sclera, application of the colorless acrylic resin layer, and finalization of the ocular prosthesis (trimming and polishing) remain unchanged. However, these steps are very important to obtain a satisfactory outcome. Ocular rehabilitation restores the compromised aesthetics, maintains the normal physiology of
the ocular area, and increases the social life and selfesteem of the patient.
ACKNOWLEDGEMENTS This research was supported by a grant from the State of Sa˜o Paulo Research Foundation (FAPESP).
DECLARATION OF INTEREST No author has a financial or proprietary interest in any material or method mentioned.
REFERENCES 1. Naveen HC, Porwal A, Nelogi S. Prosthetic rehabilitation of phthisis bulbi by digital imaging technique-A case report. Cont Lens Anterior Eye 2010;33:231–234. 2. Goiato MC, Moreno A, Santos DM, et al. Effect of polymerization and accelerated aging on iris color stability of ocular prosthesis. Cont Lens Anterior Eye 2010;33: 215–218. 3. Song JS, Oh J, Baek SH. A survey of satisfaction in anophthalmic patients wearing ocular prosthesis. Graefes Arch Clin Exp Ophthalmol 2006;244:330–335. 4. Chin K, Margolin CB, Finger PT. Early ocular prosthesis insertion improves quality of life after enucleation. Optometry 2006;77:71–75. 5. Fernandes AU, Goiato MC, Batista MA, Santos DM. Color alteration of the paint used for iris painting in ocular prostheses. Braz Oral Res 2009;23:386–392. 6. Goiato MC, Pesqueira AA, Ramos da Silva C, et al. Patient satisfaction with maxillofacial prosthesis. Literature review. J Plast Reconstr Aesthet Surg 2009;62:175–180. 7. Goiato MC, Mancuso DN, Sundefeld MLMM, et al. Aesthetic and functional ocular rehabilitation. Oral Oncol Extra 2005;41:162–164. 8. Travieso MLA, Rivero AVA, Brito BOB. Rehabilitacio´n ocular en nin˜os. Investigaciones medicoquiru´rgicas 2005;1: 25–29. 9. Chen YH, Cui HG. High density porous polyethylene material (Medpor) as an unwrapped orbital implant. J Zhejiang Univ Sci 2006;7:679–682. 10. Cheng MS, Liao SL, Lin LK. Late porous polyethylene implants exposure after motility coupling post placement. Am J Ophthalmol 2004;138:420–424. 11. Buckel M, Bovet J. The eye as an art form: the ocular prosthesis. Klin Monbl Augenheilkd 1992;200:594–595. 12. Conroy BF. A brief sortie into the history of cranio oculofacial prosthetics. Facial Plast Surg 1993;9:89–115. 13. Reisberg DJ, Habakuk SW. A history of facial and ocular prosthetics. Adv Ophthalmic Plast Reconstr Surg 1990;8: 11–24. 14. Buettner H, Bartley GB. Tissue breakdown and exposure associated with orbital hydroxyapatite implants. Am J Ophthalmol 1992;113:669–673. 15. Remulla HD, Rubin PA, Shore JW, et al. Complications of porous spherical orbital implants. Ophthalmology 1995;102: 586–593. 16. McNab A. Hydroxyapatite orbital implants. Experience with 100 cases. Aust N Z J Ophthalmol 1995;23:117–123. Orbit
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Ocular Prostheses 17. Oestreicher JH, Liu E, Berkowitz M. Complications of hydroxyapatite orbital implants: a review of 100 consecutive cases and a comparison of Dexon mesh with scleral wrapping. Ophthalmology 1997;104:324–329. 18. Patil SB, Meshramkar R, Naveen BH, Patil NP. Ocular prosthesis: a brief review and fabrication of an ocular prosthesis for a geriatric patient. Gerodontology. 2008;25: 57–62. 19. Mathews MF, Smith RM, Sutton AJ, Hudson R. The ocular impression: a review of the literature and presentation of an alternate technique. J Prosthodont 2000;9:210–216. 20. Taicher S, Steinberg HM, Tubiana I, Sela M. Modified stockeye ocular prosthesis. J Prosthet Dent. 1985;54:95–98. 21. Raizada K, Rani D. Ocular prosthesis. Cont Lens Anterior Eye 2007;30:152–162. 22. Fernandes AU, Goiato MC, Batista MA, Santos DM. Color alteration of the paint used for iris painting in ocular prostheses. Braz Oral Res 2009;23(4):386–392. 23. Fernandes AU, Goiato MC, dos Santos DM. Effect of weathering and thickness on the superficial microhardness of acrylic resin and ocular button. Cont Lens Anterior Eye 2009;32:283–287. 24. Fernandes AU, Portugal A, Veloso LR, et al. Assessment of the flexural strength of two heat-curing acrylic resins for artificial eyes. Braz Oral Res 2009;23:263–267. 25. Reitemeier B, Notni G, Heinze M, et al. Optical modeling of extraoral defects. J Prosthet Dent 2004;91:80–84. 26. Artopoulou II, Montgomery PC, Wesley PJ, Lemon JC. Digital imaging in the fabrication of ocular prostheses. J Prosthet Dent 2006;95:327–330. 27. Reis RC, Dias RB, Carvalho JCM. Evaluation of iris color stability in color prosthesis. Braz Dent J 2008;19:370–374. 28. Dietz VH. The all plastic artificial eye. Ill Dent J 1945;14: 246–248.
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29. Ogawa T, Hasegawa A. Effect of curing environment on mechanical properties and polymerizing ehaviour of methyl-methacrylate autopolymerizing resin. J Oral Rehabil 2005;32:221–226. 30. Canadas MD, Garcia LF, Consani S, Pires-de-Souza FC. Color stability, surface roughness, and surface porosity of acrylic resins for eye sclera polymerized by different heat sources. J Prosthodont 2010;19:52–57. 31. Ebadian B, Razavi M, Soleimanpour S, Mosharraf R. Evaluation of tissue reaction to some denture-base materials: an animal study. J Contemp Dent Pract 2008;9:67–74. 32. Diaz-Arnold AM, Vargas MA, Shaull KL, et al. Flexural and fatigue strengths of denture base resin. J Prosthet Dent 2008;100:47–51. 33. Koran P, Kurchner R. Effect of sequential versus continuous irradiation of a light-cures resin composite on shrinkage, viscosity, adhesion and degree of polymerization. Am J Dent 1998;11:17–22. 34. Lai CP, Tsai MH, Chen M, et al. Morphology and properties of denture acrylic resins cured by microwave energy and conventional water bath. Dent Mater 2004;20: 133–141. 35. Dog˘an A, Bek B, Cevik NN, Usanmaz A. The effect of preparation conditions of acrylic denture base materials on the level of residual monomer, mechanical properties and water absorption. J Dent 1995; 23:313–318. 36. Azzarri MJ, Cortizo MS, Alessandrini JL. Effect of the curing conditions on the properties of an acrylic denture base resin microwave-polymerised. J Dent 2003; 31:463–468. 37. Faltermeier A, Rosentritt M, Mu¨ssig D. Acrylic removable appliances: comparative evaluation of different postpolymerization methods. Am J Orthod Dentofacial Orthop 2007; 131:316–322.
REVIEW
Fabrication Techniques for Ocular Prostheses – An Overview
Orbit Downloaded from informahealthcare.com by Biblioteka Uniwersytetu Warszawskiego on 03/03/15 For personal use only.
Marcelo Coelho Goiato1, Lisiane Cristina Bannwart1, Marcela Filie´ Haddad1, Daniela Micheline dos Santos1, Aldie´ris Alves Pesqueira1, and Glauco Issamu Miyahara2 1
Department of Dental Materials and Prosthodontics and 2Department of Pathology and Propedeutic Clinic, UNESP, Univ Estadual Paulista - Arac¸atuba Dental School, Brazil
ABSTRACT The goals of treatment with ocular prostheses are to restore facial aesthetics and self-esteem to anophthalmic patients. Fabricated in acrylic resin, artificial eyes should be aesthetically pleasing, scratch-resistant, and adequately polished. Use of a prosthesis without such characteristics can lead to psychological damage, as well as infection and inflammation due to the accumulation of microorganisms and other substances on an irregularly shaped prosthesis. The present literature review describes the different techniques for fabricating ocular prostheses. Reproduction of the iris color and color stability are important factors that promote adequate aesthetics. The fabrication of an individual ocular prosthesis in acrylic resin provides satisfactory aesthetic results because the impression process establishes the defect contour. Additionally, the iris and sclera can be individually characterized. As the techniques, materials, and manufacturing methods for ocular prostheses continue to evolve, the aesthetics and functionality of prostheses will also improve. Keywords: Artificial, eye, paint, sclera
INTRODUCTION
variety of maxillofacial materials that are available, the aim of the current literature review was to overview the different techniques of fabricating ocular prostheses, in order to aid maxillofacial prosthodontists in choosing the most suitable technique, in terms of aesthetics, functional outcomes, and patient satisfaction.
Facial features are the most important non-verbal means of communication. Loss of any part of the face can cause severe mental trauma, affecting the patient’s social and professional life.1–4 Aims of treatment with an ocular prosthesis include repairing deformities of the eyeball, recovering facial aesthetics, protecting the anophthalmic cavity, restoring the lachrymal direction, and preventing accumulation of lachrymal fluid in the eye cavity.5,6 However, the presence of movable tissue layers may affect the quality of ocular prosthesis retention and cause irritation of the tissue layers.1,2,7,8 Many materials and implant types have been used to restore orbital volume and, to some extent, prosthetic mobility.9 Porous orbital implants have become increasingly popular with enucleation, evisceration, or secondary implant surgery.10 Considering the difficulty in obtaining natural facial prostheses and the
METHODS The PubMed and Bireme databases were searched for articles related to techniques used to fabricate ocular prostheses. The databases were searched with the terms ‘‘artificial eye,’’ ‘‘ocular prosthesis,’’ and ‘‘paint’’ for in vitro studies, clinical reports, and literature review articles published from 1985 to 2010. Articles dealing with other types of rehabilitation not involving ocular prosthesis fabrication were excluded.
Received 29 November 2011; Revised 7 November 2013; Accepted 6 January 2014; Published online 20 February 2014 Correspondence: Marcelo Coelho Goiato, UNESP – Arac¸atuba Dental School, Department of Dental Materials and Prosthodontics, Jose´ Bonifa´cio, 1193, Arac¸atuba – SP, Brazil, 16015-050, Tel: 55-1836363287, Fax: 55-1836363245, E-mail: [email protected]
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conjunctiva and Tenon’s capsule, or even complete implant exposure, could occur.14–17
Orbit Downloaded from informahealthcare.com by Biblioteka Uniwersytetu Warszawskiego on 03/03/15 For personal use only.
History of the Ocular Prosthesis The development of different techniques for fabricating ocular prostheses began in the Roman and Egyptian civilizations, and continued through the Renaissance period with Ambroise Pare´.11,12 From the 18th century, prostheses were fabricated in glass.12 The technical and artistic development of such prostheses continued in France, Italy, and Germany, where Ludwig Muller Uri was considered an icon in manufacturing ocular prostheses.11,12 During World War II, the import of glass-based ocular prostheses from Germany was interrupted. Because dentures were being fabricated in methylmethacrylate with good tolerance by patients, researchers began to use this material to manufacture ocular prostheses.13 In addition, because of the extreme difficulty in fabricating ocular prostheses from glass, use of the latter material became increasingly restricted.12,13
Characteristics of the Anophthalmic Cavity Since the 1940s, techniques and materials for fabricating ocular prostheses have continued to evolve, and the aesthetics and functionality of such prostheses have increased.1 A key consideration in the development of the ocular prosthesis has been the characteristics of the anophthalmic cavity. The natural appearance of the ocular prosthesis is directly related to its movement during use, which is related to the correct adaptation of the prosthesis to the ocular muscles. However, the anophthalmic socket is limited in the degree to which its residual mobility can be transmitted to the ocular prosthesis. Other concerns include the volume of the cavity and risk of implant extrusion. To overcome these limitations, various implant materials have been employed, including hydroxyapatite (HA), polyethylene, aluminum oxide, and silicone, with smooth or rough surfaces. Under normal conditions, however, these materials do not appear in the anophthalmic cavity. Therefore, high rates of extrusion and infection have led to a design of completely buried integrated implants. In the past 11 years, coralline HA has been the most widely used implant material because of its high biocompatibility and anti-inflammation properties.9 However, this material has a high surface roughness; therefore, it is essential that the sclera or fascia be covered for the attachment of the extraocular muscles. This situation may present a risk of infectious disease transmission. Moreover, if the rough surface of the implant were to be uncovered or inadequately vascularized, then erosion of the overlying
TECHNIQUES FOR OCULAR PROSTHESIS FABRICATION Impression of the Ocular Defect To provide a customized ocular prosthesis, an accurate impression of the ocular defect must first be obtained. Compared to prostheses fabricated without an impression, an acrylic resin prosthesis obtained from an adequate impression offers better aesthetics and more precise outcomes because the impression process establishes the contours of the defect. After the impression procedure, the iris and sclera are characterized.9 Dental impression materials, such as irreversible hydrocolloids and silicones, have been successfully used to register the topography of the eye socket.18,19 Numerous ocular impression techniques have been described, and the effectiveness of each method depends on the operator’s expertise and availability of materials. These techniques can be classified into different categories, including: direct impression/ external impression; impression with a stock, modified stock, or custom ocular tray; impression with a stock ocular prosthesis; ocular prosthesis modification; and the wax scleral blank technique.19–21 In some situations, it is necessary to use individual trays, such as when the anophthalmic socket is irregular or stock trays are not available. Another recommended technique involves the reduction of a premanufactured prosthesis on its posterior region, which is then used as a tray.18,19 The impression technique involves selecting an aesthetic stock eye and reducing its peripheral and posterior aspects. The stock eye is lined with a thin mix of ophthalmic alginate, which is inserted to produce a definitive impression [19].
Iris Painting Techniques The first step in painting an artificial iris is a detailed observation of the color, diameter, and morphological elements of the patient’s natural iris under indirect natural light.22–24 Different techniques for obtaining a button eye have been suggested, such as conventional painting and mixing monomer-polymer on the artificial iris,20,25 reverse painting using prefabricated caps, and using digital and hard copy images of the patient’s healthy eye.26 According to the literature, the use of prefabricated caps provides similar physical properties of the ocular prosthesis compared to the use of colorless acrylic resin in the monomer-polymer mixture.23 Orbit
Ocular Prostheses
Orbit Downloaded from informahealthcare.com by Biblioteka Uniwersytetu Warszawskiego on 03/03/15 For personal use only.
Manual iris painting Several factors play an important role in determining the aesthetic outcome of manual iris painting, as described next. Quality of iris paint. The quality of the paint used for iris painting is an important property that impacts whether the painting shows bleaching, stains, and color alterations during and after polymerization as a result of ultraviolet rays on the paint. Depending on the surface, different paints can be applied,2,22 such as varnishes and gouache, acrylic, oil, and automotive paints. Gouache and acrylic paints have been used to color the iris, but both present color alterations. Oil paint has better color stability when exposed to degradation action and environmental agents.21,23,27 Surface on which the irises are painted. Iris painting can be done on paper discs, directly on the acrylic resin sclera, ethyl-cellulose discs, acetate, and the colorless acrylic ocular bottom. An inverse painting technique can be used. For each type of surface, a specific type of paint is indicated.23 Black21 and white27 cardboards and Carmem paper2 can be used as surfaces for iris painting. Some authors do not recommend painting on paper disks, and rather suggest the use of celluloid acetate disks.28 Directly painting on an acrylic disk has been indicated to allow visualization of the color of the disk and its placement in the wax-plastic piece. A painted glass iris provides superior aesthetic results compared to all other techniques.2,22 Digital imaging Another option for artificial iris fabrication is digital imaging.26 The digital image provides acceptable aesthetic results because it closely replicates the patient’s iris with minimal color adjustments and modifications. The technique is simple, decreases treatment time, and requires minimal artistic skills, which are necessary in the iris painting technique. However, special digital photography equipment and settings as well as computer software for image adjustments are required.2,26
Sclera Fabrication The sclera corresponds to the base of the ocular prosthesis. Acrylic resin offers advantages for ocular prosthesis fabrication, such as durability, ease of cleaning, reliable mechanical retention, biocompatibility, and low cost30; therefore, it is the material of choice to manufacture the ocular prosthesis.29 Acrylic resin is composed of a polymer powder of methyl methacrylate and a liquid monomer. It has excellent resistance and is easy to color. However, !
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when used in ocular prostheses, acrylic resin (like other materials) can promote slight discomfort due to its rigidity and small ulcers due to its sharp edges.31–33 To create ocular prostheses, white-pigmented (N1) and colorless acrylic resins are used to mimic the artificial sclera.21–23 The typical resin thickness used for the artificial sclera ranges from 2 to 10 mm; for colorless resin, the thickness ranges from 1 to 3.5 mm.21,22 Different associations between the artificial resin layers can be varied to promote greater translucency, depth, and similarity to the natural eye.22,23 To provide sufficient space for characterizing the sclera and applying additional colorless acrylic resin, the anterior surface curvature of the sclera is trimmed to 1 mm in its thickness. Silk fibers, used to resemble the blood vessels, are applied using tweezers and monomer.5,6 Finally, the colorless acrylic resin is packed over the characterized sclera.
Colorless Acrylic Resin Covering Aesthetic and facial harmonies of the ocular prosthesis are achieved by choosing the appropriate volume and contour of the colorless acrylic resin. A layer of colorless acrylic resin covers the characterized blood vessels and artificial iris, and provides similar brightness when compared to the natural eye. The painted iris is also covered by a layer of colorless acrylic resin, which promotes the visual effect of a magnifying glass under the artificial iris. To overcome this optical effect when painting the iris on paper, the diameter of the artificial iris should be reduced by 1 mm compared to the patient’s natural iris.5,6 The colorless acrylic resin layer varies from 1 to 3.5 mm in thickness. This layer provides translucence, perfect visualization of the artificial iris, and a natural appearance. When inserted into the patient’s socket, the ocular prosthesis is exposed to weather degradation, and the colorless acrylic resin becomes opaque, affecting the aesthetics.5 The polymerization process of the acrylic resin has been modified to enhance its properties. Polymerization by microwave energy provides some advantages, such as reduced polymerization time, high homogeneity of the mixture, and excellent prosthetic fit.24,32–37 Properties of the acrylic resin are affected by the temperature,37 thickness, and quantity of residual monomer, as well as exposure to disinfectants.35,37 The reaction between microwavepolymerized acrylic resins and the paint components is unknown; however, it can be supposed that the direct contact of these components affects the paints’ chemical links, promoting changes of these links during polymerization of the prosthesis. This effect can be increased by the action of ultraviolet rays in a clinical situation.24
232 M. C. Goiato et al.
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POLISHING PROCESS AND INSERTION The ocular prosthesis should be polished before and periodically after insertion, to avoid the accumulation of microorganisms under its surface. The increased roughness of the ocular prosthesis can promote irritation, hormonal alterations, and, in rare cases, chronic superficial conjunctivitis.24 After insertion of the prosthesis into the patient’s eye socket, its aesthetic appearance should be evaluated. The irises of the natural and prosthetic eyes should be well aligned in the same plane. The eyelids should be similar in shape, and the eyelid openings should be the same. Usually the iris of the prosthetic eye should just touch the lower eyelid and be partially covered by the upper eyelid. The iris colors should match, but the prosthesis will not have the same sheen or sparkle as the natural eye, as the resin will not be completely wetted by lachrymal fluids. Generally, the appearance should improve during the first 2 days.18 The degree of muscle motion can be tested by asking the patient to look in different directions. The ocularist should investigate the surface of the prosthesis to check its regularity and smoothness. He or she should polish the prosthesis, if needed, to provide maximum comfort to the patient. The patient should be instructed on how to remove and insert the prosthesis. Removal consists of pulling the lower eyelid down, gazing overhead, and engaging the lower margin of the prosthesis with one finger, so that it is expelled downward into the hand. The prosthesis should be wetted before insertion, removing and washing it with soap and tepid water once a day, or more often if mucus has accumulated. Patients who have had experience with wearing an ocular prosthesis may require no further treatment, but a new patient should be given a follow-up appointment for possible adjustments.23,24
FINAL CONSIDERATIONS The literature provides several techniques for fabricating ocular prostheses, ranging from stock to custom-made prostheses. Great adaptation and a natural appearance are possible with a personalized prosthesis. Several impression techniques have been proposed, and the professional should choose the most convenient technique. Regarding iris painting, the best long-term outcomes are generally accepted to be achieved with the use of oil paint. Characterization of the sclera, application of the colorless acrylic resin layer, and finalization of the ocular prosthesis (trimming and polishing) remain unchanged. However, these steps are very important to obtain a satisfactory outcome. Ocular rehabilitation restores the compromised aesthetics, maintains the normal physiology of
the ocular area, and increases the social life and selfesteem of the patient.
ACKNOWLEDGEMENTS This research was supported by a grant from the State of Sa˜o Paulo Research Foundation (FAPESP).
DECLARATION OF INTEREST No author has a financial or proprietary interest in any material or method mentioned.
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